Fastjson Obejct/Map/JSON/String 互转
Fastjson简介
Fastjson是一个Java语言编写的高性能功能完善的JSON库。它采用一种“假定有序快速匹配”的算法，把JSON Parse的性能提升到极致，是目前Java语言中最快的JSON库。Fastjson接口简单易用，已经被广泛使用在缓存序列化、协议交互、Web输出、android客户端等多种应用场景。
主要特点：
- 快速FAST (比其它任何基于Java的解析器和生成器更快，包括jackson）
- 强大（支持普通JDK类包括任意Java Bean Class、Collection、Map、Date或enum）
- 零依赖（没有依赖其它任何类库除了JDK）
- 开源，使用Apache License 2.0协议开源。
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
2、fastjson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"));// 11String o = "{'area':{'area':'1','pagetype':'home'},'pagetype':'home'}";
System.out.println(((Map) JSONObject.parseObject(o).get("area")).get("area"));// 1String 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"));// nullSystem.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。
需要获得其他相关资料可以点：Fastjson 对象或数组转JSON 互相参考。