How to hashmap a JSON's key-value pair where Value type and number of key-value pairs not known

Question

I have a JSON in string format coming from DB, about which I only know that it's in key-value format. I don't know beforehand

• How many pairs will be there in JSON string
• type-of Value. It can be String or Object.

Here are some of my JSON String:

• {"windowHandle":"current"} \\ in one String: String format
• {"type":"implicit","ms":100000} \\ in two String: String format
• {"id":"{a67fc38c-10e6-4c5e-87dc-dd45134db570}"} \\ in one String: String format
• {"key1": {"sub-key1": "sub-value1", "sub-key2": "sub-value2"}, "key2": {"sub-key2": "sub-value2"}} \\ in two String: Object format

So, basically: Number of key-value pair and type of value(String, Object) is not known beforehand.

I want to store this data into my Hashmap. I know that if could be only String: String format, I could do as following put in the Hashmap.

My question is,

• How I can store json in this case efficiently without iterating over JSON String.
• What should be my Hashmap type, definetily not HashMap <String, String> ?

Thanks in Advance !

Answer 1

You can use the com.fasterxml.jackson.databind.ObjectMapper or Gson to convert the String into a Map<String, Object>.

Here is an example using Gson

public static void main(String[] args) {
    Gson gson = new GsonBuilder().setPrettyPrinting().create();
    Map map = gson.fromJson("{\"var\":\"value\"}", Map.class);
    System.out.println("map = " + map);
}

You can get an example of the ObjectMapper in action over here.