JPA - @JoinTable Examples

JPA JAVA EE

@JoinTable can be used to map following associations to database table: bidirectional many-to-one/one-to-many, unidirectional many-to-one, and one-to-one (both bidirectional and unidirectional) associations.

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 +
                '}';
    }
}

Original Post

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

    public String getStrA() {
        return strA;
    }

    public void setStrA(String strA) {
        this.strA = strA;
    }

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

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

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

@Entity
public class EntityB {
    @Id
    @GeneratedValue
    private int myIdB;
    private String strB;
    @ManyToOne
    @JoinTable(name = "MY_JOIN_TABLE",
            joinColumns = {@JoinColumn(name = "MY_ENTITY_B_FK", insertable = false,
                    updatable = false, referencedColumnName = "myIdB")},
            inverseJoinColumns = {@JoinColumn(name = "MY_ENTITY_A_FK", insertable = false,
                    updatable = false, referencedColumnName = "myIdA")}
    )
    private EntityA refEntityA;

    public String getStrB() {
        return strB;
    }

    public void setStrB(String strB) {
        this.strB = strB;
    }

    public EntityA getRefEntityA() {
        return refEntityA;
    }

    public void setRefEntityA(EntityA refEntityA) {
        this.refEntityA = refEntityA;
    }

    @Override
    public String toString() {
        return "EntityB{" +
                "myIdB=" + myIdB +
                ", strB='" + strB + '\'' +
                '}';
    }
}

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@OneToOne unidirectional with @JoinTable:

@Entity
public class EntityA {
    @Id
    @GeneratedValue
    private int myIdA;
    private String stringA;
    @OneToOne
    @JoinTable(name = "MY_JOIN_TABLE",
            joinColumns = {
                    @JoinColumn(name = "ENTITYA_FK", referencedColumnName = "myIdA")
            },
            inverseJoinColumns = {
                    @JoinColumn(name = "ENTITYB_FK", referencedColumnName = "myIdB", unique = true)
            }
    )
    private EntityB entityB;
    .............
}

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

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@OneToOne bidirectional with @JoinTable:

@Entity
public class EntityA {
    @Id
    @GeneratedValue
    private int myIdA;
    private String stringA;
    @OneToOne
    @JoinTable(name = "MY_JOIN_TABLE",
            joinColumns = {
                    @JoinColumn(name = "ENTITYA_FK", referencedColumnName = "myIdA")
            },
            inverseJoinColumns = {
                    @JoinColumn(name = "ENTITYB_FK", referencedColumnName = "myIdB", unique = true)
            }
    )
    private EntityB entityB;
    .............
}

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

    @OneToOne(mappedBy = "entityB")
    private EntityA entityA;
    .............
}

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

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

Original Post

JPA - @JoinTable Examples

See Also