Servlet Analysis

 1 @WebServlet("/cdiservlet")      //url映射
 2 public class NewServlet extends HttpServlet {
 3     private Message message;
 4 
 5     @Override             //重写doGet方法
 6     public void init() {
 7         message = new MessageB();    //对message初始化
 8     }
 9 
10     @Override
11     public void doGet(HttpServletRequest request, HttpServletResponse response)
12                   throws IOException {              //抛出可能出现IO异常
13         response.getWriter().write(message.get());   //捕获可能发生的异常
14     }
15 }
16 
17 public interface Message {         //servlet实现Message接口的一个对象实例
18     public String get();
19 }
20 public class MessageB implements Message {          //servlet创建以下对象的实例
21     public MessageB() { }
22 
23     @Override
24     public String get() {
25         return "message B";
26     }
27 }
28 @WebServlet("/cdiservlet")              //使用CDI，servlet声明它对Message实例的依赖性，并让它由CDI运行时自动注入
29 public class NewServlet extends HttpServlet {
30     @Inject private Message message;
31 
32     @Override
33     public void doGet(HttpServletRequest request, HttpServletResponse response)
34                   throws IOException {       //抛出可能出现IO异常
35           response.getWriter().write(message.get());  //捕获可能发生的异常
36  }
37 }