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:\tomcat\webapps\test\
2. 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: <servlet> <servlet-name>Context</servlet-name>
<servlet-class>test.Context</servlet-class> </servlet>
不同于<init-param>在Servlet内部配 <context-param><param-name>company</param-name>
<param-value>witbridge</param-value></context-param>
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("it315.properties");
//文件必和tomcat启动程序同级别目录: user=root,否则全路径:c:\\test\\it315.properties
Properties 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String
out.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("/it315.properties");
InputStream ips=this.getServletContext().getResourceAsStream("/it315.properties");
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"+"<br>");
out.print("URL"+request.getRequestURI()+"<br>");///test/servlet/Include根目录下
out.print("QueryString:"+request.getQueryString()+"<br>");//为null,得到？后面语句
out.print("Param p1:"+request.getParameter("p1")+"<br>");}} //可以得到参数的
测试：public class Include extends HttpServlet {
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
response.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response对象.
response.sendRedirect(request.getContextPath()+”/page.jsp”);
7. 为防止用户在等待过程中多次提交数据：
<script> Var isCommitted=false;//通过返回值进行判断
Function checkPost(){ if(!isCommitted){isCommitted=true;return true;}
Else { alert(“不能重复提交表单”);return false;} } </script>