Spring数据JPA-休眠多对多关系在链接实体表中插入null

Posted 2023-02-26

【中文标题】Spring数据JPA-休眠多对多关系在链接实体表中插入null

【英文标题】：Spring data JPA- Hibernate Many to Many relation is inserting null in link entity table

【发布时间】：2021-01-05 14:32:49

【问题描述】：

我在用户和角色之间有多对多的关系

用户实体：

import java.util.HashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;

import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.NoArgsConstructor;
import lombok.ToString;

@Entity
@Data
@EqualsAndHashCode(callSuper = false, exclude = "roles")
@ToString( exclude = "roles")
@NoArgsConstructor
public class User 
    
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    
    private String lanId;
    
    @OneToMany(mappedBy = "user",  cascade = CascadeType.ALL)
    private Set<UserRole> roles = new HashSet<>();

    
    public User(String lanId) 
    
        this.lanId = lanId;
    
    
    
    // Utility Method to sync on both sides
    public void addRole(Role role, boolean isPrivileged) 
        
        UserRole userRole = new UserRole();
        userRole.setUser(this);
        userRole.setRole(role);
        userRole.setPrivileged(isPrivileged);
        roles.add(userRole);
        role.getUsers().add(userRole);
        
       

角色实体：

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;

import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.NoArgsConstructor;
import lombok.ToString;

@Entity
@Data
@EqualsAndHashCode(callSuper = false, exclude = "users")
@ToString( exclude = "users")
@NoArgsConstructor
public class Role 
    
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    
    private String roleName;

    @OneToMany(mappedBy = "role" ,cascade =  CascadeType.ALL)
    private Set<UserRole> users = new HashSet<>();
    
    public  Role(String roleName) 
        this.roleName =roleName;
        
    

用户角色实体：

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.ManyToOne;

import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.NoArgsConstructor;

@Entity
@Data
@EqualsAndHashCode(callSuper = false ,exclude = "privileged")
@NoArgsConstructor
public class UserRole implements Serializable 

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    
    @Id
    @ManyToOne
    private User user;
    
    @Id
    @ManyToOne
    private Role role;
    
    private boolean privileged;

服务类：

import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import com.sample.m2m.dto.RolesDto;
import com.sample.m2m.repository.Role;
import com.sample.m2m.repository.RoleRepository;
import com.sample.m2m.repository.User;
import com.sample.m2m.repository.UserRepository;

@Service
public class SampleService 
    
    @Autowired
    private UserRepository userRepo;
    
    @Autowired
    private RoleRepository roleRepo;
    
    
    
    public void addEntity(String lanId,List<RolesDto> roles) 
        // adding roles to DB first
        addNewRoles(lanId,roles);
        addUserRole(lanId,roles);
    
    
    @Transactional
    public void addNewRoles(String lanId,List<RolesDto> roles) 
        //Set<String> roles = Set.of("admin", "read","write");
    //  Set<String> roles = Set.of("opr");
        Set<Role> roleSet = new HashSet<Role>();
        
        for(RolesDto role :roles)
        
            Role roleDB = roleRepo.findByRoleName(role.getRoleName());
            
            if(roleDB ==null) 
                roleDB = new Role(role.getRoleName());
                roleSet.add(roleDB);
            
            
            
        
        
        roleRepo.saveAll(roleSet);
        
    
    
    
    
    @Transactional
    public void addUserRole(String lanId,List<RolesDto> roles) 
        
        
        //Set<String> roles = Set.of("admin", "read","write");
        //Set<String> roles = Set.of("opr");
        User userDB  = userRepo.findByLanId(lanId);
        
        if(userDB == null) 
            userDB = new User(lanId);
            
            
            for(RolesDto role : roles) 
                Role roledb = roleRepo.findByRoleName(role.getRoleName());
                userDB.addRole(roledb, true);
                    
            
            
        
        else
        
            
            for(RolesDto role : roles) 
                Role roledb = roleRepo.findByRoleName(role.getRoleName());
                userDB.addRole(roledb, true);
                    
            
            
        
        
        userRepo.save(userDB);
        
    

示例输入：1：第一次保存 - 成功

    "lanId":"ABC123",
    "roles" :[
        "roleName" :  "opr"  
    
    ]

示例输入 2：将其他角色保存给同一用户 - 失败

    "lanId":"AB123",
    "roles" :[
        "roleName" : "admin"
    ,
        "roleName" : "read"
    ,
 
        "roleName" : "write"
    

    ]

异常：（试图将 null 插入到链接实体中的用户和角色中）

2020-09-18 11:12:34.379 DEBUG 24862 --- [nio-8080-exec-5] org.hibernate.SQL                        : 
    select
        userrole0_.user_id as user_id2_2_0_,
        userrole0_.role_id as role_id3_2_0_,
        userrole0_.privileged as privileg1_2_0_ 
    from
        pam.user_role userrole0_ 
    where
        userrole0_.user_id=? 
        and userrole0_.role_id=?
2020-09-18 11:12:34.379 TRACE 24862 --- [nio-8080-exec-5] o.h.type.descriptor.sql.BasicBinder      : binding parameter [1] as [BIGINT] - [1739260]
2020-09-18 11:12:34.379 TRACE 24862 --- [nio-8080-exec-5] o.h.type.descriptor.sql.BasicBinder      : binding parameter [2] as [BIGINT] - [1739261]
2020-09-18 11:12:34.393 ERROR 24862 --- [nio-8080-exec-5] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException: A different object with the same identifier value was already associated with the session : [com.sample.m2m.repository.UserRole#UserRole(user=null, role=null, privileged=true)]; nested exception is javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session : [com.sample.m2m.repository.UserRole#UserRole(user=null, role=null, privileged=true)]] with root cause

javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session : [com.sample.m2m.repository.UserRole#UserRole(user=null, role=null, privileged=true)]
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:123) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:181) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]

我是否在映射或用户实体的实用程序方法中遗漏了什么。非常感谢任何帮助。

【参考方案1】：

UserRole 属性不是表的主 ID，所以 @Id 不应该在这两个上。

您应该向 UserRole 添加一个 ID 属性并使用 @Id 和 @GeneratedValue 对其进行注释。

@ManyToOne 将在数据库中产生一个外键

【讨论】：

通过将 ID 属性添加到 UserRole 我能够成功保存，但只是好奇根据 Hibernate docs for Many to Many Bi Directional life cycle entity ，文档没有提到有一个单独的 ID 属性，但将 ID 添加到实体 .docs.jboss.org/hibernate/orm/5.2/userguide/html_single/….

【参考方案2】：

也尝试保存角色，在用户实体的addrole函数中更改角色后，您还没有存储角色。

【讨论】：

在我使用 Utility 方法设置用户和角色之间的链接之前，角色已经保存。