Jpa 添加关系

Question

我在 Spring Boot 中使用 JPA。我是 JPA 的新手。

我有两个实体

User.java

@Entity
@Table(name = "user")
@Data
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "user_id")
    private Long id;

    @Column(unique = true, name = "username")
    @NotNull
    private String username;

    @NotNull
    @Column(name = "password")
    private String password;



    @Column(name = "display_name")
    private String displayName;

    @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinTable(name = "user_roles_rel", joinColumns = @JoinColumn(name = "user_id", referencedColumnName = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id", referencedColumnName = "role_id"))
    private Set<Role> roles;

    @Column(name = "profile_picture_path")
    private String profilePicturePath;

}

Role.java

@Entity
@Table(name = "roles")
@Data
public class Role {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "role_id")
    private long id;

    @Column(name = "role", unique = true)
    private String role;

}

我的要求是我的应用程序将只有 5 个角色，但成千上万的用户拥有这五个角色中的任何一个。当我添加一个新用户时，应该为该用户添加这些角色中的任何一个。每次添加新用户时，上面的代码都会插入一个新角色。如何添加具有现有角色的用户？

这是用于添加新用户的 JSON 数据

{
    "username":"username",
    "password":"password",  
    "roles":[
        {
            "role_id":1
        }
        ],
    "displayName":"Dispaly Name",
    "profilePicturePath":"abc.png"
}

这里我已经在数据库中添加了一个角色 id : 1

当我添加此用户时，我希望插入角色 id 为 1 的用户。

RoleRepository.java

public interface RoleRepository extends JpaRepository<Role, Long> {

    public Role findByRole(String role);

}

UserRepository.java

public interface UserRepository extends JpaRepository<User, Long> {

    User findByUsername(String username);

}

UserService.java

@Service
public class UserService{


@Autowired
UserRepository userRep;

public void addUser(User user) {
    user.setPassword(passwordEncoder().encode(user.getPassword()));
    userRep.save(user);
    }

}

UserController.java

    @PostMapping(path = "/api/user/new_user_without_image")
    public ResponseMessage addUserWithoutImage(@RequestBody User user) {
    userService.addUser(user);
    return new ResponseMessage("The User was added successfully!");
    }

Answer 1

我认为你必须在你的用户类@OneToMany 和你的角色类@ManyToOne 注释中插入。

类角色：

@OneToMany(mappedBy = "user")
private Set<Role> roles = new HashSet<>();

班级用户：

@ManyToOne
@JoinColumn(name = "user_id")
public User user;

Answer 2

以下示例适用于我。

学生.java

package com.techoffice.example.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;


@Entity
@Table(name = "STUDENT")
public class Student {

    @Id
    @SequenceGenerator(name="student_seq", sequenceName="student_seq")
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="student_seq")
    private int id;

    @Column(name="STUDENT_NAME")
    private String studentName;

    @ManyToOne
    @JoinColumn(name = "SCHOOL_ID")
    private School school;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public School getSchool() {
        return school;
    }

    public void setSchool(School school) {
        this.school = school;
    }

    public String getStudentName() {
        return studentName;
    }

    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }

    @Override
    public String toString() {
        return id + " " + studentName;
    }


}

School.java

package com.techoffice.example.model;

import java.util.List;

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 javax.persistence.SequenceGenerator;
import javax.persistence.Table;

@Entity
@Table(name = "School")
public class School {

    @Id
    @SequenceGenerator(name="school_seq",sequenceName="school_seq")        
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="school_seq")
    private int id;

    private String name;

    @OneToMany(mappedBy = "school", cascade = CascadeType.ALL)
    private List<Student> students;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List<Student> getStudents() {
        return students;
    }

    public void setStudents(List<Student> students) {
        for (Student student: students){
            student.setSchool(this);
        }
        this.students = students;
    }


}

程序

package com.techoffice.example;

import java.util.ArrayList;
import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import com.techoffice.example.model.School;
import com.techoffice.example.model.Student;

public class Appl {
    public static void main(String[] args){
        EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory( "techoffice.example" );
        EntityManager entityManager = entityManagerFactory.createEntityManager();
        try{
            entityManager.getTransaction().begin();
            Student student1 = new Student();
            student1.setStudentName("Test 1");
            Student student2 = new Student();
            student2.setStudentName("Test 1");

            List<Student> students = new ArrayList<Student>();
            students.add(student1);
            students.add(student2);

            School school = new School();
            school.setName("School 1");
            school.setStudents(students);
            entityManager.persist(school);

            // 
            List<Student> results = entityManager.createQuery("From Student", Student.class).getResultList();
            for (Student result: results){
                System.out.println(result.toString());
            }

            entityManager.getTransaction().commit();
            entityManager.close();
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            // close the factory and release any resource it holds.
            entityManagerFactory.close();   
        }
    }
}