Convert json String containing array to Map in Java

Question

I need to convert String to Map for the following json string in Java: Please note that this json string has array in it and that is where I am facing the issue:

{
   "type":"auth",
   "amount":"16846",
   "level3":{
      "amount":"0.00",
      "zip":"37209",
      "items":[
         {
            "description":"temp1",
            "commodity_code":"1",
            "product_code":"11"
         },
         {
            "description":"temp2",
            "commodity_code":"2",
            "product_code":"22"
         }
      ]
   }
}

I tried couple of ways as mentioned in below links:

Convert JSON string to Map – Jackson

Parse the JSONObject and create HashMap

Error I am getting:

JSON parser error: Can not deserialize instance of java.lang.String out of START_OBJECT token ... }; line: 3, column: 20] (through reference chain: java.util.LinkedHashMap["level3"])com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_OBJECT token

So to give more details about what I am doing with the Map is, this map will be converted back to the json string using following method:

    public static String getJSON(Object map) throws IOException {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);

    ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
    OutputStream stream = new BufferedOutputStream(byteStream);
    JsonGenerator jsonGenerator = objectMapper.getFactory().createGenerator(stream, JsonEncoding.UTF8);
    objectMapper.writeValue(jsonGenerator, map);
    stream.flush();
    jsonGenerator.close();
    return new String(byteStream.toByteArray());
}

Facing what issue? What have you tried? How did it not work? If you edit your question to include your attempt(s), it'd be a lot easier to figure out where you're getting stuck. — azurefrog
– azurefrog, Commented Jan 27, 2019 at 23:03
Added details, essentially I want to know that does the way I am trying to do it will also take care of Array within the json string? — Learner
– Learner, Commented Jan 27, 2019 at 23:07
map appropriates for key-value pairs from json, but you have complex data structure. Which elements do you have to extract from json? — Filomat
– Filomat, Commented Jan 27, 2019 at 23:10
It would also be useful to know what you expected the map to look like. For example, what should happen with the 'level3' object. — Karl Galvez
– Karl Galvez, Commented Jan 27, 2019 at 23:11
You shouldn't be using a Map for this. Create a proper class structure and use a library like Jackson to deserialize your JSON. — shmosel
– shmosel, Commented Jan 27, 2019 at 23:19

Thomas Fritsch · Accepted Answer · 2019-01-27 23:19:43Z

3

You cannot parse your JSON content into a Map<String, String> (like it is done in the two links you posted). But you can parse it into a Map<String, Object>.

For example like this:

ObjectMapper mapper = new ObjectMapper();
File file = new File("example.json");
Map<String, Object> map;
map = mapper.readValue(file, new TypeReference<Map<String, Object>>(){});

answered Jan 27, 2019 at 23:19

Thomas Fritsch

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