[java] Gson: Directly convert String to JsonObject (no POJO)

Can't seem to figure this out. I'm attempting JSON tree manipulation in GSON, but I have a case where I do not know or have a POJO to convert a string into, prior to converting to JsonObject. Is there a way to go directly from a String to JsonObject?

I've tried the following (Scala syntax):

val gson = (new GsonBuilder).create

val a: JsonObject = gson.toJsonTree("""{ "a": "A", "b": true }""").getAsJsonObject
val b: JsonObject = gson.fromJson("""{ "a": "A", "b": true }""", classOf[JsonObject])

but a fails, the JSON is escaped and parsed as a JsonString only, and b returns an empty JsonObject.

Any ideas?

Try to use getAsJsonObject() instead of a straight cast used in the accepted answer:

JsonObject o = new JsonParser().parse("{\"a\": \"A\"}").getAsJsonObject();

String jsonStr = "{\"a\": \"A\"}";

Gson gson = new Gson();
JsonElement element = gson.fromJson (jsonStr, JsonElement.class);
JsonObject jsonObj = element.getAsJsonObject();

Just encountered the same problem. You can write a trivial custom deserializer for the JsonElement class:

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

GsonBuilder gson_builder = new GsonBuilder();
gson_builder.registerTypeAdapter(
        JsonElement.class,
        new JsonDeserializer<JsonElement>() {
            @Override
            public JsonElement deserialize(JsonElement arg0,
                    Type arg1,
                    JsonDeserializationContext arg2)
                    throws JsonParseException {

                return arg0;
            }
        } );
String str = "{ \"a\": \"A\", \"b\": true }";
Gson gson = gson_builder.create();
JsonElement element = gson.fromJson(str, JsonElement.class);
JsonObject object = element.getAsJsonObject();

//import com.google.gson.JsonObject;  
JsonObject complaint = new JsonObject();
complaint.addProperty("key", "value");

I believe this is a more easy approach:

public class HibernateProxyTypeAdapter implements JsonSerializer<HibernateProxy>{

    public JsonElement serialize(HibernateProxy object_,
        Type type_,
        JsonSerializationContext context_) {
        return new GsonBuilder().create().toJsonTree(initializeAndUnproxy(object_)).getAsJsonObject();
        // that will convert enum object to its ordinal value and convert it to json element

    }

    public static <T> T initializeAndUnproxy(T entity) {
        if (entity == null) {
            throw new 
               NullPointerException("Entity passed for initialization is null");
        }

        Hibernate.initialize(entity);
        if (entity instanceof HibernateProxy) {
            entity = (T) ((HibernateProxy) entity).getHibernateLazyInitializer()
                    .getImplementation();
        }
        return entity;
    }
}

And then you will be able to call it like this:

Gson gson = new GsonBuilder()
        .registerTypeHierarchyAdapter(HibernateProxy.class, new HibernateProxyTypeAdapter())
        .create();

This way all the hibernate objects will be converted automatically.

com.google.gson.JsonParser#parse(java.lang.String) is now deprecated

so use com.google.gson.JsonParser#parseString, it works pretty well

Kotlin Example:

val mJsonObject = JsonParser.parseString(myStringJsonbject).asJsonObject

Java Example:

JsonObject mJsonObject = JsonParser.parseString(myStringJsonbject).getAsJsonObject();

Came across a scenario with remote sorting of data store in EXTJS 4.X where the string is sent to the server as a JSON array (of only 1 object).
Similar approach to what is presented previously for a simple string, just need conversion to JsonArray first prior to JsonObject.

String from client: [{"property":"COLUMN_NAME","direction":"ASC"}]

String jsonIn = "[{\"property\":\"COLUMN_NAME\",\"direction\":\"ASC\"}]";
JsonArray o = (JsonArray)new JsonParser().parse(jsonIn);

String sortColumn = o.get(0).getAsJsonObject().get("property").getAsString());
String sortDirection = o.get(0).getAsJsonObject().get("direction").getAsString());

The simplest way is to use the JsonPrimitive class, which derives from JsonElement, as shown below:

JsonElement element = new JsonPrimitive(yourString);
JsonObject result = element.getAsJsonObject();

The JsonParser constructor has been deprecated. Use the static method instead:

JsonObject asJsonObject = JsonParser.parseString(request.schema).getAsJsonObject();