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
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
测试小例子：
JSONObject json =
new JSONObject(); json.put(
"aa",
"11"); json.put(
"bb",
"22"); json.put(
"cc",
"33"); String jsonStr = json.toString(); System.
out.println(jsonStr);
// {"aa":"11","bb":"22","cc":"33"} System.
out.println(JSONObject.parseObject(jsonStr).
get(
"aa"));
// 11 String o =
"{'area':{'area':'1','pagetype':'home'},'pagetype':'home'}"; System.
out.println(((Map) JSONObject.parseObject(o).
get(
"area")).
get(
"area"));
// 1 String text = JSON.toJSONString(o); Map<String, Object> userMap = JSON.parseObject(o,
new TypeReference<Map<String, Object>>() {}); System.
out.println(((Map) userMap.
get(
"area")).
get(
"NotExsit"));
// null System.
out.println(JSON.toJSONString((Map) userMap.
get(
"area")));
// {"area":"1","pagetype":"home"}
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。
6、Refer：
6.1 FastJSON应用前测试
http://lavasoft.blog.51cto.com/62575/723192
6.2 alibaba fastjson(json序列化器)序列化部分源码解析-1-总体分析
http://www.iflym.com/index.php/code/alibaba-fastjson-json-serializer-chapter-source-analyse-one-global-analyse.html
6.3 FastJson---高性能JSON开发包
http://blog.csdn.net/glarystar/article/details/6654494
转载于:https://www.cnblogs.com/jym-sunshine/p/5458836.html
相关资源：数据结构—成绩单生成器
