GSON（JSON字符串转换成一个相等的Java对象）

Gson这个Java类库可以把Java对象转换成JSON，也可以把JSON字符串转换成一个相等的Java对象。Gson支持任意复杂Java对象包括没有源代码的对象。
代码例子：

util.Date和sql.Date被转成长整形用于序列化传输

public class SQLDateSer

ializer implements JsonSerializer<java.sql.Date> {

public JsonElement serialize(java.sql.Date src, Type typeOfSrc,
JsonSerializationContext context) {
return new JsonPrimitive(src.getTime());
}
}

public class UtilDateSerializer implements JsonSerializer<java.util.Date> {

public JsonElement serialize(java.util.Date src, Type typeOfSrc,
JsonSerializationContext context) {
return new JsonPrimitive(src.getTime());
}
}

public class SQLDateDeserializer implements JsonDeserializer<java.sql.Date> {

public java.sql.Date deserialize(JsonElement json, Type typeOfT,
JsonDeserializationContext context) throws JsonParseException {
return new java.sql.Date(json.getAsJsonPrimitive().getAsLong());
}
}

public class UtilDateDeserializer implements JsonDeserializer<java.util.Date> {

public java.util.Date deserialize(JsonElement json, Type typeOfT,
JsonDeserializationContext context) throws JsonParseException {
return new java.util.Date(json.getAsJsonPrimitive().getAsLong());
}
}

序列化反序列化类Worker.class

private String name;

private java.sql.Date dob;

private java.util.Date inTime;

序列化反序列化类Factory.class

private String name;

private Worker worker;

private Set<Worker> workers;

private List<Worker> lws;

序列化反序列化帮助类

public class JsonUtils {

public static String bean2json(Object bean) {

Gson gson = new GsonBuilder().registerTypeAdapter(java.sql.Date.class,

new SQLDateSerializer()).registerTypeAdapter(

java.util.Date.class, new UtilDateSerializer()).setDateFormat(

DateFormat.LONG).setPrettyPrinting().create();

// gson = new Gson();

return gson.toJson(bean);

}

public static <T> T json2bean(String json, Type type) {

Gson gson = new GsonBuilder().registerTypeAdapter(java.sql.Date.class,

new SQLDateDeserializer()).registerTypeAdapter(

java.util.Date.class, new UtilDateDeserializer())

.setDateFormat(DateFormat.LONG).create();

// gson = new Gson();

return gson.fromJson(json, type);

}

}

测试代码：

public class GsonTestor {

private Worker worker;

private Factory factory;

public void setUp() {

worker = new Worker();

worker.setName("你想");

worker.setDob(new java.sql.Date(Calendar.getInstance()

.getTimeInMillis()));

worker.setInTime(Calendar.getInstance().getTime());

Worker w2 = new Worker();

w2.setName("改过");

w2.setDob(new java.sql.Date(Calendar.getInstance().getTimeInMillis()));

w2.setInTime(Calendar.getInstance().getTime());

Worker w3 = new Worker();

w3.setName("古古怪怪");

w3.setDob(new java.sql.Date(Calendar.getInstance().getTimeInMillis()));

w3.setInTime(Calendar.getInstance().getTime());

List<Worker> lws = new ArrayList<Worker>();

lws.add(worker);

lws.add(w2);

Set<Worker> sws = new HashSet<Worker>();

sws.add(w3);

sws.add(worker);

sws.add(w2);

factory = new Factory();

factory.setName("IBM");

factory.setWorker(worker);

factory.setLws(lws);

factory.setWorkers(sws);

}

public void testSerializer() {

String factoryJson = JsonUtils.bean2json(factory);

P.rintln(factoryJson);

Factory factoryCopy = (Factory) JsonUtils.json2bean(factoryJson,

Factory.class);

P.rintln(factoryCopy.getWorker().getInTime());

P.rintln(JsonUtils.bean2json(worker));

P.rintln(new java.sql.Date(1247625062171L));

P.rintln(new java.util.Date(1247625621406L));

String json = "{/"name/":/"改过/",/"dob/":1247626770406,/"inTime/":1247626770406}";

Worker w4 = (Worker) JsonUtils.json2bean(json, Worker.class);

P.rintln(w4.getName());

worker.setName(null);

String workerJson = JsonUtils.bean2json(worker);

;

P.rintln(workerJson);

}

public void testGenericType() {

List<String> holder = new ArrayList<String>();

holder.add("Hello Gson");

String json = JsonUtils.bean2json(holder);

P.rintln(json);

Type type = new TypeToken<List<String>>() {

}.getType();

Object obj = JsonUtils.json2bean(json, type);

P.rintln(obj);

P.rintln(obj.getClass());

}

}

source code: http://code.google.com/p/google-gson/