JPAオブジェクトは未保存の一時インスタンスを参照します。フラッシングする前に一時インスタンスを保存します。

Question

JPAが@ManyToManyリレーションをカスケードしない理由をデバッグするのは本当に苦労しています。私が見つけたすべての答えは、カスケード文が見つからないことと関係があります。しかし、私はそれらを持って、まだ入手できます：

によって引き起こさ

：org.hibernate.TransientObjectException：オブジェクト参照 保存されていない一時的なインスタンス - 紅潮前に一時的なインスタンスを保存します。com.example.iaa.model.Employee

コードは、このチュートリアルに基づいている：リンクで与えられるようhttps://hellokoding.com/jpa-many-to-many-relationship-mapping-example-with-spring-boot-maven-and-mysql/

Answer 1

package com.example.iaa.repository; 
import org.springframework.data.jpa.repository.JpaRepository; 
import com.example.iaa.model.Employee; 

public interface EmployeeRepository extends JpaRepository<Employee, Integer> { 
} 




package com.example.iaa.repository; 
import org.springframework.data.jpa.repository.JpaRepository; 
import com.example.iaa.model.Role; 

public interface RoleRepository extends JpaRepository<Role, Integer> { 
} 




package com.example.iaa.model; 

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

import javax.persistence.CascadeType; 
import javax.persistence.ElementCollection; 
import javax.persistence.Entity; 
import javax.persistence.GeneratedValue; 
import javax.persistence.Id; 
import javax.persistence.JoinTable; 
import javax.persistence.ManyToMany; 
import javax.persistence.Table; 

@Entity 
@Table//(name = "role") 
public class Role { 

    @Id 
    @GeneratedValue 
    private int id; 

    private String name; 

    @ElementCollection 
    @ManyToMany(cascade = CascadeType.ALL) 
    @JoinTable//(name = "employee_role", joinColumns = @JoinColumn(name = "id_role", referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name = "id_employee", referencedColumnName = "id")) 
    private Set<Employee> employees; 

    public Role(String name, HashSet<Employee> employees) { 
     this.name = name; 
     this.employees = employees; 
    } 

    public Role(String name) { 
     this.name = name; 
    } 

    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 Set<Employee> getEmployees() { 
     return employees; 
    } 

    public void setEmployees(Set<Employee> employees) { 
     this.employees = employees; 
    } 

} 




package com.example.iaa.model; 

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

import javax.persistence.CascadeType; 
import javax.persistence.ElementCollection; 
import javax.persistence.Entity; 
import javax.persistence.GeneratedValue; 
import javax.persistence.Id; 
import javax.persistence.JoinTable; 
import javax.persistence.ManyToMany; 
import javax.persistence.Table; 

@Entity 
@Table//(name = "employee") 
public class Employee { 

    @Id 
    @GeneratedValue 
    private int id; 

    private String firstName; 
    private String lastName; 

    @ElementCollection 
    @ManyToMany(cascade = CascadeType.ALL) 
    @JoinTable//(name = "employee_role", joinColumns = @JoinColumn(name = "id_employee", referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name = "id_role", referencedColumnName = "id")) 
    private Set<Role> roles; 

    public Employee(String firstName) { 
     this.firstName = firstName; 
    } 

    public Employee() { 
     roles = new HashSet<Role>(); 
    } 

    public Employee(String name, HashSet<Role> roles) { 
     this.firstName = name; 
     this.roles = roles; 
    } 

    public int getId() { 
     return id; 
    } 

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

    public String getDisplayName() { 
     return firstName + " " + lastName; 
    } 

    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 void addRole(Role role) { 
     roles.add(role); 
    } 

    public Set<Role> getRoles() { 
     return Collections.unmodifiableSet(roles); 
    } 

    public void setRoles(Set<Role> roles) { 
     this.roles = roles; 
    } 

    public boolean hasRole(Role role) { 
     return roles.contains(role); 
    } 

    @Override 
    public String toString() { 
     String ret = ""; 
     ret += "id: " + id + "\n"; 
     ret += "firstName: " + firstName + "\n"; 
     ret += "lastName: " + lastName + "\n"; 
     ret += "displayName: " + getDisplayName() + "\n"; 
     ret += "roles: "; 

     String delim = ""; 
     for (Role role : roles) { 
      ret += delim + role; 
      delim = ","; 
     } 
     return ret; 
    } 
} 




package com.example.iaa.controller; 

import java.util.HashSet; 

import javax.transaction.Transactional; 

import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.ui.Model; 
import org.springframework.web.bind.annotation.RequestMapping; 

import com.example.iaa.model.Employee; 
import com.example.iaa.model.Role; 
import com.example.iaa.repository.EmployeeRepository; 
import com.example.iaa.repository.RoleRepository; 

public class HelloJpaApplication { 
    private static final Logger logger = LoggerFactory.getLogger(HelloJpaApplication.class); 

    @Autowired 
    private RoleRepository roleRepository; 

    @Autowired 
    private EmployeeRepository employeeRepository; 

    @RequestMapping(value = "/jpa") 
    @Transactional 
    public String testJPA(final Model model) throws Exception { 
     // save a couple of roles 
     final Employee employeeA = new Employee("Employee A"); 
     final Employee employeeB = new Employee("Employee B"); 
     final Employee employeeC = new Employee("Employee C"); 

     roleRepository.save(new HashSet<Role>(){{ 
      add(new Role("Role A", new HashSet<Employee>(){{ 
       add(employeeA); 
       add(employeeB); 
      }})); 

      add(new Role("Role B", new HashSet<Employee>(){{ 
       add(employeeA); 
       add(employeeC); 
      }})); 
     }}); 

     // fetch all roles 
     for(Role role : roleRepository.findAll()) { 
      logger.info(role.toString()); 
     } 

     // save a couple of employees 
     final Role roleA = new Role("Role A"); 
     final Role roleB = new Role("Role B"); 

     employeeRepository.save(new HashSet<Employee>() {{ 
      add(new Employee("Employee A", new HashSet<Role>() {{ 
       add(roleA); 
       add(roleB); 
      }})); 

      add(new Employee("Employee B", new HashSet<Role>() {{ 
       add(roleA); 
       add(roleB); 
      }})); 
     }}); 

     // fetch all employees 
     for(Employee employee : employeeRepository.findAll()) { 
      logger.info(employee.toString()); 
     } 
     return "soy:iaa.index"; 
    } 
} 

、Iは

下に変更しました

@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER) 
@JoinTable(name = "employee_role", joinColumns = @JoinColumn(name = "id_employee", referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name = "id_role", referencedColumnName = "id")) 
private Set<Employee> employees; 

と

@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "employees") 
private Set<Role> roles; 

も、デフォルトコンストラクタと熱心なフェッチを追加、それが働きました。