JPA - @JoinColumn Examples

package com.logicbig.example;

import javax.persistence.*;

@Entity
public class EntityA {
    @Id
    @GeneratedValue
    private int myIdA;
    @OneToOne
    @JoinColumn(name = "MY_JOIN_COLUMN")
    private EntityB entityB;

    public EntityB getEntityB() {
        return entityB;
    }

    public void setEntityB(EntityB entityB) {
        this.entityB = entityB;
    }
}

package com.logicbig.example;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class EntityB {
    @Id
    @GeneratedValue
    private int myIdB;
    private String stringB;

    public String getStringB() {
        return stringB;
    }

    public void setStringB(String stringB) {
        this.stringB = stringB;
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1"
             xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">

    <persistence-unit name="test1" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <class>com.logicbig.example.EntityA</class>
        <class>com.logicbig.example.EntityB</class>
        <exclude-unlisted-classes>true</exclude-unlisted-classes>
        <properties>
            <property name="javax.persistence.schema-generation.database.action" value="create"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:h2:mem:test;DB_CLOSE_DELAY=-1"/>
        </properties>
    </persistence-unit>
</persistence>

<?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.logicbig.example</groupId>
    <artifactId>jpa-one-to-one-with-join-column-example</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>1.4.193</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.2.8.Final</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

package com.logicbig.example;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;
import java.util.Arrays;
import java.util.List;

public class ExampleMain {

    public static void main(String[] args) {
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("test1");
        try {
            EntityManager em = emf.createEntityManager();
            nativeQuery(em, "SHOW TABLES");
            nativeQuery(em, "SHOW COLUMNS from EntityA");
            nativeQuery(em, "SHOW COLUMNS from EntityB");
            emf.close();
        } finally {
            emf.close();
        }
    }

    public static void nativeQuery(EntityManager em, String s) {
        System.out.println("--------\n" + s);
        Query query = em.createNativeQuery(s);
        List list = query.getResultList();
        for (Object o : list) {
            System.out.println(Arrays.toString((Object[]) o));
        }
    }
}

@Entity
public class EntityA {
    @Id
    @GeneratedValue
    private int myIdA;
    private String strA;
    @OneToMany
    @JoinColumn(name = "MY_FK_COL")
    private List<EntityB> entityBList;
    .............
}

@Entity
public class EntityB {
    @Id
    @GeneratedValue
    private int myIdB;
    private String strB;
    .............
}

import javax.persistence.*;
import java.util.List;

@Entity
public class EntityA {
    @Id
    @GeneratedValue
    private int myIdA;
    @OneToMany
    @JoinTable(name = "MY_JOIN_TABLE",
            joinColumns = {@JoinColumn(name = "MY_ENTITY_A_FK")},
            inverseJoinColumns = {@JoinColumn(name = "MY_ENTITY_B_FK")}
    )
    private List<EntityB> entityBList;

    public List<EntityB> getEntityBList() {
        return entityBList;
    }

    public void setEntityBList(List<EntityB> entityBList) {
        this.entityBList = entityBList;
    }

    @Override
    public String toString() {
        return "EntityA{" +
                "myIdA=" + myIdA +
                ", entityBList=" + entityBList +
                '}';
    }
}

@Entity
public class Employee {
    @Id
    @GeneratedValue
    private long id;
    private String name;
    @OneToMany
    @JoinColumn(name = "EMPLOYEE_FK")
    @MapKeyColumn(name = "TASK_DATE", nullable = true)
    private Map<Date, Task> tasks;
    .............
}

@Entity
public class Task {
    @Id
    @GeneratedValue
    private long id;
    private String name;
    private String description;
    .............
}