Java时间戳与Date对象的转换详解

01.//转换器   
02.        GsonBuilder builder = new GsonBuilder();   
03.        // 不转换没有 @Expose 注解的字段    
04.        builder.excludeFieldsWithoutExposeAnnotation();  
05.        Gson gson = builder.create();   
06.          
07.        //1、对象转string   
08.        Student stu = new Student();  
09.        stu.setStudentId(333);  
10.        stu.setStudentName("qqq");  
11.        String stuStr = gson.toJson(stu);  
12.        System.out.println(stuStr); //{"studentName":"qqq","studentId":333}   
13.          
14.          
15.        //2、string转对象   
16.        Student user2 = gson.fromJson(stuStr, Student.class);   
17.        System.out.println(user2);   
18.        String stuTemp = "{\"studentName\":\"qqq2\",\"studentId\":3335}";  
19.        Student user4 = gson.fromJson(stuTemp, Student.class);   
20.        System.out.println(user4);   
21.  
22.        //3、对象List转string   
23.        List<Student> testBeanList = new ArrayList<Student>();   
24.        Student testBean = new Student();   
25.        testBean.setStudentId(555);  
26.        testBean.setStudentName("552");  
27.        testBeanList.add(testBean);   
28.          
29.        //Gson gsonList = new Gson();    
30.        Type type = new TypeToken<List<Student>>(){}.getType();  //指定集合对象属性   

31.        String beanListToJson = gson.toJson(testBeanList, type);   
32.        System.out.println(beanListToJson); //[{"studentName":"552","studentId":555}]    
33.  
34.        //集合string转对象list   
35.        List<Student> testBeanListFromJson = gson.fromJson(beanListToJson, type);   
36.        System.out.println(testBeanListFromJson); //[555:552]   
37.  
38.        //4、集合如果不指定类型 默认为String   
39.        List<String> testList = new ArrayList<String>();   
40.        testList.add("first");   
41.        testList.add("second");   
42.        String listToJson = gson.toJson(testList);   
43.        System.out.println(listToJson); //["first","second"]    
44.          
45.        //5、集合字符串转回来需要指定类型   
46.        List<String> testList2 = (List<String>) gson.fromJson(listToJson,   
47.          new TypeToken<List<String>>() {   
48.          }.getType());   
49.        System.out.println(testList2);   
50.  
51.        //6、 将HashMap字符串转换为 JSON    
52.        Map<String, String> testMap = new HashMap<String, String>();   
53.        testMap.put("id", "id.first");   
54.        testMap.put("name", "name.second");   
55.        String mapToJson = gson.toJson(testMap);   
56.        System.out.println(mapToJson); //{"id":"id.first","name":"name.second"}   
57.        //7、stringMap转对象   
58.        Map<String, String> userMap2 = (Map<String, String>) gson.fromJson(mapToJson,   
59.                new TypeToken<Map<String, String>>() {   
60.            }.getType());