HttpServlet

HttpServlet

1)是一个Servlet，继承自GenericServlet。针对于HTTP协议所制定

2）在service()方法中直接把ServletRequest和ServletResponse转为HttpServletRequest和HttpServletResponse，并调用了重载的service(HttpServletRequest,HttpServletResponse)

3)在service(HttpServletRequest,HttpServletResponse)获取了请求方式：request.getMethod().根据请求方式创建了doXxx()方法（xxx为具体的请求方式，比如doGet，doPost）

4）实际开发中，直接继承HttpServlet，并根据请求方式复写doXxx()方法

5）优点：直接有针对性的覆盖doXxx()方法

public class MyHttpServlet extends GenericServlet{
    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        HttpServletRequest request;
        HttpServletResponse response;
        try {
            request = (HttpServletRequest) servletRequest;
            response = (HttpServletResponse) servletResponse;
        }catch (ClassCastException e){
            throw new ServletException("non-HTTP request or response");
        }
        service(request,response);
    }
    public void service(HttpServletRequest httpServletRequest,HttpServletResponse httpServletResponse){
        String method = httpServletRequest.getMethod();
        if ("GET".equalsIgnoreCase(method)){
            doGet(httpServletRequest,httpServletResponse);
        }else if ("POST".equalsIgnoreCase(method)){
            doPost(httpServletRequest,httpServletResponse);
        }
    }

    public void doGet(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) {
    }

    public void doPost(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) {
    }
    
}