spring-boot - 关系 CRUD API Spring Boot

Question

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，我得到下面的消息，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。你认为问题出在哪里？

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;
    }


}

score 0 · Accepted Answer

您是否将该实体直接作为 json 返回。可以在下面的字段中添加@JsonIgnore。

@JsonIgnore
private List<Role> roles;

score 0 · Accepted Answer

您可以将获取类型设置为FetchType.EAGER实体中的多对多关系。
试试这个，让我知道发生了什么。

score 0 · Accepted Answer

here is the log error on MSSQL Server

2021-07-10 11:20:59.333 WARN 3124 --- [nio-6120-exec-4] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: failed to lazily initialize a collection of role: fdsa.edu.PNUFDSA.Model.AnneeAcademique.paiements, could not initialize proxy - no Session; nested exception is com.fasterxml.jackson.databind.JsonMappingException: failed to lazily initialize a collection of role: fdsa.edu.PNUFDSA.Model.AnneeAcademique.paiements, could not initialize proxy - no Session (through reference chain: java.util.ArrayList[0]->fdsa.edu.PNUFDSA.Model.AnneeAcademique["paiements"])]

the Entity is:

 * "Visual Paradigm: DO NOT MODIFY THIS FILE!"
 * 
 * This is an automatic generated file. It will be regenerated every time 
 * you generate persistence class.
 * 
 * Modifying its content may cause the program not work, or your work may lost.
 */

/**
 * Licensee: 
 * License Type: Evaluation
 */
package fdsa.edu.PNUFDSA.Model;
import com.fasterxml.jackson.annotation.JsonIgnore;
import lombok.Data;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import javax.persistence.*;
@Entity
@Data
//@org.hibernate.annotations.Proxy(lazy=false)

@Table(name="AnneeAcademique")
public class AnneeAcademique implements Serializable {
    public AnneeAcademique() {
    }
    
    @Column(name="ID", nullable=false, length=10)   
    @Id 
    @GeneratedValue(generator="PNU_ANNEEACADEMIQUE_ID_GENERATOR")   
    @org.hibernate.annotations.GenericGenerator(name="PNU_ANNEEACADEMIQUE_ID_GENERATOR", strategy="native") 
    private int id;
    
    @Column(name="Debut", nullable=true)    
    @Temporal(TemporalType.DATE)    
    private java.util.Date debut;
    
    @Column(name="Fin", nullable=true)  
    @Temporal(TemporalType.DATE)    
    private java.util.Date fin;
    @JsonIgnore
    @ManyToMany(mappedBy="anneeAcademiques", targetEntity=fdsa.edu.PNUFDSA.Model.Cours.class)   
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE, org.hibernate.annotations.CascadeType.LOCK}) 
    @org.hibernate.annotations.LazyCollection(org.hibernate.annotations.LazyCollectionOption.TRUE)  
    private java.util.Set cours = new java.util.HashSet();
        
        
       
    @JsonIgnore
    @OneToMany(mappedBy="anneeAcademique", targetEntity=fdsa.edu.PNUFDSA.Model.Paiement.class)  
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE, org.hibernate.annotations.CascadeType.LOCK}) 
    @org.hibernate.annotations.LazyCollection(org.hibernate.annotations.LazyCollectionOption.TRUE)  
    private List paiements = new ArrayList();
    
    private void setId(int value) {
        this.id = value;
    }
    
    public int getId() {
        return id;
    }
    
    public int getORMID() {
        return getId();
    }
    
    public void setDebut(java.util.Date value) {
        this.debut = value;
    }
    
    public java.util.Date getDebut() {
        return debut;
    }
    
    public void setFin(java.util.Date value) {
        this.fin = value;
    }
    
    public java.util.Date getFin() {
        return fin;
    }
    
    public void setCours(java.util.Set value) {
        this.cours = value;
    }
    
    public java.util.Set getCours() {
        return cours;
    }
    
    
    public void setPaiements(List value) {
        this.paiements = value;
    }
    
    public List getPaiements() {
        return paiements;
    }
    
    
    public String toString() {
        return String.valueOf(getId());
    }
    
}

spring-boot - 关系 CRUD API Spring Boot

3 回答 3

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