前端页面定义公共变量

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前端页面定义公共变量（做项目的工程中用到jsp页面显示图片没上线之前用本地的路径、上线之后更改成线上的路径。这样定义公变量就避免了上线后更改多处路径）

例如：页面显示图片路径

1.java代码

package gt.common;import java.io.IOException;import java.util.Iterator;import java.util.Map;import java.util.Set;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;/** * 类名称:RequestFilter.java * 类描述: * 作    者:why * 时    间:2017年7月5日 */public class RequestFilter implements Filter {/* (non-Javadoc) * @see javax.servlet.Filter#destroy() */@Overridepublic void destroy() {// TODO Auto-generated method stub}/* (non-Javadoc) * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain) */@Overridepublic void doFilter(ServletRequest arg0, ServletResponse arg1,FilterChain arg2) throws IOException, ServletException {HttpServletRequest request = (HttpServletRequest) arg0;HttpServletResponse response = (HttpServletResponse) arg1;GetHttpServletRequestWrapper req = new GetHttpServletRequestWrapper((HttpServletRequest)arg0,"utf-8",request.getRequestURI());req.setAttribute("PIC_URL", “填写你想要放的位置的路径”);arg2.doFilter(req, response);}/* (non-Javadoc) * @see javax.servlet.Filter#init(javax.servlet.FilterConfig) */@Overridepublic void init(FilterConfig arg0) throws ServletException {// TODO Auto-generated method stub}}

2.web.xml 配置过滤

<filter>    <filter-name>RequestFilter</filter-name>    <filter-class>gt.common.RequestFilter</filter-class>    <async-supported>true</async-supported>  </filter>  <filter-mapping>    <filter-name>RequestFilter</filter-name>    <url-pattern>*.action</url-pattern>  </filter-mapping>  <filter-mapping>    <filter-name>RequestFilter</filter-name>    <url-pattern>*.jsp</url-pattern>  </filter-mapping>

3.jsp页面读取方式

<img src="${PIC_URL}">

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