spring - 如何修复 Spring Boot 一对多双向无限循环？

Question

我尝试使用 spring boot 和 spring data jpa 创建一对多双向映射，请查看下面的实体

Employer Entity

@Entity  
public class Employer  
{  
private Long id;  
private String employerName;  
private List<Employee> employees;  

@Id  
@GeneratedValue(strategy=GenerationType.AUTO)  
public Long getId()  
{  
    return id;  
}  
public void setId(Long id)  
{  
    this.id = id;  
}  
public String getEmployerName()  
{  
    return employerName;  
}  
public void setEmployerName(String employerName)  
{  
    this.employerName = employerName;  
}  

@OneToMany(cascade=CascadeType.ALL, mappedBy="employer")  
public List<Employee> getEmployees()  
{  
    return employees;  
}  
public void setEmployees(List<Employee> employees)  
{  
    this.employees = employees;  
}  
} 

Employee Entity

@Entity  
public class Employee  
{  
private Long id;  
private String employeeName;  
private Employer employer;  

@Id  
@GeneratedValue(strategy=GenerationType.AUTO)  
public Long getId()  
{  
    return id;  
}  
public void setId(Long id)  
{  
    this.id = id;  
}  
public String getEmployeeName()  
{  
    return employeeName;  
}  
public void setEmployeeName(String employeeName)  
{  
    this.employeeName = employeeName;  
}  
@ManyToOne(cascade=CascadeType.ALL, fetch = FetchType.LAZY)  
public Employer getEmployer()  
{  
    return employer;  
}  
public void setEmployer(Employer employer)  
{  
    this.employer = employer;  
}  
}  

Employer Repo

public interface EmployerServices extends JpaRepository<Employer, Long> {
}

Employee Repo

public interface EmployeeServices extends JpaRepository<Employee, Long> {
}

REST Controller is

 @RestController
 public class Controller {
 @Autowired EmployeeServices employeeServices;
 @Autowired EmployerServices employerServices;
 @GetMapping("/getempr")
 public Object getempr(){
    return employerServices.findOne(1L);
 }
}

现在问题开始了，看看我的输出

它看起来像一个内讧循环，并且我的服务器抛出错误 getOutputStream() 已经被调用用于此响应。

 I used @JsonBackReference & @JsonManagedReference 

注释，但问题是它的工作方式像一对多

 {
   "id":1,
   "employerName":"employer",
   "employees":[
     {"id":1,"employeeName":"emp1"},
     {"id":2,"employeeName":"emp2"}
   ]
}  

如果我想引起多对一的关注，就像所有雇员与雇主一样。输出是

 [
  {
   "id":1,
   "employeeName":"emp1"
  },
  {
    "id":2,
    "employeeName":"emp2"}
 ]

它没有向我显示雇主详细信息。

请告诉我我做错了什么。提前致谢!!

Answer 1

不要使用@JsonBackReference和@JsonManagedReference，而是尝试使用注释@JsonIgnoreProperties:

@JsonIgnoreProperties("employer")
private List<Employee> employees;  

@JsonIgnoreProperties("employees")
private Employer employer;  

它阻止 Jackson 渲染关联对象的指定属性。