JSONP cross-domain access services

Some time ago in the product development, need to interact with the company's Web site, we developed the product is placed in a domain name, the company's website that block is under another domain name, so in the page call

Site over the interface there is a cross-domain problem, at that time in order not to modify the interface over the site, so the use of the server through the WebService way to invoke the site interface, the problem is quickly resolved, then I was thinking

If you need to directly access in JS, it involves cross-domain issues, then how to solve this problem, I went online to find some information, and finally adopted the JSONP way to solve. Let me share with you the following

Solve cross-domain problems in a jsonp way. Divided into the following steps:

1, introduce jquery.js, use $.ajax () to define JSONP, as follows:

<%@ page language= "java"  contenttype= "text/html;  Charset=utf-8 " pageencoding=" Utf-8 " %><%string path = request.getcontextpath (); %><! doctype html public  "-//w3c//dtd xhtml 1.0 transitional//en"   "HTTP// Www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">
 2, server-side processing: 
 
package com.mall.web.action;import java.io.ioexception;import java.io.printwriter;import  java.util.hashmap;import java.util.map;import javax.servlet.http.httpservletrequest;import  javax.servlet.http.httpservletresponse;import org.springframework.stereotype.controller;import  org.springframework.web.bind.annotation.modelattribute;import  org.springframework.web.bind.annotation.requestmapping;import  Org.springframework.web.bind.annotation.requestmethod;import org.springframework.web.servlet.modelandview ;import com.alibaba.fastjson.jsonobject; @Controller @requestmapping ("/demo/") public class  demoaction {private httpservletrequest request;private httpservletresponse response;@ Modelattributepublic void setrequestandresponse (httpservletrequest request,httpservletresponse  response) {this.request = request;this.response = response;} @RequestMapping (value= "Jsonp", Method=requestmethod.get) Public void jsonp () { try {           response.setcontenttype ("Text/plain");           response.setheader ("Pragma",  "No-cache");           response.setheader ("Cache-control",  "No-cache");           response.setdateheader ("Expires",  0);           printwriter out = response.getwriter ();                jsonobject resultjson = new jsonobject ();         resultjson.put ("name",  "Wen");         resultjson.put ("Age",  ";        ") string jsonpcallback = request.getparameter ("Jsonpcallback");//Client request Parameters            system.out.println ("-------------------->" +jsonpcallback);         system.out.println ("-------------------->" +resultjson.tojsonstring ());         out.println (jsonpcallback+ "(" +resultjson.tojsonstring () + ")");//return JSONP format data            out.flush ();           out.close ();        } catch  (IOException e)   {         e.printstacktrace ();         }  }}
The URL address for this visit is:/demo/jsonp.action? jsonpcallback= "Showage"
In the above examples, the following points need to be noted:
1. Only get requests can be used in Jsonp, datatype is JSONP in AJAX request
2. The parameter name in the URL address defined by JSONP defaults to callback
3, Jsonpcallback defines the value of the JSONP-defined parameter, and the server needs a callback function, if jsonpcallback to define the value, the default callback success function
4. After the server accepts the request, it needs to return the callback function passed by the parameter as follows:
Out.println (jsonpcallback+ "(" +resultjson.tojsonstring () + ")");//return JSONP format data

The above is JSONP's visit process, here need everybody to understand well. Because using JSONP cross-domain access requires that the client and server define a rule, the rule for the callback function, so
In the development process, the client and server developers are required to define a rule together.
In fact, we can also through the $.get () and $.getjson () way to cross-domain access, here is not to tell you, if interested friends, you can get to know the next, today to share this to you,
We'll see you next time, and then we'll share some of Android's knowledge.

This article is from the "technology endless, learning needs more Brain" blog, please be sure to keep this source http://wenqiangv.blog.51cto.com/7889138/1433339