Servlet实例应用.doc

Servlet实例应用1.虽然可以用:String name=getServletConfig().getServletName()得到Servlet名称,但可以从GenericServlet直接继承getServletName方法更方便. Service就不用象doPost激活了public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException response.setContentType(text/html);PrintWriter out=response.getWriter(); out.print( this.getServletName( ) );Enumeration e=this.getInitParameterNames();/得到多个参数玫举数组 while(e.hasMoreElements() String key=(String)e.nextElement(); String value=getInitParameter(key); out.print(key+=+value); ServletContext context=this.getServletContext();/也可从GenericServlet中直接得到String path=context.getRealPath(/); out.print(path); 得到:C:tomcatwebappstest2. 用ServletContext得到初始化参数:(从GenericServlet中直接得到)public class Context extends HttpServlet public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException PrintWriter out=response.getWriter();Enumeration e=getServletContext().getInitParameterNames(); while(e.hasMoreElements()String key=(String)e.nextElement();String value=getServletContext().getInitParameter(key);out.print(key+=+value);ServletContext在web.xml中的配置: Context test.Context 不同于在Servlet内部配 company witbridge 3使用输入流访问资源文件：public class FileAccess extends HttpServlet public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException PrintWriter out=response.getWriter();FileInputStream fis=new FileInputStream(perties);/文件必和tomcat启动程序同级别目录: user=root,否则全路径:c:pertiesProperties props=new Properties(); props.load(fis); /Properties保存在流中或从流中加载, load从输入流中读取属性列表,getPXX返回Stringout.print(props.getProperty(user); fis.close(); /用指定键在属性列表中搜索属性4.使用ServletContext接口访问资源文件：public class Resource extends HttpServlet protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException PrintWriter out=response.getWriter();URL urlIt315=this.getServletContext().getResource(/perties);InputStream ips=this.getServletContext().getResourceAsStream(/perties); out.print(urlIt315.toString();Properties props=new Properties();props.load(ips);out.print(props.getProperty(dataBase); /好处：路径与调试环境无关，只要/setHeader(java.lang.String name, java.lang.String value)5.HttpServletResponse的应用：响应消息头：如setContentType(“text/html;charset=”);a.SetHeader（自动刷新,URL覆盖）public class Refresh extends HttpServlet protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException /response.setHeader(Refresh, 2);response.setHeader(Refresh, 1;URL=http:/localhost:8080/ ); b.禁止浏览器缓存显示动态图片：public class Cache extends HttpServlet protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException response.setContentType(text/html );response.setDateHeader(Expires, 0); response.setHeader(Pragma, no-cache);response.setHeader(Cache-Control, no-cache); /防止不同浏览器支持不同响应头PrintWriter out=response.getWriter();out.print(Math.random();response.setBufferSize(0);int len=response.getBufferSize( );out.print(len);/8192 6.RequestDispatcher(共享数据和URL不变)和response.SendRidirect:a.Include:被包含的Servlet程序不能改变响应消息的状态码和响应头，如果他里面存在这样的语句执行结果将被忽略:public class Included extends HttpServlet protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException response.setContentType(text/html;charset=GB2312);/被包含执行时将被忽略PrintWriter out=response.getWriter();out.print(中国+);out.print(URL+request.getRequestURI()+);/test/servlet/Include根目录下out.print(QueryString:+request.getQueryString()+);/为null,得到？后面语句out.print(Param p1:+request.getParameter(p1)+); /可以得到参数的测试：public class Include extends HttpServlet protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOExceptionresponse.setContentType(text/html;charset=GB2312);PrintWriter out=response.getWriter();String china=中国;RequestDispatcher rd=this.getServletContext().getRequestDispatcher(/servlet/Included?p1=+china); rd.include(request, response); /从Config中继承b.forward:在调用者和被调用者程序中设置响应状态码和状态头都不会被忽略，URL仍为调用方response.setContentType(text/html;charset=GB2312);/也需要设置，转向全部元素全路径RequestDispatcher rd=this.getServletContext().getRequestDispatcher(/index.jsp);rd.forward(request, response);c:sendRedirect方法用于生成302响应码和Location响应头，从而通知客户端去重新访问Location响应头中指定的URL,调用和被调用者之间就不能共同享用request和