fastJson

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FastJSON是一个很好的java开源json工具类库，相比其他同类的json类库，它的速度的确是fast，最快！但是文档做得不好，在应用前不得不亲测一些功能。

实际上其他的json处理工具都和它差不多，api也有几分相似。

一、JSON规范

JSON是一个标准规范，用于数据交互，规范的中文文档如下：

http://www.json.org/json-zh.html

参看规范，来对比JSON类库处理结果。

二、fastjson的一些简要说明

1、了解fastjson

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。http://code.alibabatech.com/wiki/display/FastJSON/Home

如果获得Fastjson？
SVN:http://code.alibabatech.com/svn/fastjson/trunk/
WIKI:http://code.alibabatech.com/wiki/display/FastJSON/Home
Issue Tracking:http://code.alibabatech.com/jira/browse/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。

三、测试代码

package lavasoft.stu.json; import com.alibaba.fastjson.JSON; import com.alibaba.fastjson.serializer.SerializeConfig; import com.alibaba.fastjson.serializer.SimpleDateFormatSerializer; import java.util.*; /** * Created by IntelliJ IDEA. * * @author leizhimin 11-11-22 上午9:15 */ public class Foo {         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; //        private Date vdate = new Date();         private Date dddd = new Date();         private Date vDate = new Date();         private Date v_Date = new Date();         private Object vnull = null;         private String[] avString = {"aaa", "bbb", "ccc"};         private int[] avint = {1, 2, 3, 4};         private boolean[] avboolean = {true, false, true, true};         private List<String> listString = new ArrayList<String>();         private Map<String, String> map = new HashMap<String, String>();         private Bar bar = new Bar();         private Bar[] avBar = {new Bar(), new Bar()};         private List<Bar> listBar = new ArrayList<Bar>();         {                 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 getDddd() {                 return dddd;         }         public void setDddd(Date dddd) {                 this.dddd = dddd;         }         public Date getV_Date() {                 return v_Date;         }         public void setV_Date(Date v_Date) {                 this.v_Date = v_Date;         }         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;         } } package lavasoft.stu.json; import com.alibaba.fastjson.JSON; import com.alibaba.fastjson.serializer.SerializeConfig; import com.alibaba.fastjson.serializer.SimpleDateFormatSerializer; import java.util.Date; import java.util.Random; /** * Created by IntelliJ IDEA. * * @author leizhimin 11-11-22 上午9:15 */ public class Bar {         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"));         }         {                 Random r = new Random();                 barName = "sss_"+String.valueOf(r.nextFloat());                 barAge = r.nextInt();         }         public static void main(String[] args) {                 Object obj = JSON.toJSON(new Bar());                 String x1 = JSON.toJSONString(new Bar(), true);                 System.out.println(x1);                 String x2 = JSON.toJSONString(new Bar(), mapping);                 System.out.println(x2);         }         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 +                                 '}';         } }

package lavasoft.stu.json; import com.alibaba.fastjson.JSON; import com.alibaba.fastjson.JSONArray; import com.alibaba.fastjson.serializer.SerializeConfig; import com.alibaba.fastjson.serializer.SimpleDateFormatSerializer; import java.util.*; /** * 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) {                 Foo f1 = new Foo();                 Date date = new Date();                 String text = JSON.toJSONString(date, mapping);                 System.out.println(text);                 System.out.println(JSON.toJSONString(f1, true));                 String x2 =JSON.toJSONString(f1, mapping);                 System.out.println(x2);         }         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[] arr_String    = {"a","b","c"};                 String json_arr_String = JSON.toJSONString(arr_String,true);                 System.out.println(json_arr_String);                 JSONArray jsonArray = JSON.parseArray(json_arr_String);                 for (Object o : jsonArray) {                         System.out.println(o);                 }                 System.out.println(jsonArray);         }         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 map = new HashMap();                 map.put("a","aaa");                 map.put("b","bbb");                 map.put("c","ccc");                 String json=JSON.toJSONString(map);                 System.out.println(json);                 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());                 }         } }  说明：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。有关需要带类型的全类型序列化过程，需要调用JSON.toJSONStringZ()方法。需要美化输出时候，需要打开序列化美化开关，在方法中true那个参数。  输出结果："2011-11-23 23:30:33" {   "avBar":[{     "barAge":174398800,     "barDate":1322062233062,     "barName":"sss_0.62378174"   },{     "barAge":38938962,     "barDate":1322062233062,     "barName":"sss_0.36014742"   }],   "avString":["aaa","bbb","ccc"],   "avboolean":[true,false,true,true],   "avint":[1,2,3,4],   "bar":{     "barAge":1601495948,     "barDate":1322062233062,     "barName":"sss_0.46644872"   },   "dddd":1322062233046,   "listBar":[     {       "barAge":-1090113522,       "barDate":1322062233062,       "barName":"sss_0.83562374"     },     {       "barAge":478603194,       "barDate":1322062233062,       "barName":"sss_0.59483266"     },     {       "barAge":1118357669,       "barDate":1322062233062,       "barName":"sss_0.9961642"     }   ],   "listString":[     "listString1",     "listString2",     "listString3"   ],   "map":{"x":"s11111x","y":"s22222y","z":"s33333z"},   "v_Date":1322062233046,   "vboolean":false,   "vbyte":64,   "vchar":"x",   "vdouble":22.203,   "vfloat":12.1,   "vint":65535,   "vlong":9999999,   "vshort":128 } {"avBar":[{"barAge":174398800,"barDate":"2011-11-23 23:30:33","barName":"sss_0.62378174"},{"barAge":38938962,"barDate":"2011-11-23 23:30:33","barName":"sss_0.36014742"}],"avString":["aaa","bbb","ccc"],"avboolean":[true,false,true,true],"avint":[1,2,3,4],"bar":{"barAge":1601495948,"barDate":"2011-11-23 23:30:33","barName":"sss_0.46644872"},"dddd":"2011-11-23 23:30:33","listBar":[{"barAge":-1090113522,"barDate":"2011-11-23 23:30:33","barName":"sss_0.83562374"},{"barAge":478603194,"barDate":"2011-11-23 23:30:33","barName":"sss_0.59483266"},{"barAge":1118357669,"barDate":"2011-11-23 23:30:33","barName":"sss_0.9961642"}],"listString":["listString1","listString2","listString3"],"map":{"x":"s11111x","y":"s22222y","z":"s33333z"},"v_Date":"2011-11-23 23:30:33","vboolean":false,"vbyte":64,"vchar":"x","vdouble":22.203,"vfloat":12.1,"vint":65535,"vlong":9999999,"vshort":128} Process finished with exit code 0

fastjson通过各方面测试都很好，功能性能都是No.1，喜欢，它的源代码质量很高，作者也煞费苦心，将性能做到了最好，全免超越其他的json类库。

从其中的源代码中，可以学到很多东西，在阅读源码后，不得不佩服作者高超的程序设计水平，和高质量的编码。

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