JSON技术实战

JSON作为一种信息的载体伴随着AJAX的红火也越来越得到广大用户的青睐和认可！在没有使用JSON的时候，数据
从后台数据库到前台AJAX的返回显示，一般都要经过SQL查询--数据封装(封装成字符串或者XML文本)--前台解析
字符串或者XML文本，提取需要的东西出来。这其中包含了太多的转换关系，劳明伤财，也有很多人在探索一种
能够使大家都能认识的数据结构，这个时候大家都想到了JSON,可以说JSON也不是新的东西，出来好多年了，
Javascript一直都内置了JSON的支持，很多时候我们都是使用JSON的语法来定义一个Javascript的对象！看一看
JSON的官方网站(http://json.org/)就知道它目前基本上已经覆盖了大多数语言，这意味着大多数情况下的跨语言
环境下的数据交换，使用JSON是一个不错的选择！
1. Javascript(虽然已经内置支持，但是这里有一个开发包可以使用)
  (1) 使用JSON语法定义一个Javascript对象
  var myJSONObject = {"bindings": [
        {"ircEvent": "PRIVMSG", "method": "newURI", "regex": "^http://.*"},
        {"ircEvent": "PRIVMSG", "method": "deleteURI", "regex": "^delete.*"},
        {"ircEvent": "PRIVMSG", "method": "randomURI", "regex": "^random.*"}
    ]
  };
  myJSONObject.bindings[0].method 将返回newURI
  (2) 把普通字符串转换成JavaScript对象(需要扩展包支持)
  var myObject = JSON.parse(myJSONtext, filter);
  myData = JSON.parse(text, function (key, value) { return key.indexOf('date') >= 0 ? new Date(value) : value;    });
  (3) JSON对象转换成字符串
  var myJSONText = JSON.stringify(myObject);

2. Java对JSON的支持(没有原生的支持，需要使用第三方的扩展包来实现)
   Java的JSON开发包很多，也有很多实用且功能强大的
   (1) json-lib (http://json-lib.sourceforge.net/usage.html)
   a.) JSON和Java的类型对应关系
JSON  Java
string <=> java.lang.String, java.lang.Character, char
number <=> java.lang.Number, byte, short, int, long, float, double
true|false <=> java.lang.Boolean, boolean
null <=> null
function <=> net.sf.json.JSONFunction
array <=> net.sf.json.JSONArray (object, string, number, boolean, function)
object <=> net.sf.json.JSONObject
b.) json-lib的依赖库
jakarta commons-lang 2.3
jakarta commons-beanutils 1.7.0
jakarta commons-collections 3.2
jakarta commons-logging 1.1
ezmorph 1.0.3
xom 1.1(如果要用到xml文件的解析的话)
  c.) 可运行实例
package com.gomt.json.jsonlib;

import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
import net.sf.json.xml.XMLSerializer;

import org.apache.commons.beanutils.PropertyUtils;

public class JsonLibMain {

public JsonLibMain() {
// TODO Auto-generated constructor stub
}

/**
* @param args
* @throws NoSuchMethodException
* @throws InvocationTargetException
* @throws IllegalAccessException
*/
public static void main(String[] args) throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {
boolean[] boolArray = new boolean[]{true,false,true};  
JSONArray jsonArray = JSONArray.fromObject( boolArray );  
System.out.println("***1*** = " + jsonArray );

Collection<String> list = new ArrayList<String>();  
list.add( "first" );  
list.add( "second" );  
jsonArray = JSONArray.fromObject( list );  
System.out.println("***2*** = " + jsonArray );

jsonArray = JSONArray.fromObject( "['json','is','easy']" );  
System.out.println("***3*** = " + jsonArray );

Map<String, Object> map = new HashMap<String, Object>();  
map.put( "name", "json" );  
map.put( "bool", Boolean.TRUE );  
map.put( "int", new Integer(1) );  
map.put( "arr", new String[]{"a","b"} );  
map.put( "func", "function(i){ return this.arr[i]; }" );  
 
JSONObject jsonObject = JSONObject.fromObject( map );  
System.out.println("***4*** = " + jsonObject );

jsonObject = JSONObject.fromObject( new MyBean() );  
System.out.println("***5*** = " +  jsonObject );

String json = "{name=\"json\",bool:true,int:1,double:2.2,func:function(a){ return a; },array:[1,2]}";  

jsonObject = JSONObject.fromObject( json );  
Object bean = JSONObject.toBean( jsonObject );  
System.out.print("***6*** = " +  jsonObject.get( "name" ) + " " + PropertyUtils.getProperty( bean, "name" ) );  
System.out.print("\t " +  jsonObject.get( "bool" ) + " = " + PropertyUtils.getProperty( bean, "bool" ) );  
System.out.print("\t " +  jsonObject.get( "int" ) + " = " + PropertyUtils.getProperty( bean, "int" ) );  
System.out.print("\t " +  jsonObject.get( "double" ) + " = " + PropertyUtils.getProperty( bean, "double" ) );  
System.out.print("\t " +  jsonObject.get( "func" ) + " = " + PropertyUtils.getProperty( bean, "func" ) );  
List expected = JSONArray.toList( jsonObject.getJSONArray( "array" ) );  
System.out.println("\t " +  expected + " = " + (List) PropertyUtils.getProperty( bean, "array" ) );

json = "{bool:true,integer:1,string:\"json\"}";  
jsonObject = JSONObject.fromObject( json );  
MyBean myBean = (MyBean) JSONObject.toBean( jsonObject, MyBean.class );  
System.out.print("***7*** = " +  jsonObject.get( "bool" ) + " = " + Boolean.valueOf( myBean.isBool() ) );  
System.out.print("\t " +  jsonObject.get( "integer" ) + " = " +new Integer( myBean.getInteger() ) );  
System.out.println("\t " +  jsonObject.get( "string" )+ " = " + myBean.getString() );

//需要用到ezmorph
json = "{'data':[{'name':'clarance','userId':100001},{'name':'peng','userId':100002}]}";  
Map<String,Class<Person>> classMap = new HashMap<String,Class<Person>>();  
classMap.put( "data", Person.class );
myBean = (MyBean)JSONObject.toBean(JSONObject.fromObject(json), MyBean.class, classMap);
if(myBean != null && myBean.getData() != null) {
for(Person p : myBean.getData()) {
System.out.println("***8*** = " +  "用户id: " + p.getUserId() + " 用户名: " + p.getName());
}
}

/*
Morpher dynaMorpher = new BeanMorpher( Person.class, JSONUtils.getMorpherRegistry() );  
MorpherRegistry morpherRegistry = new MorpherRegistry();
morpherRegistry.registerMorpher( dynaMorpher );  
List output = new ArrayList();  
for( Iterator i = myBean.getData().iterator(); i.hasNext(); ){  
   output.add( morpherRegistry.morph( Person.class, i.next() ) );  
}  
myBean.setData( output );
*/
/**
* XML和JSON之间的转换,需要用到xom
*/
jsonObject = new JSONObject( true );  
XMLSerializer xmls = new XMLSerializer();
String xml = xmls.write( jsonObject );
System.out.println("***9*** = " + xml);

jsonObject = JSONObject.fromObject("{\"name\":\"json\",\"bool\":true,\"int\":1}");  
xmls = new XMLSerializer();
xml = xmls.write( jsonObject );
System.out.println("***10*** = " + xml);

jsonArray = JSONArray.fromObject("[1,2,3]");  
xmls = new XMLSerializer();
xml = xmls.write( jsonArray );
System.out.println("***11*** = " + xml);

xml = "<a class=\"array\"><e type=\"function\" params=\"i,j\">return matrix[i][j];</e></a> ";
xmls = new XMLSerializer();
jsonArray = (JSONArray) xmls.read( xml);
System.out.println("***12*** = " +  jsonArray );

}

}

package com.gomt.json.jsonlib;

import java.util.List;

import net.sf.json.JSONFunction;

public class MyBean implements java.io.Serializable {
private static final long serialVersionUID = -784610042144660631L;
private String name = "json";  
   private int pojoId = 1;  
   private char[] options = new char[]{'a','f'};  
   private String func1 = "function(i){ return this.options[i]; }";  
   private JSONFunction func2 = new JSONFunction(new String[]{"i"},"return this.options[i];");
   private Integer integer;
   private Boolean bool;
   private String string;
   private List<Person> data;
  
public Boolean isBool() {
return bool;
}
public void setBool(Boolean bool) {
this.bool = bool;
}
public String getString() {
return string;
}
public void setString(String string) {
this.string = string;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getPojoId() {
return pojoId;
}
public void setPojoId(int pojoId) {
this.pojoId = pojoId;
}
public char[] getOptions() {
return options;
}
public void setOptions(char[] options) {
this.options = options;
}
public String getFunc1() {
return func1;
}
public void setFunc1(String func1) {
this.func1 = func1;
}
public JSONFunction getFunc2() {
return func2;
}
public void setFunc2(JSONFunction func2) {
this.func2 = func2;
}
public Integer getInteger() {
return integer;
}
public void setInteger(Integer integer) {
this.integer = integer;
}
public Boolean getBool() {
return bool;
}
public List<Person> getData() {
return data;
}
public void setData(List<Person> data) {
this.data = data;
}
     
}
 

package com.gomt.json.jsonlib;

import java.io.Serializable;

public class Person implements Serializable {

private static final long serialVersionUID = 7699163849016962711L;
private int userId;
private String name;
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}

d.) 运行结果
***1*** = [true,false,true]
***2*** = ["first","second"]
***3*** = ["json","is","easy"]
***4*** = {"func":function(i){ return this.arr[i]; },"arr":["a","b"],"int":1,"name":"json","bool":true}
***5*** = {"string":"","integer":0,"func1":function(i){ return this.options[i]; },"data":[],"pojoId":1,"name":"json","bool":false,"options":["a","f"],"func2":function(i){ return this.options[i]; }}
***6*** = json json true = true 1 = 1 2.2 = 2.2 function(a){ return a; } = function(a){ return a; } [1, 2] = [1, 2]
***7*** = true = true 1 = 1 json = json
***8*** = 用户id: 100001 用户名: clarance
***8*** = 用户id: 100002 用户名: peng
***9*** = <?xml version="1.0" encoding="UTF-8"?>
<o null="true"/>

***10*** = <?xml version="1.0" encoding="UTF-8"?>
<o><bool type="boolean">true</bool><int type="number">1</int><name type="string">json</name></o>

***11*** = <?xml version="1.0" encoding="UTF-8"?>
<a><e type="number">1</e><e type="number">2</e><e type="number">3</e></a>

2007-12-7 9:08:29 net.sf.json.xml.XMLSerializer getType
信息: Using default type string
***12*** = [function(i,j){ return matrix[i][j]; }]

评论

3 楼 clarancepeng 2008-06-20  

json-lib本身不支持java.util.Date, java.sql.Date, Timestamp，不过通过扩展它提供的接口还是可以用的，可以参照
http://dojotoolkit.org/forum/dojo-core-dojo-0-9/dojo-core-support/json-json-lib-and-date

2 楼 rmn190 2008-06-19  

若在Person类里加一个java.util.Date类型的birthday,这样在调用JSONObject的toBean方法时又怎么来处理?

1 楼 clarancepeng 2007-12-07  

(2) json-taglib (http://json-taglib.sourceforge.net/examples.html)
    它是建立在org.json库的基础上(对应于包里面的atg.taglib.json.util.*),采用jsp的自定义标签,它定义了object,property,array这三种json的类型(没有定义function), 下面是它的官方网站上面的例子.

<%@ taglib prefix="json" uri="http://www.atg.com/taglibs/json" %>

<json:object>
  <json:property name="itemCount" value="${cart.itemCount}"/>
  <json:property name="subtotal" value="${cart.subtotal}"/>
  <json:array name="items" var="item" items="${cart.lineItems}">
    <json:object>
      <json:property name="title" value="${item.title}"/>
      <json:property name="description" value="${item.description}"/>
      <json:property name="imageUrl" value="${item.imageUrl"/>
      <json:property name="price" value="${item.price}"/>
      <json:property name="qty" value="${item.qty}"/>
    </json:object>
  </json:array>
</json:object>
-----------------------------------------------------
输出结果:
{
  itemCount: 2,
  subtotal: "$15.50",
  items:[
    {
      title: "The Big Book of Foo",
      description: "Bestselling book of Foo by A.N. Other",
      imageUrl: "/images/books/12345.gif",
      price: "$10.00",
      qty: 1
    },
    {
      title: "Javascript Pocket Reference",
      description: "Handy pocket-sized reference for the Javascript language",
      imageUrl: "/images/books/56789.gif",
      price: "$5.50",
      qty: 1
    }
  ]
}

-----------------------------------------------------
<%@ taglib prefix="json" uri="http://www.atg.com/taglibs/json" %>
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>

<json:object>
  <json:property name="itemCount" value="${cart.itemCount}"/>
  <json:property name="subtotal">
    <fmt:formatNumber value="${cart.subtotal}" type="currency" currencyCode="${cart.currency}"/>
  </json:property>
  <json:array name="items" var="item" items="${cart.lineItems}">
    <json:object>
      <json:property name="title" value="${item.title}"/>
      <json:property name="description" value="${item.description}"/>
      <json:property name="imageUrl" value="${item.imageUrl"/>
      <json:property name="price">
        <fmt:formatNumber value="${item.price}" type="currency" currencyCode="${cart.currency}"/>
      </json:property>
      <json:property name="qty" value="${item.qty}"/>
    </json:object>
  </json:array>
</json:object>