Gson序列化POJO ArrayList的问题

Question

我一直在计划使用simpleXML来处理序列化需求，但是我想我会尝试使用JSON来学习新的东西。

这是我用来尝试使用Gson 1.7.1序列化测试POJO的ArrayList的代码。

注意：为了简化代码，我删除了字符串“s”的Reader/Writers。

package test; 

import java.io.IOException; 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.List; 

import com.google.gson.Gson; 

public class TestGsonSerialDeserialList { 
    public static void main(String[] args) throws IOException{ 
     Gson gson = new Gson(); 

     //Make Serial 
     String s; 
     List<TestObject> list = Collections.synchronizedList(new ArrayList<TestObject>()); 
     list.add(new TestObject()); 
     list.add(new TestObject()); 

     s = gson.toJson(list, ArrayList.class); 
     System.out.println(s); 

     //Eat Serial 
     List<TestObject> list2 = Collections.synchronizedList(gson.fromJson(s, ArrayList.class)); 
     System.out.println(list2.get(0)); 
     System.out.println(list2.get(1)); 
    } 
} 

这里是输出我得到：

[{"objectID":1,"i1":12345,"name":"abcdefg","s":["a","b","c"]},{"objectID":2,"i1":12345,"name":"abcdefg","s":["a","b","c"]}] 
java.lang.Object@5c74c3aa 
java.lang.Object@75d9fd51 

为了我的新手眼里这看起来是正确的。只有DeSerialized对象列表包含基本对象，而不是TestObject的I序列化。任何人都可以向我解释什么，如果有的话，我可以做什么，使这项工作？

编辑：

修正测试：由于ColinD

package test; 

import java.io.FileInputStream; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.io.OutputStreamWriter; 
import java.io.Reader; 
import java.io.Writer; 
import java.lang.reflect.Type; 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.List; 

import com.google.gson.Gson; 
import com.google.gson.reflect.TypeToken; 

public class TestGsonSerialDeserialList { 
    public static void main(String[] args) throws IOException{ 
     System.out.println("--- Serialize/Deserialize Started ---"); 
     String fileName = "json\\testList.json"; 

     Gson gson = new Gson(); 
     Type listOfTestObject = new TypeToken<List<TestObject>>(){}.getType(); 

     //Make Serial 
     Writer osWriter = new OutputStreamWriter(new FileOutputStream(fileName)); 
     List<TestObject> list = Collections.synchronizedList(new ArrayList<TestObject>()); 
     list.add(new TestObject()); 
     list.add(new TestObject()); 
     list.add(new TestObject()); 
     list.add(new TestObject()); 
     gson.toJson(list, osWriter); 
     osWriter.close(); 


     //Eat Serial 
     Reader isReader = new InputStreamReader(new FileInputStream((fileName))); 
     List<TestObject> list2 = Collections.synchronizedList(
      (List<TestObject>)gson.fromJson(isReader, listOfTestObject) 
     ); 
     isReader.close(); 
     System.out.println(list2.get(0)); 
     System.out.println(list2.get(1)); 
     System.out.println(list2.get(2)); 
     System.out.println(list2.get(3)); 
     System.out.println("--- Serialize/Deserialize Ended ---"); 
    } 
} 

输出：

--- Serialize/Deserialize Started --- 
ID#: 1, i1: 12345, name: abcdefg, s[]: [Ljava.lang.String;@95c083 
ID#: 2, i1: 12345, name: abcdefg, s[]: [Ljava.lang.String;@6791d8c1 
ID#: 3, i1: 12345, name: abcdefg, s[]: [Ljava.lang.String;@182d9c06 
ID#: 4, i1: 12345, name: abcdefg, s[]: [Ljava.lang.String;@5a5e5a50 
--- Serialize/Deserialize Ended --- 

EDIT2：

老实说，我不知道是什么原因，但是wh我用一个ArrayList替换了我的TestObject中嵌入的简单String []，它开始正确地序列化。

--- Serialize/Deserialize Started --- 
ID#: 1, i1: 12345, name: abcdefg, s[]: [a, b, c] 
ID#: 2, i1: 12345, name: abcdefg, s[]: [a, b, c] 
ID#: 3, i1: 12345, name: abcdefg, s[]: [a, b, c] 
ID#: 4, i1: 12345, name: abcdefg, s[]: [a, b, c] 
--- Serialize/Deserialize Ended --- 

Answer 1

你需要给上的List具体的泛型类型，你正在使用（或者你用它使用任何通用型）GSON信息。特别是在反序列化JSON时，它需要这些信息能够确定它应该反序列化每个数组元素的类型。

Type listOfTestObject = new TypeToken<List<TestObject>>(){}.getType(); 
String s = gson.toJson(list, listOfTestObject); 
List<TestObject> list2 = gson.fromJson(s, listOfTestObject); 

这记录在Gson user guide中。