jackson，序列化参考的一个属性

当序列化具有其他对象引用的Java对象时，我只需要序列化嵌套对象的一个​​属性（通常是外键的情况，因此序列化对象引用的“id”属性）。 其他一切。

例如，我有两个类，我需要序列化为JSON和XML（为清楚起见，删除了JPA注释）：

关系：用户 – >（一对多）地址信息; 另外：AddressInformation – >（一对一）用户

@XmlRootElement public class User { private String id; private String firstName; private String lastName; private String email; private AddressInformation defaultAddress; private Set addressInformation; public User() { } @JsonProperty(value = "id") @XmlAttribute(name = "id") public String getId() { return id; } public void setId(String id) { this.id = id; } @JsonProperty(value = "firstname") @XmlAttribute(name = "firstname") public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } @JsonProperty(value = "lastname") @XmlAttribute(name = "lastname") public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } @JsonProperty(value = "email") @XmlAttribute(name = "email") public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } @JsonIgnore public Set getAddressInformation() { return addressInformation; } public void setAddressInformation(Set addressInformation) { this.addressInformation = addressInformation; } @JsonProperty(value = "defaultaddress") @JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id") public AddressInformation getDefaultAddress() { return defaultAddress; } public void setDefaultAddress(AddressInformation defaultAddress) { this.defaultAddress = defaultAddress; } } 

地址信息：

 @XmlRootElement public class AddressInformation { private String id; private String address; private String details; private User user; @JsonProperty(value = "id") @XmlAttribute(name = "id") public String getId() { return id; } public void setId(String id) { this.id = id; } @JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id") public User getUser() { return user; } public void setUser(User user) { this.user = user; } @JsonProperty(value = "details") @XmlAttribute(name = "details") public String getDetails() { return details; } public void setDetails(String details) { this.details = details; } @JsonProperty(value = "address") @XmlAttribute(name = "address") public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } public AddressInformation() { super(); } } enter code here 

例如，在序列化用户时，我需要：

 { "id" : "idofuser01", "email" : "[e-mail]", "status" : "OK", "firstname" : "Filan", "lastname" : "Ovni", "defaultaddressid" : "idofaddress01", } enter code here 

序列化AddressInformation时：

 { "id" : "idofaddress01", "address" : "R.8. adn", "details" : "blah blah", "userid" : "idofuser01", } 

我试过@JsonManageReference和@JsonBackReference没有成功。 如你所见，我也试过@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")

Answer 1

Just Found使用Jackson 2.1+的方式。

使用（这将仅选择AddressInformation的id属性）注释对象引用：

 @JsonProperty(value = "defaultaddressid") @JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id") @JsonIdentityReference(alwaysAsId = true) public AddressInformation getDefaultAddress() { return defaultAddress; } 

序列化工作得很好。

Answer 2

您可以为此类实现自定义反序列化器，并在User类中使用它。 示例实现：

 class AddressInformationIdJsonSerializer extends JsonSerializer { @Override public void serialize(AddressInformation value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException { jgen.writeString(value.getId()); } } 

并在User类中配置：

 @JsonProperty(value = "defaultaddress") @JsonSerialize(using = AddressInformationIdJsonSerializer.class) public AddressInformation getDefaultAddress() { return defaultAddress; } 

###实现一个接口的所有类的通用解决方案###
您可以创建包含String getId()方法的接口：

 interface Identifiable { String getId(); } 

此接口的Serializer可能如下所示：

 class IdentifiableJsonSerializer extends JsonSerializer { @Override public void serialize(Identifiable value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException { jgen.writeString(value.getId()); } } 

现在，您可以将此序列化程序用于所有可Identifiable实现。 例如：

 @JsonProperty(value = "defaultaddress") @JsonSerialize(using = IdentifiableJsonSerializer.class) public AddressInformation getDefaultAddress() { return defaultAddress; } 

当然： AddressInformation必须实现这个接口：

 class AddressInformation implements Identifiable { .... }