How can i implement JPA to a non Spring java project?-CodePudding

I want to implement OneToOne annotations on a class. I downloaded the jar containing JPA Data code but i know it doesn't work that way. What else do i need to do to make it work?

CodePudding user response：

If you use Maven then you should choose a JPA implementation, usually its Hibernate and add it to your dependencies.

e.g.

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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>jpa-hibernate</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.4.21.Final</version>
        </dependency>
    </dependencies>

</project>

Hibernate brings along JPA api (persistence-api) and you can annotate your entity classes as per it's annotations.

E.g. with the above pom.xml file you can create some Entities

@Entity
@Table(name = "users")
public class User {
    
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id; 

    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "address_id", referencedColumnName = "id")
    private Address address;

}

and

@Entity
@Table(name = "address")
public class Address {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;

    @OneToOne(mappedBy = "address")
    private User user;

}

and use the annotations accordingly. However please note that @OneToOne annotation should be used on a @Entity class, you can't just put it in a class that is not annotated @Entity.

What's is not shown here is the configuration of Hibernate, usually it is done in xml with a file called persistence.xml placed into src\main\resources\META-INF directory.

CodePudding user response：

You need a Java server and a relational database. I suggest Apache TomEE (server) and HSQLDB (in-memory relational database).

Here's an example: https://tomee.apache.org/latest/examples/jpa-hibernate.html