Tomcat 与java web 开发技术详解笔记(二)----Servlet

 

Servlet 由两个包组成---javax.servlet和javax.servlet.http;

javax.servlet.Servlet是Servlet的核心接口，所有的Servlet都必须实现这一接口。

 javax.servlet.Servlet中定义了以下方法:

public void init(ServletConfig config)
          throws ServletException                          //初始化Servlet

public ServletConfig getServletConfig() //返回ServletConfig

public void service(ServletRequest req,                    ServletResponse res)             throws ServletException,                    java.io.IOException    //响应客户请求
 
public java.lang.String getServletInfo()   //返回Servlet信息
 
public void destroy()                      //注销Servlet 

 
Servlet的生命周期:
init()-->service()-->destroy()
 
自定义Servlet两种方法:
 
1.扩展javax.servlet.GenericServlet
2.扩展javax.servlet.http.HttpServlet(HttpServlet 继承自GenericServlet 通常使用此方法来自定义Servlet)
 
Servlet响应流程:
 
 Web Client           Servlet Container            HttpServletRequest HttpServletResponse HttpServlet
  |                        |                              |                |                |
 send http request         |                              |                |                |    
        |         ----> parse http request                |                |                |
        |                   new instance()------------->  |                |                |
        |                  new instance()--------------------------------->|                |
        |                  call service method--------------------------------------------->|
        |                    |                            |<-------------------------get request infomation
        |                    |                                             |<---------output response infomation 
        |<--------------send http response