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在Java中有时会遇见乱码的情况，这里提供了几种转换方法

（一）Java中的编码转换

（二）可以在web.xml文件中配置的自己写的过滤器

    第一种方法最简单也最方便，但是只能用在少量的地方或是偶尔一两次转码，如果大面积使用就不方便了，也大大增加了编码量，如果你的项目里没有用Spring的框架开发，用web.xml配置自定义过滤器可以一劳永逸的解决 

    1.首先要编写自己的过滤器类(实现了javax.servlet.Filter)：

     package fck.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;public class CodeFilter implements Filter { public void destroy() { // TODO Auto-generated method stub } public void doFilter(ServletRequest request, ServletResponse response, FilterChain filter) throws IOException, ServletException { // TODO Auto-generated method stub request.setCharacterEncoding("utf-8"); filter.doFilter(request, response); } public void init(FilterConfig arg0) throws ServletException { // TODO Auto-generated method stub }}

    2.在web.xml文件中编写过滤器配置：

     <filter> <!--CodeFilter是自己随便取的名字--> <filter-name>CodeFilter</filter-name> <!--写好对应的过滤器类的路径--> <filter-class>fck.filter.CodeFilter</filter-class> </filter> <filter-mapping> <filter-name>CodeFilter</filter-name> <!--“/*”代表所有的请求都经过过滤--> <url-pattern>/*</url-pattern> </filter-mapping>

 之后不用再做什么代码的改变，过滤器就将所有的访问都转码了

 (三)使浏览器不缓存页面的过滤器

 import javax.servlet.*; import javax.servlet.http.HttpServletResponse; import java.io.IOException; /** *//** * 用于的使 Browser 不缓存页面的过滤器 */ public class ForceNoCacheFilter implements Filter { public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException{ ((HttpServletResponse) response).setHeader("Cache-Control","no-cache"); ((HttpServletResponse) response).setHeader("Pragma","no-cache"); ((HttpServletResponse) response).setDateHeader ("Expires", -1); filterChain.doFilter(request, response); } public void destroy() { } public void init(FilterConfig filterConfig) throws ServletException { } }

 (四)检测用户是否登陆的过滤器

 import javax.servlet.*;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;import java.util.List;import java.util.ArrayList;import java.util.StringTokenizer;import java.io.IOException;/** *//** * 用于检测用户是否登陆的过滤器，如果未登录，则重定向到指的登录页面 * 配置参数 * checkSessionKey 需检查的在 Session 中保存的关键字 * redirectURL 如果用户未登录，则重定向到指定的页面，URL不包括 ContextPath * notCheckURLList 不做检查的URL列表，以分号分开，并且 URL 中不包括 ContextPath */public class T implements Filter { protected FilterConfig filterConfig = null; private String redirectURL = null; private List notCheckURLList = new ArrayList(); private String sessionKey = null; public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest) servletRequest; HttpServletResponse response = (HttpServletResponse) servletResponse; HttpSession session = request.getSession(); if (sessionKey == null) { filterChain.doFilter(request, response); return; } if ((!checkRequestURIIntNotFilterList(request)) && session.getAttribute(sessionKey) == null) { response.sendRedirect(request.getContextPath() + redirectURL); return; } filterChain.doFilter(servletRequest, servletResponse); } public void destroy() { notCheckURLList.clear(); } private boolean checkRequestURIIntNotFilterList(HttpServletRequest request) { String uri = request.getServletPath() + (request.getPathInfo() == null ? "" : request.getPathInfo()); return notCheckURLList.contains(uri); } public void init(FilterConfig filterConfig) throws ServletException { this.filterConfig = filterConfig; redirectURL = filterConfig.getInitParameter("redirectURL"); sessionKey = filterConfig.getInitParameter("checkSessionKey"); String notCheckURLListStr = filterConfig.getInitParameter("notCheckURLList"); if (notCheckURLListStr != null) { StringTokenizer st = new StringTokenizer(notCheckURLListStr, ";"); notCheckURLList.clear(); while (st.hasMoreTokens()) { notCheckURLList.add(st.nextToken()); } } }}

 (五)资源保护过滤器

 import javax.servlet.Filter;import javax.servlet.FilterConfig;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.FilterChain;import javax.servlet.ServletException;import javax.servlet.http.HttpServletRequest;import java.io.IOException;import java.util.Iterator;import java.util.Set;import java.util.HashSet; // import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;/** *//** * This Filter class handle the security of the application. * * It should be configured inside the web.xml. * * @author Derek Y. Shen */public class SecurityFilter implements Filter { // the login page uri private static final String LOGIN_PAGE_URI = "login.jsf"; // the logger object private Log logger = LogFactory.getLog(this.getClass()); // a set of restricted resources private Set restrictedResources; /** */ /** * Initializes the Filter. */ public void init(FilterConfig filterConfig) throws ServletException { this.restrictedResources = new HashSet(); this.restrictedResources.add("/createProduct.jsf"); this.restrictedResources.add("/editProduct.jsf"); this.restrictedResources.add("/productList.jsf"); } /** */ /** * Standard doFilter object. */ public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { this.logger.debug("doFilter"); String contextPath = ((HttpServletRequest) req).getContextPath(); String requestUri = ((HttpServletRequest) req).getRequestURI(); this.logger.debug("contextPath = " + contextPath); this.logger.debug("requestUri = " + requestUri); if (this.contains(requestUri, contextPath) && !this.authorize((HttpServletRequest) req)) { this.logger.debug("authorization failed"); ((HttpServletRequest) req).getRequestDispatcher(LOGIN_PAGE_URI) .forward(req, res); } else { this.logger.debug("authorization succeeded"); chain.doFilter(req, res); } } public void destroy() { } private boolean contains(String value, String contextPath) { Iterator ite = this.restrictedResources.iterator(); while (ite.hasNext()) { String restrictedResource = (String) ite.next(); if ((contextPath + restrictedResource).equalsIgnoreCase(value)) { return true; } } return false; } private boolean authorize(HttpServletRequest req) { // 处理用户登录 /**//* * UserBean user = * (UserBean)req.getSession().getAttribute(BeanNames.USER_BEAN); * * if (user != null && user.getLoggedIn()) { //user logged in return * true; } else { return false; } */ }}

 (六) 利用Filter限制用户浏览权限

 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;public class T implements Filter { public void destroy() { } public void doFilter(ServletRequest sreq, ServletResponse sres, FilterChain arg2) throws IOException, ServletException { // 获取uri地址 HttpServletRequest request = (HttpServletRequest) sreq; String uri = request.getRequestURI(); String ctx = request.getContextPath(); uri = uri.substring(ctx.length()); // 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(sreq, sres); 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 init(FilterConfig arg0) throws ServletException { }}

 配置文件写入：

<!-- 判断页面的访问权限 --> <filter> <filter-name>RightFilter</filter-name> <filter-class>cn.itkui.filter.RightFilter</filter-class> </filter> <filter-mapping> <filter-name>RightFilter</filter-name> <url-pattern>/admin/**//*</url-pattern> </filter-mapping> <filter-mapping> <filter-name>RightFilter</filter-name> <url-pattern>/manage/*</url-pattern> </filter-mapping>

    最简单也是可以少量用的方法就是在java类中使用的编码方式转换

比如在项目中输出String Name；是“&#（）@（￥*@”乱码，那么可以采用：

 String strNew = ""; //转化后的字符串strNew = new String(str.getBytes("iso8859-1"),"utf-8");

 这样得到的strNew就是转换成“utf-8”后的编码

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