1. publicclass UserVo{ 
2.       private String name; 
3.       privateint age; 
4.       privatelong phone; 
5.        
6.       private List<UserVo> friends; 
7.       …… 
8. } 

1. UserVo src = new UserVo();   
2. src.setName("Yaoming");   
3. src.setAge(30);   
4. src.setPhone(13789878978L);   
5.        
6. UserVo f1 = new UserVo();   
7. f1.setName("tmac");   
8. f1.setAge(32);   
9. f1.setPhone(138999898989L);   
10. UserVo f2 = new UserVo();   
11. f2.setName("liuwei");   
12. f2.setAge(29);   
13. f2.setPhone(138999899989L);   
14.            
15. List<UserVo> friends = new ArrayList<UserVo>();   
16. friends.add(f1);   
17. friends.add(f2);   
18. src.setFriends(friends);  

1. Gson gson = new Gson();   
2. String json = gson.toJson(src);  

1. {"name":"Yaoming","age":30,"phone":13789878978,"friends":[{"name":"tmac","age":32,"phone":138999898989},{"name":"liuwei","age":29,"phone":138999899989}]} 

1. publicclass UserVo implements Serializable{ 
3. privatestaticfinallong serialVersionUID = -5726374138698742258L; 
4. private String name; 
5. privateint age; 
6. privatelong phone; 
7.  
8. private List<UserVo> friends; 

1. ByteArrayOutputStream bos = new ByteArrayOutputStream();   
2. ObjectOutputStream os = new ObjectOutputStream(bos);   
3. os.writeObject(src);   
4. os.flush();   
5. os.close();   
6. byte[] b = bos.toByteArray();   
7. bos.close();  

1. ObjectInputStream ois = new ObjectInputStream(fis);   
2. vo = (UserVo) ois.readObject();   
3. ois.close();   
4. fis.close();  

1. publicclass UserVo implements Serializable{ 
2. private String name; 
3. privateint age; 
4. privatelong phone; 
5.  
6. private List<UserVo> friends; 

1. ByteArrayOutputStream bos = new ByteArrayOutputStream();   
2. ObjectOutputStream os = new ObjectOutputStream(bos);   
3. os.writeObject(src);   
4. os.flush();   
5. os.close();   
6. byte[] b = bos.toByteArray();   
7. bos.close();   
9. FileOutputStream fos = new FileOutputStream(dataFile);   
10. fos.write(b);   
11. fos.close();  

1. FileInputStream fis = new FileInputStream(dataFile);   
2. ObjectInputStream ois = new ObjectInputStream(fis);   
3. vo = (UserVo) ois.readObject();   
4. ois.close();   
5. fis.close();  

1. Exception in thread "main" java.io.InvalidClassException: serialize.obj.UserVo; local class incompatible: stream classdesc serialVersionUID = 3305402508581390189, local class serialVersionUID = 7174371419787432394
2.     at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:560)   
3.     at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1582)   
4.     at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1495)   
5.     at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1731)   
6.     at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1328)   
7.     at java.io.ObjectInputStream.readObject(ObjectInputStream.java:350)   
8.     at serialize.obj.ObjectSerialize.read(ObjectSerialize.java:74)   
9.     at serialize.obj.ObjectSerialize.main(ObjectSerialize.java:27)  

1. tar zxvf protobuf-2.5.0rc1.tar.gz   
2. ./configure   
3. ./make   
4. ./make install  

1. MacBook-Air:~ ming$ protoc --version   
2. libprotoc 2.5.0

1. package serialize; 
3. option java_package = "serialize"; 
4. option java_outer_classname="UserVoProtos"; 
6. message UserVo{ 
7.        optional string name = 1; 
8.        optional int32 age = 2; 
9.        optional int64 phone = 3; 
10.        repeated serialize.UserVo friends = 4; 
11. } 

required: a well-formed message must have exactly one of this field.

optional: a well-formed message can have zero or one of this field (but not more than one).

repeated: this field can be repeated any number of times (including zero) in a well-formed message. The order of the repeated values will be preserved.