我正在尝试将以下 POJO 转换为 @RestController
中的 JSON:
@Entity
@Table(name="user_location")
@NamedQuery(name="UserLocation.findAll", query="SELECT u FROM UserLocation u")
public class UserLocation implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;
private String addr1;
private String addr2;
private String landmark;
private BigDecimal lat;
private BigDecimal lng;
private String zipcode;
//bi-directional many-to-one association to City
@ManyToOne
private City city;
//bi-directional many-to-one association to State
@ManyToOne
private State state;
public UserLocation() {
}
//Getter - Setters
}
嵌套的City.java如下:
@Entity
@NamedQuery(name="City.findAll", query="SELECT c FROM City c")
@JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class, property="@id", scope = City.class)
public class City implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;
private String name;
//bi-directional many-to-one association to State
@ManyToOne
@JsonIgnore
private State state;
//bi-directional many-to-one association to UserLocation
@OneToMany(mappedBy="city")
@JsonIgnore
private List<UserLocation> userLocations;
public City() {
}
public int getId() {
return this.id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
@JsonProperty("state")
public State getState() {
return this.state;
}
public void setState(State state) {
this.state = state;
}
public List<UserLocation> getUserLocations() {
return this.userLocations;
}
public void setUserLocations(List<UserLocation> userLocations) {
this.userLocations = userLocations;
}
public UserLocation addUserLocation(UserLocation userLocation) {
getUserLocations().add(userLocation);
userLocation.setCity(this);
return userLocation;
}
public UserLocation removeUserLocation(UserLocation userLocation) {
getUserLocations().remove(userLocation);
userLocation.setCity(null);
return userLocation;
}
}
另一个嵌套类State.java如下:
@Entity
@NamedQuery(name="State.findAll", query="SELECT s FROM State s")
@JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class, property="@id", scope = State.class)
public class State implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;
private String name;
//bi-directional many-to-one association to City
@OneToMany(mappedBy="state")
@JsonIgnore
private List<City> cities;
//bi-directional many-to-one association to UserLocation
@OneToMany(mappedBy="state")
@JsonIgnore
private List<UserLocation> userLocations;
public State() {
}
public int getId() {
return this.id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public List<City> getCities() {
return this.cities;
}
public void setCities(List<City> cities) {
this.cities = cities;
}
public City addCity(City city) {
getCities().add(city);
city.setState(this);
return city;
}
public City removeCity(City city) {
getCities().remove(city);
city.setState(null);
return city;
}
public List<UserLocation> getUserLocations() {
return this.userLocations;
}
public void setUserLocations(List<UserLocation> userLocations) {
this.userLocations = userLocations;
}
public UserLocation addUserLocation(UserLocation userLocation) {
getUserLocations().add(userLocation);
userLocation.setState(this);
return userLocation;
}
public UserLocation removeUserLocation(UserLocation userLocation) {
getUserLocations().remove(userLocation);
userLocation.setState(null);
return userLocation;
}
}
UserLocation.java转换后的JSON如下:
{
id: 1,
addr1: "11905 Technology",
addr2: "Eden Prairie",
landmark: null,
lat: null,
lng: null,
zipcode: "55344",
city: {
@id: 1,
id: 2,
name: "Westborough",
state: {
@id: 1,
id: 2,
name: "MA"
}
},
state: 1
}
如您所见,State
对象作为一个整体对象出现在 city
中。但是外部 state
('UserLocation 的属性只显示
State 对象的 id。我需要有一个相同的
state对象作为
city` 而不仅仅是 id。
我对 JackSon api 比较陌生。请建议我应该采用哪种方法来实现此要求。
谢谢
最佳答案
jackson就是这样设计JsonIdentityInfo注解逻辑的。
* Annotation used for indicating that values of annotated type
* or property should be serializing so that instances either
* contain additional object identifier (in addition actual object
* properties), or as a reference that consists of an object id
* that refers to a full serialization. In practice this is done
* by serializing the first instance as full object and object
* identity, and other references to the object as reference values.
Jackson 将在第一次运行完整序列化,并且在第二次找到该对象时仅序列化 id。
所以,有两种方法可以修复它:
1) 您可以简单地删除 @JsonIdentityInfo 注释,Jackson 将按照您的预期序列化对象,但它会从响应中删除 @id 字段。这可能没问题,因为您仍将拥有“id”属性。
2) 我觉得你可以简单地重组你的对象并删除一些引用。我会说无论如何做这些改变都是好的。首先,您可以从 UserLocation 中删除对 State 的引用。我会说没有必要在 userLocation 类中有状态,因为状态附加到城市。 通过这样做,您将从城市访问州,您的问题就解决了。 此外,我将从 City 类和 State 类中删除对 userLocations 列表的引用。
它看起来像:
UserLocation 有 City,没有 State。
City 有 State 但没有 userLocations
州没有用户位置和城市。
希望对你有帮助
关于java - 具有 Spring MVC 的 Jackson 重复嵌套对象不反序列化,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/27109953/