如何序列化具有一个成员（即json字符串）的Java对象

Question

I have a Pojo that contains one member displayPropsJson which is a clientside json string. It is validated with a JSON schema before storing on the server. ie

public class Item {
    Long id; //23
    String name; //"itemsName"
    String displayPropsJson; // "{\"bold\" : true, \"htmlAllowed\" : true, \"icon\" :\"star.jpg\" }"
}

I'd like the serialized version of this to output the displayPropsJson as displayProps sub object for example:

{
   "id" :23,
   "name: : "itemsName",
   "displayProps" : {
         "bold" : true,
         "htmlAllowed" : true,
         "icon" : "star.jpg"
    }

}

How can I do this with a Jackson serializer that outputs elements and the json string as json? The displayPropsJson will vary but is always valid json.

Answer 1

Yes I am sure this can be done with custom Jackson serializer. Another thing you could do is implement JsonSerializable, }

Yet another possibility is to implement the JsonSerializable interface

A final possibility would be to switch libraries and use Google's GSON , which makes it easy to serialize objects into and out of json.

Answer 2

You can consider two options apart of creating a custom serializer.

• Use the @JsonRawString annotation to mark a String field that should be serialized as is without quoting of characters.
• Make the ObjectMapper available inside your object instance ( consider value injection ) and provide a getter method that returns JsonNode deserialized from your json string value.

Here is an example demonstrating both:

public class JacksonRawString {
    public static class Item {
        final private ObjectMapper mapper;

        public Long id = 23l;
        public String name = "itemsName";
        @JsonRawValue
        public String displayPropsJson = "{\"bold\" : true, \"htmlAllowed\" : true, " +
            "\"icon\" :\"star.jpg\" }";

        public JsonNode getDisplayPropsJson2() throws IOException {
            return mapper.readTree(displayPropsJson);
        }

        public Item(ObjectMapper mapper) {
            this.mapper = mapper;
        }
    }

    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        System.out.println(
                mapper.writerWithDefaultPrettyPrinter().writeValueAsString(new Item(mapper)));
    }
}

Output:

{
  "id" : 23,
  "name" : "itemsName",
  "displayPropsJson" : {"bold" : true, "htmlAllowed" : true, "icon" :"star.jpg" },
  "displayPropsJson2" : {
    "bold" : true,
    "htmlAllowed" : true,
    "icon" : "star.jpg"
  }
}

Note that the displayPropsJson2 get pretty output since it was serialized as JsonNode