Servlet概念视频笔记_代码007(未授权)

本文介绍: 1.是Jav aEE规范之一。规范就是接口2.Se r v let-&g t;Jav aWe b 三大组件之一。三大组件分别是：Se r v let 程序、Filt e r 程序、Li stene r 监听器。3. Se r v let是运行在服务器上的一个 java 小程序，它可以(通过HTTP超文本传输协议)接收客户端发送过来的请求，并响应数据给客户端1、Ser v letCon text是一个接口，它表示 Ser v let 上下文对象2、一个 web 工程，只有一个 Serv letCon text 对象实例。

1.Servlet技术

a.什么是Servlet

b.手动实现Servlet程序

c.url地址如何定位到Servlet程序去访问

d.Servlet的生命周期

<?xml version="1.0" encoding="UTF-8"?&gt;
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0"&gt;


    <!--servlet标签给Tomcat配置Servlet程序 --&gt;
    <servlet&gt;
        <!--servlet-name标签 Servlet程序起一个别名(一般是类名）--&gt;
        <servlet-name&gt;HelloServlet</servlet-name&gt;
        <!--servlet-class是Servlet程序的全类名-->
        <servlet-class>com.example.servlet.HelloServlet</servlet-class>
    </servlet>

    <!--servlet-mapping标签给servlet程序配置访问地址-->
    <servlet-mapping>
        <!--servlet-name标签告诉服务器我当前配置的地址给哪个Servlet程序使用-->
        <servlet-name>HelloServlet</servlet-name>
        <!--url-pattern标签配置访问地址(自定义访问路径)
            /    斜杠在服务器解析的时候，表示地址为: http://ip:port/工程路径     <br/>
            /hello  表示地址为: http://ip:port/工程路径/hello   <br/>
        -->
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>
    
</web-app>

package com.example.servlet;

import java.io.IOException;
import javax.servlet.*;
import javax.servlet.annotation.*;

public class HelloServlet implements Servlet{


    @Override
    public void init(ServletConfig servletConfig) throws ServletException {

    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }

    /**
     * service方法是专门用来处理请求和响应的
     * @param servletRequest
     * @param servletResponse
     * @throws ServletException
     * @throws IOException
     */
    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("Hello Servlet 被访问了");

    }

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public void destroy() {

    }
}

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
  <form action="http://localhost:8080/Days2_war_exploded/hello" method="get">
    <input type="submit" >
  </form>


</body>
</html>

    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("3 service === Hello Servlet 被访问了");
        // 类型转换（因为它有getMethod()方法)
        HttpServletRequest httpServletRequest=(HttpServletRequest)servletRequest;
        // 获取请求的方式
        String method=httpServletRequest.getMethod();

        System.out.println(method);

//        System.out.println("get请求");
//        System.out.println("post请求");
    }

 @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("3 service === Hello Servlet 被访问了");
        // 类型转换（因为它有getMethod()方法)
        HttpServletRequest httpServletRequest=(HttpServletRequest)servletRequest;
        // 获取请求的方式
        String method=httpServletRequest.getMethod();
        if("GET".equals(method))
        {
          doGet();
        }else if ("POST".equals(method))
        {
           doPost();
        }

    }

    /**
     * 做get请求的操作
     */
    public void doGet()
    {
        System.out.println("get请求");
    }

    /**
     * 做post请求的操作
     */
    public void doPost()
    {
        System.out.println("post请求");
    }

package com.example.servlet;

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

public class HelloServlet2 extends HttpServlet {
    /**
     *doGet() 在get请求时调用
     * @param req
     * @param resp
     * @throws ServletException
     * @throws IOException
     */
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("HelloServlet2 的doGet方法");
    }
    /**
     *doPost() 在post请求时调用
     * @param req
     * @param resp
     * @throws ServletException
     * @throws IOException
     */
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("HelloServlet2 的doPost方法");
    }
}

 <servlet>
        <servlet-name>HelloServlet2</servlet-name>
        <servlet-class>com.example.servlet.HelloServlet2</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>HelloServlet2</servlet-name>
        <url-pattern>/hello2</url-pattern>
    </servlet-mapping>

package com.example.servlet;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;

public class HelloServlet3 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("HelloServlet3的doGet方法");
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("HelloServlet3的doPost方法");
    }
}

    @Override
    public void init(ServletConfig servletConfig) throws ServletException {
        System.out.println("2 init初始化");
        //获取别名Servlet-name的值
        System.out.println("HelloServlet程序的别名是:"+servletConfig.getServletName());
        //获取初始化参数init-param
        System.out.println("初始化参数username的值:"+servletConfig.getInitParameter("username"));
        //获取ServletContext对象
        System.out.println(servletConfig.getServletContext());

    }

<servlet>
        <servlet-name>HelloServlet2</servlet-name>
        <servlet-class>com.example.servlet.HelloServlet2</servlet-class>
        <!--init-param是初始化参数-->
        <init-param>
            <!--是参数名-->
            <param-name>username</param-name>
            <!--是参数值-->
            <param-value>root2</param-value>
        </init-param>
    </servlet>

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("HelloServlet2 的doGet方法");

        //也可以使用
        ServletConfig servletConfig=getServletConfig();
        System.out.println(servletConfig);
        //获取初始化参数init-param
        System.out.println("初始化参数username的值是:"+servletConfig.getInitParameter("username"));

    }

    @Override
    public void init(ServletConfig config) throws ServletException {
        super.init(config);
        System.out.println("重写了init初始化方法,做了一些工作");

    }

package com.example.servlet;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;

public class ContextServlet1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     ServletContext servletContext  =getServletContext();

        System.out.println(servletContext);
        System.out.println("保存之前: Context1 中获取域数据key1的值是:"+servletContext.getAttribute("key1"));
        servletContext.setAttribute("key1","value1");

        System.out.println("Context1 中获取域数据key1的值是:"+servletContext.getAttribute("key1"));

    }


}

package com.example.servlet;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;

public class ContextServlet2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletContext servletContext  =getServletContext();
        System.out.println(servletContext);
        System.out.println("Context2 中获取域数据key1的值是:"+servletContext.getAttribute("key1"));


    }


}