输出json数据时,过滤不需要的字段,提高性能
publicstaticvoidmain(String[]args){
//模拟数据库,json数据
Provincep1=newProvince(1,"吉林省");
Provincep2=newProvince(2,"辽宁省");
Provincep3=newProvince(3,"山东省");
Listlist=newArrayList();
list.add(p1);
list.add(p2);
list.add(p3);
JsonConfigconfig=newJsonConfig();
//过滤pid,提高性能
//list集合存放的province这个对象的pid的属性不生成json
config.setExcludes(newString[]{"pid"});
//[{"pid":1,"pname":"吉林省"},{"pid":2,"pname":"辽宁省"},{"pid":3,"pname":"山东省"}]
JSONArrayjsonarray=JSONArray.fromObject(list,config);
System.out.println(jsonarray.toString());
Provincep=newProvince(4,"海南省");
//过滤pid
//JSONObjectjsonobject=JSONObject.fromObject(p,config);
//没有过滤pid
JSONObjectjsonobject=JSONObject.fromObject(p);
//输出json字符串
System.out.println(jsonobject.toString());
}
ajax后台接收服务器json数据
json.html
<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01Transitional//EN">
<html>
<head>
<title>form.html</title>
<metahttp-equiv="keywords"content="keyword1,keyword2,keyword3">
<metahttp-equiv="description"content="thisismypage">
<metahttp-equiv="content-type"content="text/html;charset=UTF-8">
</head>
<body>
<selectid="province"name="province">
<optionvalue="">请选择....</option>
</select>
<selectid="city"name="city">
<optionvalue="">请选择.....</option>
</select>
</body>
<scriptlanguage="JavaScript">
window.onload=function(){
varxmlHttp=ajaxFunction();
xmlHttp.onreadystatechange=function(){
if(xmlHttp.readyState==4){
if(xmlHttp.status==200||xmlHttp.status==304){
//data:从服务器端传递过来时,就是一个普通的字符串,此字符串不能被javaScript识别
vardata=xmlHttp.responseText;
//alert(data);
//alert(data.length);
//函数eval把字符串转化为javaScript可以识别的格式
vardataObj=eval("("+data+")");
//alert(dataObj);
//alert(dataObj.length);
//处理服务器响应,输出服务传送过来的数据
for(vari=0;i<dataObj.length;i++){
alert(dataObj[i].pid+":"+dataObj[i].pname);//从服务器获取json数据输出到页面
}
}
}
}
//post提交,可以带数据
xmlHttp.open("post","../jsonServlet?timeStamp="+newDate().getTime(),true);
xmlHttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
xmlHttp.send(null);
}
functionajaxFunction(){
varxmlHttp;
try{//Firefox,Opera8.0+,Safari
xmlHttp=newXMLHttpRequest();
}
catch(e){
try{//InternetExplorer
xmlHttp=newActiveXObject("Msxml2.XMLHTTP");
}
catch(e){
try{
xmlHttp=newActiveXObject("Microsoft.XMLHTTP");
}
catch(e){}
}
}
returnxmlHttp;
}
</script>
</html>
注意servlet要在web.xml中配置
JsonServler
packagecn.itcast.web;
importjava.io.IOException;
importjava.io.PrintWriter;
importjava.util.ArrayList;
importjava.util.List;
importjavax.servlet.ServletException;
importjavax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
importnet.sf.json.JSONArray;
importcn.itcast.bean.Province;
@SuppressWarnings("serial")
publicclassJsonServletextendsHttpServlet{
publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)
throwsServletException,IOException{
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
PrintWriterout=response.getWriter();//实例一个
//模拟数据库
Provincep1=newProvince(1,"吉林省");
Provincep2=newProvince(2,"辽宁省");
Provincep3=newProvince(3,"山东省");
Listlist=newArrayList();
list.add(p1);
list.add(p2);
list.add(p3);
////符合json格式:
//StringjsonStr="[{'pid':1,'pname':'吉林省'},{'pid':2,'pname':'辽宁省'},{'pid':3,'pname':'山东省'}]";
//out.print(jsonStr);
JSONArrayjsonarray=JSONArray.fromObject(list);//把list集合转换成json格式的数据
System.out.print(jsonarray.toString());
out.print(jsonarray.toString());//向页面输出json格式数据
}
}