通过定义过滤器filter解决跨域问题

        跨域是比较常见问题，比较简单的方式就是直接定义一个过滤器filter，然后在请求头里面加上一些参数。下面来看看具体的写法吧。

一、java代码

package com.hj.userapi.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.HttpServletResponse;

/**
 * 功能描述：解决跨域过滤器 
 * 2017年9月4日
 */
public class ContextFilter implements Filter{
    private final int time = 20*24*60*60;
    /**
     * @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // TODO Auto-generated method stub
        
    }

    /**
     * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)
     */
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse resp = (HttpServletResponse) response;
        // 添加参数，允许任意domain访问
        resp.setHeader("Access-Control-Allow-Origin", "*");
        // 这个allow-headers要配为*，这样才能允许所有的请求头 --- update by zxy  in 2018-10-19
        resp.setHeader("Access-Control-Allow-Headers", "*");
        resp.setHeader("Access-Control-Allow-Methods","PUT,POST,GET,DELETE,OPTIONS");
        resp.setHeader("Access-Control-Max-Age", time+"");
        chain.doFilter(request, resp);
    }

    /**
     * @see javax.servlet.Filter#destroy()
     */
    @Override
    public void destroy() {
        // TODO Auto-generated method stub
        
    }

}

x

 

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package com.hj.userapi.core.filter;

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import java.io.IOException;

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import javax.servlet.Filter;

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import javax.servlet.FilterChain;

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import javax.servlet.FilterConfig;

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import javax.servlet.ServletException;

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import javax.servlet.ServletRequest;

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import javax.servlet.ServletResponse;

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import javax.servlet.http.HttpServletResponse;

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/**

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 * 功能描述：解决跨域过滤器 

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 * 2017年9月4日

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 */

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public class ContextFilter implements Filter{

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    private final int time = 20*24*60*60;

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    /**

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     * @see javax.servlet.Filter#init(javax.servlet.FilterConfig)

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     */

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    @Override

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    public void init(FilterConfig filterConfig) throws ServletException {

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        // TODO Auto-generated method stub

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    }

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    /**

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     * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)

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     */

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    @Override

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    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

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        HttpServletResponse resp = (HttpServletResponse) response;

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        // 添加参数，允许任意domain访问

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

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        // 这个allow-headers要配为*，这样才能允许所有的请求头 --- update by zxy  in 2018-10-19

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        resp.setHeader("Access-Control-Allow-Headers", "*");

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

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        resp.setHeader("Access-Control-Max-Age", time+"");

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        chain.doFilter(request, resp);

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    }

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    /**

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     * @see javax.servlet.Filter#destroy()

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     */

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    @Override

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    public void destroy() {

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        // TODO Auto-generated method stub

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    }

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}

二、web.xml中的配置

	<filter>
	    <filter-name>contextFilter</filter-name>
	    <filter-class>com.hj.userapi.core.filter.ContextFilter</filter-class>
	</filter>
	<filter-mapping>
	    <filter-name>contextFilter</filter-name>
	    <url-pattern>/*</url-pattern>
	</filter-mapping>

 

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    <filter>

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        <filter-name>contextFilter</filter-name>

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        <filter-class>com.hj.userapi.core.filter.ContextFilter</filter-class>

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    </filter>

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    <filter-mapping>

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        <filter-name>contextFilter</filter-name>

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        <url-pattern>/*</url-pattern>

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    </filter-mapping>

三、小结

        碰到跨域问题时，可以通过自定义过滤器，然后在请求头上添加参数来解决。