Servlet3.0的注解

1.@WebListener注解

表示的就是我们之前的在xml中配置的

<listener>

<listener-class>ListenerClass</listener-class>

</listener>

下面我们只需要在我们写好的Listener类上面加上这个@WebListener注解就OK啦

使用Listener的类必须使用下列的几个接口

ServletContextListener ServletContextAttributeListener ServletRequestListener ServletRequestAttributeListener HttpSessionListener HttpSessionAttributeListener

例子：

package com.hotusm.web.listener;  import javax.servlet.annotation.WebListener; import javax.servlet.http.HttpSessionEvent; import javax.servlet.http.HttpSessionListener;  @WebListener public class MyHttpSessionListener implements HttpSessionListener{      @Override     public void sessionCreated(HttpSessionEvent se) {         System.out.println("创建session ");     }      @Override     public void sessionDestroyed(HttpSessionEvent se) {         System.out.println("销毁session ");     }  }

这样，在我们启动的时候 就会自动的帮助我们创建一个Listener了，这个注解有一个属性，是这个listener的描述信息

2.@WebFilter 这个注解就是表示的拦截器 同样的也是直接注解在写好的Filter上面就ok了。

package com.hotusm.web.filter;  import javax.servlet.*; import javax.servlet.annotation.WebFilter; import javax.servlet.annotation.WebInitParam; import javax.servlet.http.HttpServletRequest; import java.io.IOException;  @WebFilter(filterName = "filter1", urlPatterns="/*",         dispatcherTypes = {DispatcherType.REQUEST, DispatcherType.FORWARD},         initParams={@WebInitParam(name="account",value="1234"),@WebInitParam(name="hotusm",value="1234")}         )  public class MyFilter implements Filter {     @Override     public void init(final FilterConfig filterConfig) throws ServletException {                  String account = filterConfig.getInitParameter("account");         String hotusm = filterConfig.getInitParameter("hotusm");                  System.out.println("account:"+account+" hotusm:"+hotusm);     }      @Override     public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain) throws IOException, ServletException {              chain.doFilter(request, response);     }      @Override     public void destroy() {              } }

注解的主要参数及其含义

3.@WebServlet 这个注解表示的就是一般的Servlet

package com.hotusm.web.servlet;  import javax.servlet.ServletException; import javax.servlet.annotation.WebInitParam; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession;  import java.io.IOException;  @WebServlet(name = "servlet1", urlPatterns = {"/url1", "/url2","url3/*"}, loadOnStartup = 1,         initParams = {                 @WebInitParam(name = "name", value="hotusm")         }) public class MyServlet extends HttpServlet {          private String name;      public MyServlet() {         System.out.println("load on startup");     }      @Override     public void init() throws ServletException {         super.init();         name= this.getInitParameter("name");     }      @Override     protected void doGet(final HttpServletRequest req, final HttpServletResponse resp) throws ServletException, IOException {         HttpSession session = req.getSession();         System.out.println(session);         System.out.println("name:"+name);     } }

注解主要参数

参数和Filter差不多

4.其中在上面的注解Filter和Servlet用到的@WebInitParam 注解 表示的就是参数啦 相当于<init-param>

参数以及含义

5.@MultipartConfig 该注解主要是为了辅助 Servlet 3.0 中 HttpServletRequest 提供的对上传文件的支持。该注解标注在 Servlet 上面，以表示该 Servlet 希望处理的请求的 MIME 类型是 multipart/form-data。另外，它还提供了若干属性用于简化对上传文件的处理。具体如下：

例子：

<form action="upload" enctype="multipart/form-data" method="POST">     <input name="file" type="file" />     <input type="submit" value="Upload" /> </form>

package com.hotusm.web.servlet;  import java.io.File; import java.io.IOException; import java.io.PrintWriter;  import javax.servlet.ServletException; import javax.servlet.annotation.MultipartConfig; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.Part;  @MultipartConfig(location="C://upload") @WebServlet(name="upload",urlPatterns={"/upload"}) public class UploadServlet extends HttpServlet{          @Override     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {         req.setCharacterEncoding("utf-8");           resp.setContentType("text/html; charset=UTF-8");           PrintWriter out = resp.getWriter();           Part part = req.getPart("file");           String fileName = part.getHeader("content-disposition");         System.out.println(fileName);         System.out.println(fileName.substring(fileName.lastIndexOf(File.separator)+1, fileName.length()-1));         part.write( fileName.substring(fileName.lastIndexOf(File.separator)+1, fileName.length()-1));         out.write("{'type':'1','msg':'success'}");     } }