本文参考:http://www.tuicool.com/articles/zUbQfa
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、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
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
作者：BosyJ
轉載：https://www.cnblogs.com/pejsidney/
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