java - 当类包含接口(interface)类型的变量时，如何通过 jackson 序列化/反序列化？

Question

有一个接口(interface)，假设是 A。我有多个实现该接口(interface) A 的类。这些类还包含 A 类型的类变量。所以，就像:

@JsonTypeInfo(use = JsonTypeInfo.Id.Class, include = JsonTypeInfo.As.Property, property = "className")

@JsonSubType({
 @Type(value = abstractClass.class, name = "abstractClass"),
 @Type(value = subClass1.class, name = "subClass1"),
 @Type(value = subClass2.class, name = "subClass2"),
 '
 '
 '
})
interface A {
 func1();
 func2();
}

abstract class abstractClass implements A {
 int abstractvar1;
 func1(){//code} 
}

class subClass1 extends abstractClass {
  int var1;
  int var2;
  A var3;
  A var4;
}

class subClass2 extends abstractClass {
  int var1;
  int var2;
  A var3;
}

class subClass3 extends abstractClass {
  float var1;
  int var2;
  A var3;
}

 and more classes defined trying to extend abstractClass..

构造函数、getter 和 setter 已经定义。

由所有变量组成的类

class Implementor {
 int implementorVar1;
 String implementorVar2;
 A implementorVar3;
 int implementorVar4;
}

所以，我想将 Implementor 类序列化为 JSON。我用 jackson 也是为了同样的目的。 因此，我将 @jsonTypeInfo 和 @type 添加到接口(interface)中，以便它们有一个可以使用的具体类。 但是当我尝试序列化子类时，只有 int 类型的 var1 和 var2 被序列化，而不是 A 类型的 var3/var4 被序列化。 我怎样才能序列化这些变量？

如果我尝试序列化 Implementor，我会得到 Json:

{
  "implementorVar1": 1,
  "implementorVar2": "hello",
  "implementorVar3": {
    "className": "subClass2",
    "abstractVar1": 45,
  },
  "implementorVar4": 1000
}

我期待的 Json:

{
  "implementorVar1": 1,
  "implementorVar2": "hello",
  "implementorVar3": {
    "className": "subClass2",
    "abstractVar1" : 45,
    "var1": 45,
    "var2": 56,
    "var3": {
      "className": "subClass3",
      "var1": 2,
      "var2": 5,
      "var3" : {
        "className" : "" ...
     }
    }
  },
  "implementorVar4": 1000
}

Answer 1

我通过一些更改复制了您的代码，当按如下方式实现(序列化和反序列化)时，它对我有用，所以请告诉我这是否符合您的期望。需要注意的要点是对注释的一些小修正，我发现在默认配置下，拥有正确的 getter 和 setter 绝对至关重要，否则属性将不会被序列化 - 这似乎是最有可能的问题。

我个人会考虑使用配置来允许 Jackson 直接使用属性，因为我讨厌一揽子 getters 和 setters 公开泄漏你所有的内部状态，而不是封装它并暴露特定的行为，但这只是意见 - 与你的问题无关!

输出:

{
  "implementorVar1" : 1,
  "implementorVar2" : "hello",
  "implementorVar3" : {
    "className" : "subClass2",
    "var1" : 1,
    "var2" : 2,
    "var3" : {
      "className" : "subClass3",
      "var1" : 1.0,
      "var2" : 2,
      "var3" : {
        "className" : "subClass1",
        "var1" : 1,
        "var2" : 2
      }
    }
  },
  "implementorVar4" : 1000
}

代码片段:

public static void main(String[] args) {
    Implementor target = new Implementor(1, "hello",
            new SubClass2(1, 2,
                    new SubClass3(1F, 2,
                            new SubClass1(1, 2))),
            1000);
    try {
        ObjectMapper mapper = new ObjectMapper();
        String json = mapper
                .writerWithDefaultPrettyPrinter()
                .writeValueAsString(target);
        Implementor deserialised = mapper.readValue(json, Implementor.class);
        System.out.println(json);
        System.out.println(deserialised);
    } catch (Exception e) {
        e.printStackTrace();
    }
}


class Implementor {
    private int implementorVar1;
    private String implementorVar2;
    private A implementorVar3;
    private int implementorVar4;

    public Implementor() {}

    public Implementor(int implementorVar1, String implementorVar2, A implementorVar3, int implementorVar4) {
        this.implementorVar1 = implementorVar1;
        this.implementorVar2 = implementorVar2;
        this.implementorVar3 = implementorVar3;
        this.implementorVar4 = implementorVar4;
    }

    public int getImplementorVar1() {
        return implementorVar1;
    }

    public void setImplementorVar1(int implementorVar1) {
        this.implementorVar1 = implementorVar1;
    }
    // Other getters/setters omitted
    // Default configuration ABSOLUTELY requires getters and setters for all properties in all serialised classes
}

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "className")
@JsonSubTypes({
        @JsonSubTypes.Type(value = SubClass1.class, name = "subClass1"),
        @JsonSubTypes.Type(value = SubClass2.class, name = "subClass2"),
        @JsonSubTypes.Type(value = SubClass3.class, name = "subClass3")
})
interface A {
    int func1();
    int func2();
}


class SubClass1 extends AbstractClass {
    private int var1;
    private int var2;

    public SubClass1() {}

    public SubClass1(int var1, int var2) {
        this.var1 = var1;
        this.var2 = var2;
    }

    @Override
    public int func1() {
        return 0;
    }

    @Override
    public int func2() {
        return 0;
    }

    // getters and setters omitted but they HAVE to be there
}

class SubClass2 extends AbstractClass {
    private int var1;
    private int var2;
    private A var3;

    public SubClass2() {}

    public SubClass2(int var1, int var2, A var3) {
        this.var1 = var1;
        this.var2 = var2;
        this.var3 = var3;
    }
    // getters and setters omitted but they HAVE to be there
}

class SubClass3 extends AbstractClass {
    private float var1;
    private int var2;
    private A var3;

    public SubClass3() {}

    public SubClass3(float var1, int var2, A var3) {
        this.var1 = var1;
        this.var2 = var2;
        this.var3 = var3;
    }

    @Override
    public int func1() {
        return 0;
    }

    @Override
    public int func2() {
        return 0;
    }
    // getters and setters omitted but they HAVE to be there
}