json-gson ???解析泛型及解析null

参考：//public static class paraJson {
public ??class paraJson{
 ???static Gson gson ?= new GsonBuilder().registerTypeAdapterFactory(new NullStringToEmptyAdapterFactory()).create();

// ???static Gson gson = new Gson();
 ???//解析 Json对象
 ???public static <T> T parseJson(Class<T> type,String jsonStr)throws Exception{
// ?????Gson gson ?= new GsonBuilder().registerTypeAdapterFactory(new NullStringToEmptyAdapterFactory()).create();
 ???????return gson.fromJson(jsonStr,type);
 ???}
 ???// 将Json数组解析成相应的映射对象列表
 ???public static <T> ArrayList<T> parseJsonArray(Class<T> myClass, String jsonStr)throws Exception{
 ???????Type type = new ListParameterizedType(myClass);
 ???????return gson.fromJson(jsonStr, type);
 ???}

 ???private static class ListParameterizedType implements ParameterizedType {
 ???????private Type type;
 ???????private ListParameterizedType(Type type) {
 ???????????this.type = type;
 ???????}
 ???????@Override
 ???????public Type[] getActualTypeArguments() {
 ???????????return new Type[] {type};
 ???????}
 ???????@Override
 ???????public Type getRawType() {
 ???????????return ArrayList.class;
 ???????}
 ???????@Override
 ???????public Type getOwnerType() {
 ???????????return null;
 ???????}
 ???????// implement equals method too! (as per javadoc)
 ???}

 ???/**
 ????* @return 不区分类型 传什么解析什么
 ????*/
 ???public static <T> T toObj(String jsonStr, Type type) {
 ???????return gson.fromJson(jsonStr, type);
 ???}
}

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json解析有很多工具，这里说的是最常用也是解析速度最快的Gson，Gson是google家出的，有一个缺点就是无法设置null替换，
我们只能手动的批量替换服务器返回的null了，正常的接口定义的时候是绝对不允许服务器返回null的，后台结果却总会出现null！
如果搜索的话有一个常见的答案，
Gson gson = new GsonBuilder().serializeNulls().create();
但是这个却无法解决反序列问题,怎么解决呢？我在stackoverflow上找到了这个问题，亲测有效
http://stackoverflow.com/questions/9483348/gson-treat-null-as-empty-string/24252578#24252578

解决办法如下：

Gson gson ?= new GsonBuilder().registerTypeAdapterFactory(new NullStringToEmptyAdapterFactory()).create();//然后用上面一行写的gson来序列化和反序列化实体类typegson.fromJson(json, type);gson.toJson(type);

//NullStringToEmptyAdapterFactory的代码

public class NullStringToEmptyAdapterFactory<T> implements TypeAdapterFactory { ???@SuppressWarnings("unchecked") ???public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) { ???????Class<T> rawType = (Class<T>) type.getRawType(); ???????if (rawType != String.class) { ???????????return null; ???????} ???????return (TypeAdapter<T>) new StringNullAdapter(); ???}}

// StringNullAdapter代码

public class StringNullAdapter extends TypeAdapter<String> { ???@Override ???public String read(JsonReader reader) throws IOException { ???????// TODO Auto-generated method stub ???????if (reader.peek() == JsonToken.NULL) { ???????????reader.nextNull(); ???????????return ""; ???????} ???????return reader.nextString(); ???} ???@Override ???public void write(JsonWriter writer, String value) throws IOException { ???????// TODO Auto-generated method stub ???????if (value == null) { ???????????writer.nullValue(); ???????????return; ???????} ???????writer.value(value); ???}}

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参考 ?http://blog.csdn.net/gl_mine_csdn/article/details/59652313
http://blog.csdn.net/a332324956/article/details/50792120

json-gson ???解析泛型及解析null

原文地址：http://www.cnblogs.com/manmanlu/p/7531207.html