Wsrtjtyk

I have manyToMany relationship mapping and couldn't get it to work. I have read many posts and articles and couldn't figure this one out. If anyone has some idea please share.

I have tried to simplify diagram and code as much.

My database is designed like this:

My entities look like this (at least final attempt before asking):
Client:

@Entity

@Table(name = "client")

public class Client implements Serializable {

    @Id

    @Column(name = "client_id")

    private int id;



    ... other fields

}

Project:

@Entity

@Table(name = "project")

public class Project implements Serializable {

    @EmbeddedId

    private ProjectId id;



    ... other fields



    @Embeddable

    class ProjectId implements Serializable {

        @ManyToOne(fetch = FetchType.LAZY)

        @JoinColumn(name = "client_id", insertable = false, updatable = false)

        private Client client;



        @Column(name = "project_id")

        private int projectId;

    }

}

User:

@Entity

@Table(name = "user")

public class User implements Serializable {

    @EmbeddedId

    private UserId id;



    ... other fields



    @Embeddable

    class UserId implements Serializable {

        @ManyToOne(fetch = FetchType.LAZY)

        @JoinColumn(name = "client_id", insertable = false, updatable = false)

        private Client client;



        @Column(name = "user_id")

        private int userId;

    }

}

ProjectUser:

@Entity

@Table(name = "project_user")

public class ProjectUser implements Serializable {

    @EmbeddedId

    private ProjectUserId id;



    ... other fields



    @Embeddable

    class ProjectUserId implements Serializable {

        @ManyToOne(fetch = FetchType.LAZY)

        @JoinColumn(name = "client_id", insertable = false, updatable = false)

        private Client client;



        @ManyToOne(fetch = FetchType.LAZY)

        @JoinColumns({

            @JoinColumn(name = "client_id", referencedColumnName = "client_id", insertable = false, updatable = false),

            @JoinColumn(name = "project_id", referencedColumnName = "project_id", insertable = false, updatable = false) })

        private Project project;



        @ManyToOne(fetch = FetchType.LAZY)

        @JoinColumns({

            @JoinColumn(name = "client_id", referencedColumnName = "client_id", insertable = false, updatable = false),

            @JoinColumn(name = "user_id", referencedColumnName = "user_id", insertable = false, updatable = false) })

        private User user;

    }

}

Before adding ProjectUser entity everything is working fine.

Now when I'm starting server it says:

Repeated column in mapping for entity: ProjectUser column: client_id
(should be mapped with insert="false" update="false")"}}

So, the question is how do I make this work?

EDIT:
Java application will be mostly REST services providing data. Database design is as is. It has logical sense and most of the business logic will be in database. We have people with very good DB knowledge working on this and it would not make much sense changing database design because of JPA/Hibernate limitations.

The code below will let hibernate create a structure for your entities:

    @ManyToOne(fetch = FetchType.LAZY)

    @JoinColumn(name = "client_id", insertable = false, updatable = false)

    private Client client;



    @ManyToOne(fetch = FetchType.LAZY)

    @JoinColumns({

            @JoinColumn(name = "project_client_id", referencedColumnName = "client_id", insertable = false, updatable = false),

            @JoinColumn(name = "project_id", referencedColumnName = "project_id", insertable = false, updatable = false) })

    private Project project;



    @ManyToOne(fetch = FetchType.LAZY)

    @JoinColumns({

            @JoinColumn(name = "user_client_id", referencedColumnName = "client_id", insertable = false, updatable = false),

            @JoinColumn(name = "user_id", referencedColumnName = "user_id", insertable = false, updatable = false) })

    private User user;

But to make a scheme as on the picture in your question, get rid of all these EmbeddedId. Use simple ids and add validation in your code, if you want project and user inside your ProjectUser have the same client_id.