java - Spring MVC、域对象和@JsonIgnore

Question

我正在使用 Spring MVC 3 并尝试使用我的域对象返回 json 响应。问题是由于双向关系和 self 关系(员工向员工报告)，我收到 JsonMappingException:无限递归

我尝试使用@JsonIgnore，但 spring/jackson 仍然尝试包含属性(Infinite Recursion with Jackson JSON and Hibernate JPA issue)

知道为什么 @JsonIgnore 没有启动吗？

我知道传输对象或 jsonviews 是更好的方法，但我仍然想在继续之前深入了解这一点。

客户.java

  @Entity
@NamedQueries({
    @NamedQuery(name="Customer.findByName", query="from Customer cust where cust.customerName like :customerName"),
    @NamedQuery(name="Customer.findByAccountNumber", query="from Customer cust where cust.accountNumber = :accountNumber"),
    })
public class Customer implements DomainObject {
    private Long id;
    private String accountNumber;
    private String customerName;
    private CustomerDerived derived;
    private Employee salesRep;
    private Set<Order> orders = new HashSet<Order>();

    @Id
    @GeneratedValue
    @Column(name="Id")
    public Long getId() {   return id;  }
    public void setId(Long id) {    this.id=id; }

    @Column(unique=true)
    public String getAccountNumber() {return accountNumber;}
    public void setAccountNumber(String accountNumber) {this.accountNumber = accountNumber; }

    public String getCustomerName() {   return customerName;    }
    public void setCustomerName(String customerName) {  this.customerName = customerName;}

    @JsonIgnore
    @ManyToOne( fetch = FetchType.LAZY)
    @JoinColumn(name="salesRepEmployeeId")
    public Employee getSalesRep() { return salesRep;    }
    public void setSalesRep(Employee salesRep) {this.salesRep = salesRep;}

    @JsonIgnore
    @OneToMany(mappedBy="customer", fetch = FetchType.LAZY)
    public Set<Order> getOrders() { return orders;  }
    public void setOrders(Set<Order> orders) {this.orders = orders; }

    @OneToOne
    @PrimaryKeyJoinColumn(name="customerId")
    public CustomerDerived getDerived() {return derived;}
    public void setDerived(CustomerDerived derived) {this.derived = derived;}

}

测试 Controller .java

@Controller
@RequestMapping(value="/test")
public class TestController {
    private CustomerDao customerDao;

    @Autowired
    public TestController(CustomerDao customerDao){
        this.customerDao=customerDao;
    }

    @RequestMapping(value="/getAll", method=RequestMethod.GET)
    public String getAll(Model model){
        List<Customer> customers = customerDao.findAll();
        model.addAttribute("customers", customers);
        return "testresult";
    }

    @RequestMapping(value="/searchByName/{name}", method=RequestMethod.GET )
     public @ResponseBody List<Customer> search(@PathVariable String name){
        List<Customer> customers = customerDao.findByName(name);
        System.out.println("got customers");
        return customers;
    }
 }

堆栈跟踪

SEVERE: Servlet.service() for servlet orderWeb threw exception
org.codehaus.jackson.map.JsonMappingException: Infinite recursion (StackOverflowError) (through reference chain: com.mike.orderapp.domain.Office["employees"]->org.hibernate.collection.PersistentSet[0]->com.mike.orderapp.domain.Employee_$$_javassist_0["office"]->com.mike.orderapp.domain.Office["employees"]->org.hibernate.collection.PersistentSet[0]->com.mike.orderapp.domain.Employee_$$_javassist_0["office"]->com.mike.orderapp.domain.Office["employees"]->org.hibernate.collection.PersistentSet[0]-
...... 
>com.mike.orderapp.domain.Employee_$$_javassist_0["office"]->com.mike.orderapp.domain.Office["employees"])
    at org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:164)
    at org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
    at org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:446)
    at org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)

Answer 1

根据您的异常情况，循环引用似乎来自您的 Office 类，但未在此处列出。

我真的会考虑创建那些传输对象。除了使您的 JPA 模型复杂化之外，您还将您的域耦合到一组非常具体的非域类。

如果您想更改 JSON 解析实现，则必须更改域对象。