FastJson的使用方法总结

本文参考:http://www.tuicool.com/articles/zUbQfa

还可参考:https://www.iflym.com/index.php/code/alibaba-fastjson-json-serializer-chapter-source-analyse-one-global-analyse.html

http://blog.csdn.net/glarystar/article/details/6654494

在日志解析，前后端数据传输交互中，经常会遇到 String 与 map、json、xml 等格式相互转换与解析的场景，其中 json 基本成为了跨语言、跨前后端的事实上的标准数据交互格式。应该来说各个语言中 解析 json 的库都一大片（具体 json 格式与三方库的介绍请见：http://www.json.org/json-zh.html），比如 python 都集成在了内置库中，成为标准 API，今天我们要聊的是 java 中如何方便的使用 json 格式。

从上面的链接介绍中我们可以看到，java 的三方 json 库是最多的，可谓百花齐放百家争鸣的节奏。。。但是，某些库存在链式依赖的问题，使用的时候要注意，如果你没用 maven 管你你的依赖，用起来会很痛苦，比如 json-lib、smart-json 等。下面我要推荐的是阿里巴巴工程师开源的一个 json 库：FastJSON，这个库在解析速度和易用性上来说都很不错。

1、了解fastjson

1.1 Fastjson介绍

Fastjson是一个Java语言编写的JSON处理器。 
1、遵循 http://json.org 标准，为其官方网站收录的参考实现之一。 
2、功能qiang打，支持JDK的各种类型，包括基本的JavaBean、Collection、Map、Date、Enum、泛型。 
3、无依赖，不需要例外额外的jar，能够直接跑在JDK上。 
4、开源，使用Apache License 2.0协议开源。

1.2 如果获得Fastjson？ 
https://github.com/alibaba/fastjson

2、主要的使用入口

Fastjson API入口类是com.alibaba.fastjson.JSON，常用的序列化操作都可以在JSON类上的静态方法直接完成。

 public static final Object parse(String text); // 把JSON文本parse为JSONObject或者JSONArray
 public static final JSONObject parseObject(String text)； // 把JSON文本parse成JSONObject
 public static final <T> T parseObject(String text, Class<T> clazz); // 把JSON文本parse为JavaBean
 public static final JSONArray parseArray(String text); // 把JSON文本parse成JSONArray
 public static final <T> List<T> parseArray(String text, Class<T> clazz); //把JSON文本parse成JavaBean集合
 public static final String toJSONString(Object object); // 将JavaBean序列化为JSON文本
 public static final String toJSONString(Object object, boolean prettyFormat); // 将JavaBean序列化为带格式的JSON文本
 public static final Object toJSON(Object javaObject); 将JavaBean转换为JSONObject或者JSONArray。

3、有关类库的一些说明

SerializeWriter：相当于StringBuffer

JSONArray：相当于List<Object>

JSONObject：相当于Map<String, Object>

JSON反序列化没有真正数组，本质类型都是List<Object>

4、fastjson还有很多很高级的特性

比如支持注解、支持全类型序列化，这些都是很好的特性，功能强大，不在本次测试范围。

5、测试代码

Bar.java

 import java.util.Date;
 import java.util.Random;

 import com.alibaba.fastjson.JSON;
 import com.alibaba.fastjson.serializer.SerializeConfig;
 import com.alibaba.fastjson.serializer.SimpleDateFormatSerializer;

 /**
 * @author leizhimin 11-11-22 上午9:15
 */
 public class Bar {
   //SerializeConfig：是对序列化过程中一些序列化过程的特殊配置，这里用作日期格式的定义。
   public static SerializeConfig mapping = new SerializeConfig(); 

   private String barName;
   private int barAge;
   private Date barDate = new Date();

   static {
     mapping.put(Date.class, new SimpleDateFormatSerializer("yyyy-MM-dd"));
   } 

   //代码块给Bar对象中的barName和barAge赋值.
   {
     Random random = new Random();
     barName = "name_"+String.valueOf(random.nextInt());
     barAge = random.nextInt();
   } 

   public static void main(String[] args) {
     //把Bar对象转换成JSON格式的Object类型
     Object obj = JSON.toJSON(new Bar());
     System.out.println(obj);
     //输出{"barAge":-664880579,"barDate":1471348117095,"barName":"name_464160862"}

     //Bar对象转换成String类型的字符串
     String x1 = JSON.toJSONString(new Bar(), true);
     System.out.println(x1);
     //输出:
     /*
     {
         "barAge":1553774697,
         "barDate":1471348117144,
         "barName":"name_-1034255192"
     }
     */

     //格式化时间的JSON字符串
     String x2 = JSON.toJSONString(new Bar(), mapping);
     System.out.println(x2);
     //输出:{"barAge":1755982737,"barDate":"2016-08-16","barName":"name_453018403"}
   } 

   public String getBarName() {
     return barName;
   } 

   public void setBarName(String barName) {
     this.barName = barName;
   } 

   public int getBarAge() {
     return barAge;
   } 

   public void setBarAge(int barAge) {
     this.barAge = barAge;
   } 

   public Date getBarDate() {
     return barDate;
   } 

   public void setBarDate(Date barDate) {
     this.barDate = barDate;
   } 

   @Override
   public String toString() {
     return "Bar{" +
         "barName='" + barName + '\'' +
         ", barAge=" + barAge +
         ", barDate=" + barDate +
         '}';
   }
 }

Foo.java

 import java.util.ArrayList;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;

 /**
 * @author leizhimin 11-11-22 上午9:15
 */
 public class Foo {
   //声明Java中的8种基本变量和String类型变量.
   private String vString = "vStringhehhehe";

   private char vchar = 'x';
   private byte vbyte = 64;
   private short vshort = 128;
   private int vint = 65535;
   private long vlong = 9999999L;
   private float vfloat = 12.1f;
   private double vdouble = 22.203d;
   private boolean vboolean = false; 

   //Date和Object类型变量
   private Date vDate = new Date();
   private Object vnull = null; 

   //String,int,boolean类型的数组
   private String[] avString = {"aaa", "bbb", "ccc"};
   private int[] avint = {1, 2, 3, 4};
   private boolean[] avboolean = {true, false, true, true}; 

   //List和Map类型变量
   private List<String> listString = new ArrayList<String>();
   private Map<String, String> map = new HashMap<String, String>(); 

   //封装的Bar对象
   private Bar bar = new Bar();
   private Bar[] avBar = {new Bar(), new Bar()};
   private List<Bar> listBar = new ArrayList<Bar>(); 

   //代码块封装数据
   {
     listString.add("listString1");
     listString.add("listString2");
     listString.add("listString3"); 

     map.put("x", "s11111x");
     map.put("y", "s22222y");
     map.put("z", "s33333z"); 

     listBar.add(new Bar());
     listBar.add(new Bar());
     listBar.add(new Bar());
   } 

   public String getvString() {
     return vString;
   } 

   public void setvString(String vString) {
     this.vString = vString;
   } 

   public char getVchar() {
     return vchar;
   } 

   public void setVchar(char vchar) {
     this.vchar = vchar;
   } 

   public byte getVbyte() {
     return vbyte;
   } 

   public void setVbyte(byte vbyte) {
     this.vbyte = vbyte;
   } 

   public short getVshort() {
     return vshort;
   } 

   public void setVshort(short vshort) {
     this.vshort = vshort;
   } 

   public int getVint() {
     return vint;
   } 

   public void setVint(int vint) {
     this.vint = vint;
   } 

   public long getVlong() {
     return vlong;
   } 

   public void setVlong(long vlong) {
     this.vlong = vlong;
   } 

   public float getVfloat() {
     return vfloat;
   } 

   public void setVfloat(float vfloat) {
     this.vfloat = vfloat;
   } 

   public double getVdouble() {
     return vdouble;
   } 

   public void setVdouble(double vdouble) {
     this.vdouble = vdouble;
   } 

   public boolean isVboolean() {
     return vboolean;
   } 

   public void setVboolean(boolean vboolean) {
     this.vboolean = vboolean;
   } 

   public Date getvDate() {
     return vDate;
   } 

   public void setvDate(Date vDate) {
     this.vDate = vDate;
   } 

   public Object getVnull() {
     return vnull;
   } 

   public void setVnull(Object vnull) {
     this.vnull = vnull;
   } 

   public String[] getAvString() {
     return avString;
   } 

   public void setAvString(String[] avString) {
     this.avString = avString;
   } 

   public int[] getAvint() {
     return avint;
   } 

   public void setAvint(int[] avint) {
     this.avint = avint;
   } 

   public boolean[] getAvboolean() {
     return avboolean;
   } 

   public void setAvboolean(boolean[] avboolean) {
     this.avboolean = avboolean;
   } 

   public List<String> getListString() {
     return listString;
   } 

   public void setListString(List<String> listString) {
     this.listString = listString;
   } 

   public Map<String, String> getMap() {
     return map;
   } 

   public void setMap(Map<String, String> map) {
     this.map = map;
   } 

   public Bar getBar() {
     return bar;
   } 

   public void setBar(Bar bar) {
     this.bar = bar;
   } 

   public Bar[] getAvBar() {
     return avBar;
   } 

   public void setAvBar(Bar[] avBar) {
     this.avBar = avBar;
   } 

   public List<Bar> getListBar() {
     return listBar;
   } 

   public void setListBar(List<Bar> listBar) {
     this.listBar = listBar;
   }
 }

Test.java

 import java.util.ArrayList;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;

 import com.alibaba.fastjson.JSON;
 import com.alibaba.fastjson.JSONArray;
 import com.alibaba.fastjson.serializer.SerializeConfig;
 import com.alibaba.fastjson.serializer.SimpleDateFormatSerializer;

 /**
 * Created by 2IntelliJ IDEA.
 *
 * @author leizhimin 11-11-22 上午9:45
 */
 public class Test {
   private static SerializeConfig mapping = new SerializeConfig();
   static {
     mapping.put(Date.class, new SimpleDateFormatSerializer("yyyy-MM-dd HH:mm:ss"));
   } 

   public static void main(String[] args) { 

     Date date = new Date();
     String text = JSON.toJSONString(date, mapping);
     System.out.println(text);//输出"2016-08-16 19:53:07"

     Foo f1 = new Foo();
     System.out.println(JSON.toJSONString(f1, true));

     String x2 =JSON.toJSONString(f1, mapping);
     System.out.println(x2); 

     //List -> JSON array
     json2List();

     json2Map();

     //普通类型Array数组和JSON的相互转换
      array2JSON();

      array2JSON2();

      //普通类型Map和JSON的相互转换
      map2JSON();
   } 

   public static void json2List(){
     //List -> JSON array
     List<Bar> barList = new ArrayList<Bar>();
     barList.add(new Bar());
     barList.add(new Bar());
     barList.add(new Bar());
     String json= JSON.toJSONString(barList, true);
     System.out.println(json); 

     //JSON array -> List
     List<Bar> barList1 = JSON.parseArray(json,Bar.class);
     for (Bar bar : barList1) {
       System.out.println(bar.toString());
     }
   } 

   public static void json2Map(){
     //Map -> JSON
     Map<String,Bar> map = new HashMap<String, Bar>();
     map.put("a",new Bar());
     map.put("b",new Bar());
     map.put("c",new Bar());
     String json = JSON.toJSONString(map,true);
     System.out.println(json); 

     //JSON -> Map
     Map<String,Bar> map1 = (Map<String,Bar>)JSON.parse(json);
     for (String key : map1.keySet()) {
       System.out.println(key+":"+map1.get(key));
     }
   } 

   public static void array2JSON(){
     //String数组转换成JSON
     String[] arr_String  = {"a","b","c"};
     String json_arr_String = JSON.toJSONString(arr_String,true);
     System.out.println(json_arr_String); //输出["a","b","c"]

     //JSON转换成array
     JSONArray jsonArray = JSON.parseArray(json_arr_String);
     for (Object o : jsonArray) {
       System.out.println(o);
     }
     /* 输出:
      a
      b
      c
      */
     System.out.println(jsonArray);//输出:["a","b","c"]
   } 

   public static void array2JSON2(){
     Bar[] arr_Bar    = {new Bar(),new Bar(),new Bar()};
     String json_arr_Bar = JSON.toJSONString(arr_Bar,true);
     System.out.println(json_arr_Bar);
     JSONArray jsonArray = JSON.parseArray(json_arr_Bar);
     for (Object o : jsonArray) {
       System.out.println(o);
     }
     System.out.println(jsonArray);
   } 

   public static void map2JSON(){

     //Map转换成JSON
     Map<String,String> map = new HashMap<String,String>();
     map.put("a","aaa");
     map.put("b","bbb");
     map.put("c","ccc");
     String json=JSON.toJSONString(map);
     System.out.println(json);//输出{"a":"aaa","b":"bbb","c":"ccc"}

     //JSON转换成Map
     Map map1 = JSON.parseObject(json);
     for (Object o : map.entrySet()) {
       Map.Entry<String,String> entry = (Map.Entry<String,String>)o;
       System.out.println(entry.getKey()+"--->"+entry.getValue());
     }
     /*
      b--->bbb
      c--->ccc
      a--->aaa
     */
   }
 }

程序输出:

 "System.out.println(text);"
 "2016-08-17 10:16:18"

 System.out.println(JSON.toJSONString(f1, true));
 {
     "avBar":[{
         "barAge":-480029500,
         "barDate":1471400178210,
         "barName":"name_-2129248362"
     },{
         "barAge":634833464,
         "barDate":1471400178210,
         "barName":"name_-1877607258"
     }],
     "avString":["aaa","bbb","ccc"],
     "avboolean":[true,false,true,true],
     "avint":[1,2,3,4],
     "bar":{
         "barAge":-1335514550,
         "barDate":1471400178210,
         "barName":"name_-1069927371"
     },
     "listBar":[
         {
             "barAge":357976541,
             "barDate":1471400178210,
             "barName":"name_1051748274"
         },
         {
             "barAge":1253923759,
             "barDate":1471400178210,
             "barName":"name_1279150198"
         },
         {
             "barAge":357167456,
             "barDate":1471400178210,
             "barName":"name_-737334111"
         }
     ],
     "listString":[
         "listString1",
         "listString2",
         "listString3"
     ],
     "map":{
         "x":"s11111x",
         "y":"s22222y",
         "z":"s33333z"
     },
     "vDate":1471400178209,
     "vString":"vStringhehhehe",
     "vboolean":false,
     "vbyte":64,
     "vchar":"x",
     "vdouble":22.203,
     "vfloat":12.1,
     "vint":65535,
     "vlong":9999999,
     "vshort":128
 }
 System.out.println(x2);
 {"avBar":[{"barAge":-480029500,"barDate":"2016-08-17 10:16:18","barName":"name_-2129248362"},{"barAge":634833464,"barDate":"2016-08-17 10:16:18","barName":"name_-1877607258"}],"avString":["aaa","bbb","ccc"],"avboolean":[true,false,true,true],"avint":[1,2,3,4],"bar":{"barAge":-1335514550,"barDate":"2016-08-17 10:16:18","barName":"name_-1069927371"},"listBar":[{"barAge":357976541,"barDate":"2016-08-17 10:16:18","barName":"name_1051748274"},{"barAge":1253923759,"barDate":"2016-08-17 10:16:18","barName":"name_1279150198"},{"barAge":357167456,"barDate":"2016-08-17 10:16:18","barName":"name_-737334111"}],"listString":["listString1","listString2","listString3"],"map":{"x":"s11111x","y":"s22222y","z":"s33333z"},"vDate":"2016-08-17 10:16:18","vString":"vStringhehhehe","vboolean":false,"vbyte":64,"vchar":"x","vdouble":22.203,"vfloat":12.1,"vint":65535,"vlong":9999999,"vshort":128}

 json2List();
 [
     {
         "barAge":-2022440599,
         "barDate":1471400178284,
         "barName":"name_-590972614"
     },
     {
         "barAge":1704306424,
         "barDate":1471400178284,
         "barName":"name_1482085108"
     },
     {
         "barAge":1907038490,
         "barDate":1471400178284,
         "barName":"name_651427557"
     }
 ]

 Bar{barName='name_-590972614', barAge=-2022440599, barDate=Wed Aug 17 10:16:18 CST 2016}
 Bar{barName='name_1482085108', barAge=1704306424, barDate=Wed Aug 17 10:16:18 CST 2016}
 Bar{barName='name_651427557', barAge=1907038490, barDate=Wed Aug 17 10:16:18 CST 2016}

 json2Map();
 {
     "a":{
         "barAge":877829686,
         "barDate":1471400178308,
         "barName":"name_558391664"
     },
     "b":{
         "barAge":375478040,
         "barDate":1471400178308,
         "barName":"name_-1233383964"
     },
     "c":{
         "barAge":-1043862971,
         "barDate":1471400178308,
         "barName":"name_-823025454"
     }
 }

 b:{"barAge":375478040,"barDate":1471400178308,"barName":"name_-1233383964"}
 c:{"barAge":-1043862971,"barDate":1471400178308,"barName":"name_-823025454"}
 a:{"barAge":877829686,"barDate":1471400178308,"barName":"name_558391664"}

 array2JSON()
 ["a","b","c"]
 a
 b
 c
 ["a","b","c"]

 array2JSON2()
 [{
     "barAge":-842219577,
     "barDate":1471400178310,
     "barName":"name_-1204063138"
 },{
     "barAge":1450191787,
     "barDate":1471400178310,
     "barName":"name_650041812"
 },{
     "barAge":-732707567,
     "barDate":1471400178310,
     "barName":"name_159117539"
 }]

 {"barAge":-842219577,"barDate":1471400178310,"barName":"name_-1204063138"}
 {"barAge":1450191787,"barDate":1471400178310,"barName":"name_650041812"}
 {"barAge":-732707567,"barDate":1471400178310,"barName":"name_159117539"}
 [{"barAge":-842219577,"barDate":1471400178310,"barName":"name_-1204063138"},{"barAge":1450191787,"barDate":1471400178310,"barName":"name_650041812"},{"barAge":-732707567,"barDate":1471400178310,"barName":"name_159117539"}]

 map2JSON()
 {"a":"aaa","b":"bbb","c":"ccc"}
 b--->bbb
 c--->ccc
 a--->aaa