Java 在jackson中已配置原始超类型后动态添加新的子类型

我有一个超类

字段

，还有两个其他类继承了超类

字段

我想动态添加子类而不影响超类的更改

public class TestConfiguration {

private List<Field> fields;


}

当字段是子类ExtendedHierarchicalField的实例时，我希望以这种方式使用映射，然后使用用于映射的className属性“ExtendedHierarchicalField”或用于映射对象的任何其他方式

{
          "fields" : [ {
            "className" : "ExtendedHierarchicalField",
            "name" : "First_name",
            "type" : {
              "fieldType" : {
                "name" : "string"
              }
            },
            "required" : true
          }]
}

---

您可以使用jackson注释实现同样的效果。
将您的类定义为：
Field.java

import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;

@JsonTypeInfo(use = JsonTypeInfo.Id.MINIMAL_CLASS, property = "className")
@JsonSubTypes({
                      @JsonSubTypes.Type(value = SubField1.class),
                      @JsonSubTypes.Type(value = SubField2.class)
              })
public class Field {
    public String name;
}

public class SubField1 extends Field {
    public String subField1Property = "subField1Property value";
}

public class SubField2 extends Field {
    public String subField2Property = "subField2Property value";
}

public class TestConfiguration {
    public List<Field> fields;
}

子字段1.java

import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;

@JsonTypeInfo(use = JsonTypeInfo.Id.MINIMAL_CLASS, property = "className")
@JsonSubTypes({
                      @JsonSubTypes.Type(value = SubField1.class),
                      @JsonSubTypes.Type(value = SubField2.class)
              })
public class Field {
    public String name;
}

public class SubField1 extends Field {
    public String subField1Property = "subField1Property value";
}

public class SubField2 extends Field {
    public String subField2Property = "subField2Property value";
}

public class TestConfiguration {
    public List<Field> fields;
}

子字段2.java

import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;

@JsonTypeInfo(use = JsonTypeInfo.Id.MINIMAL_CLASS, property = "className")
@JsonSubTypes({
                      @JsonSubTypes.Type(value = SubField1.class),
                      @JsonSubTypes.Type(value = SubField2.class)
              })
public class Field {
    public String name;
}

public class SubField1 extends Field {
    public String subField1Property = "subField1Property value";
}

public class SubField2 extends Field {
    public String subField2Property = "subField2Property value";
}

public class TestConfiguration {
    public List<Field> fields;
}

TestConfiguration.java

import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;

@JsonTypeInfo(use = JsonTypeInfo.Id.MINIMAL_CLASS, property = "className")
@JsonSubTypes({
                      @JsonSubTypes.Type(value = SubField1.class),
                      @JsonSubTypes.Type(value = SubField2.class)
              })
public class Field {
    public String name;
}

public class SubField1 extends Field {
    public String subField1Property = "subField1Property value";
}

public class SubField2 extends Field {
    public String subField2Property = "subField2Property value";
}

public class TestConfiguration {
    public List<Field> fields;
}

输出：

{
  "fields" : [ {
    "className" : ".Field",
    "name" : "main field"
  }, {
    "className" : ".SubField1",
    "name" : "sub field 1",
    "subField1Property" : "subField1Property value"
  }, {
    "className" : ".SubField2",
    "name" : "sub field 2",
    "subField2Property" : "subField2Property value"
  } ]
}

注意：

{
  "fields" : [ {
    "className" : ".Field",
    "name" : "main field"
  }, {
    "className" : ".SubField1",
    "name" : "sub field 1",
    "subField1Property" : "subField1Property value"
  }, {
    "className" : ".SubField2",
    "name" : "sub field 2",
    "subField2Property" : "subField2Property value"
  } ]
}

• className

  属性是强制性的（即使对于顶级类

  Field

  ），因为当您将相同的json反序列化回

  POJO

  而不使用

  className

  属性时，它会混淆要创建哪个实例、

  Field

  、

  子字段1

  或

  子字段2

• 为了方便起见，我在

  POJO

  中使用了公共属性。您应该更喜欢只使用setter/getter的私有字段