重写HttpServlet

自己写一个MyServlet

package com.servlet;

import java.io.IOException;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyServlet implements Servlet{

	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		
	}

	@Override
	public ServletConfig getServletConfig() {
		// TODO Auto-generated method stub
		return servletConfig;
	}

	@Override
	public String getServletInfo() {
		// TODO Auto-generated method stub
		return null;
	}

	ServletConfig servletConfig;
	@Override
	public void init(ServletConfig arg0) throws ServletException {
		// TODO Auto-generated method stub
		servletConfig=arg0;
		init();
	}
	public void init() {
		
	}

	@Override
	public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		
		//因为request没有getMethod()方法，所以需要他的子类
		HttpServletRequest req=(HttpServletRequest)request;
		HttpServletResponse spe=(HttpServletResponse)response;
		
		service(req,spe);
		
		System.out.println(req.getMethod());
	}
	//重载service，当子类重写时原来父类的不会被重写
	public void service(HttpServletRequest request,HttpServletResponse response) {
		//对不同的请求做不同的回应
		if(request.getMethod().equals("GET")) {
			doGet(request,response);
		}
		if(request.getMethod().equals("POST")){
			doPost(request,response);
		}
	}
	//增加get和post方法供子类继承
	public void doGet(HttpServletRequest request,HttpServletResponse response) {
		
	}
	public void doPost(HttpServletRequest request,HttpServletResponse response) {
		
	}

}

然后用一个LoginServlet去继承MyServlet

package com.servlet;

import java.io.IOException;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends MyServlet{

	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		
	}

	@Override
	public ServletConfig getServletConfig() {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public String getServletInfo() {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public void init(ServletConfig arg0) throws ServletException {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void service(ServletRequest arg0, ServletResponse arg1) throws ServletException, IOException {
		// TODO Auto-generated method stub
		
	}
	public void doGet(HttpServletRequest request,HttpServletResponse response) {
		System.out.println("GET");
	}
	public void doPost(HttpServletRequest request,HttpServletResponse response) {
		System.out.println("POST");
	}

}

所以

后来我们在eclipse直接去新建一个servlet的时候，IDE自动给我们完成这些事了，例如我们新建一个TestServlet，会自动继承HttpServlet

package com.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class TestServlet
 */
public class TestServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public TestServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}