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>