FastJson的使用方法总结

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JSON
116     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Map
124     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--->bbb
131      c--->ccc
132      a--->aaa
133     */
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 a
113 b
114 c
115 ["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--->bbb
140 c--->ccc
141 a--->aaa

本文转自SummerChill博客园博客，原文链接：http://www.cnblogs.com/DreamDrive/p/5778959.html，如需转载请自行联系原作者