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This article introduces the knowledge of "the perfect solution to Ajax cross-domain query". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Reason: browser security restrictions prohibit ajax from obtaining data across domains.

Solution: data in JSON format can be obtained across domains through the $. GetJSON () provided by jquery. Advantages: strong compatibility.

Java background code:

The copy code is as follows:

Protected void doPost (HttpServletRequest req, HttpServletResponse resp)

Throws ServletException, IOException {

String callback = req.getParameter ("callback"); / / the custom function name generated by jquery

Resp.setCharacterEncoding ("UTF-8")

Resp.setContentType ("text/html;charset=utf-8")

PrintWriter out = resp.getWriter ()

/ / returns a string in json format. Note that the output to the foreground must be in callback (string in json format)

/ / callback is the custom function name generated by jquery. If this format is returned, the foreground jquery code will automatically replace it.

/ / callback function is a callback function, thus achieving cross-domain effect. There are other cross-domain solutions on the Internet, such as AJAJ.

/ / the principle should be the same as this method. The disadvantages are: the amount of data returned should not be too large, the security is poor, and important data is not recommended.

/ / to be transmitted in this form.

Out.print (callback+ "({name:'111',sex:'222'});")

Out.flush ()

Out.close ()

}

Js foreground call code:

The copy code is as follows:

$(function () {)

/ / parameters that need to be passed may not be passed.

Var data= {param1: "param1", param2: "param2"}

/ / Note that url must be callback=? The callback parameter name can be customized

/ / but the backend must also synchronize the obtained parameter name

Var url = 'http://192.168.1.216:8080/DSFA/getUser?callback=?';

$.getJSON (url,data,function (backdata) {

/ / in fact, the function returned by the backend has been replaced with this function, so backdata

/ / it is the json object that you passed from the background.

Alert (backdata)

});

})

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