JSON

轻量级，易于阅读，基于Javascript，丰富的语言支持。

key/value(hash),集合(array)

                            
 { "appid" : "album",
  "content" : "asdfasdfafd",
  "ext" : { "piclist" : [ { "content" : null,
            "cover130" : "http://test2.img.pp.sohu.com.cn/2011/11/10/14/16/u163937567_1344a50f638g134_s.gif",
            "coverId" : 337942648
          },
          { "content" : null,
            "cover130" : "http://test1.img.pp.sohu.com.cn/2011/11/10/14/15/u163937567_1344a502ebbg134_s.gif",
            "coverId" : 337942641
          }
        ],
      "total" : 2
    },
  "id" : "337942648_337942641",
  "status" : 0,
  "title" : "20111119",
  "url" : "http://kaktos.i.sohu.com/photoset/41069588/photos/"
}                           
                        

数据类型

• String
• Number
• Object
• Array
• Boolean
• null

语言支持-Javascript

var feed = eval("(" + feedText + ")");

更安全的做法

var feed = JSON.parse(feedText);

语言支持-Java

Jackson

Gson

Protocol Buffers

定义格式

                            
//--------------------------------------- photopark.proto
package photopark;
option java_package = "photopark.protobuf";
enum PhotoPrivilege {
	PUBLIC_PHOTO = 0;
	PRIVATE_PHOTO = 1;
}
message Photo {
	optional int64 id = 1;
	optional int64 photoset_id = 2;
	required int64 user_id = 3;
	optional string name = 4;
	optional PhotoPrivilege privilege = 5 [default = PUBLIC_PHOTO];
	optional string hosturl = 6;
	optional string img_names = 7;
	optional string dimensions = 8;
	optional int32 image_size = 9;
	optional int64 upload_time = 11;
	optional string upload_ip = 12;
	optional int64 last_modified = 14;
	optional int32 status = 15;
}                            
                            
                        

编译

protoc –java_out=$DST_DIR $SRC_DIR/photopark.proto

↓

Photopark.java

protoc –python_out=$DST_DIR $SRC_DIR/photopark.proto

↓

photopark_pb2.py

使用

序列化(java)

    	Photo.Builder photo = Photo.newBuilder();
    	photo.setStatus(1); 
    	photo.setUserId(userId);
    	photo.setName(filename);
    	photo.setHosturl(_hosturl);
    	photo.setImgNames(_imagNames);
    	photo.setImageSize((int)lsize);  
        photo.setDimensions(dimensions.trim());
      	photo.setUploadIp(uploadIP);
    	photo.setUploadTime(System.currentTimeMillis());
    	photo.setLastModified(System.currentTimeMillis()); 
        photo.build().toByteArray();       
                        

反序列化(python)

photopark.Photo().ParseFromString(data)

编码

Varints是一种用一个或者多个字节序列化整数的方法

                        1010 1100 0000 0010 #300 
                        

                        
                        1010 1100 0000 0010
                        → 010 1100  000 0010
                        → 000 0010 010 1100
                        → 100101100
                        →  256 + 32 + 8 + 4 = 300
                        
                        

编码

• PB的message是一系列的key-value对
• 使用varints数字（包含了别名以及属性类型信息）来作为key

Thrift

Facebook开源的RPC框架

                            
          struct UserProfile {
            1: i32 uid,
            2: string name,
            3: string blurb
          }
          service UserStorage {
            void store(1: UserProfile user),
            UserProfile retrieve(1: i32 uid)
          }                        
                            
                        

数据类型

• bool: A boolean value (true or false)
• byte: An 8-bit signed integer
• i16: A 16-bit signed integer
• i32: A 32-bit signed integer
• i64: A 64-bit signed integer
• double: A 64-bit floating point number
• string: A text string encoded using UTF-8 encoding
• binary
• List, Set, Map