mappedBy reference an unknown target entity property - hibernate error

Question

first, my classes:

User

package com.patpuc.model;

import java.util.List;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import com.patpuc.model.RolesMap;

@Entity
@Table(name = "users")
public class User {
    @Id
    @Column(name = "USER_ID", unique = true, nullable = false)
    private int user_id;
    @Column(name = "NAME", nullable = false)
    private String name;
    @Column(name = "SURNAME", unique = true, nullable = false)
    private String surname;
    @Column(name = "USERNAME_U", unique = true, nullable = false)
    private String username_u; // zamiast username
    @Column(name = "PASSWORD", unique = true, nullable = false)
    private String password;
    @Column(name = "USER_DESCRIPTION", nullable = false)
    private String userDescription;
    @Column(name = "AUTHORITY", nullable = false)
    private String authority = "ROLE_USER";
    @Column(name = "ENABLED", nullable = false)
    private int enabled;

    @OneToMany(mappedBy = "rUser")
    private List<RolesMap> rolesMap;

    public List<RolesMap> getRolesMap() {
        return rolesMap;
    }

    public void setRolesMap(List<RolesMap> rolesMap) {
        this.rolesMap = rolesMap;
    }

    /**
     * @return the user_id
     */
    public int getUser_id() {
        return user_id;
    }

    /**
     * @param user_id
     *            the user_id to set
     */
    public void setUser_id(int user_id) {
        this.user_id = user_id;
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name
     *            the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * @return the surname
     */
    public String getSurname() {
        return surname;
    }

    /**
     * @param surname
     *            the surname to set
     */
    public void setSurname(String surname) {
        this.surname = surname;
    }

    /**
     * @return the username_u
     */
    public String getUsername_u() {
        return username_u;
    }

    /**
     * @param username_u
     *            the username_u to set
     */
    public void setUsername_u(String username_u) {
        this.username_u = username_u;
    }

    /**
     * @return the password
     */
    public String getPassword() {
        return password;
    }

    /**
     * @param password
     *            the password to set
     */
    public void setPassword(String password) {
        this.password = password;
    }

    /**
     * @return the userDescription
     */
    public String getUserDescription() {
        return userDescription;
    }

    /**
     * @param userDescription
     *            the userDescription to set
     */
    public void setUserDescription(String userDescription) {
        this.userDescription = userDescription;
    }

    /**
     * @return the authority
     */
    public String getAuthority() {
        return authority;
    }

    /**
     * @param authority
     *            the authority to set
     */
    public void setAuthority(String authority) {
        this.authority = authority;
    }

    /**
     * @return the enabled
     */
    public int getEnabled() {
        return enabled;
    }

    /**
     * @param enabled
     *            the enabled to set
     */
    public void setEnabled(int enabled) {
        this.enabled = enabled;
    }

    @Override
    public String toString() {
        StringBuffer strBuff = new StringBuffer();
        strBuff.append("id : ").append(getUser_id());
        strBuff.append(", name : ").append(getName());
        strBuff.append(", surname : ").append(getSurname());
        return strBuff.toString();
    }
}

RolesMap.java

package com.patpuc.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
import com.patpuc.model.User;

@Entity
@Table(name = "roles_map")
public class RolesMap {
    private int rm_id;
    private String username_a;
    private String username_l;
    //private String username_u;
    private String password;
    private int role_id;

    @ManyToOne
    @JoinColumn(name="username_u", nullable=false)
    private User rUser;
   public RolesMap(){

    }
    /**
     * @return the user
     */
    public User getUser() {
        return rUser;
    }
    /**
     * @param user the user to set
     */
    public void setUser(User rUser) {
        this.rUser = rUser;
    }


    @Id
    @Column(name = "RM_ID", unique = true, nullable = false)
    public int getRmId() {
        return rm_id;
    }
    public void setRmId(int rm_id) {
        this.rm_id = rm_id;
    }

    @Column(name = "USERNAME_A", unique = true)
    public String getUsernameA() {
        return username_a;
    }
    public void setUsernameA(String username_a) {
        this.username_a = username_a;
    }

    @Column(name = "USERNAME_L", unique = true)
    public String getUsernameL() {
        return username_l;
    }
    public void setUsernameL(String username_l) {
        this.username_l = username_l;
    }



    @Column(name = "PASSWORD", unique = true, nullable = false)
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }

    @Column(name = "ROLE_ID", unique = true, nullable = false)
    public int getRoleId() {
        return role_id;
    }
    public void setRoleId(int role_id) {
        this.role_id = role_id;
    }

}

when i try run this on server i have exception like this: Error creating bean with name 'SessionFactory' defined in ServletContext resource [/WEB-INF/classes/baseBeans.xml]: Invocation of init method failed; nested exception is org.hibernate.AnnotationException: mappedBy reference an unknown target entity property: com.patpuc.model.RolesMap.users in com.patpuc.model.User.rolesMap

But i don't exaclu know what i'm doing wrong. Can somebody help me fix this problem?

Answer 1

By default, when you define your entity you can either use field-based or property-based access, but not both. "Access type" basically means where your JPA provider looks to determine the state of your entity. If field access is used, it looks at the instance variables. If property access is used, it looks at the getters.

In your case, you didn't explicitly define an access type, so JPA tries to figure it out by looking at where you placed your annotations. I think Hibernate decides based on the placement of the @Id annotation. Since your @Id annotation is placed on a getter, Hibernate is using property-based access for RolesMap.

With property-based access, you do not have a property named rUser because you don't have a getter named getRUser().

The spec states that you should not mix your placement of annotations like that:

All such classes in the entity hierarchy whose access type is defaulted in this way must be consistent in their placement of annotations on either fields or properties, such that a single, consistent default access type applies within the hierarchy

What I suggest doing to solve the problem:

Place your annotations consistently so that there is no ambiguity (e.g. always put your annotations on the instance variables). This would result in the following changes to RolesMap:

@Entity
@Table(name = "roles_map")
public class RolesMap {
    @Id
    @Column(name = "RM_ID", unique = true, nullable = false)
    private int rm_id;
    @Column(name = "USERNAME_A", unique = true)
    private String username_a;
    @Column(name = "USERNAME_L", unique = true)
    private String username_l;
    @Column(name = "PASSWORD", unique = true, nullable = false)
    private String password;
    @Column(name = "ROLE_ID", unique = true, nullable = false)
    private int role_id;
    @ManyToOne
    @JoinColumn(name="username_u", nullable=false)
    private User rUser;

    // ... constructor(s), getters/setters, etc ...
}