myjoybar / TypeCreator

create the type for gson

TypeCreator

Chinese README

For the deserialization of Gson to create Type While using the deserialisation of Gson, it will generate Type conveniently.

Not long age, one of my colleague used this code while using Gson to deserialise the Map.

  public static <T> Map<String, T> GsonToMaps(String gsonString) {
        Map<String, T> map = null;
        if (gson != null) {
            map = gson.fromJson(gsonString, new TypeToken<Map<String, T>>() {
            }.getType());
        }
        return map;
    }

The reported error/s as follow:

	
java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap cannot be cast to xxxentity
	

While checking for the reason of the error/s, I found that because the new TypeToken<Map<String, T>>() { }.getType() did not returns the correct type of the runtime class. In order to generate Type conveniently (because I do not like to write a long list of codes TypeToken), that is why you are reading this blog .

For instance：

1. To parse JOPO StudentsBean

  	Type type = TypeGenerator
                .newInstance(StudentsBean.class)
                .build();

    StudentsBean obj = GsonUtil.parseJsonStrToBean(jsonStr, type);

2. To parse List<StudentsBean>

	Type type = TypeGenerator
                .newInstance(ArrayList.class)
                .addTypeArgument(StudentsBean.class)
                .build();

    List<StudentsBean> obj = GsonUtil.parseJsonStrToBean(jsonStr, type);

3. To parse Map<String, StudentsBean>

    Type type = TypeGenerator
            .newInstance(HashMap.class)
            .addTypeArgument(String.class)
            .addTypeArgument(StudentsBean.class)
            .build();

    Map<String, StudentsBean> obj = GsonUtil.parseJsonStrToBean(jsonStr, type);

    

4. A more complicated version List<Map<String, Map<String, List<StudentsBean>>>>

        Type type = TypeGenerator
                .newInstance(ArrayList.class)
                .addChildTypeGenerator(
                        TypeGenerator
                        .newInstance(HashMap.class)
                        .addTypeArgument(String.class)
                        . addChildTypeGenerator(
                                TypeGenerator
                                .newInstance(HashMap.class)
                                .addTypeArgument(String.class)
                                .addChildTypeGenerator(
                                        TypeGenerator
                                        .newInstance(ArrayList.class)
                                        .addTypeArgument(StudentsBean.class))))
                .build();

        List<Map<String, Map<String, List<StudentsBean>>>> obj = GsonUtil.parseJsonStrToBean(jsonStr, type);