[Spring Boot Basics] Spring Data JPA và Hibernate trong Spring Boot: Entity, @Id, @GeneratedValue và CRUD với JpaRepository

./gradlew dependencies --configuration runtimeClasspath

+--- org.springframework.boot:spring-boot-starter-data-jpa -> 4.1.1
|    +--- org.springframework.boot:spring-boot-starter-jdbc:4.1.1
|    |    +--- org.springframework.boot:spring-boot-jdbc:4.1.1
|    |    \--- com.zaxxer:HikariCP:7.0.2
|    +--- org.springframework.boot:spring-boot-data-jpa:4.1.1
|    |    +--- org.springframework.boot:spring-boot-data-commons:4.1.1
|    |    |    \--- org.springframework.data:spring-data-commons:4.1.1
|    |    +--- org.springframework.boot:spring-boot-hibernate:4.1.1
|    |    |    +--- org.springframework.boot:spring-boot-jpa:4.1.1
|    |    |    |    +--- jakarta.persistence:jakarta.persistence-api:3.2.0
|    |    |    |    \--- org.springframework:spring-orm:7.0.9
|    |    |    +--- org.hibernate.orm:hibernate-core:7.4.5.Final
|    |    |    \--- org.springframework:spring-orm:7.0.9 (*)
|    |    +--- org.springframework.data:spring-data-jpa:4.1.1
|    |    \--- org.springframework:spring-aspects:7.0.9
|    \--- org.springframework.boot:spring-boot-jdbc:4.1.1 (*)

package com.example.demo.product;
 
public enum ProductStatus {
    ACTIVE, OUT_OF_STOCK, DISCONTINUED
}

package com.example.demo.product;
 
import java.math.BigDecimal;
 
import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.EnumType;
import jakarta.persistence.Enumerated;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
 
@Entity
@Table(name = "products")
public class Product {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
 
    @Column(nullable = false, length = 120)
    private String name;
 
    @Column(nullable = false, length = 40, unique = true)
    private String sku;
 
    @Column(nullable = false, precision = 10, scale = 2)
    private BigDecimal price;
 
    private int stock;
 
    @Column(nullable = false, length = 60)
    private String category;
 
    @Enumerated(EnumType.STRING)
    @Column(nullable = false, length = 20)
    private ProductStatus status = ProductStatus.ACTIVE;
 
    protected Product() {
    }
 
    public Product(String name, String sku, BigDecimal price, int stock, String category) {
        this.name = name;
        this.sku = sku;
        this.price = price;
        this.stock = stock;
        this.category = category;
    }
 
    public Long getId() { return id; }
 
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
 
    public String getSku() { return sku; }
 
    public BigDecimal getPrice() { return price; }
    public void setPrice(BigDecimal price) { this.price = price; }
 
    public int getStock() { return stock; }
    public void setStock(int stock) { this.stock = stock; }
 
    public String getCategory() { return category; }
    public void setCategory(String category) { this.category = category; }
 
    public ProductStatus getStatus() { return status; }
    public void setStatus(ProductStatus status) { this.status = status; }
 
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Product other)) return false;
        return id != null && id.equals(other.getId());
    }
 
    @Override
    public int hashCode() {
        return Product.class.hashCode();
    }
 
    @Override
    public String toString() {
        return "Product[id=" + id + ", sku=" + sku + ", price=" + price + ", stock=" + stock + ", status=" + status + "]";
    }
}

2026-09-13T16:10:42.204+07:00  INFO 9316 --- [demo] [           main] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Added connection conn0: url=jdbc:h2:mem:d3b1b5b4-d92e-4b0b-a61e-62b69972d717 user=SA
2026-09-13T16:10:42.812+07:00 DEBUG 9316 --- [demo] [           main] org.hibernate.SQL                        : drop table if exists products cascade
2026-09-13T16:10:42.814+07:00 DEBUG 9316 --- [demo] [           main] org.hibernate.SQL                        : create table products (price numeric(10,2) not null, stock integer not null, id bigint generated by default as identity, sku varchar(40) not null unique, category varchar(60) not null, name varchar(120) not null, status enum ('ACTIVE','DISCONTINUED','OUT_OF_STOCK') not null, primary key (id))

spring.datasource.url=jdbc:postgresql://localhost:55426/catalog
spring.datasource.username=catalog
spring.datasource.password=catalog

2026-09-13T16:12:48.451+07:00 DEBUG 9835 --- [demo] [           main] org.hibernate.SQL                        : set client_min_messages = WARNING
2026-09-13T16:12:48.452+07:00 DEBUG 9835 --- [demo] [           main] org.hibernate.SQL                        : drop table if exists products cascade
2026-09-13T16:12:48.454+07:00 DEBUG 9835 --- [demo] [           main] org.hibernate.SQL                        : create table products (price numeric(10,2) not null, stock integer not null, id bigint generated by default as identity, status varchar(20) not null check ((status in ('ACTIVE','OUT_OF_STOCK','DISCONTINUED'))), sku varchar(40) not null unique, category varchar(60) not null, name varchar(120) not null, primary key (id))

docker exec sb-a26-pg psql -U catalog -d catalog -c '\d products'

                                   Table "public.products"
  Column  |          Type          | Collation | Nullable |             Default
----------+------------------------+-----------+----------+----------------------------------
 price    | numeric(10,2)          |           | not null |
 stock    | integer                |           | not null |
 id       | bigint                 |           | not null | generated by default as identity
 status   | character varying(20)  |           | not null |
 sku      | character varying(40)  |           | not null |
 category | character varying(60)  |           | not null |
 name     | character varying(120) |           | not null |
Indexes:
    "products_pkey" PRIMARY KEY, btree (id)
    "products_sku_key" UNIQUE CONSTRAINT, btree (sku)
Check constraints:
    "products_status_check" CHECK (status::text = ANY (ARRAY['ACTIVE'::character varying, 'OUT_OF_STOCK'::character varying, 'DISCONTINUED'::character varying]::text[]))

    @Enumerated(EnumType.STRING) 
    @Column(nullable = false, length = 20) 
    @Enumerated
    @Column(nullable = false) 
    private ProductStatus status = ProductStatus.ACTIVE;

SQL: create table products (price numeric(10,2) not null, status tinyint not null check ((status between 0 and 2)), stock integer not null, id bigint generated by default as identity, sku varchar(40) not null unique, category varchar(60) not null, name varchar(120) not null, primary key (id))

SQL: create table products (price numeric(10,2) not null, status smallint not null check ((status between 0 and 2)), stock integer not null, id bigint generated by default as identity, sku varchar(40) not null unique, category varchar(60) not null, name varchar(120) not null, primary key (id))

package com.example.demo.lab;
 
import java.math.BigDecimal;
import java.util.List;
 
import com.example.demo.product.Product;
import com.example.demo.product.ProductRepository;
import com.example.demo.product.ProductStatus;
 
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.CommandLineRunner;
import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Component;
 
@Component
@Profile("ids")
class IdTour implements CommandLineRunner {
 
    private static final Logger log = LoggerFactory.getLogger(IdTour.class);
 
    private final ProductRepository repository;
    private final String run;
    private final String mode;
 
    IdTour(ProductRepository repository, @Value("${tour.run:1}") String run, @Value("${tour.mode:ids}") String mode) {
        this.repository = repository;
        this.run = run;
        this.mode = mode;
    }
 
    @Override
    public void run(String... args) {
        if (mode.equals("read")) {
            repository.findAll().forEach(p -> log.info("{}", p));
            return;
        }
        Product keyboard = new Product("Mechanical keyboard", "KB-0" + run, new BigDecimal("89.90"), 25, "Keyboards");
        Product mouse = new Product("Wireless mouse", "MS-0" + run, new BigDecimal("24.50"), 0, "Mice");
        Product hub = new Product("USB-C hub", "HUB-0" + run, new BigDecimal("39.00"), 10, "Accessories");
        if (mode.equals("statuses")) {
            mouse.setStatus(ProductStatus.OUT_OF_STOCK);
            hub.setStatus(ProductStatus.DISCONTINUED);
        }
        log.info("-- saveAll(three new products)");
        List<Product> saved = repository.saveAll(List.of(keyboard, mouse, hub));
        log.info("ids={}", saved.stream().map(Product::getId).toList());
        if (mode.equals("statuses")) {
            repository.findAll().forEach(p -> log.info("{}", p));
        }
    }
}

IdTour: -- saveAll(three new products)
SQL: insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)
SQL: insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)
SQL: insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)
IdTour: ids=[1, 2, 3]
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0
IdTour: Product[id=1, sku=KB-01, price=89.90, stock=25, status=ACTIVE]
IdTour: Product[id=2, sku=MS-01, price=24.50, stock=0, status=OUT_OF_STOCK]
IdTour: Product[id=3, sku=HUB-01, price=39.00, stock=10, status=DISCONTINUED]

docker exec sb-a26-pg psql -U catalog -d catalog -c 'select id, sku, status from products order by id'

 id |  sku   | status
----+--------+--------
  1 | KB-01  |      0
  2 | MS-01  |      1
  3 | HUB-01 |      2
(3 rows)

public enum ProductStatus {
    ACTIVE, OUT_OF_STOCK, DISCONTINUED 
    ACTIVE, DISCONTINUED, OUT_OF_STOCK 
}

IdTour: Product[id=1, sku=KB-01, price=89.90, stock=25, status=ACTIVE]
IdTour: Product[id=2, sku=MS-01, price=24.50, stock=0, status=DISCONTINUED]
IdTour: Product[id=3, sku=HUB-01, price=39.00, stock=10, status=OUT_OF_STOCK]

    protected Product() { 
    } 

2026-09-13T16:16:37.975+07:00  INFO 10669 --- [demo] [           main] org.hibernate.orm.core                   : HHH000182: No default (no-argument) constructor for class [com.example.demo.product.Product] (class must be instantiated by Interceptor)
2026-09-13T16:16:38.208+07:00  INFO 10669 --- [demo] [           main] com.example.demo.lab.IdTour              : -- saveAll(three new products)
2026-09-13T16:16:38.242+07:00 DEBUG 10669 --- [demo] [           main] org.hibernate.SQL                        : insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
2026-09-13T16:16:38.261+07:00 DEBUG 10669 --- [demo] [           main] org.hibernate.SQL                        : insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
2026-09-13T16:16:38.262+07:00 DEBUG 10669 --- [demo] [           main] org.hibernate.SQL                        : insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
2026-09-13T16:16:38.267+07:00  INFO 10669 --- [demo] [           main] com.example.demo.lab.IdTour              : ids=[1, 2, 3]
2026-09-13T16:16:38.329+07:00 DEBUG 10669 --- [demo] [           main] org.hibernate.SQL                        : select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0
2026-09-13T16:16:38.340+07:00 ERROR 10669 --- [demo] [           main] o.s.boot.SpringApplication               : Application run failed
 
org.springframework.orm.jpa.JpaSystemException: No default constructor for entity 'com.example.demo.product.Product'
...
Caused by: org.hibernate.InstantiationException: No default constructor for entity 'com.example.demo.product.Product'
	at org.hibernate.metamodel.internal.EntityInstantiatorPojoStandard.instantiate(EntityInstantiatorPojoStandard.java:94) ~[hibernate-core-7.4.5.Final.jar!/:7.4.5.Final]

package com.example.demo.product;
 
import java.math.BigDecimal;
 
import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.EnumType;
import jakarta.persistence.Enumerated;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
 
@Entity
@Table(name = "products")
public record Product(
        @Id @GeneratedValue(strategy = GenerationType.IDENTITY) Long id,
        @Column(nullable = false, length = 120) String name,
        @Column(nullable = false, length = 40, unique = true) String sku,
        @Column(nullable = false, precision = 10, scale = 2) BigDecimal price,
        int stock,
        @Column(nullable = false, length = 60) String category,
        @Enumerated(EnumType.STRING) @Column(nullable = false, length = 20) ProductStatus status) {
}

2026-09-13T16:16:42.788+07:00  INFO 10721 --- [demo] [           main] org.hibernate.orm.core                   : HHH000182: No default (no-argument) constructor for class [com.example.demo.product.Product] (class must be instantiated by Interceptor)
2026-09-13T16:16:43.121+07:00 DEBUG 10721 --- [demo] [           main] org.hibernate.SQL                        : insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
2026-09-13T16:16:43.150+07:00 ERROR 10721 --- [demo] [           main] o.s.boot.SpringApplication               : Application run failed
 
org.springframework.orm.jpa.JpaSystemException: Could not set value of type [java.lang.Long]: 'com.example.demo.product.Product.id' (setter)
...
Caused by: org.hibernate.PropertyAccessException: Could not set value of type [java.lang.Long]: 'com.example.demo.product.Product.id' (setter)
...
	at org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:119) ~[hibernate-core-7.4.5.Final.jar!/:7.4.5.Final]
...
Caused by: java.lang.IllegalAccessException: Can not set final java.lang.Long field com.example.demo.product.Product.id to java.lang.Long

package com.example.demo.lab;
 
import java.math.BigDecimal;
 
import com.example.demo.product.Product;
import com.example.demo.product.ProductRepository;
 
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Component;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.support.TransactionTemplate;
 
@Component
@Profile("reference")
class ReferenceTour implements CommandLineRunner {
 
    private static final Logger log = LoggerFactory.getLogger(ReferenceTour.class);
 
    private final ProductRepository repository;
    private final TransactionTemplate tx;
 
    ReferenceTour(ProductRepository repository, PlatformTransactionManager transactionManager) {
        this.repository = repository;
        this.tx = new TransactionTemplate(transactionManager);
    }
 
    @Override
    public void run(String... args) {
        Product saved = repository.save(new Product("Webcam", "REF-01", new BigDecimal("59.00"), 4, "Cameras"));
        tx.executeWithoutResult(status -> {
            log.info("-- getReferenceById({})", saved.getId());
            Product reference = repository.getReferenceById(saved.getId());
            log.info("class={}", reference.getClass().getName());
            log.info("sku={}", reference.getSku());
        });
    }
}

ReferenceTour: -- getReferenceById(1)
ReferenceTour: class=com.example.demo.product.Product$HibernateProxy
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
ReferenceTour: sku=REF-01

2026-09-13T16:16:40.778+07:00  INFO 10693 --- [demo] [           main] com.example.demo.lab.ReferenceTour       : -- getReferenceById(4)
2026-09-13T16:16:40.780+07:00 DEBUG 10693 --- [demo] [           main] org.hibernate.SQL                        : select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
2026-09-13T16:16:40.780+07:00  INFO 10693 --- [demo] [           main] com.example.demo.lab.ReferenceTour       : class=com.example.demo.product.Product
2026-09-13T16:16:40.780+07:00  INFO 10693 --- [demo] [           main] com.example.demo.lab.ReferenceTour       : sku=REF-01

IdTour: -- saveAll(three new products)
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
IdTour: ids=[1, 2, 3]

IdTour: -- saveAll(three new products)
SQL: insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)
SQL: insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)
SQL: insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)
IdTour: ids=[1, 2, 3]

IdTour: -- saveAll(three new products)
SQL: insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)
SQL: insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)
SQL: insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)
IdTour: ids=[4, 5, 6]

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY) 
    @GeneratedValue(strategy = GenerationType.SEQUENCE) 
    private Long id;

SQL: drop table if exists products cascade
SQL: drop sequence if exists products_seq
SQL: create sequence products_seq start with 1 increment by 50
SQL: create table products (price numeric(10,2) not null, stock integer not null, id bigint not null, sku varchar(40) not null unique, category varchar(60) not null, name varchar(120) not null, status enum ('ACTIVE','DISCONTINUED','OUT_OF_STOCK') not null, primary key (id))

IdTour: -- saveAll(three new products)
SQL: select nextval('products_seq')
SQL: select nextval('products_seq')
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,?)
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,?)
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,?)
IdTour: ids=[1, 2, 3]

IdTour: -- saveAll(three new products)
SQL: select nextval('products_seq')
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,?)
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,?)
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,?)
IdTour: ids=[52, 53, 54]

docker exec sb-a26-pg psql -U catalog -d catalog -c "select sequencename, start_value, increment_by, last_value from pg_sequences"

 sequencename | start_value | increment_by | last_value
--------------+-------------+--------------+------------
 products_seq |           1 |           50 |        101
(1 row)

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE) 
    @GeneratedValue
    private Long id;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY) 
    private Long id; 
    @GeneratedValue(strategy = GenerationType.UUID) 
    private UUID id; 

SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,?)
bind: binding parameter (1:VARCHAR) <- [Keyboards]
bind: binding parameter (2:VARCHAR) <- [Mechanical keyboard]
bind: binding parameter (3:NUMERIC) <- [89.90]
bind: binding parameter (4:VARCHAR) <- [KB-01]
bind: binding parameter (5:ENUM) <- [ACTIVE]
bind: binding parameter (6:INTEGER) <- [25]
bind: binding parameter (7:UUID) <- [c74d4195-3340-49d3-af5a-e2f89d785d9f]

2026-09-13T16:10:47.997+07:00  INFO 9333 --- [demo] [           main] com.example.demo.lab.CrudTour            : -- save(new Product)
Hibernate: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
2026-09-13T16:10:48.049+07:00  INFO 9333 --- [demo] [           main] com.example.demo.lab.CrudTour            : id=1, same instance=true, still found in HashSet=true

2026-09-13T16:10:49.892+07:00 DEBUG 9345 --- [demo] [           main] org.hibernate.SQL                        : insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)

logging.level.org.hibernate.SQL=DEBUG
logging.level.org.hibernate.orm.jdbc.bind=TRACE

2026-09-13T16:10:49.863+07:00  INFO 9345 --- [demo] [           main] com.example.demo.lab.CrudTour            : -- save(new Product)
2026-09-13T16:10:49.892+07:00 DEBUG 9345 --- [demo] [           main] org.hibernate.SQL                        : insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
2026-09-13T16:10:49.894+07:00 TRACE 9345 --- [demo] [           main] org.hibernate.orm.jdbc.bind              : binding parameter (1:VARCHAR) <- [Keyboards]
2026-09-13T16:10:49.894+07:00 TRACE 9345 --- [demo] [           main] org.hibernate.orm.jdbc.bind              : binding parameter (2:VARCHAR) <- [Mechanical keyboard]
2026-09-13T16:10:49.894+07:00 TRACE 9345 --- [demo] [           main] org.hibernate.orm.jdbc.bind              : binding parameter (3:NUMERIC) <- [89.90]
2026-09-13T16:10:49.894+07:00 TRACE 9345 --- [demo] [           main] org.hibernate.orm.jdbc.bind              : binding parameter (4:VARCHAR) <- [KB-01]
2026-09-13T16:10:49.895+07:00 TRACE 9345 --- [demo] [           main] org.hibernate.orm.jdbc.bind              : binding parameter (5:ENUM) <- [ACTIVE]
2026-09-13T16:10:49.895+07:00 TRACE 9345 --- [demo] [           main] org.hibernate.orm.jdbc.bind              : binding parameter (6:INTEGER) <- [25]

2026-09-13T16:10:49.929+07:00 DEBUG 9345 --- [demo] [           main] org.hibernate.SQL                        : select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
2026-09-13T16:10:49.929+07:00 TRACE 9345 --- [demo] [           main] org.hibernate.orm.jdbc.bind              : binding parameter (1:BIGINT) <- [1]

spring.jpa.properties.hibernate.format_sql=true

2026-09-13T16:10:51.788+07:00  INFO 9353 --- [demo] [           main] com.example.demo.lab.CrudTour            : -- save(new Product)
2026-09-13T16:10:51.820+07:00 DEBUG 9353 --- [demo] [           main] org.hibernate.SQL                        :
    insert
    into
        products
        (category, name, price, sku, status, stock, id)
    values
        (?, ?, ?, ?, ?, ?, default)

package com.example.demo.lab;
 
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.sql.Connection;
import java.util.Arrays;
 
import javax.sql.DataSource;
 
import com.example.demo.product.ProductRepository;
 
import jakarta.persistence.EntityManagerFactory;
 
import org.springframework.aop.framework.AopProxyUtils;
import org.springframework.aop.support.AopUtils;
import org.springframework.boot.CommandLineRunner;
import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Component;
 
@Component
@Profile("inspect")
class RepositoryInspector implements CommandLineRunner {
 
    private final ProductRepository repository;
    private final EntityManagerFactory entityManagerFactory;
    private final DataSource dataSource;
 
    RepositoryInspector(ProductRepository repository, EntityManagerFactory entityManagerFactory, DataSource dataSource) {
        this.repository = repository;
        this.entityManagerFactory = entityManagerFactory;
        this.dataSource = dataSource;
    }
 
    @Override
    public void run(String... args) throws Exception {
        System.out.println("bean class      : " + repository.getClass().getName());
        System.out.println("JDK proxy       : " + AopUtils.isJdkDynamicProxy(repository));
        System.out.println("target class    : " + AopProxyUtils.ultimateTargetClass(repository).getName());
        System.out.println("proxy implements: " + Arrays.stream(repository.getClass().getInterfaces()).map(Class::getSimpleName).toList());
        printHierarchy(ProductRepository.class, 0);
        System.out.println("hibernate.hbm2ddl.auto = " + entityManagerFactory.getProperties().get("hibernate.hbm2ddl.auto"));
        try (Connection connection = dataSource.getConnection()) {
            var meta = connection.getMetaData();
            System.out.println("database        : " + meta.getDatabaseProductName() + " " + meta.getDatabaseProductVersion() + " at " + meta.getURL());
        }
    }
 
    private static void printHierarchy(Type type, int depth) {
        Class<?> raw = type instanceof ParameterizedType p ? (Class<?>) p.getRawType() : (Class<?>) type;
        System.out.println("  ".repeat(depth) + type.getTypeName().replaceAll("[a-z][a-z0-9_]*\\.", ""));
        for (Type parent : raw.getGenericInterfaces()) {
            printHierarchy(parent, depth + 1);
        }
    }
}

hibernate.hbm2ddl.auto = create-drop
database        : H2 2.4.240 (2025-09-22) at jdbc:h2:mem:d3b1b5b4-d92e-4b0b-a61e-62b69972d717

hibernate.hbm2ddl.auto = null
database        : PostgreSQL 18.6 (Debian 18.6-1.pgdg13+2) at jdbc:postgresql://localhost:55426/catalog

javap -c -p -classpath spring-boot-hibernate-4.1.1.jar org.springframework.boot.hibernate.autoconfigure.HibernateDefaultDdlAutoProvider

  java.lang.String getDefaultDdlAuto(javax.sql.DataSource);
    Code:
       0: aload_1
       1: invokestatic  #13                 // Method org/springframework/boot/jdbc/EmbeddedDatabaseConnection.isEmbedded:(Ljavax/sql/DataSource;)Z
       4: ifne          10
       7: ldc           #19                 // String none
       9: areturn
      10: aload_0
      11: aload_1
      12: invokevirtual #21                 // Method getSchemaManagement:(Ljavax/sql/DataSource;)Lorg/springframework/boot/jdbc/SchemaManagement;
      15: astore_2
      16: getstatic     #25                 // Field org/springframework/boot/jdbc/SchemaManagement.MANAGED:Lorg/springframework/boot/jdbc/SchemaManagement;
      19: aload_2
      20: invokevirtual #31                 // Method org/springframework/boot/jdbc/SchemaManagement.equals:(Ljava/lang/Object;)Z
      23: ifeq          29
      26: ldc           #19                 // String none
      28: areturn
      29: ldc           #35                 // String create-drop
      31: areturn

2026-09-13T16:12:46.938+07:00 DEBUG 9828 --- [demo] [           main] org.hibernate.SQL                        : insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)
2026-09-13T16:12:46.945+07:00  WARN 9828 --- [demo] [           main] org.hibernate.orm.jdbc.error             : HHH000247: ErrorCode: 0, SQLState: 42P01
2026-09-13T16:12:46.945+07:00  WARN 9828 --- [demo] [           main] org.hibernate.orm.jdbc.error             : ERROR: relation "products" does not exist
  Position: 13
...
org.springframework.dao.InvalidDataAccessResourceUsageException: could not execute statement [ERROR: relation "products" does not exist
  Position: 13] [insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)]; SQL [insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)]
...
Caused by: org.hibernate.exception.SQLGrammarException: could not execute statement [ERROR: relation "products" does not exist
  Position: 13] [insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)]
...
Caused by: org.postgresql.util.PSQLException: ERROR: relation "products" does not exist
  Position: 13

2026-09-13T16:10:42.985+07:00  INFO 9316 --- [demo] [ionShutdownHook] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'
2026-09-13T16:10:42.985+07:00 DEBUG 9316 --- [demo] [ionShutdownHook] org.hibernate.SQL                        : drop table if exists products cascade

2026-09-13T16:12:59.865+07:00 DEBUG 9877 --- [demo] [           main] org.hibernate.SQL                        : create table products (id bigint generated by default as identity, category varchar(60) not null, name varchar(120) not null, price numeric(10,2) not null, sku varchar(40) not null, status varchar(20) not null check ((status in ('ACTIVE','OUT_OF_STOCK','DISCONTINUED'))), stock integer not null, primary key (id))
2026-09-13T16:12:59.870+07:00 DEBUG 9877 --- [demo] [           main] org.hibernate.SQL                        : alter table if exists products drop constraint if exists UKfhmd06dsmj6k0n90swsh8ie9g
2026-09-13T16:12:59.872+07:00  WARN 9877 --- [demo] [           main] org.hibernate.orm.jdbc.warn              : HHH000247: ErrorCode: 0, SQLState: 00000
2026-09-13T16:12:59.872+07:00  WARN 9877 --- [demo] [           main] org.hibernate.orm.jdbc.warn              : constraint "ukfhmd06dsmj6k0n90swsh8ie9g" of relation "products" does not exist, skipping
2026-09-13T16:12:59.872+07:00 DEBUG 9877 --- [demo] [           main] org.hibernate.SQL                        : alter table if exists products add constraint UKfhmd06dsmj6k0n90swsh8ie9g unique (sku)

2026-09-13T16:16:48.073+07:00 ERROR 10786 --- [demo] [           main] j.LocalContainerEntityManagerFactoryBean : Failed to initialize JPA EntityManagerFactory: Unable to build Hibernate SessionFactory  [persistence unit: default] ; nested exception is org.hibernate.tool.schema.spi.SchemaManagementException: Schema validation: missing column [brand] in table [products]

2026-09-13T16:16:50.356+07:00 DEBUG 10818 --- [demo] [           main] org.hibernate.SQL                        : alter table if exists products add column brand varchar(80)

package com.example.demo.product;
 
import org.springframework.data.jpa.repository.JpaRepository;
 
public interface ProductRepository extends JpaRepository<Product, Long> {
}

find build/classes/java/main -name '*.class' | sort | sed 's|build/classes/java/main/||'

com/example/demo/product/CreateProductRequest.class
com/example/demo/product/Product.class
com/example/demo/product/ProductController.class
com/example/demo/product/ProductMapper.class
com/example/demo/product/ProductNotFoundException.class
com/example/demo/product/ProductRepository.class
com/example/demo/product/ProductResponse.class
com/example/demo/product/ProductService.class
com/example/demo/product/ProductStatus.class

bean class      : jdk.proxy2.$Proxy116
JDK proxy       : true
target class    : org.springframework.data.jpa.repository.support.SimpleJpaRepository
proxy implements: [ProductRepository, Repository, TransactionalProxy, Advised, DecoratingProxy]
ProductRepository
  JpaRepository<Product, Long>
    ListCrudRepository<T, ID>
      CrudRepository<T, ID>
        Repository<T, ID>
    ListPagingAndSortingRepository<T, ID>
      PagingAndSortingRepository<T, ID>
        Repository<T, ID>
    QueryByExampleExecutor<T>

package com.example.demo.lab;
 
import java.math.BigDecimal;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;
 
import com.example.demo.product.Product;
import com.example.demo.product.ProductRepository;
 
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Component;
 
@Component
@Profile("crud")
class CrudTour implements CommandLineRunner {
 
    private static final Logger log = LoggerFactory.getLogger(CrudTour.class);
 
    private final ProductRepository repository;
 
    CrudTour(ProductRepository repository) {
        this.repository = repository;
    }
 
    @Override
    public void run(String... args) {
        log.info("-- save(new Product)");
        Product keyboard = new Product("Mechanical keyboard", "KB-01", new BigDecimal("89.90"), 25, "Keyboards");
        Set<Product> set = new HashSet<>();
        set.add(keyboard);
        Product saved = repository.save(keyboard);
        log.info("id={}, same instance={}, still found in HashSet={}", saved.getId(), saved == keyboard, set.contains(saved));
 
        log.info("-- saveAll(two new products)");
        List<Product> more = repository.saveAll(List.of(
                new Product("Wireless mouse", "MS-01", new BigDecimal("24.50"), 3, "Mice"),
                new Product("USB-C hub", "HUB-07", new BigDecimal("39.00"), 10, "Accessories")));
        log.info("ids={}", more.stream().map(Product::getId).toList());
 
        log.info("-- findById(1)");
        Optional<Product> found = repository.findById(1L);
        log.info("{}", found);
 
        log.info("-- findById(99)");
        log.info("{}", repository.findById(99L));
 
        log.info("-- findAll()");
        log.info("{} products", repository.findAll().size());
 
        log.info("-- existsById(2)");
        log.info("{}", repository.existsById(2L));
 
        log.info("-- count()");
        log.info("{}", repository.count());
 
        log.info("-- save(the product loaded by findById(1), price changed)");
        Product loaded = found.orElseThrow();
        loaded.setPrice(new BigDecimal("79.90"));
        Product merged = repository.save(loaded);
        log.info("same instance={}", merged == loaded);
 
        log.info("-- save(a stale copy of product 3 after it was deleted)");
        Product hub = repository.findById(3L).orElseThrow();
        repository.deleteById(3L);
        hub.setStock(0);
        try {
            Product result = repository.save(hub);
            log.info("saved {}", result);
        } catch (RuntimeException e) {
            log.info("{}: {}", e.getClass().getName(), e.getMessage());
        }
 
        log.info("-- delete(product 1, loaded earlier)");
        repository.delete(merged);
 
        log.info("-- deleteById(99)");
        try {
            repository.deleteById(99L);
            log.info("no exception");
        } catch (RuntimeException e) {
            log.info("{}: {}", e.getClass().getName(), e.getMessage());
        }
 
        log.info("-- count()");
        log.info("{}", repository.count());
    }
}

CrudTour: -- save(new Product)
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
CrudTour: id=1, same instance=true, still found in HashSet=true
CrudTour: -- saveAll(two new products)
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
CrudTour: ids=[2, 3]
CrudTour: -- findById(1)
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
CrudTour: Optional[Product[id=1, sku=KB-01, price=89.90, stock=25, status=ACTIVE]]
CrudTour: -- findById(99)
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
CrudTour: Optional.empty
CrudTour: -- findAll()
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0
CrudTour: 3 products
CrudTour: -- existsById(2)
SQL: select count(*) from products p1_0 where p1_0.id=?
CrudTour: true
CrudTour: -- count()
SQL: select count(*) from products p1_0
CrudTour: 3
CrudTour: -- save(the product loaded by findById(1), price changed)
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
SQL: update products set category=?,name=?,price=?,sku=?,status=?,stock=? where id=?
CrudTour: same instance=false
CrudTour: -- save(a stale copy of product 3 after it was deleted)
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
SQL: delete from products where id=?
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
CrudTour: org.springframework.orm.ObjectOptimisticLockingFailureException: Row was already updated or deleted by another transaction for entity [com.example.demo.product.Product with id '3']
CrudTour: -- delete(product 1, loaded earlier)
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
SQL: delete from products where id=?
CrudTour: -- deleteById(99)
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
CrudTour: no exception
CrudTour: -- count()
SQL: select count(*) from products p1_0
CrudTour: 1

package com.example.demo.lab;
 
import java.math.BigDecimal;
 
import com.example.demo.product.Product;
import com.example.demo.product.ProductRepository;
 
import jakarta.persistence.EntityManager;
 
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Component;
import org.springframework.transaction.annotation.Transactional;
 
@Component
@Profile("context")
public class PersistenceContextDemo {
 
    private static final Logger log = LoggerFactory.getLogger(PersistenceContextDemo.class);
 
    private final ProductRepository repository;
    private final EntityManager entityManager;
 
    PersistenceContextDemo(ProductRepository repository, EntityManager entityManager) {
        this.repository = repository;
        this.entityManager = entityManager;
    }
 
    @Transactional
    public void changePriceWithoutSave(Long id) {
        Product product = repository.findById(id).orElseThrow();
        product.setPrice(new BigDecimal("84.90"));
        log.info("price set to 84.90, save() not called, leaving the method");
    }
 
    @Transactional
    public Product findTwice(Long id) {
        Product first = repository.findById(id).orElseThrow();
        log.info("first findById returned");
        Product second = repository.findById(id).orElseThrow();
        log.info("second findById returned, same instance={}, managed={}", first == second, entityManager.contains(first));
        return first;
    }
}

package com.example.demo.lab;
 
import java.math.BigDecimal;
 
import com.example.demo.product.Product;
import com.example.demo.product.ProductRepository;
 
import jakarta.persistence.EntityManager;
 
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Component;
 
@Component
@Profile("context")
class PersistenceContextTour implements CommandLineRunner {
 
    private static final Logger log = LoggerFactory.getLogger(PersistenceContextTour.class);
 
    private final ProductRepository repository;
    private final PersistenceContextDemo demo;
    private final EntityManager entityManager;
 
    PersistenceContextTour(ProductRepository repository, PersistenceContextDemo demo, EntityManager entityManager) {
        this.repository = repository;
        this.demo = demo;
        this.entityManager = entityManager;
    }
 
    @Override
    public void run(String... args) {
        repository.save(new Product("Mechanical keyboard", "KB-01", new BigDecimal("89.90"), 25, "Keyboards"));
 
        log.info("-- dirty checking");
        demo.changePriceWithoutSave(1L);
        log.info("method returned, transaction committed");
 
        log.info("-- first-level cache");
        Product product = demo.findTwice(1L);
        log.info("method returned, transaction committed");
 
        log.info("-- detached");
        log.info("managed={}", entityManager.contains(product));
        product.setStock(0);
        log.info("stock set to 0 on the detached entity");
        log.info("stock in the database: {}", repository.findById(1L).orElseThrow().getStock());
 
        log.info("-- save(detached entity)");
        repository.save(product);
        log.info("stock in the database: {}", repository.findById(1L).orElseThrow().getStock());
    }
}

SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
PersistenceContextTour: -- dirty checking
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
PersistenceContextDemo: price set to 84.90, save() not called, leaving the method
SQL: update products set category=?,name=?,price=?,sku=?,status=?,stock=? where id=?
PersistenceContextTour: method returned, transaction committed
PersistenceContextTour: -- first-level cache
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
PersistenceContextDemo: first findById returned
PersistenceContextDemo: second findById returned, same instance=true, managed=true
PersistenceContextTour: method returned, transaction committed
PersistenceContextTour: -- detached
PersistenceContextTour: managed=false
PersistenceContextTour: stock set to 0 on the detached entity
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
PersistenceContextTour: stock in the database: 25
PersistenceContextTour: -- save(detached entity)
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
SQL: update products set category=?,name=?,price=?,sku=?,status=?,stock=? where id=?
SQL: select p1_0.id,p1_0.category,p1_0.name,p1_0.price,p1_0.sku,p1_0.status,p1_0.stock from products p1_0 where p1_0.id=?
PersistenceContextTour: stock in the database: 0

package com.example.demo.product;
 
import java.math.BigDecimal;
 
import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.NotNull;
import jakarta.validation.constraints.Positive;
import jakarta.validation.constraints.PositiveOrZero;
import jakarta.validation.constraints.Size; 
 
public record CreateProductRequest(
        @NotBlank String name, 
        @NotBlank String sku, 
        @NotBlank @Size(max = 120) String name, 
        @NotBlank @Size(max = 40) String sku, 
        @NotNull @Positive BigDecimal price,
        @NotNull @PositiveOrZero Integer stock) { 
        @NotNull @PositiveOrZero Integer stock, 
        @NotBlank @Size(max = 60) String category) { 
}

package com.example.demo.product;
 
import java.math.BigDecimal;
 
public record ProductResponse(Long id, String name, String sku, BigDecimal price, int stock) { 
public record ProductResponse(Long id, String name, String sku, BigDecimal price, int stock, String category) { 
}

package com.example.demo.product;
 
import org.springframework.stereotype.Component;
 
@Component
public class ProductMapper {
 
    public Product toProduct(CreateProductRequest request) {
        return new Product(null, request.name(), request.sku(), request.price(), request.stock()); 
        return new Product(request.name(), request.sku(), request.price(), request.stock(), request.category()); 
    }
 
    public ProductResponse toResponse(Product product) {
        return new ProductResponse(product.id(), product.name(), product.sku(), product.price(), product.stock()); 
        return new ProductResponse(product.getId(), product.getName(), product.getSku(), product.getPrice(), 
                product.getStock(), product.getCategory()); 
    }
}

package com.example.demo.product;
 
import java.util.List;
 
import org.springframework.stereotype.Service;
 
@Service
public class ProductService {
 
    private final ProductRepository repository;
 
    public ProductService(ProductRepository repository) {
        this.repository = repository;
    }
 
    public List<Product> findAll() {
        return repository.findAll();
    }
 
    public Product findById(Long id) {
        return repository.findById(id).orElseThrow(() -> new ProductNotFoundException(id));
    }
 
    public Product create(Product product) {
        if (repository.existsBySku(product.sku())) { 
            throw new DuplicateSkuException(product.sku()); 
        } 
        return repository.save(product);
    }
 
    public Product reserveStock(Long id, int quantity) { 
        Product product = findById(id); 
        if (product.stock() < quantity) { 
            throw new InsufficientStockException(product.sku(), product.stock(), quantity); 
        } 
        return repository.save(product.withStock(product.stock() - quantity)); 
    } 
    public void delete(Long id) { 
        if (!repository.existsById(id)) { 
            throw new ProductNotFoundException(id); 
        } 
        repository.deleteById(id); 
    } 
}

package com.example.demo.product;
 
import java.net.URI;
import java.util.List;
 
import jakarta.validation.Valid;
 
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.DeleteMapping; 
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
 
@RestController
@RequestMapping("/api/products")
public class ProductController {
 
    private final ProductService service;
    private final ProductMapper mapper;
 
    public ProductController(ProductService service, ProductMapper mapper) {
        this.service = service;
        this.mapper = mapper;
    }
 
    @GetMapping
    public List<ProductResponse> findAll() {
        return service.findAll().stream()
                .map(mapper::toResponse)
                .toList();
    }
 
    @GetMapping("/{id}")
    public ProductResponse findById(@PathVariable Long id) {
        return mapper.toResponse(service.findById(id));
    }
 
    @PostMapping
    public ResponseEntity<ProductResponse> create(@Valid @RequestBody CreateProductRequest request) {
        Product product = service.create(mapper.toProduct(request));
        URI location = ServletUriComponentsBuilder.fromCurrentRequest()
                .path("/{id}")
                .buildAndExpand(product.id()) 
                .buildAndExpand(product.getId()) 
                .toUri();
        return ResponseEntity.created(location).body(mapper.toResponse(product));
    }
 
    @DeleteMapping("/{id}") 
    public ResponseEntity<Void> delete(@PathVariable Long id) { 
        service.delete(id); 
        return ResponseEntity.noContent().build(); 
    } 
}

package com.example.demo.lab;
 
import java.math.BigDecimal;
 
import com.example.demo.product.Product;
import com.example.demo.product.ProductRepository;
 
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Component;
 
@Component
@Profile("duplicate")
class DuplicateTour implements CommandLineRunner {
 
    private static final Logger log = LoggerFactory.getLogger(DuplicateTour.class);
 
    private final ProductRepository repository;
 
    DuplicateTour(ProductRepository repository) {
        this.repository = repository;
    }
 
    @Override
    public void run(String... args) {
        repository.save(new Product("Mechanical keyboard", "KB-01", new BigDecimal("89.90"), 25, "Keyboards"));
        try {
            repository.save(new Product("Compact keyboard", "KB-01", new BigDecimal("59.00"), 5, "Keyboards"));
        } catch (RuntimeException e) {
            for (Throwable t = e; t != null; t = t.getCause()) {
                log.info("{}", t.getClass().getName());
            }
            log.info("message: {}", e.getMessage());
        }
    }
}

SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
SQL: insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)
error: HHH000247: ErrorCode: 23505, SQLState: 23505
error: Unique index or primary key violation: "PUBLIC.CONSTRAINT_F INDEX PUBLIC.CONSTRAINT_INDEX_F ON PUBLIC.PRODUCTS(SKU NULLS FIRST) VALUES ( /* 1 */ 'KB-01' )"; SQL statement:
insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default) [23505-240]
DuplicateTour: org.springframework.dao.DataIntegrityViolationException
DuplicateTour: org.hibernate.exception.ConstraintViolationException
DuplicateTour: org.h2.jdbc.JdbcSQLIntegrityConstraintViolationException
DuplicateTour: message: could not execute statement [Unique index or primary key violation: "PUBLIC.CONSTRAINT_F INDEX PUBLIC.CONSTRAINT_INDEX_F ON PUBLIC.PRODUCTS(SKU NULLS FIRST) VALUES ( /* 1 */ 'KB-01' )"; SQL statement:
insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default) [23505-240]] [insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)]; SQL [insert into products (category,name,price,sku,status,stock,id) values (?,?,?,?,?,?,default)]; constraint [PUBLIC.CONSTRAINT_F INDEX PUBLIC.CONSTRAINT_INDEX_F]

2026-09-13T16:12:50.585+07:00  WARN 9841 --- [demo] [           main] org.hibernate.orm.jdbc.error             : HHH000247: ErrorCode: 0, SQLState: 23505
2026-09-13T16:12:50.585+07:00  WARN 9841 --- [demo] [           main] org.hibernate.orm.jdbc.error             : ERROR: duplicate key value violates unique constraint "products_sku_key"
  Detail: Key (sku)=(KB-01) already exists.
2026-09-13T16:12:50.589+07:00  INFO 9841 --- [demo] [           main] com.example.demo.lab.DuplicateTour       : org.springframework.dao.DataIntegrityViolationException
2026-09-13T16:12:50.589+07:00  INFO 9841 --- [demo] [           main] com.example.demo.lab.DuplicateTour       : org.hibernate.exception.ConstraintViolationException
2026-09-13T16:12:50.589+07:00  INFO 9841 --- [demo] [           main] com.example.demo.lab.DuplicateTour       : org.postgresql.util.PSQLException
2026-09-13T16:12:50.589+07:00  INFO 9841 --- [demo] [           main] com.example.demo.lab.DuplicateTour       : message: could not execute statement [ERROR: duplicate key value violates unique constraint "products_sku_key"
  Detail: Key (sku)=(KB-01) already exists.] [insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)]; SQL [insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)]; constraint [products_sku_key]

package com.example.demo.common;
 
import java.util.stream.Collectors;
 
import com.example.demo.product.DuplicateSkuException; 
import com.example.demo.product.ProductNotFoundException;
 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
import org.springframework.dao.DataIntegrityViolationException; 
import org.springframework.http.HttpStatus;
import org.springframework.http.ProblemDetail;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
 
@RestControllerAdvice
public class GlobalExceptionHandler {
 
    private static final Logger log = LoggerFactory.getLogger(GlobalExceptionHandler.class); 
 
    @ExceptionHandler(ProductNotFoundException.class)
    public ProblemDetail notFound(RuntimeException e) {
        return ProblemDetail.forStatusAndDetail(HttpStatus.NOT_FOUND, e.getMessage());
    }
 
    @ExceptionHandler(DuplicateSkuException.class) 
    public ProblemDetail conflict(RuntimeException e) { 
        return ProblemDetail.forStatusAndDetail(HttpStatus.CONFLICT, e.getMessage()); 
    @ExceptionHandler(DataIntegrityViolationException.class) 
    public ProblemDetail conflict(DataIntegrityViolationException e) { 
        log.warn("Constraint violation: {}", e.getMostSpecificCause().getMessage()); 
        return ProblemDetail.forStatusAndDetail(HttpStatus.CONFLICT, 
                "The product conflicts with an existing one, for example a duplicate SKU"); 
    }
 
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ProblemDetail invalid(MethodArgumentNotValidException e) {
        String detail = e.getBindingResult().getFieldErrors().stream()
                .map(error -> error.getField() + " " + error.getDefaultMessage())
                .sorted()
                .collect(Collectors.joining(", "));
        return ProblemDetail.forStatusAndDetail(HttpStatus.UNPROCESSABLE_CONTENT, detail);
    }
}

java -jar build/libs/demo-0.0.1-SNAPSHOT.jar --server.port=8126 --spring.profiles.active=postgres --spring.jpa.hibernate.ddl-auto=update --spring.jpa.open-in-view=false --logging.level.org.hibernate.SQL=DEBUG

curl -i -s -H 'Content-Type: application/json' -d '{"name":"Mechanical keyboard","sku":"KB-01","price":89.90,"stock":25,"category":"Keyboards"}' http://localhost:8126/api/products

HTTP/1.1 201
Location: http://localhost:8126/api/products/1
Content-Type: application/json
Transfer-Encoding: chunked
Date: Sun, 13 Sep 2026 09:13:00 GMT
 
{"id":1,"name":"Mechanical keyboard","sku":"KB-01","price":89.90,"stock":25,"category":"Keyboards"}

curl -i -s -H 'Content-Type: application/json' -d '{"name":"Compact keyboard","sku":"KB-01","price":59.00,"stock":5,"category":"Keyboards"}' http://localhost:8126/api/products

HTTP/1.1 409
Content-Type: application/problem+json
Transfer-Encoding: chunked
Date: Sun, 13 Sep 2026 09:13:00 GMT
 
{"detail":"The product conflicts with an existing one, for example a duplicate SKU","instance":"/api/products","status":409,"title":"Conflict"}

2026-09-13T16:13:00.916+07:00 DEBUG 9877 --- [demo] [nio-8126-exec-6] org.hibernate.SQL                        : insert into products (category,name,price,sku,status,stock) values (?,?,?,?,?,?)
2026-09-13T16:13:00.919+07:00  WARN 9877 --- [demo] [nio-8126-exec-6] org.hibernate.orm.jdbc.error             : HHH000247: ErrorCode: 0, SQLState: 23505
2026-09-13T16:13:00.919+07:00  WARN 9877 --- [demo] [nio-8126-exec-6] org.hibernate.orm.jdbc.error             : ERROR: duplicate key value violates unique constraint "ukfhmd06dsmj6k0n90swsh8ie9g"
  Detail: Key (sku)=(KB-01) already exists.
2026-09-13T16:13:00.923+07:00  WARN 9877 --- [demo] [nio-8126-exec-6] c.e.demo.common.GlobalExceptionHandler   : Constraint violation: ERROR: duplicate key value violates unique constraint "ukfhmd06dsmj6k0n90swsh8ie9g"
  Detail: Key (sku)=(KB-01) already exists.

curl -i -s -H 'Content-Type: application/json' -d '{"name":"USB-C hub","sku":"HUB-07","price":39.00,"stock":10,"category":"Accessories"}' http://localhost:8126/api/products

HTTP/1.1 201
Location: http://localhost:8126/api/products/4
Content-Type: application/json
Transfer-Encoding: chunked
Date: Sun, 13 Sep 2026 09:13:00 GMT
 
{"id":4,"name":"USB-C hub","sku":"HUB-07","price":39.00,"stock":10,"category":"Accessories"}

curl -i -s http://localhost:8126/api/products/99
curl -i -s -X DELETE http://localhost:8126/api/products/2
curl -i -s -X DELETE http://localhost:8126/api/products/2

HTTP/1.1 404
Content-Type: application/problem+json
Transfer-Encoding: chunked
Date: Sun, 13 Sep 2026 09:13:00 GMT
 
{"detail":"Product 99 not found","instance":"/api/products/99","status":404,"title":"Not Found"}
HTTP/1.1 204
Date: Sun, 13 Sep 2026 09:13:01 GMT
 
HTTP/1.1 404
Content-Type: application/problem+json
Transfer-Encoding: chunked
Date: Sun, 13 Sep 2026 09:13:01 GMT
 
{"detail":"Product 2 not found","instance":"/api/products/2","status":404,"title":"Not Found"}

curl -i -s http://localhost:8126/api/products

HTTP/1.1 200
Content-Type: application/json
Content-Length: 194
Date: Sun, 13 Sep 2026 09:13:01 GMT
 
[{"id":1,"name":"Mechanical keyboard","sku":"KB-01","price":89.90,"stock":25,"category":"Keyboards"},{"id":4,"name":"USB-C hub","sku":"HUB-07","price":39.00,"stock":10,"category":"Accessories"}]

2026-09-13T16:12:57.781+07:00  WARN 9866 --- [demo] [           main] JpaBaseConfiguration$JpaWebConfiguration : spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning

spring.application.name=demo
spring.jpa.open-in-view=false