Example of cross-origin request submission using JQuery and Servlet

Example of cross-origin request submission using JQuery and Servlet

This article describes how to use JQuery and Servlet to implement cross-origin request submission. For more information, see

Principle: JavaScript Ajax cannot be cross-origin, but requests can be sent to a local Servlet, And the Servlet completes cross-origin. Return the remote structure to the client. In this way, Ajax can be cross-origin. Later, I will release another PHP version. Please pay attention to it. Below is the code

 

JS Code:

 

Note: In Post mode, param1 and param2 are the parameter values that are sent remotely. There can be multiple parameters.

 

The Code is as follows:

// GET Method

Function reqeustCrossDomainProxyGet (){

Var url = "http://www.baidu.com"; // remote request address

Var param = {'requesturl': url, 'typedata': 'json '};

Var data = getCrossDomainProxyRemote (param, "json ");

}

// Post method

Function reqeustCrossDomainProxyPost (param1, param2 ){

Var url = apiServer + "/api/lucene/query ";

Var param = {'requesturl': url, 'typedata': 'json', 'param1': param1, 'param2': param2 };

Var data = getCrossDomainProxyRemote (param, "json ");

}

 

/**

* JS sends a POST request to a Servlet at the address, all parameters about the remote request.

* The parameter POST is sent to the Servlet.

* @ Param remote Request Parameter

* @ Param rtype JS return type (not used currently)

* @ Return

*/

Function getCrossDomainProxyRemote (param, rtype ){

Var url = "/cross/proxy"; // Servlet URL

Var returndata;

$. Ajax ({

Url: url, type: 'post', dataType: rtype, timeout: 40000, data: param, async: false,

Error: function (response, error) {alert (response. status );},

Success: function (data) {returndata = data ;}

});

Return returndata;

}

 

 

 

Java code:

 

The Code is as follows:

Public class CorssDomainProxy extends HttpServlet {

 

Public void doGet (HttpServletRequest req, HttpServletResponse resp)

Throws ServletException, IOException {

This. doPost (req, resp );

}

 

Public void doPost (HttpServletRequest req, HttpServletResponse resp)

Throws ServletException, IOException {

Boolean requestType = false; // indicates the remote request type. The default value is GET.

PrintWriter out = resp. getWriter ();

Enumeration keys = req. getParameterNames (); // retrieve all parameter names passed by the client

ArrayList <String> params = new ArrayList <String> ();

String url = null;

While (keys. hasMoreElements ()){

String key = (String) keys. nextElement ();

/**

* If the request parameters are described as follows, this parameter is not used in remote requests.

*/

If (key. equals ("requesturl") {// determines whether the parameter is a remote request address

Url = req. getParameter (key );

} Else if (key. equals ("typedata") {// you can specify the request data type.

 

} Else if (key. equals ("returntype") {// you can specify the type of the returned request.

 

} Else {

Params. add (key); // other parameters added to the List, which are the parameters involved in the remote request.

RequestType = true; // modify the flag. The table finds that the remote request is POST.

}

}

 

HttpClient client = new HttpClient ();

HttpMethod method = null;

If (requestType) {// determine the request method, and instantiate the HttpMethod object, true: POST, false: GET

Method = new UTF8PostMethod (url );

For (String name: params) {// iterate the POST parameter and add it to the request

String _ value = req. getParameter (name );

(PostMethod) method). setParameter (name, _ value );

}

} Else {

Method = new GetMethod (url );

}

Client.exe cuteMethod (method); // executes the request

String bodystr = method. getResponseBodyAsString (); // The returned result.

Out. println (bodystr); // return the result to the client.

}

 

/**

* Internal class that converts a URL string to a UTF-8

* @ Author Administrator

*

*/

Private static class UTF8PostMethod extends PostMethod {

Public UTF8PostMethod (String url ){

Super (url );

}

@ Override

Public String getRequestCharSet (){

Return "UTF-8 ";

}

}

 

}