三、servlet如何配置

生命周期

可以第一次请求时就实例化，也可以web容器启动时就实例化

WebServlet(loadOnStartUp=1)

<loadOnStartUp.../>

直接收整型值，越小优先级越高

完整配置实例

annotation:

 @WebServlet(name = "testServletAnnotation", urlPatterns = { "/testservletannotation/*","/asd/*" }, initParams = { @WebInitParam(name = "a", value = "aaa") })
 public class testServletAnnotation extends HttpServlet {
     private static final long serialVersionUID = 1L;
     @SuppressWarnings("unused")
     private ServletConfig config;

     public void init(ServletConfig config) throws ServletException {
         this.config = config;
     }

     public void service(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         request.setCharacterEncoding("utf-8");
         response.setContentType("text/html;charSet=utf-8");
         HttpSession session = request.getSession();
         ServletContext cxt = request.getServletContext();
         cxt.setAttribute("hate", "Deep hating!");
         PrintStream out = new PrintStream(response.getOutputStream());
         String a = config.getInitParameter("a");
         out.println("just a servlet test! <br /> @annotation依然有效！ <br /> ");
         out.println("session:" + session.getAttribute("love")+"<br />");
         out.println("a:" + a);
     }

 }

XML:

   <servlet>
       <servlet-name>testServletXml</servlet-name>
       <servlet-class>servlet.testServletXml</servlet-class>
   </servlet>
   <servlet-mapping>
       <servlet-name>testServletXml</servlet-name>
       <url-pattern>/testservletxml</url-pattern>
   </servlet-mapping>

获取Servlet配置参数

Annotation配置

 @WebServlet(name = "testServletAnnotation", urlPatterns = { "/testservletannotation/*","/asd/*" }, initParams = { @WebInitParam(name = "a", value = "aaa") })
 2
 3
 4 ServletContext cxt = request.getServletContext();
 5
 6
 7 out.println("a:" + a);

xml参数配置

 <init-param>
     <param-name>a</param-name>
     <param-value>aaa</param-value>
 </init-param>