AJAX的跨域访问-两种有效的解决方法介绍

新的W3C策略实现了HTTP跨域访问，还亏我找了很久的资料解决这个问题：
只需要在servlet中返回的头部信息中添加Access-Control-Allow-Origin这个既可。
比如我要开放所有我本地的跨域访问，就设置如下：response.setHeader("Access-Control-Allow-Origin", "http://127.0.0.1/*");
这样我本地的A工程中的AJAX请求就可以跨域请求B工程中的servlet。
代码如下：
HTML的JS的ajax请求：

复制代码 代码如下:

/* Create a new XMLHttpRequest object to talk to the Web server */
var xmlHttp = false;
/*@cc_on @*/
/*@if (@_jscript_version >= 5)
try {
    xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
    try {
  xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    } catch (e2) {
  xmlHttp = false;
    }
}
@end @*/
if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {
     xmlHttp = new XMLHttpRequest();
}
var url = "http://127.0.0.1:2012/esb/servlet/HttpClient?randomType=MIX";
xmlHttp.open("GET", url, true);
//Setup a function for the server to run when it's done
xmlHttp.onreadystatechange = function(){
    if (xmlHttp.readyState == 4) {
  var response = xmlHttp.responseText;
  alert(response);
}
}
//Send the request
xmlHttp.send(null);

复制代码 代码如下:

protected void service(HttpServletRequest req, HttpServletResponse resp)
 throws ServletException, java.io.IOException {
resp.setHeader("Pragma", "no-cache");
resp.setHeader("Cache-Control", "no-cache");
//下面那句是核心
resp.setHeader("Access-Control-Allow-Origin", "http://127.0.0.1/*");
resp.setDateHeader("Expires", 0);
ServletOutputStream sos = resp.getOutputStream();
try {
     sos.write(obj.toString().getBytes("GBK"));
 } catch (Exception e) {
     System.out.println(e.toString90)
 } finally {
  try {
sos.close();
  } catch (Exception e) {
LOG.error(e);
  }
 }
}

复制代码 代码如下:

function loadAjax(){
     id="testesbscript";
     oScript = document.getElementById(id);
     var head = document.getElementsByTagName("head").item(0);
     if (oScript) {
  head.removeChild(oScript);
    }
    oScript = document.createElement("script");
    var url = "http://127.0.0.1:2012/esb/servlet/HttpClient?randomType=MIX&success=justHandle
    oScript.setAttribute("id",id);
    oScript.setAttribute("type","text/javascript");
    oScript.setAttribute("language","javascript");
    head.appendChild(oScript);
}
//jsutHandle这个函数是反调函数。servlet代码中会使用eval这种方式来执行。
function justHandle(dd){
    alert(dd);
}

复制代码 代码如下:

protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, java.io.IOException {

Object obj = "test";
ServletOutputStream sos = resp.getOutputStream();
StringBuffer sb = new StringBuffer();
resp.setCharacterEncoding("GBK");

resp.setHeader("Charset","GBK");
resp.setContentType("charset=GBK");
//下面那句表明是javascript脚本文件
resp.setContentType("text/javascript");

sb.append("eval(/""+paramMap.get("success")+"(/'"+obj.toString()+"/')/")");
try {
    sos.write(sb.toString().getBytes(this.character_encoding));
} catch (Exception e) {
    System.out.println(e.toString());
} finally {
     try {
   sos.close();
} catch (Exception e) {
   System.out.println(e.toString());
}
}
}