【Access-Control-Allow-Origin】跨域问题

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【前言】

在实际项目中，可能是多个项目共同完成某个功能，他们之间需要实现数据的交互。这样就会需要有跨域的问题。

比如，发布在不同电脑上的不同项目之间，用不同语言开发的项目之间……

【JSONP】

当使用Ajax 跨域访问的时候，比较常用的方法是 JSONP，这种方法目前只支持GET 方法

function TestAjax() {

	var url ="/geturl";

	var data = $.parseJSON('{

			"equObjCode" : "1111"

		}');

	$.ajax({

		type : "get",

		async : false,

		url : url,

		data : data,

		//cache : false, //默认值true

		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(默认为:callback)

		jsonpCallback : "jsonpCallback",

		//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

		//如果这里自定了jsonp的回调函数，则success函数则不起作用;否则success将起作用

		success : function(data) {

			alert(JSON.stringify(data));

		},

		error : function(XMLHttpRequest, textStatus) {

			alert(XMLHttpRequest.status + ","

					+ XMLHttpRequest.readyState + ",error="

					+ textStatus);

		}

	});

}

【java】

在java web 项目中实现跨域方式，可以用 filter 实现跨域访问问题

web.xml 中需要添加此filter的配置

	<filter>

		<filter-name>crossOrigin</filter-name>

		<filter-class>com.bkc.core.filter.CrossOriginFilter</filter-class>

		<init-param>

			<param-name>isAllowCross</param-name>

			<param-value>true</param-value>

		</init-param>

	</filter>

	<filter-mapping>

		<filter-name>crossOrigin</filter-name>

		<url-pattern>/*</url-pattern>

	</filter-mapping>

实现 Filter 接口

package com.bkc.core.filter;

import java.io.IOException;

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class CrossOriginFilter implements Filter

{

    private boolean isAllowCross = false;

    @Override

    public void destroy()

    {

        isAllowCross = false;

    }

    @Override

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

        throws IOException, ServletException

    {

        if(isAllowCross){

            HttpServletRequest httpServletRequest = (HttpServletRequest)request;

            HttpServletResponse httpServletResponse = (HttpServletResponse)response;

            System.out.println("拦截请求: "+httpServletRequest.getServletPath());

            httpServletResponse.setHeader("Access-Control-Allow-Origin", "*");

            httpServletResponse.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");

            httpServletResponse.setHeader("Access-Control-Max-Age", "0");

            httpServletResponse.setHeader("Access-Control-Allow-Headers", "Origin, No-Cache, X-Requested-With, If-Modified-Since, Pragma, Last-Modified, Cache-Control, Expires, Content-Type, X-E4M-With,userId,token");

            httpServletResponse.setHeader("Access-Control-Allow-Credentials", "true");

            httpServletResponse.setHeader("XDomainRequestAllowed","1");

        }

        chain.doFilter(request, response);

    }

    @Override

    public void init(FilterConfig filterConfig)

        throws ServletException

    {

        String isAllowCrossStr = filterConfig.getInitParameter("isAllowCross");

        isAllowCross = isAllowCrossStr.equals("true");

    }

}