【发布时间】：2021-09-20 06:52:25
【问题描述】：
我正在创建一个角色和用户之间具有多对多关系的 crud api。当我发出 Get HTTP 请求时，我收到下面的消息，但是当我删除所有关系并在单个表上创建 findall 时，它可以完美地工作。您认为问题出在哪里？
邮递员中的错误消息
{
"timestamp": "2021-07-10T04:28:24.877+0000",
"status": 500,
"error": "Internal Server Error",
"message": "JSON mapping problem: java.util.ArrayList[0]->com.notyfyd.entity.User[\"roles\"]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: failed to lazily initialize a collection of role: com.notyfyd.entity.User.roles, could not initialize proxy - no Session (through reference chain: java.util.ArrayList[0]->com.notyfyd.entity.User[\"roles\"])",
"path": "/user/all"
}
角色实体
package com.notyfyd.entity;
import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;
import javax.persistence.*;
import java.util.List;
@Entity
@Table(name = "t_role")
@JsonIdentityInfo(
generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class Role {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private String description;
@ManyToMany(targetEntity = User.class, mappedBy = "roles", cascade = {CascadeType.PERSIST, CascadeType.DETACH,CascadeType.MERGE,CascadeType.REFRESH})
private List<User> users;
public Long getId() {
return this.id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return this.description;
}
public void setDescription(String description) {
this.description = description;
}
public List<User> getUsers() {
return users;
}
public void setUsers(List<User> users) {
this.users = users;
}
}
用户实体
import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;
import javax.persistence.*;
import java.util.List;
@Entity
@Table(name = "t_user")
@JsonIdentityInfo(
generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String firstName;
private String lastName;
private String mobile;
@Column(unique = true)
private String email;
@ManyToMany(targetEntity = Role.class, cascade = {CascadeType.PERSIST, CascadeType.DETACH,CascadeType.MERGE,CascadeType.REFRESH} )
@JoinTable(
name="t_user_roles",
joinColumns=
@JoinColumn( name="user_id", referencedColumnName="id"),
inverseJoinColumns=@JoinColumn(name="role_id", referencedColumnName="id"))
private List<Role> roles;
public List<Role> getRoles() {
return roles;
}
public void setRoles(List<Role> roles) {
this.roles = roles;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getMobile() {
return mobile;
}
public void setMobile(String mobile) {
this.mobile = mobile;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
}
【问题讨论】：
标签： spring-boot rest spring-data-jpa crud-repository