FastJson的使用方法总结

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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。

1 public static final Object parse(String text); // 把JSON文本parse为JSONObject或者JSONArray 2 public static final JSONObject parseObject(String text)； // 把JSON文本parse成JSONObject    3 public static final <T> T parseObject(String text, Class<T> clazz); // 把JSON文本parse为JavaBean 4 public static final JSONArray parseArray(String text); // 把JSON文本parse成JSONArray 5 public static final <T> List<T> parseArray(String text, Class<T> clazz); //把JSON文本parse成JavaBean集合 6 public static final String toJSONString(Object object); // 将JavaBean序列化为JSON文本 7 public static final String toJSONString(Object object, boolean prettyFormat); // 将JavaBean序列化为带格式的JSON文本 8 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

 1 import java.util.Date; 2 import java.util.Random; 3  4 import com.alibaba.fastjson.JSON; 5 import com.alibaba.fastjson.serializer.SerializeConfig; 6 import com.alibaba.fastjson.serializer.SimpleDateFormatSerializer; 7  8 /**  9 * @author leizhimin 11-11-22 上午9:15 10 */ 11 public class Bar { 12   //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。    13   public static SerializeConfig mapping = new SerializeConfig(); 14   15   private String barName; 16   private int barAge; 17   private Date barDate = new Date();18   19   static { 20     mapping.put(Date.class, new SimpleDateFormatSerializer("yyyy-MM-dd")); 21   } 22   23   //代码块给Bar对象中的barName和barAge赋值.24   { 25     Random random = new Random(); 26     barName = "name_"+String.valueOf(random.nextInt()); 27     barAge = random.nextInt(); 28   } 29 30   public static void main(String[] args) { 31     //把Bar对象转换成JSON格式的Object类型32     Object obj = JSON.toJSON(new Bar()); 33     System.out.println(obj);34     //输出{"barAge":-664880579,"barDate":1471348117095,"barName":"name_464160862"}35     36     //Bar对象转换成String类型的字符串37     String x1 = JSON.toJSONString(new Bar(), true);38     System.out.println(x1); 39     //输出:40     /*41     {42         "barAge":1553774697,43         "barDate":1471348117144,44         "barName":"name_-1034255192"45     }46     */47     48     //格式化时间的JSON字符串49     String x2 = JSON.toJSONString(new Bar(), mapping); 50     System.out.println(x2); 51     //输出:{"barAge":1755982737,"barDate":"2016-08-16","barName":"name_453018403"}52   } 53 54   public String getBarName() { 55     return barName; 56   } 57 58   public void setBarName(String barName) { 59     this.barName = barName; 60   } 61 62   public int getBarAge() { 63     return barAge; 64   } 65 66   public void setBarAge(int barAge) { 67     this.barAge = barAge; 68   } 69 70   public Date getBarDate() { 71     return barDate; 72   } 73 74   public void setBarDate(Date barDate) { 75     this.barDate = barDate; 76   } 77 78   @Override 79   public String toString() { 80     return "Bar{" + 81         "barName='" + barName + '\'' + 82         ", barAge=" + barAge + 83         ", barDate=" + barDate + 84         '}'; 85   } 86 }

Foo.java

  1 import java.util.ArrayList;  2 import java.util.Date;  3 import java.util.HashMap;  4 import java.util.List;  5 import java.util.Map;  6   7 /**   8 * @author leizhimin 11-11-22 上午9:15   9 */  10 public class Foo {  11   //声明Java中的8种基本变量和String类型变量. 12   private String vString = "vStringhehhehe"; 13    14   private char vchar = 'x';  15   private byte vbyte = 64;  16   private short vshort = 128;  17   private int vint = 65535;  18   private long vlong = 9999999L;  19   private float vfloat = 12.1f;  20   private double vdouble = 22.203d;  21   private boolean vboolean = false;  22  23   //Date和Object类型变量 24   private Date vDate = new Date();  25   private Object vnull = null;  26  27   //String,int,boolean类型的数组 28   private String[] avString = {"aaa", "bbb", "ccc"};  29   private int[] avint = {1, 2, 3, 4};  30   private boolean[] avboolean = {true, false, true, true};  31    32   //List和Map类型变量 33   private List<String> listString = new ArrayList<String>();  34   private Map<String, String> map = new HashMap<String, String>();  35  36   //封装的Bar对象 37   private Bar bar = new Bar();  38   private Bar[] avBar = {new Bar(), new Bar()};  39   private List<Bar> listBar = new ArrayList<Bar>();  40    41   //代码块封装数据 42   {  43     listString.add("listString1");  44     listString.add("listString2");  45     listString.add("listString3");  46  47     map.put("x", "s11111x");  48     map.put("y", "s22222y");  49     map.put("z", "s33333z");  50  51     listBar.add(new Bar());  52     listBar.add(new Bar());  53     listBar.add(new Bar());  54   }  55  56   public String getvString() {  57     return vString;  58   }  59  60   public void setvString(String vString) {  61     this.vString = vString;  62   }  63  64   public char getVchar() {  65     return vchar;  66   }  67  68   public void setVchar(char vchar) {  69     this.vchar = vchar;  70   }  71  72   public byte getVbyte() {  73     return vbyte;  74   }  75  76   public void setVbyte(byte vbyte) {  77     this.vbyte = vbyte;  78   }  79  80   public short getVshort() {  81     return vshort;  82   }  83  84   public void setVshort(short vshort) {  85     this.vshort = vshort;  86   }  87  88   public int getVint() {  89     return vint;  90   }  91  92   public void setVint(int vint) {  93     this.vint = vint;  94   }  95  96   public long getVlong() {  97     return vlong;  98   }  99 100   public void setVlong(long vlong) { 101     this.vlong = vlong; 102   } 103 104   public float getVfloat() { 105     return vfloat; 106   } 107 108   public void setVfloat(float vfloat) { 109     this.vfloat = vfloat; 110   } 111 112   public double getVdouble() { 113     return vdouble; 114   } 115 116   public void setVdouble(double vdouble) { 117     this.vdouble = vdouble; 118   } 119 120   public boolean isVboolean() { 121     return vboolean; 122   } 123 124   public void setVboolean(boolean vboolean) { 125     this.vboolean = vboolean; 126   } 127 128   public Date getvDate() { 129     return vDate; 130   } 131 132   public void setvDate(Date vDate) { 133     this.vDate = vDate; 134   } 135 136   public Object getVnull() { 137     return vnull; 138   } 139 140   public void setVnull(Object vnull) { 141     this.vnull = vnull; 142   } 143 144   public String[] getAvString() { 145     return avString; 146   } 147 148   public void setAvString(String[] avString) { 149     this.avString = avString; 150   } 151 152   public int[] getAvint() { 153     return avint; 154   } 155 156   public void setAvint(int[] avint) { 157     this.avint = avint; 158   } 159 160   public boolean[] getAvboolean() { 161     return avboolean; 162   } 163 164   public void setAvboolean(boolean[] avboolean) { 165     this.avboolean = avboolean; 166   } 167 168   public List<String> getListString() { 169     return listString; 170   } 171 172   public void setListString(List<String> listString) { 173     this.listString = listString; 174   } 175 176   public Map<String, String> getMap() { 177     return map; 178   } 179 180   public void setMap(Map<String, String> map) { 181     this.map = map; 182   } 183 184   public Bar getBar() { 185     return bar; 186   } 187 188   public void setBar(Bar bar) { 189     this.bar = bar; 190   } 191 192   public Bar[] getAvBar() { 193     return avBar; 194   } 195 196   public void setAvBar(Bar[] avBar) { 197     this.avBar = avBar; 198   } 199 200   public List<Bar> getListBar() { 201     return listBar; 202   } 203 204   public void setListBar(List<Bar> listBar) { 205     this.listBar = listBar; 206   } 207 }

Test.java

  1 import java.util.ArrayList;  2 import java.util.Date;  3 import java.util.HashMap;  4 import java.util.List;  5 import java.util.Map;  6   7 import com.alibaba.fastjson.JSON;  8 import com.alibaba.fastjson.JSONArray;  9 import com.alibaba.fastjson.serializer.SerializeConfig; 10 import com.alibaba.fastjson.serializer.SimpleDateFormatSerializer; 11  12 /**  13 * Created by 2IntelliJ IDEA.  14 *  15 * @author leizhimin 11-11-22 上午9:45  16 */  17 public class Test {  18   private static SerializeConfig mapping = new SerializeConfig();  19   static {  20     mapping.put(Date.class, new SimpleDateFormatSerializer("yyyy-MM-dd HH:mm:ss"));  21   }  22  23   public static void main(String[] args) {  24      25     Date date = new Date(); 26     String text = JSON.toJSONString(date, mapping); 27     System.out.println(text);//输出"2016-08-16 19:53:07" 28      29     Foo f1 = new Foo(); 30     System.out.println(JSON.toJSONString(f1, true)); 31       32     String x2 =JSON.toJSONString(f1, mapping);  33     System.out.println(x2);  34      35     //List -> JSON array  36     json2List(); 37      38     json2Map(); 39      40     //普通类型Array数组和JSON的相互转换 41      array2JSON(); 42      43      array2JSON2(); 44        45      //普通类型Map和JSON的相互转换 46      map2JSON(); 47   }  48  49   public static void json2List(){  50     //List -> JSON array  51     List<Bar> barList = new ArrayList<Bar>();  52     barList.add(new Bar());  53     barList.add(new Bar());  54     barList.add(new Bar());  55     String json= JSON.toJSONString(barList, true);  56     System.out.println(json);  57      58     //JSON array -> List  59     List<Bar> barList1 = JSON.parseArray(json,Bar.class);  60     for (Bar bar : barList1) {  61       System.out.println(bar.toString());  62     }  63   }  64  65   public static void json2Map(){  66     //Map -> JSON  67     Map<String,Bar> map = new HashMap<String, Bar>();  68     map.put("a",new Bar());  69     map.put("b",new Bar());  70     map.put("c",new Bar());  71     String json = JSON.toJSONString(map,true);  72     System.out.println(json);  73      74     //JSON -> Map  75     Map<String,Bar> map1 = (Map<String,Bar>)JSON.parse(json);  76     for (String key : map1.keySet()) {  77       System.out.println(key+":"+map1.get(key));  78     }  79   }  80    81    82   public static void array2JSON(){  83     //String数组转换成JSON 84     String[] arr_String  = {"a","b","c"};  85     String json_arr_String = JSON.toJSONString(arr_String,true);  86     System.out.println(json_arr_String); //输出["a","b","c"] 87      88     //JSON转换成array 89     JSONArray jsonArray = JSON.parseArray(json_arr_String);  90     for (Object o : jsonArray) {  91       System.out.println(o);  92     }  93     /* 输出: 94      a 95      b 96      c 97      */ 98     System.out.println(jsonArray);//输出:["a","b","c"]  99   } 100   101   public static void array2JSON2(){ 102     Bar[] arr_Bar    = {new Bar(),new Bar(),new Bar()}; 103     String json_arr_Bar = JSON.toJSONString(arr_Bar,true); 104     System.out.println(json_arr_Bar); 105     JSONArray jsonArray = JSON.parseArray(json_arr_Bar); 106     for (Object o : jsonArray) { 107       System.out.println(o); 108     } 109     System.out.println(jsonArray); 110   } 111 112   113   public static void map2JSON(){114     115     //Map转换成JSON116     Map<String,String> map = new HashMap<String,String>(); 117     map.put("a","aaa"); 118     map.put("b","bbb"); 119     map.put("c","ccc"); 120     String json=JSON.toJSONString(map); 121     System.out.println(json);//输出{"a":"aaa","b":"bbb","c":"ccc"}122     123     //JSON转换成Map124     Map map1 = JSON.parseObject(json); 125     for (Object o : map.entrySet()) { 126       Map.Entry<String,String> entry = (Map.Entry<String,String>)o; 127       System.out.println(entry.getKey()+"--->"+entry.getValue()); 128     } 129     /*130      b--->bbb131      c--->ccc132      a--->aaa133     */134   } 135 }

程序输出:

  1 "System.out.println(text);"  2 "2016-08-17 10:16:18"  3   4 System.out.println(JSON.toJSONString(f1, true));  5 {  6     "avBar":[{  7         "barAge":-480029500,  8         "barDate":1471400178210,  9         "barName":"name_-2129248362" 10     },{ 11         "barAge":634833464, 12         "barDate":1471400178210, 13         "barName":"name_-1877607258" 14     }], 15     "avString":["aaa","bbb","ccc"], 16     "avboolean":[true,false,true,true], 17     "avint":[1,2,3,4], 18     "bar":{ 19         "barAge":-1335514550, 20         "barDate":1471400178210, 21         "barName":"name_-1069927371" 22     }, 23     "listBar":[ 24         { 25             "barAge":357976541, 26             "barDate":1471400178210, 27             "barName":"name_1051748274" 28         }, 29         { 30             "barAge":1253923759, 31             "barDate":1471400178210, 32             "barName":"name_1279150198" 33         }, 34         { 35             "barAge":357167456, 36             "barDate":1471400178210, 37             "barName":"name_-737334111" 38         } 39     ], 40     "listString":[ 41         "listString1", 42         "listString2", 43         "listString3" 44     ], 45     "map":{ 46         "x":"s11111x", 47         "y":"s22222y", 48         "z":"s33333z" 49     }, 50     "vDate":1471400178209, 51     "vString":"vStringhehhehe", 52     "vboolean":false, 53     "vbyte":64, 54     "vchar":"x", 55     "vdouble":22.203, 56     "vfloat":12.1, 57     "vint":65535, 58     "vlong":9999999, 59     "vshort":128 60 } 61 System.out.println(x2);  62 {"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} 63  64 json2List(); 65 [ 66     { 67         "barAge":-2022440599, 68         "barDate":1471400178284, 69         "barName":"name_-590972614" 70     }, 71     { 72         "barAge":1704306424, 73         "barDate":1471400178284, 74         "barName":"name_1482085108" 75     }, 76     { 77         "barAge":1907038490, 78         "barDate":1471400178284, 79         "barName":"name_651427557" 80     } 81 ] 82  83 Bar{barName='name_-590972614', barAge=-2022440599, barDate=Wed Aug 17 10:16:18 CST 2016} 84 Bar{barName='name_1482085108', barAge=1704306424, barDate=Wed Aug 17 10:16:18 CST 2016} 85 Bar{barName='name_651427557', barAge=1907038490, barDate=Wed Aug 17 10:16:18 CST 2016} 86  87 json2Map(); 88 { 89     "a":{ 90         "barAge":877829686, 91         "barDate":1471400178308, 92         "barName":"name_558391664" 93     }, 94     "b":{ 95         "barAge":375478040, 96         "barDate":1471400178308, 97         "barName":"name_-1233383964" 98     }, 99     "c":{100         "barAge":-1043862971,101         "barDate":1471400178308,102         "barName":"name_-823025454"103     }104 }105 106 b:{"barAge":375478040,"barDate":1471400178308,"barName":"name_-1233383964"}107 c:{"barAge":-1043862971,"barDate":1471400178308,"barName":"name_-823025454"}108 a:{"barAge":877829686,"barDate":1471400178308,"barName":"name_558391664"}109 110 array2JSON()111 ["a","b","c"]112 a113 b114 c115 ["a","b","c"]116 117 array2JSON2()118 [{119     "barAge":-842219577,120     "barDate":1471400178310,121     "barName":"name_-1204063138"122 },{123     "barAge":1450191787,124     "barDate":1471400178310,125     "barName":"name_650041812"126 },{127     "barAge":-732707567,128     "barDate":1471400178310,129     "barName":"name_159117539"130 }]131 132 {"barAge":-842219577,"barDate":1471400178310,"barName":"name_-1204063138"}133 {"barAge":1450191787,"barDate":1471400178310,"barName":"name_650041812"}134 {"barAge":-732707567,"barDate":1471400178310,"barName":"name_159117539"}135 [{"barAge":-842219577,"barDate":1471400178310,"barName":"name_-1204063138"},{"barAge":1450191787,"barDate":1471400178310,"barName":"name_650041812"},{"barAge":-732707567,"barDate":1471400178310,"barName":"name_159117539"}]136 137 map2JSON()138 {"a":"aaa","b":"bbb","c":"ccc"}139 b--->bbb140 c--->ccc141 a--->aaa

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