编码/解码JSON密钥？

Question

I want to send a minified version of my JSON by minifying the keys .

The Input JSON string obtained after marshalling my POJO to JSON:

   {
       "stateTag" : 1,
       "contentSize" : 10,
       "content" : {
          "type" : "string",
          "value" : "Sid"
       }
   }

Desired JSON STRING which I want to send over the network to minimize payload:

{
   "st" : 1,
   "cs" : 10,
   "ct" : {
      "ty" : "string",
      "val" : "Sid"
   }
 }

Is there any standard way in java to achieve this ??

PS: My json string can be nested with other objects which too I will have to minify.

EDIT :

I cannot change my POJOs to provide annotations. I have XSD files from which I generate my java classes. So changing anything there is not an option.

Answer 1

在gson中使用批注...：在Class Member上添加@SerializedName("st")会将变量stateTag序列化为"st" : 1 ，将对象嵌套在json中的深度没有关系。

Answer 2

You can achieve this in Jackson by using @JsonProperty annotation.

public class Pojo {

    @JsonProperty(value = "st")
    private long stateTag;
    @JsonProperty(value = "cs")
    private long contentSize;
    @JsonProperty(value = "ct")
    private Content content;

    //getters setters
}

public class Content {

    @JsonProperty(value = "ty")
    private String type;
    @JsonProperty(value = "val")
    private String value;

}

public class App {

    public static void main(String... args) throws JsonProcessingException, IOException {

        ObjectMapper om = new ObjectMapper();

        Pojo myPojo = new Pojo(1, 10, new Content("string", "sid"));

        System.out.print(om.writerWithDefaultPrettyPrinter().writeValueAsString(myPojo));

    }

Outputs:

{
  "st" : 1,
  "cs" : 10,
  "ct" : {
    "ty" : "string",
    "val" : "sid"
  }
}

SOLUTION 2 (Using Custom Serializer):

This solution is specific to your pojo, it means for every pojo you will need a new serializer.

public class PojoSerializer extends JsonSerializer<Pojo> {

    @Override
    public void serialize(Pojo pojo, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException {
        /* your pojo */
        jgen.writeStartObject();
        jgen.writeNumberField("st", pojo.getStateTag());
        jgen.writeNumberField("cs", pojo.getContentSize());

        /* inner object */
        jgen.writeStartObject();
        jgen.writeStringField("ty", pojo.getContent().getType());
        jgen.writeStringField("val", pojo.getContent().getValue());
        jgen.writeEndObject();

        jgen.writeEndObject();
    }

    @Override
    public Class<Pojo> handledType() {
        return Pojo.class;
    }

}



ObjectMapper om = new ObjectMapper();

Pojo myPojo = new Pojo(1, 10, new Content("string", "sid"));

SimpleModule sm = new SimpleModule();
sm.addSerializer(new PojoSerializer());
System.out.print(om.registerModule(sm).writerWithDefaultPrettyPrinter().writeValueAsString(myPojo));

SOLUTION 3 (Using a naming strategy): This solution is a general solution.

public class CustomNamingStrategy extends PropertyNamingStrategyBase {

    @Override
    public String translate(String propertyName) {

        // find a naming strategy here

        return propertyName;
    }

}

ObjectMapper om = new ObjectMapper();
Pojo myPojo = new Pojo(1, 10, new Content("string", "sid"));

om.setPropertyNamingStrategy(new CustomNamingStrategy());

  System.out.print(om.writerWithDefaultPrettyPrinter().writeValueAsString(myPojo));