引自：http://kb.cnblogs.com/page/139725/
Web页面上调用js文件时则不受是否跨域的影响（不仅如此，我们还发现凡是拥有”src”这个属性的标签都拥有跨域的能力，比如<script>、<img>、<iframe>）；
JSONP通过将数据(json)格式化为js的形式来实现跨域的数据调用。
<%@ page language="java" contentType="text/html; charset=GB18030" pageEncoding="GB18030"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=GB18030"> <title>Insert title here</title> </head> <script type="text/javascript" src="jquery-1.9.1.js"></script> <script> function handleData(data){ alert(JSON.stringify(data)); } function loadData(){ var url = "/myweb/TestJsonp?code=CA1998&callback=handleData"; //跨域url // 提供jsonp服务的url地址（不管是什么类型的地址，最终生成的返回值都是一段javascript代码） // 创建script标签，设置其属性 var script = document.createElement('script'); script.setAttribute('src', url); // 把script标签加入head，此时调用开始 document.getElementsByTagName('head')[0].appendChild(script); } function loadAjax(){ var url = "/myweb/TestJsonp?code=CA1998"; //跨域url $.ajax({ type: "get", //jsonp 类型下只能使用GET,不能用POST,这里不写默认为GET async: false, url: url, dataType: "jsonp", jsonp: "callback",//传递给请求处理程序或页面的，用以获得jsonp回调函数名的参数名(一般默认为:callback) // jsonpCallback:"handleData",//自定义的jsonp回调函数名称，默认为jQuery自动生成的随机函数名，也可以写"?"，jQuery会自动为你处理数据 success: function(json){ handleData(json); alert('您查询到航班信息'); }, error: function(){ alert('fail'); } }); } </script> <body onload="loadAjax()"> </body> </html>
package bookstore; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Servlet implementation class TestJsonp */ @WebServlet("/TestJsonp") public class TestJsonp extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public TestJsonp() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doPost(request,response); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub String code = request.getParameter("code"); String callback = request.getParameter("callback"); response.getWriter().write( callback+"({code:'"+code+"'})"); } }