servlet有三種手動建立的方式：

第一種：實現Servlet介面

瞭解一下Servlet生命週期

A、在容器中建立一個Servlet物件 （放到容器中,如果容器中存在，不建立）

B、初使化Servlet(呼叫init方法)

C、呼叫service方法，服務使用者的請求;

D、呼叫destroyed方法，銷燬物件;

package cn.lanqiao.servlet;

import java.io.IOException;
import java.util.Enumeration;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class Servlet6 implements Servlet {

	private ServletConfig config;

	// 1.建立servlet物件
	public Servlet6() {
		System.out.println("1 servlet物件建立。。。");
	}

	// 2.初始化servlet
	@Override
	public void init(ServletConfig conf) throws ServletException {
		// TODO Auto-generated method stub
		System.out.println("2,servlet初始化 了。。。。。。");
		this.config = conf;
	}

	@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 service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
		// System.out.println(res);
		// res.getWriter().write("呼叫service方法。。。");
		res.getOutputStream().write("hello".getBytes());
		System.out.println("3 service方法被呼叫，響應使用者請求");
		// 通過servletconfig拿初始化引數
		// String name = config.getInitParameter("uname");
		// String upassword = config.getInitParameter("upassword");
		// System.out.println(name);
		// System.out.println(upassword);
		Enumeration<String> names = config.getInitParameterNames();
		while (names.hasMoreElements()) {
			String str = (String) names.nextElement();
			System.out.println(str + "---" + config.getInitParameter(str));

		}
	}

	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		System.out.println("4 銷燬物件。。。。。");
	}

}
 

第二種：繼承GenericServlet，實現裡面的Service方法

package cn.lanqiao.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class Servlet2 extends GenericServlet {

	@Override
	public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
		// TODO Auto-generated method stub
		PrintWriter pw = res.getWriter();
		pw.write("hello,servlet2，，，，，，，");
	}

}
 

第三種：繼承HttpServlet，實現裡面的doGet方法和doPost方法，一般我們都是用這個建立Servlet物件

package cn.lanqiao.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Servlet5 extends HttpServlet {
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

		doPost(req, resp);
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		resp.getWriter().write("hello,servlet5...");
	}
}
 

以上三種手動建立Servlet物件的方法在釋出的時候需要去配置web.xml檔案

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>servletproject</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <servlet-name>Servlet1</servlet-name>
    <servlet-class>cn.lanqiao.servlet.Servlet1</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Servlet1</servlet-name>
    <url-pattern>/Servlet1</url-pattern>
  </servlet-mapping>
  
  
</web-app>

但是我們使用直接建立一個Servlet的時候，會自動幫我們在web.xml中配置，對於新手還是使用第三種手動建立物件的方法好，這種直接建立的方法在以後的工作中使用可以提高效率。