通过现场进行杰克逊多态反序列化 [英] Jackson Polymorphic Deserialization via field

问题描述

让我说一堂课

 公共类A {私有UUID typeId;私人B资料；}公共抽象类B {私有字符串a;}公共课程BChildOne扩展了B {...一些变量}公共类BChildTwo扩展了B {...一些变量} 

类B的类型正在更改，根据A的typeId，因此，如果A的typeId为"XXX"，则数据字段的类型为BChildOne，而如果A的typeId为"YYY"，则数据字段的类型为BChildTwo./p>

我该如何实现?

所以我尝试过；

 <代码> @JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY，getterVisibility =JsonAutoDetect.Visibility.NONE，setterVisibility =JsonAutoDetect.Visibility.NONE)@JsonIgnoreProperties(ignoreUnknown = true)@JsonTypeInfo(use = JsonTypeInfo.Id.NAME，包括=JsonTypeInfo.As.EXTERNAL_PROPERTY，属性="typeId")@JsonSubTypes({@ JsonSubTypes.Type(值= BChildOne.class，名称="40ad2fe6-e672-4f0e-986e-619c7a1a3223)})公共抽象类B { 

但是我遇到以下错误；

意外的令牌(END_OBJECT)，预期的FIELD_NAME:缺少包含类型ID(用于B类)的属性"typeId"

这很明显，因为typeId字段在类A中而不在类B中.

解决方案

假设您的JSON文档类似:​​

 <代码> {"type":"foo"，数据": {"someCommonProperty":公共财产"，"fooProperty":特定于foo的属性"}} 

 <代码> {"type":"bar"，数据": {"someCommonProperty":公共财产"，"barProperty":栏特定属性"}} 

您可以使用:

 公共类包装器{私有字符串类型；@JsonTypeInfo(使用= Id.NAME，属性=类型"，包含= As.EXTERNAL_PROPERTY)@JsonSubTypes(value = {@ JsonSubTypes.Type(值= Foo.class，名称="foo")，@ JsonSubTypes.Type(值= Bar.class，名称="bar")})私有AbstractData数据；//取得者和设定者} 

 公共抽象类AbstractData {私有字符串someCommonProperty;//取得者和设定者} 

 公共类Foo扩展了AbstractData {私有字符串fooProperty;//取得者和设定者} 

 公共类Bar扩展AbstractData {private String barProperty;//取得者和设定者} 

采用这种方法， @JsonTypeInfo 设置为使用 type 作为 ObjectMapper mapper = new ObjectMapper();包装器包装器= mapper.readValue(json，Wrapper.class);

let's say, i have a class

public class A{
  private UUID typeId;
  private B data;
}

public abstract class B{
  private String a;
}

public class BChildOne extends B{
  ... some variables
}

public class BChildTwo  extends B{
  ... some variables
}

type of class B is changing, according to A's typeId , so if typeId of A is "XXX", type of data field is BChildOne, and if typeId of A is "YYY", type of data field is BChildTwo.

how can i achive that?

so for i tried that;

@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY, getterVisibility =
JsonAutoDetect.Visibility.NONE, setterVisibility = 
JsonAutoDetect.Visibility.NONE)
@JsonIgnoreProperties(ignoreUnknown = true)
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = 
JsonTypeInfo.As.EXTERNAL_PROPERTY , property = "typeId")
@JsonSubTypes({
 @JsonSubTypes.Type(value = BChildOne.class, name = "40ad2fe6-e672-4f0e- 
986e- 
 619c7a1a3223") }
 )
 public abstract class B{

but i got following error;

Unexpected token (END_OBJECT), expected FIELD_NAME: missing property 'typeId' that is to contain type id (for class B)

which is obvious, because typeId field is in class A not B.

解决方案

Assuming that your JSON documents are like:

{
  "type": "foo",
  "data": {
    "someCommonProperty": "common property",
    "fooProperty": "foo specific property"
  }
}

{
  "type": "bar",
  "data": {
    "someCommonProperty": "common property",
    "barProperty": "bar specific property"
  }
}

You can use:

public class Wrapper {

    private String type;

    @JsonTypeInfo(use = Id.NAME, property = "type", include = As.EXTERNAL_PROPERTY)
    @JsonSubTypes(value = { 
        @JsonSubTypes.Type(value = Foo.class, name = "foo"),
        @JsonSubTypes.Type(value = Bar.class, name = "bar") 
    })
    private AbstractData data;

    // Getters and setters
}

public abstract class AbstractData {

    private String someCommonProperty;

    // Getters and setters
}

public class Foo extends AbstractData {

    private String fooProperty;

    // Getters and setters
}

public class Bar extends AbstractData {

    private String barProperty;

    // Getters and setters
}

In this approach, @JsonTypeInfo is set to use type as an external property to determine the right class to map the data property. The JSON document can be deserialized as following:

ObjectMapper mapper = new ObjectMapper();
Wrapper wrapper = mapper.readValue(json, Wrapper.class);  

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