JavaWeb同步学习笔记之十二、JavaWeb_HttpServlet

HttpServlet

• 1.HttpServlet 是一个Servlet，继承自 GenericServlet。针对于 HTTP 协议所定制。
• 2.在 service() 方法中直接把 ServletReuqest 和 ServletResponse 转为 HttpServletRequest 和 HttpServletResponse。并调用了重载的 service(HttpServletRequest, HttpServletResponse) 。在 service(HttpServletRequest, HttpServletResponse) 获取了请求方式: request.getMethod()。

	@Override
	public void service(ServletRequest req, ServletResponse res)
		throws ServletException, IOException {
		
	    HttpServletRequest  request;
	    HttpServletResponse response;
	    
	    try {
	        request = (HttpServletRequest) req;
	        response = (HttpServletResponse) res;
	    } catch (ClassCastException e) {
	        throw new ServletException("non-HTTP request or response");
	    }
	    service(request, response);
	}

	public void service(HttpServletRequest request, HttpServletResponse response)
		throws ServletException, IOException {
		//1. 获取请求方式.
		String method = request.getMethod();
		
		//2. 根据请求方式再调用对应的处理方法
		if("GET".equalsIgnoreCase(method)){
			doGet(request, response);
		}else if("POST".equalsIgnoreCase(method)){
			doPost(request, response);
		}
	}
	
	public void doPost(HttpServletRequest request, HttpServletResponse response) 
		throws ServletException, IOException{
		// TODO Auto-generated method stub
			
	}

	public void doGet(HttpServletRequest request, HttpServletResponse response) 
		throws ServletException, IOException {
		// TODO Auto-generated method stub
			
	}

根据请求方式有创建了 doXxx() 方法 (Xxx) 为具体的请求方式，比如 doGet，doPost)。

• 3.实际开发中，直接继承 HttpServlet ，并根据请求方式复写 doXxx() 方法接口。
• 4.好处：直接由针对性的覆盖 doXxx() 方法；直接使用 HttpServletRequest 和 HttpServletResponse，不再需要强转。