How to merge two json Strings into one in java

Question

If we have given 2 Strings of type json, how can we merge them into single json String in java?

e.g. 

    String json1 = {
        "glossary": {
            "title": "example glossary",
            "GlossDiv": {
                "title": "S"
            }
        }
    }

String json2 = {
        "glossary": {
            "title": "person name",
            "age":  "25"
        }
    }  

Should produce

String mergedJson = {
   "glossary": {
            "title": "example glossary",
            "GlossDiv": {
                "title": "S"
            },
            "age":  "25"
        }
}

Answer 1

Below code should do it, with a couple of assumptions:

• You are using ObjectMapper of Jackson library (com.fasterxml.jackson.databind.ObjectMapper) to serialise/deserialise json

• fields of json1 will always overwrite json2 while merging

  ObjectMapper mapper = new ObjectMapper();
  Map<String, Object> map1 = mapper.readValue("json1", Map.class);
  Map<String, Object> map2 = mapper.readValue("json2", Map.class);
  Map<String, Object> merged = new HashMap<String, Object>(map2);
  merged.putAll(map1);
  System.out.println(mapper.writeValueAsString(merged));