Spring Data JPA Primary Key Violation Constraint Not Working - spring-data-jpa

Question

Code and Configuration :
DB used - H2 in Memory database
User Entity :
#Entity
#Table(name = "users")
#Data
#AllArgsConstructor
#NoArgsConstructor
public class User implements Serializable {
/**
*
*/
private static final long serialVersionUID = 455202739064202185L;
#Id // please note is not auto generated but manually generated
#Column(name = "id",unique=true)
#NotNull
private long id;
#Column(name = "firstName")
#NotEmpty(message = "First name is required")
private String firstName;
#Column(name = "lastName")
#NotEmpty(message = "Last name is required")
private String lastName;
#Column(name = "email")
#NotEmpty(message = "Email is required")
#Email(message="Email Must be well formed")
private String email;
}
UserRepository :
public interface UserJpaRepository extends JpaRepository<User, Long> {
}
UserServiceImpl :
this.userJpaRepository.saveAll(users);
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.4.2</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.exostar</groupId>
<artifactId>FileUpload</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>FileUpload</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-csv</artifactId>
<version>1.8</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-validation</artifactId>
</dependency>
</dependencies>
</project>
Issue :
As per the User entity class , #Id is manually generated.
(I have a CSV file which has Id field which is read in User entity)
So Id is not auto generated
Whenever I call this.userJpaRepository.saveAll(users) and even when there is an User entity with Id already existing , the User entity gets overwritten.
That is , Id with same entity gets overwritten with new data.
It has to throw - Unique index or primary key violation error
However, when I try to insert duplicate entry into H2 database MANUALLY , it throws exception - Unique index or primary key violation
I also tried adding unique=true to Id field in User Entity but its not working
Can anybody please help on resolving this issue please ?

Answer 1

Well as it turns out that the behavior that you are seeing is because of the call to em.merge(...) in the save() implementation. Here is what actually happens:
#Transactional
#Override
public <S extends T> S save(S entity) {
Assert.notNull(entity, "Entity must not be null.");
if (entityInformation.isNew(entity)) {
em.persist(entity);
return entity;
} else {
return em.merge(entity); // Update if the entity is not new
}
}
This is a sample code from SimpleJpaRepository implementation. you can use your own query methods for updating the existing query something like this:
#Modifying
#Query("update User u set u.firstname = ?1 where u.lastname = ?2")
int setFixedFirstnameFor(String firstname, String lastname);