org.hibernate.engine.jdbc.spi.SqlExceptionHelpeC语言 'field list'中的未知列

Question

请提供帮助。我是刚开始休眠5+MySQL的，所以这可能是一个愚蠢的场景。

我正在尝试创建一个非常基本的社交媒体应用程序，允许注册、登录和添加朋友。我得到这个错误：

23:47:57.340 [http-nio-8080-exec-6] ERROR     org.hibernate.engine.jdbc.spi.SqlExceptionHelper - Unknown column 'friends0_.User_Id' in 'field list'
javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not extract ResultSet
at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:149)
at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:157)
at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1423)
at com.alonso.socialnetworks.dao.UserDAO.getUserByName(UserDAO.java:29)
at com.alonso.socialnetworks.action.LoginAction.validate(LoginAction.java:34)
at com.opensymphony.xwork2.validator.ValidationInterceptor.doBeforeInvocation(ValidationInterceptor.java:250)
at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:262)
at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:49)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:99)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.doIntercept(ConversionErrorInterceptor.java:142)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:99)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:137)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:99)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:137)

当我试图创建一个表来处理添加好友功能时，会引发错误。

我继续创建了一个表，将用户与他们的朋友联系起来，如下所示：

表名：users_users

列：

users_id-int(11(

friends_id-int(11(

这是我的模型类：

package com.alonso.socialnetworks.model;
import java.util.Set;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import org.hibernate.annotations.GenericGenerator;
@Entity
@Table(name = "Users")
public class User {
@Id
@GenericGenerator(name = "inc", strategy = "increment")
@GeneratedValue(generator = "inc")
@Column(name = "Id")
private Integer id;
@Column(name = "name")
private String userName;
@Column(name = "password")
private String password;
@OneToMany(fetch=FetchType.EAGER)
@JoinTable(name="users_users")
@JoinColumn(name="users_id")
private Set<User> friends;
public Set<User> getFriends() {
return friends;
}
public void setFriends(Set<User> friends) {
this.friends = friends;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}

这是我正在使用的代码。

https://github.com/JAlonsoHdz/SocialNetworkWebApp

我做错了什么？hibernate似乎没有映射users_users和列。

Answer 1

我将实体映射更改为这种方法

这就是我的代码在用户模型类上的样子：

@Entity
@Table(name = "Users")
public class User {
@Id
@GenericGenerator(name = "inc", strategy = "increment")
@GeneratedValue(generator = "inc")
@Column(name = "Id")
private Integer id;
@Column(name = "name")
private String userName;
@Column(name = "password")
private String password;
@ManyToMany(fetch=FetchType.EAGER)
@JoinTable(name="users_users",
joinColumns=@JoinColumn(name="users_Id"),
inverseJoinColumns=@JoinColumn(name="friends_id")
)
private Set<User> friends;
@ManyToMany
@JoinTable(name="users_users",
joinColumns=@JoinColumn(name="friends_id"),
inverseJoinColumns=@JoinColumn(name="users_Id")
)
private Set<User> friendOf;

最后，当用户试图添加一个不存在的朋友时，我不得不处理一个空指针异常。这就成功了。