一、tomcat基础

1.基础功能

提供Socket服务：实现对某些端口的监听，从而实现请求到来时，Tomcat可以感知到。同时该Socket服务也需要支持HTTP协议。
封装请求和响应：通过之前的介绍，我们知道在我们开发Servlet时，Web容器已经将Context、Request、Response替我们封装好了，可以直接使用。Tomcat作为一款Servlet容器，肯定要支持这项功能。
请求分发：一个Tomcat可以提供多个Web服务，那么Tomcat需要支持将不同的url分发到不同的应用，调用不同的Servlet。

2.通信过程

3.HTTP报文请求和响应示例

二、代码实现

1、Servlet接口

package com.lijiacheng;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * @ClassName : MyServer  //类名
 * @Description :  //描述
 * @Author : 李嘉诚  //作者
 * @Date: 2022-01-20 22:05 //日期
 */
public class MyServer {
    public static void startServer(int port) throws Exception{
        //定义服务器套接字
        ServerSocket serverSocket=new ServerSocket(port);
        //定义客户端服务器
        Socket socket=null;
        while(true){
            socket=serverSocket.accept();
            //获取输入流和输出流
            InputStream inputStream= socket.getInputStream();
            OutputStream outputStream= socket.getOutputStream();
            //定义请求对象
            MyRequest request=new MyRequest(inputStream);
            //定义响应对象
            MyResponse response=new MyResponse(outputStream);
            String clazz=new MyMapping().getMapping().get(request.getRequestUrl());
            if(clazz!=null){
                Class<MyServlet> myServletClass=(Class<MyServlet>)Class.forName(clazz);
                //根据myServletClass创建对象
                MyServlet myServlet = myServletClass.newInstance();
                myServlet.service(request,response);
            }
        }
    }

    public static void main(String[] args) {
        try {
            startServer(10086);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

package com.lijiacheng;

import java.io.IOException;

/**
 * @ClassName : MyHttpServlet  //类名
 * @Description :  //描述
 * @Author : 李嘉诚  //作者
 * @Date: 2022-01-11 23:00 //日期
 */
public abstract class MyHttpServlet {
    public static final String METHOD_GET="GET";
    public static final String METHOD_POST="POST";
    public abstract void doGET(MyRequest myRequest,MyResponse myResponse) throws IOException;
    public abstract void doPOST(MyRequest myRequest,MyResponse myResponse) throws IOException;
    public void service(MyRequest myRequest,MyResponse myResponse) throws IOException {
        if(METHOD_GET.equals(myRequest.getRequestMethod())){
            doGET(myRequest,myResponse);
        }else if(METHOD_POST.equals(myRequest.getRequestMethod())){
            doPOST(myRequest,myResponse);
        }
    }
}

2.Request\Response抽象

package com.lijiacheng;

import java.io.IOException;
import java.io.InputStream;

public class MyRequest {
    private String requestMethod;
    private String requestUrl;
    public MyRequest(InputStream inputStream) throws Exception {
        byte[] buffer=new byte[1024];
        int len=0;
        String str=null;
        if((len=inputStream.read(buffer))>0){
            str=new String(buffer,0,len);
        }
        String data=str.split("\n")[0];
        String[] params=str.split(" ");
        this.requestMethod=params[0];
        this.requestUrl=params[1];
    }

    public String getRequestMethod() {
        return requestMethod;
    }

    public void setRequestMethod(String requestMethod) {
        this.requestMethod = requestMethod;
    }

    public String getRequestUrl() {
        return requestUrl;
    }

    public void setRequestUrl(String requestUrl) {
        this.requestUrl = requestUrl;
    }
}

package com.lijiacheng;

import java.io.IOException;
import java.io.OutputStream;

public class MyResponse {
    private OutputStream outputStream;

    public MyResponse(OutputStream outputStream) {
        this.outputStream = outputStream;
    }
    public void write(String str) throws IOException {
        StringBuilder builder=new StringBuilder();
        builder.append("HTTP://1.1 200 OK")
                .append("Content-Type:text/html\n")
                .append("\r\n")
                .append("<html>")
                .append("<body>")
                .append("<h1>"+str+"</h1>")
                .append("</body>")
                .append("</html>");
        this.outputStream.write(builder.toString().getBytes());
        this.outputStream.flush();
        this.outputStream.close();
    }
}

3.Servlet映射

package com.lijiacheng;

import java.util.HashMap;

public class MyMapping {
    public static HashMap<String,String> mapping=new HashMap<String,String>();
    static {
        mapping.put("/mytomcat","com.lijiacheng.MyServlet");
    }
    public HashMap<String,String> getMapping(){
        return mapping;
    }
}

4.server实现

package com.lijiacheng;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * @ClassName : MyServer  //类名
 * @Description :  //描述
 * @Author : 李嘉诚  //作者
 * @Date: 2022-01-20 22:05 //日期
 */
public class MyServer {
    public static void startServer(int port) throws Exception{
        //定义服务器套接字
        ServerSocket serverSocket=new ServerSocket(port);
        //定义客户端服务器
        Socket socket=null;
        while(true){
            socket=serverSocket.accept();
            //获取输入流和输出流
            InputStream inputStream= socket.getInputStream();
            OutputStream outputStream= socket.getOutputStream();
            //定义请求对象
            MyRequest request=new MyRequest(inputStream);
            //定义响应对象
            MyResponse response=new MyResponse(outputStream);
            String clazz=new MyMapping().getMapping().get(request.getRequestUrl());
            if(clazz!=null){
                Class<MyServlet> myServletClass=(Class<MyServlet>)Class.forName(clazz);
                //根据myServletClass创建对象
                MyServlet myServlet = myServletClass.newInstance();
                myServlet.service(request,response);
            }
        }
    }

    public static void main(String[] args) {
        try {
            startServer(10086);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}