通過定義過濾器filter解決跨域問題

        跨域是比較常見問題，比較簡單的方式就是直接定義一個過濾器filter，然后在請求頭里面加上一些參數。下面來看看具體的寫法吧。

一、java代碼

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：解決跨域過濾器 
 * 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;
        // 添加參數，允許任意domain訪問
        resp.setHeader("Access-Control-Allow-Origin", "*");
        // 這個allow-headers要配為*，這樣才能允許所有的請求頭 --- 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：解決跨域過濾器 

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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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        // 添加參數，允許任意domain訪問

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

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        // 這個allow-headers要配為*，這樣才能允許所有的請求頭 --- 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、小結

        碰到跨域問題時，可以通過自定義過濾器，然后在請求頭上添加參數來解決。