title: mappedBy reference an unknown target entity property - hibernate error
body: <p>first, my classes:</p>
  
  <p><strong>User</strong></p>
  
  <pre><code>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&lt;RolesMap&gt; rolesMap;
  
      public List&lt;RolesMap&gt; getRolesMap() {
          return rolesMap;
      }
  
      public void setRolesMap(List&lt;RolesMap&gt; 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();
      }
  }
  </code></pre>
  
  <p><strong>RolesMap.java</strong></p>
  
  <pre><code>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;
      }
  
  }
  </code></pre>
  
  <p>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</p>
  
  <p>But i don't exaclu know what i'm doing wrong. Can somebody help me fix this problem?</p>