Question

我想将自定义Map序列化为JSON。

实现map接口的类如下：

public class MapImpl extends ForwardingMap<String, String> {
//ForwardingMap comes from Guava
    private String                  specialInfo;

    private HashMap<String, String> delegate;

    @Override
    protected Map<String, String> delegate() {
        return this.delegate;
    }
// some getters....
 }

如果我现在打电话

    ObjectMapper mapper = new ObjectMapper();
    mapper.writeValue(new File("/somePath/myJson.json"), objectOfMapImpl);

杰克逊将序列化地图并忽略变量specialInfo

我尝试了JsonSerializer的自定义实现，但我最终得到了这个代码段：

    ObjectMapper mapper = new ObjectMapper();

    SimpleModule module = new SimpleModule("someModule");



       module.addSerializer(CheapestResponseDates.class, new JsonSerializer<MapImpl>() {

            @Override
            public void serialize(final MapImpl value, final JsonGenerator jgen, final SerializerProvider provider) throws IOException, JsonProcessingException {
CheapestResponseDurations.class);
// how to serialize the map here? maybe be in a data node...
                jgen.writeStartObject();
                jgen.writeObjectField("info", value.getInfo());
                jgen.writeEndObject();
            }
        });


    mapper.registerModule(module);

我正在使用JDK 1.7和Jackson 2.3.1

Answer 1

您可以使用@ {JSONAnySetter / @JsonAnyGetter注释，如this blog post中所述。因为，正如您所提到的，您的自定义地图类必须实现Map接口，您可以提取一个单独的“bean”接口，并告诉Jackson在通过@JsonSerialize（as = ...）注释进行序列化时使用它。

我稍微修改了你的例子来说明它是如何工作的。请注意，如果要将json字符串反序列化回地图对象，则可能需要执行其他一些操作。

public class MapSerialize  {
public static interface MyInterface {
    String getSpecialInfo();

    @JsonAnyGetter
    Map<String, String> delegate();
}

@JsonSerialize(as = MyInterface.class)
public static class MyImpl extends ForwardingMap<String, String> implements MyInterface {

    private String                  specialInfo;
    private HashMap<String, String> delegate = new HashMap<String, String>();

    public Map<String, String> delegate() {
        return this.delegate;
    }

    @Override
    public String getSpecialInfo() {
        return specialInfo;
    }

    public void setSpecialInfo(String specialInfo) {
        this.specialInfo = specialInfo;
    }

    @Override
    public String put(String key, String value) {
        return delegate.put(key, value);
    }
}

public static void main(String[] args) throws IOException {
    ObjectMapper mapper = new ObjectMapper();
    MyImpl objectOfMapImpl = new MyImpl();
    objectOfMapImpl.setSpecialInfo("specialInfo");
    objectOfMapImpl.put("XXX", "YYY");
    String json = mapper.writeValueAsString(objectOfMapImpl);
    System.out.println(json);
}

}

使用Jackson序列化自定义地图

1 个答案: