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:

 1 @WebServlet(name = "testServletAnnotation", urlPatterns = { "/testservletannotation/*","/asd/*" }, initParams = { @WebInitParam(name = "a", value = "aaa") })
 2 public class testServletAnnotation extends HttpServlet {
 3     private static final long serialVersionUID = 1L;
 4     @SuppressWarnings("unused")
 5     private ServletConfig config;
 6 
 7     public void init(ServletConfig config) throws ServletException {
 8         this.config = config;
 9     }
10 
11     public void service(HttpServletRequest request, HttpServletResponse response)
12             throws ServletException, IOException {
13         request.setCharacterEncoding("utf-8");
14         response.setContentType("text/html;charSet=utf-8");
15         HttpSession session = request.getSession();
16         ServletContext cxt = request.getServletContext();
17         cxt.setAttribute("hate", "Deep hating!");
18         PrintStream out = new PrintStream(response.getOutputStream());
19         String a = config.getInitParameter("a");
20         out.println("just a servlet test! <br /> @annotation依然有效！ <br /> ");
21         out.println("session:" + session.getAttribute("love")+"<br />");
22         out.println("a:" + a);
23     }
24 
25 }

XML:

1   <servlet>
2       <servlet-name>testServletXml</servlet-name>
3       <servlet-class>servlet.testServletXml</servlet-class>
4   </servlet>
5   <servlet-mapping>
6       <servlet-name>testServletXml</servlet-name>
7       <url-pattern>/testservletxml</url-pattern>
8   </servlet-mapping>

获取Servlet配置参数

Annotation配置

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

xml参数配置

1 <init-param>
2     <param-name>a</param-name>
3     <param-value>aaa</param-value>
4 </init-param>