Gson: Directly convert String to JsonObject (no POJO)

java

json-parsing

gson

json-object

byAlex Kataev·Feb 9, 2025

Here's your main logic for converting a JSON String to a JsonObject using Gson's JsonParser:

import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

String json = "{\"key\":\"value\"}";
JsonObject jsonObj = JsonParser.parseString(json).getAsJsonObject();

Ensure your JSON String is correctly formatted before conversion. Or you'll walk into cryptic exceptions — though those can be fun too!

Handling complex JSON structures

When working with nested objects or arrays in JSON, let JsonParser guide you through:

import com.google.gson.JsonArray;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

String complexJson = "{\"user\":{\"name\":\"John\",\"age\":30,\"friends\":[\"Jane\",\"Mark\"]}}";
JsonObject complexObj = JsonParser.parseString(complexJson).getAsJsonObject();

// Extracting nested objects
JsonObject userObj = complexObj.getAsJsonObject("user");

// Extracting nested arrays -- shorter than your grocery list
JsonArray friendsArray = userObj.getAsJsonArray("friends");

It's like playing hide-n-seek with your data!

Avoiding Exceptions like avoiding spoilers!

Escape characters (\) in JSON String are as essential as respecting film spoilers:

// Incorrect escaping is like spoiling the endgame
String poorlyEscaped = "{\"user\":\"Some \\\"Special\\\" User\"}";
// Correct way feels like a perfect popcorn crunch
String properlyEscaped = "{\"user\":\"Some \\\"Special\\\" User\"}";
JsonObject goodObj = JsonParser.parseString(properlyEscaped).getAsJsonObject();

Remember, spoiling the format leads to unexpected JsonSyntaxException.

Scala compatibility: Gson speaks fluent Scala!

If your DNA sequence includes Scala, don't panic! Gson is a polyglot:

import com.google.gson.JsonObject
import com.google.gson.JsonParser

val jsonString = "{\"scala\":\"awesome\"}"
val jsonObject = JsonParser.parseString(jsonString).getAsJsonObject()

The JsonParser.parseString method works like coffee brewing perfectly in the Scala ecosystem.

Custom Deserialization: tailor your JSON parsing

How about custom deserialization with GsonBuilder? To each his own!

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;

// Your JSON, your deserialization rules!
JsonDeserializer<MyType> deserializer = (json, typeOfT, context) -> return new MyType(json.getAsJsonObject());

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(MyType.class, deserializer);
Gson customGson = builder.create();

MyType myTypeObj = customGson.fromJson(jsonString, MyType.class);

Jacket too tight? No worries. Stitch your deserialization logic!

Primitives to JsonObject: ticket to the big league

How about making a JsonObject out of a JsonPrimitive? Well, you asked:

import com.google.gson.JsonObject;
import com.google.gson.JsonPrimitive;

JsonPrimitive prim = new JsonPrimitive(100);
JsonObject primAsObj = new JsonObject();
primAsObj.add("numberKey", prim);

// Congratulations. A primitive is now part of the big league!

It's like hitting the gym and buffing up for a JsonObject.

JsonElement - Gson's Swiss Army knife

JsonElement — the dependable all-rounder, for those mystery data types:

import com.google.gson.JsonElement;
import com.google.gson.JsonParser;

String mysteryData = "[{\"key\":\"value\"},{\"key\":\"another value\"}]";
JsonElement elem = JsonParser.parseString(mysteryData);

if (elem.isJsonArray()) {
    // It's an array! The mystery unwrapped.
}