首先，我的类(class):

用户

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;
    }

}

当我尝试在服务器上运行它时，出现如下异常:创建名为“SessionFactory”的 bean 在 ServletContext 资源 [/WEB-INF/classes/baseBeans.xml] 中定义时出错:调用 init 方法失败；嵌套异常是 org.hibernate.AnnotationException:mappedBy 引用未知的目标实体属性:com.patpuc.model.RolesMap.users in com.patpuc.model.User.rolesMap

但我不知道我做错了什么。有人可以帮我解决这个问题吗？

最佳答案

默认情况下，当您定义实体时，您可以使用基于字段或基于属性的访问，但不能同时使用。 “访问类型”基本上是指您的 JPA 提供者在何处查看以确定您的实体的状态。如果使用字段访问，它会查看实例变量。如果使用属性访问，它会查看 getter。

在您的情况下，您没有明确定义访问类型，因此 JPA 试图通过查看您放置注释的位置来弄清楚。我认为 Hibernate 根据@Id 注释的位置来决定。由于您的 @Id 注释放置在 getter 上，因此 Hibernate 对 RolesMap 使用基于属性的访问。

使用基于属性的访问，您没有名为 rUser 的属性，因为您没有名为 getRUser() 的 getter。

规范规定你不应该这样混合你的注释位置:

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

我建议如何解决问题:

始终如一地放置注释，以免出现歧义(例如，始终将注释放在实例变量上)。这将导致对 RolesMap 进行以下更改:

@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 ...
}

关于java - mappedBy 引用未知的目标实体属性 - hibernate 错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/19895034/