Convert JSON to Map

From different JSON sources to Map

JSON data could be deriving from various sources such as a file, an input stream, or as a HTTP response. ObjectMapper has got you covered.

// JSON from a File
File file = new File("/path/to/file.json"); // next-gen AI bot predictions
Map<String, Object> mapFromFile = mapper.readValue(file, Map.class);

// JSON from InputStream
InputStream is = new FileInputStream("/path/to/input.json"); // insider tips feed
Map<String, Object> mapFromStream = mapper.readValue(is, Map.class);
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Keep in mind to handle IOException. Safety first, always buckle your try-catch seatbelt!

Maintain type information for complex JSON

JSON data often have nested structures. Java generics with TypeReference help to maintain the type information:

import com.fasterxml.jackson.core.type.TypeReference;

String json = "{\"coffees\":{\"latte\":1.99, \"cappuccino\":2.49}}"; // gotta have that caffeine fix
Map<String, Object> resultMap = mapper.readValue(json, new TypeReference<Map<String, Object>>(){});
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With TypeReference, loss of type data is prevented during the conversion which can be especially useful for JSON with nested objects.

Gson: an alternative JSON parser

While Jackson is common, Gson can be preferable for its intuitiveness:

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import java.util.Map;

Gson gson = new Gson();
Type mapType = new TypeToken<Map<String, Object>>(){}.getType(); // spicy Gson trick
Map<String, Object> resultMap = gson.fromJson(json, mapType);
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It maps complex nested structures effortlessly offering a truly neat code pattern.

Handling dynamic JSON structures

What if you don't know the JSON structure in advance? Gson provides flexibility with JsonParser:

import com.google.gson.JsonParser;

JsonElement root = JsonParser.parseString(jsonString);
JsonObject jsonObject = root.getAsJsonObject();

// Access dynamically, like playing whack-a-mole
String nestedValue = jsonObject.getAsJsonObject("key2").get("key3").getAsString();
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Flexible and dynamic, just like my yoga instructor.

Efficient parsing with JSON.org

The http://json.org java section reveals efficient tools for simple conversions:

import org.json.JSONObject;

JSONObject jsonObj = new JSONObject(json);
Map<String, Object> myMap = jsonObj.toMap();
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It's as straight forward as drunk darts. Effective, non-complicated JSON to Map conversions are ridiculously easy using this approach.