常用Servlet过滤器

---

解决POST请求参数中文和输出中文的乱码过滤器

过滤器代码

package com.study.java.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; /** * @Name: SetCharacterEncodingFilter * @Description: 过滤器应用案例一：解决POST请求参数中文和输出中文的乱码过滤器 * @Author: XXX * @CreateDate: XXX * @Version: V1.0 */ public class SetCharacterEncodingFilter implements Filter { private FilterConfig filterConfig ; public void init(FilterConfig filterConfig) throws ServletException { this.filterConfig = filterConfig ; } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { //拦截客户端请求 //设置客户端请求参数内容编码，针对post请求 String encode = filterConfig.getInitParameter("encode") ; if(encode == null || "".equals(encode.toString().trim())) { encode = "UTF-8" ; } request.setCharacterEncoding(encode) ; //设置服务端响应内容编码 response.setContentType("text/html;charset=" + encode) ; //放行，让目标资源执行 chain.doFilter(request, response) ; } public void destroy() { } }

web.xml配置

<!-- 解决POST请求参数中文和输出中文的乱码 --> <filter> <filter-name>SetCharacterEncodingFilter</filter-name> <filter-class>com.study.java.filter.SetCharacterEncodingFilter</filter-class> <!-- 设置客户端请求参数编码 --> <init-param> <param-name>encode</param-name> <param-value>UTF-8</param-value> </init-param> </filter> <!-- 过滤器执行顺序以此标签定义的顺序为准 --> <filter-mapping> <filter-name>SetCharacterEncodingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>

控制动态资源不要在客户端缓存过滤器

过滤器代码

package com.study.java.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; /** * @Name: DynamicResourceNoCacheFilter * @Description: 过滤器应用案例二：控制动态资源不要在客户端缓存 * @Author: XXX * @CreateDate: XXX * @Version: V1.0 */ public class DynamicResourceNoCacheFilter implements Filter { public void init(FilterConfig filterConfig) throws ServletException { } public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { //拦截客户端请求 //对请求与响应对象进行类型转换，参考HttpServlet的service()方法实现 HttpServletRequest request; HttpServletResponse response; try { request = (HttpServletRequest)req; response = (HttpServletResponse)res; } catch(ClassCastException e) { throw new ServletException("non-HTTP request or response"); } //设置http响应头信息：禁止浏览器缓存 response.setHeader("expires", "-1") ; response.setHeader("cache-control", "no-cache") ; response.setHeader("pragma", "no-cache") ; //放行，让目标资源执行 chain.doFilter(request, response) ; } public void destroy() { } }

web.xml配置

<!-- 控制动态资源不要在客户端缓存 --> <filter> <filter-name>DynamicResourceNoCacheFilter</filter-name> <filter-class>com.study.java.filter.DynamicResourceNoCacheFilter</filter-class> </filter> <filter-mapping> <filter-name>DynamicResourceNoCacheFilter</filter-name> <url-pattern>*.jsp</url-pattern> </filter-mapping> <filter-mapping> <filter-name>DynamicResourceNoCacheFilter</filter-name> <url-pattern>/servlet/*</url-pattern> </filter-mapping>

控制静态资源的缓存时间过滤器

过滤器代码

package com.study.java.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; /** * @Name: SetStaticResourceCacheTime * @Description: 过滤器应用案例三：控制静态资源的缓存时间 * @Author: XXX * @CreateDate: XXX * @Version: V1.0 */ public class SetStaticResourceCacheTime implements Filter { private FilterConfig filterconfig ; public void init(FilterConfig filterconfig) throws ServletException { this.filterconfig = filterconfig ; } public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterchain) throws IOException, ServletException { //拦截客户端请求 //对请求与响应对象进行类型转换，参考HttpServlet的service()方法实现 HttpServletRequest request; HttpServletResponse response; try { request = (HttpServletRequest)req; response = (HttpServletResponse)res; } catch(ClassCastException e) { throw new ServletException("non-HTTP request or response"); } //缓存时间：毫秒为单位 long time = 0 ; //获取用户的访问资源类型 String uri = request.getRequestURI() ; //截取扩展名 String subname = uri.substring(uri.lastIndexOf(".") + 1) ; //说明访问的是html资源 if("html".equals(subname)) { String value = filterconfig.getInitParameter(subname) ; time = Long.parseLong(value) * 60 * 60 * 1000 ; } //说明访问的是css资源 if("css".equals(subname)) { String value = filterconfig.getInitParameter(subname) ; time = Long.parseLong(value) * 60 * 60 * 1000 ; } //说明访问的是js资源 if("js".equals(subname)) { String value = filterconfig.getInitParameter(subname) ; time = Long.parseLong(value) * 60 * 60 * 1000 ; } //设置缓存过期时间 response.setDateHeader("Expires", System.currentTimeMillis() + time) ; //放行，让目标资源执行 filterchain.doFilter(request, response) ; } public void destroy() { } }

web.xml配置

<!-- 控制静态资源的缓存时间 --> <filter> <filter-name>SetStaticResourceCacheTime</filter-name> <filter-class>com.study.java.filter.SetStaticResourceCacheTime</filter-class> <init-param> <param-name>html</param-name> <!-- 单位：小时 --> <param-value>1</param-value> </init-param> <init-param> <param-name>js</param-name> <!-- 单位：小时 --> <param-value>2</param-value> </init-param> <init-param> <param-name>css</param-name> <!-- 单位：小时 --> <param-value>3</param-value> </init-param> </filter> <filter-mapping> <filter-name>SetStaticResourceCacheTime</filter-name> <url-pattern>*.html</url-pattern> </filter-mapping> <filter-mapping> <filter-name>SetStaticResourceCacheTime</filter-name> <url-pattern>*.css</url-pattern> </filter-mapping> <filter-mapping> <filter-name>SetStaticResourceCacheTime</filter-name> <url-pattern>*.js</url-pattern> </filter-mapping>

控制用户资源访问权限过滤器

过滤器代码

package com.study.java.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; /** * @Name: ResourceAuthorityFilter * @Description: 过滤器应用案例四：控制用户资源访问权限 * @Author: XXX * @CreateDate: XXX * @Version: V1.0 */ public class ResourceAuthorityFilter implements Filter { public void init(FilterConfig filterconfig) throws ServletException { } public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterchain) throws IOException, ServletException { //拦截客户端请求 //对请求与响应对象进行类型转换，参考HttpServlet的service()方法实现 HttpServletRequest request; HttpServletResponse response; try { request = (HttpServletRequest)req; response = (HttpServletResponse)res; } catch(ClassCastException e) { throw new ServletException("non-HTTP request or response"); } //获取请求uri地址 String uri = request.getRequestURI() ; //应用名+资源访问路径 String resourcePath = uri.substring(request.getContextPath().length()) ; //资源访问路径 //判断admin级别网页的浏览权限 if(uri.startsWith("/admin")) { if(request.getSession().getAttribute("admin")==null) { request.setAttribute("message","您没有这个权限"); request.getRequestDispatcher("/login.jsp").forward(request,response); return; } } //判断manage级别网页的浏览权限 if(uri.startsWith("/manage")) { //这里省去 } //下面还可以添加其他的用户权限，省去。 } public void destroy() { } }

web.xml配置

<!-- 控制用户资源访问权限过滤器 --> <filter> <filter-name>ResourceAuthorityFilter</filter-name> <filter-class>com.study.java.filter.ResourceAuthorityFilter</filter-class> </filter> <filter-mapping> <filter-name>ResourceAuthorityFilter</filter-name> <url-pattern>/admin/*</url-pattern> </filter-mapping> <filter-mapping> <filter-name>ResourceAuthorityFilter</filter-name> <url-pattern>/manage/*</url-pattern> </filter-mapping>