Hibernate: map a foreign key that points to unique key

Question

I have a table with composite primary key composed of two columns and that table also have a unique key. That unique key in another table is mapped as foreign key. How to implement this mapping with Hibernate? I make an @Embedable class for the composite primary key and in the entity I use it with annotation @EmbeddedId. In the second table I declare a field:

 @ManyToOne
 @JoinColumn(name = "user_code", nullable = false)
 public User userCode;

which is the unique key from the first table, but I'm getting an exception: A Foreign key refering com.users.maintenance.User from com.users.maintenance.Code has the wrong number of column. should be 2.

Edit This is my User class:

 @Entity
 @Table(name = "Users")
 public class User {

      @EmbeddedId
      public UserPk userId;

      @column(name = "code")
      public int code;

      public UserPk getUserId() {
          return this.userId;
      }

      public void setUserId(UserPk userId) {
           this.userId = userId;
      }

      public String getEmail() {
          return this.email;
      }

      public void setEmail(String email) {
           this.email = email;
      }

      @Embeddable
      private class UserPk implements Seriazible {

            @Column(name = "user_name")
            public String userName;

            @Column(name = "email")
            public String email; 

            public String getUserName() {
                return this.userName;
            }

            public void setUserName(String userName) {
                this.userName = userName;
            }

            public String getEmail() {
                return this.email;
            }

            public void setEmail(String email) {
                this.email = email;
            } 

            @Override
            public int hashCode() {
                return this.hashCode();
            }

            @Override
            public boolean equals(Object obj) {
                if (obj == this) {
        return true;
        }

        if (!(obj instanceof UserPk)) {
        return false;
        }

        UserPk pk = (UserPk)obj;

        return pk.userName == userName && pk.email == email;
           }
      }
 }

Answer 1

You need tell Hibernate what User columns you are referring to (if it's not a primary key). To do this, add referencedColumnName in the second entity:

 @ManyToOne
 @JoinColumn(name = "user_code", nullable = false, referencedColumnName = "code")
 public User userCode;

I haven't checked that, but maybe you will also have to specify that the code column is unique in User class:

public class User {
...

      @Column(name = "code", unique=true)
      public int code;
...

Just as a side note: don't make all fields public, use encapsulation properly.