Java-filter过滤器在项目开发中的应用.docx

过滤器在项目开发中的应用javaee过滤器在项目怒开发中通常有三种应用：应用一：统一项目的字符编码：我们新建个名为Encode.java的文件，内容是:package filter;import java.io.lOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;public class Encode implements Filter public void destroy() (/ TODO Auto-generated method stubpublic void doFilter(ServletRequest request, ServletResponse response,Filterchain chain) throws lOException, ServletException request.setCharacterEncoding(utf-8n);response.setCharacterEncoding(nutf-8);chain.doFilter(request, response);public void init (FilterConfig argO) throws ServletException / TODO Auto-generated method stub程序在dofilter的方法中设置了request和response的编码为utf-8这样便可以解决开发 中的乱码问题，配置文件web. xml这样写：encodingfilter.Encodeencoding/*应用二：限制所有未经登陆的用户通过地址直接请求资源。 我们的项目文件结构如图：，矽 mulanchi，抄 src，廊 filterJ） Bosscheck .javaT| Encode .javaT Unlogin .javaffi javabean.dateffi ffi javabean. partpagesIB loginM Java EE 5 Libraries咨 Referenced Libraries* JRE System Library jdkl.7.0 fab WebRoot& META-INF，砂 pages4 accounter & css images& picture吊 usermanagej* accounterindex.jsp/ bossindex .jsp成 error .jsp成 login.jspZ loginerror .jspZ saleindex .jspt & picture，& WEB-INF&lib团 web.xml所有的页面文件都在pages的文件夹下（包括第一个登陆页面）。 先建一个Unlogin,java,内容为：package filter;防止未登录访问页面的过滤器import java.io.lOException;import javax.servlet.Filter;import javax.servlet.Filterchain;import javax.servlet.FilterConfig;import javax.servlet.RequestDispatcher;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http. HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class Unlogin implements Filter (public void destroy() (/ TODO Auto-generated method stub)public void doFilter(ServletRequest request, ServletResponse response,Filterchain chain) throws IOExceptionz ServletException (RequestDispatcherdispatcher=request.getRequestDispatcherf/pages/login.jsp);/ 这里设置如果没有登陆将要转发到 的页面HttpServletRequest req = (HttpServletRequest) request;HttpServletResponse res = (HttpServletResponse) response;HttpSession session = req.getSession(true);排除登陆页面不被过滤String request_uri = req.getRequestURI();String ctx_path = req.getContextPathf);这里假设是排除登陆页面login.jsp 。排除文件夹是一样的，例如排除 admin 文件夹：/adminif(request_uri.substring(ctx_path.length().equals( /pages/login.jsp)(chain.doFilterfrequest,response);return;/从session里取的用户名信息String username = (String) session.getAttribute(name)；/这里获取 session,为了检查session里有没有保存用户信息，没有的话回转发到登陆页面System.out.println(username);/判断如果没有取到用户信息，就跳转到登陆页面if (username = null 11 .equals(username)/跳转到登陆页面dispatcher.forward(request,response);/System.out.println(用户没有登陆，不允许操作”)；res.setHeaderCCache-Contror/no-store);res.setDateHeader(ExpireszO);res.setHeaderCPragmaVno-cache);)else(/己经登陆,继续此次请求chain.doFilter(request,response);/System.out.printlnf用户己经登陆，允许操作)；)public void init(FilterConfig argO) throws ServletException (/TODO Auto-generated method stub)注意在doFilter方法中先进行了对象的强制转换。设置好未登录将被转发到的请求页 面，然后排除login.jsp不被过滤，注意这种用法，也可用于排除某个目录不被过滤。 Web.xml这样配置：unloginfilter.Unloginunlogin/pages/*表示所有对pages下的页面请求都会接受过滤。应用三：防止己经登陆的用户越权访问不该自己访问的目录。新建一个Bosscheck, java,用于拦截普通用户强行访问管理员的页面。管理员的页面在 pages/usermanage文件夹下，内容如卜：package filter;import java.io.lOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.RequestDispatcher;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class Bosscheck implements Filter public void destroy() / TODO Auto-generated method stub)public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws lOException, ServletException (HttpServletRequest req = (HttpServletRequest) request;HttpServletResponse res = (HttpServletResponse) response;HttpSession session = req.getSession(true);String user=(String)session.getAttribute(usertype); if(boss.equals(user)(chain.doFilter(request,response);return;RequestDispatcher dispatcher = request.getRequestDispatcher(/pages/error.jsp); dispatcher.forwardfrequest, response);public void init(FilterConfig filterConfig) throws ServletException / TODO Auto-generated method stub可以看出session中，只有内容为boss才会放行，否则进入error.jsp