<?xml version="1.0" encoding="UTF-8"?>
<Server>
    <Host name = "localhost">
        <Context path="/b" docBase="d:/project/diytomcat/b" />
    </Host>
</Server>

package cn.how2j.diytomcat.util;

import cn.how2j.diytomcat.catalina.Context;
import cn.hutool.core.io.FileUtil;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

import java.util.ArrayList;
import java.util.List;

public class ServerXMLUtil {
    public static List<Context> getContexts() {
        List<Context> result = new ArrayList<>();
        String xml = FileUtil.readUtf8String(Constant.serverXmlFile);
        Document d = Jsoup.parse(xml);

        Elements es = d.select("Context");
        for (Element e : es) {
            String path = e.attr("path");
            String docBase = e.attr("docBase");
            Context context = new Context(path, docBase);
            result.add(context);
        }
        return result;
    }

    public static String getHostName() {
        String xml = FileUtil.readUtf8String(Constant.serverXmlFile);
        Document d = Jsoup.parse(xml);

        Element host = d.select("Host").first();
        return host.attr("name");
    }
}

package cn.how2j.diytomcat.catalina;

import cn.how2j.diytomcat.util.Constant;
import cn.how2j.diytomcat.util.ServerXMLUtil;

import java.io.File;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Host {
    private String name;
    private Map<String, Context> contextMap;

    public Host(){
        this.contextMap = new HashMap<>();
        this.name =  ServerXMLUtil.getHostName();

        scanContextsOnWebAppsFolder();
        scanContextsInServerXML();

    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    private  void scanContextsInServerXML() {
        List<Context> contexts = ServerXMLUtil.getContexts();
        for (Context context : contexts) {
            contextMap.put(context.getPath(), context);
        }
    }

    private  void scanContextsOnWebAppsFolder() {
        File[] folders = Constant.webappsFolder.listFiles();
        for (File folder : folders) {
            if (!folder.isDirectory())
                continue;
            loadContext(folder);
        }
    }
    private  void loadContext(File folder) {
        String path = folder.getName();
        if ("ROOT".equals(path))
            path = "/";
        else
            path = "/" + path;

        String docBase = folder.getAbsolutePath();
        Context context = new Context(path,docBase);

        contextMap.put(context.getPath(), context);
    }

    public Context getContext(String path) {
        return contextMap.get(path);
    }
}

package cn.how2j.diytomcat.http;

import cn.how2j.diytomcat.Bootstrap;
import cn.how2j.diytomcat.catalina.Context;
import cn.how2j.diytomcat.catalina.Host;
import cn.how2j.diytomcat.util.MiniBrowser;
import cn.hutool.core.util.StrUtil;

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

public class Request {

    private String requestString;
    private String uri;
    private Socket socket;
    private Context context;
    private Host host;
    public Request(Socket socket, Host host) throws IOException {
        this.socket = socket;
        this.host = host;
        parseHttpRequest();
        if(StrUtil.isEmpty(requestString))
            return;
        parseUri();
        parseContext();
        if(!"/".equals(context.getPath()))
            uri = StrUtil.removePrefix(uri, context.getPath());

    }

    private void parseContext() {
        String path = StrUtil.subBetween(uri, "/", "/");
        if (null == path)
            path = "/";
        else
            path = "/" + path;

        context = host.getContext(path);
        if (null == context)
            context = host.getContext("/");
    }

    private void parseHttpRequest() throws IOException {
        InputStream is = this.socket.getInputStream();
        byte[] bytes = MiniBrowser.readBytes(is);
        requestString = new String(bytes, "utf-8");
    }

    private void parseUri() {
        String temp;

        temp = StrUtil.subBetween(requestString, " ", " ");
        if (!StrUtil.contains(temp, '?')) {
            uri = temp;
            return;
        }
        temp = StrUtil.subBefore(temp, '?', false);
        uri = temp;
    }

    public Context getContext() {
        return context;
    }

    public String getUri() {
        return uri;
    }

    public String getRequestString(){
        return requestString;
    }

}

package cn.how2j.diytomcat;

import cn.how2j.diytomcat.catalina.Context;
import cn.how2j.diytomcat.catalina.Host;
import cn.how2j.diytomcat.http.Request;
import cn.how2j.diytomcat.http.Response;
import cn.how2j.diytomcat.util.Constant;
import cn.how2j.diytomcat.util.ServerXMLUtil;
import cn.how2j.diytomcat.util.ThreadPoolUtil;
import cn.hutool.core.io.FileUtil;
import cn.hutool.core.thread.ThreadUtil;
import cn.hutool.core.util.ArrayUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.log.LogFactory;
import cn.hutool.system.SystemUtil;

import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.*;

public class Bootstrap {
    public static void main(String[] args) {
        try {
            logJVM();

            Host host = new Host();
            int port = 18080;

            ServerSocket ss = new ServerSocket(port);

            while(true) {
                Socket s =  ss.accept();
                Runnable r = new Runnable(){
                    @Override
                    public void run() {
                        try {
                            Request request = new Request(s,host);
                            Response response = new Response();
                            String uri = request.getUri();
                            if(null==uri)
                                return;
                            System.out.println("uri:"+uri);

                            Context context = request.getContext();

                            if("/".equals(uri)){
                                String html = "Hello DIY Tomcat from how2j.cn";
                                response.getWriter().println(html);
                            }
                            else{
                                String fileName = StrUtil.removePrefix(uri, "/");
                                File file = FileUtil.file(context.getDocBase(),fileName);
                                if(file.exists()){
                                    String fileContent = FileUtil.readUtf8String(file);
                                    response.getWriter().println(fileContent);

                                    if(fileName.equals("timeConsume.html")){
                                        ThreadUtil.sleep(1000);
                                    }

                                }
                                else{
                                    response.getWriter().println("File Not Found");
                                }
                            }
                            handle200(s, response);
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                };

                ThreadPoolUtil.run(r);

            }
        } catch (IOException e) {
            LogFactory.get().error(e);
            e.printStackTrace();
        }

    }

    private static void logJVM() {
        Map<String,String> infos = new LinkedHashMap<>();
        infos.put("Server version", "How2J DiyTomcat/1.0.1");
        infos.put("Server built", "2020-04-08 10:20:22");
        infos.put("Server number", "1.0.1");
        infos.put("OS Name\t", SystemUtil.get("os.name"));
        infos.put("OS Version", SystemUtil.get("os.version"));
        infos.put("Architecture", SystemUtil.get("os.arch"));
        infos.put("Java Home", SystemUtil.get("java.home"));
        infos.put("JVM Version", SystemUtil.get("java.runtime.version"));
        infos.put("JVM Vendor", SystemUtil.get("java.vm.specification.vendor"));

        Set<String> keys = infos.keySet();
        for (String key : keys) {
            LogFactory.get().info(key+":\t\t" + infos.get(key));
        }
    }

    private static void handle200(Socket s, Response response) throws IOException {
        String contentType = response.getContentType();
        String headText = Constant.response_head_202;
        headText = StrUtil.format(headText, contentType);
        byte[] head = headText.getBytes();

        byte[] body = response.getBody();

        byte[] responseBytes = new byte[head.length + body.length];
        ArrayUtil.copy(head, 0, responseBytes, 0, head.length);
        ArrayUtil.copy(body, 0, responseBytes, head.length, body.length);

        OutputStream os = s.getOutputStream();
        os.write(responseBytes);
        s.close();
    }
}