第五篇 - 手写Tomcat(基于Netty)热部署

Github源码下载地址：https://github.com/chenxingxing6/sourcecode/tree/master/code-netty-tomcat

一、前言

Tomcat是一个轻量级的应用服务器，或者说是一个Servlet容器。Tomcat默认的Http实现是采用阻塞的Socket通信，每个请求都需要创建一个线程处理，当线程>500，性能非常低。Tomcat默认最大请求数为150，具体需要看硬件配置。此篇博客，需要通过netty实现tomcat通信，提高tomcat的并发量，同时加深对netty的学习。除此之外，我们还将了解一下热部署的原理，自己简单实现一个热部署。

二、Netty实现简易Tomcat

2.1 依赖配置文件

 <dependencies><dependency><groupId>io.netty</groupId><artifactId>netty-all</artifactId><version>4.1.31.Final</version></dependency>
</dependencies>

2.2项目结构目录

2.3 配置文件

application.name=web## 这里为了解析方便，我们用properties进行配置
servlet.test=testServlet
servlet.test.className=com.catalina.servlet.TestServlet
servlet.test.urlPattern=/test*

2.4 核心代码Tomcat

package com.catalina.server;import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.http.HttpRequestDecoder;
import io.netty.handler.codec.http.HttpResponseEncoder;/*** User: lanxinghua* Date: 2019/10/9 09:30* Desc:*/
public class Tomcat {/*** 开启服务* @param port* @throws Exception*/public void start(int port) {EventLoopGroup bossGroup = new NioEventLoopGroup();EventLoopGroup workGroup = new NioEventLoopGroup();try {// 配置ServerBootstrap bootstrap = new ServerBootstrap();bootstrap.group(bossGroup, workGroup)// 主线程处理类.channel(NioServerSocketChannel.class)// 子线程处理类.childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel socketChannel) {// response编码socketChannel.pipeline().addLast(new HttpResponseEncoder());// request解码socketChannel.pipeline().addLast(new HttpRequestDecoder());// 业务逻辑处理socketChannel.pipeline().addLast(new TomcatHandler());}})// 对主线程，最大分配128个线程.option(ChannelOption.SO_BACKLOG, 128)// 子线程保存长连接.childOption(ChannelOption.SO_KEEPALIVE, true);// 启动服务器ChannelFuture f = bootstrap.bind(port).sync();System.out.println("Netty Tomcat Server Is Start...http://localhost:" + port);// 主线程waitf.channel().closeFuture().sync();}catch (Exception e){e.printStackTrace();}finally {bossGroup.shutdownGracefully();workGroup.shutdownGracefully();}}
}

2.5 核心代码TomcatHandler

package com.catalina.server;import com.catalina.config.Config;
import com.catalina.http.Request;
import com.catalina.http.Response;
import com.catalina.http.Servlet;
import com.hot.MyClassLoader;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.codec.http.HttpRequest;import java.util.HashMap;
import java.util.Map;
import java.util.regex.Pattern;/*** User: lanxinghua* Date: 2019/10/9 09:41* Desc:*/
public class TomcatHandler extends ChannelInboundHandlerAdapter {private static final Map<Pattern,String> servletMapping = new HashMap<Pattern, String>();private static String applicationName;static {Config.load("web.properties");applicationName = Config.getValue("application.name");for (String key : Config.getKeys()) {if (key.startsWith("servlet")){String name = key.replaceFirst("servlet.", "");if (name.indexOf(".") != -1){name = name.substring(0, name.indexOf("."));}String pattern = Config.getValue("servlet." + name + ".urlPattern").replaceAll("\\*", ".*");if (applicationName != null){pattern = "/"+ applicationName + pattern;}String className = Config.getValue("servlet." + name + ".className");if (!servletMapping.containsKey(pattern)){try {servletMapping.put(Pattern.compile(pattern), className);}catch (Exception e){e.printStackTrace();}}}}}@Overridepublic void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {if (msg instanceof HttpRequest){HttpRequest httpRequest = (HttpRequest) msg;Request request = new Request(ctx, httpRequest);Response response = new Response(ctx, httpRequest);doServlet(request, response);}}public void doServlet(Request request, Response response){String uri = request.getUri();String requestType = request.getRequestType();System.out.println("请求：" + uri + "type:" + requestType);if (applicationName != null && !uri.contains(applicationName)){String out = String.format("404 Not Found");response.write(out);return;}try {boolean hasPattern = false;for (Map.Entry<Pattern, String> entry : servletMapping.entrySet()) {if (entry.getKey().matcher(uri).matches()){// 自定义类加载器，实现热部署Class<?> clz = null;try {// 用自定义类加载器，是为了实现热部署MyClassLoader myLoader = new MyClassLoader();clz = myLoader.findClass(entry.getValue());}catch (Exception e){throw new RuntimeException("类加载异常，" + e.getMessage());}Servlet servlet = (Servlet) clz.newInstance();if ("get".equalsIgnoreCase(requestType)){servlet.doGet(request, response);}else {servlet.doPost(request, response);}hasPattern = true;}}if (!hasPattern){String out = String.format("404 Not Found");response.write(out);return;}}catch (Exception e){String out = String.format("500 Error msg:%s", e.getStackTrace());response.write(out);}}
}

2.6 服务启动BootStrap

package com.catalina.server;
/*** User: lanxinghua* Date: 2019/10/9 09:31* Desc: 服务启动*/
public class BootStrap {public static void main(String[] args) {new Tomcat().start(8080);}
}

2.7 测试结果

到这里一个基于netty简易版的Tomcat就实现了。全部代码，可以看github哦，亲…

三、热部署

3.1 类加载器

Java类的加载是由虚拟机来完成的,虚拟机把描述类的Class文件加载到内存,并对数据进行校验,解析和初始化,最终形成能被Java虚拟机直接使用的Java类型, 这就是虚拟机的类加载机制.JVM中用来完成上述功能的具体实现就是类加载器.类加载器读取.class字节码文件将其转换成java.lang.Class类的一个实例.每个实例用来表示一个java类.通过该实例的newInstance()方法可以创建出一个该类的对象.

3.2 热部署

对于Java应用程序来说，热部署就是在运行时更新Java类文件。也就是不重启服务器的情况下实现java类文件的替换修改等.举个例子，就像电脑可以在不重启的情况下，更换U盘。简单一句话让JVM重新加载新的class文件!

3.3 实现思路

1.监听修改文件，生成class文件，并进行替换
2.创建新的类加载器，加载更新的class文件

3.4 核心代码FileMonitor

package com.hot;import sun.nio.ch.IOUtil;import javax.tools.JavaCompiler;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.file.*;
import java.util.concurrent.TimeUnit;/*** User: lanxinghua* Date: 2019/10/9 15:00* Desc: 开启热部署,com.catalina.servlet下的文件* 修改servlet文件，保存，会自动实现热更新部署*/
public class FileMonitor {private static final String projectName = "code-netty-tomcat";private static final String packagePath = "com/catalina/servlet/";public static void main(String[] args) {new FileMonitor().start();}public void start(){System.out.println("开启热部署.....");try {Path path = Paths.get(projectName + "/src/main/java/" + packagePath);WatchService watcher = FileSystems.getDefault().newWatchService();path.register(watcher, StandardWatchEventKinds.ENTRY_MODIFY);new Thread(() -> {while (true) {try {WatchKey key = watcher.take();for (WatchEvent<?> event : key.pollEvents()) {if (event.kind() == StandardWatchEventKinds.OVERFLOW){// 事件可能是lost or discardedcontinue;}Path p = (Path) event.context();System.out.println("------------ start 热部署 --------------");hotDeploy(p);System.out.println("------------- end 热部署 --------------");}if (!key.reset()){break;}}catch (Exception e){e.printStackTrace();}}}).start();}catch (Exception e){e.printStackTrace();}try {TimeUnit.SECONDS.sleep(60*10);}catch (Exception e){e.printStackTrace();}}/*** 热部署* @param path*/public static void hotDeploy(Path path){String fileName = path.toFile().getName();// java源码路径String prefixPath = projectName + "/src/main/java/" + packagePath;String sourceCodePath = prefixPath+fileName;fileName = fileName.replace(".java", ".class");try {System.gc();String p = projectName + "/target/classes/"+ packagePath +fileName;File oldFile = new File(p);oldFile.delete();// 对源码进行编译doCompile(sourceCodePath);// 编译后端class文件移动到target对应的目录中去moveFile(prefixPath + fileName, p);}catch (Exception e){e.printStackTrace();}}private static void doCompile(String sourceCodePath){try {System.out.println("源码文件进行编译："+sourceCodePath);File file = new File(sourceCodePath);JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();StandardJavaFileManager manager = compiler.getStandardFileManager(null, null, null);Iterable iterable = manager.getJavaFileObjects(file);JavaCompiler.CompilationTask task = compiler.getTask(null, manager, null, null, null, iterable);task.call();manager.close();}catch (Exception e){e.printStackTrace();}}private static void moveFile(String srcPathStr, String desPathStr) {try{// 创建输入输出流对象File file = new File(desPathStr);if (!file.exists()){file.createNewFile();}FileInputStream fis = new FileInputStream(srcPathStr);FileOutputStream fos = new FileOutputStream(desPathStr);//创建搬运工具byte datas[] = new byte[1024*8];//创建长度int len = 0;//循环读取数据while((len = fis.read(datas))!=-1){fos.write(datas,0,len);}//释放资源fis.close();fis.close();File srcFile = new File(srcPathStr);srcFile.delete();}catch (Exception e){e.printStackTrace();}}
}

这里我们默认监听servlet目录下的文件，修改servlet文件后，可以实现自动热部署。

3.5 修改servlet文件TestServlet

public class TestServlet extends Servlet {public void doGet(Request req, Response resp) throws Exception {this.doPost(req, resp);}public void doPost(Request req, Response resp) throws Exception {String name = req.getParamter("name");resp.setCharSet("UTF-8");resp.setContentType("text/html; charset=utf-8");String html = "<h2>自己手写Netty实现Tomcat&热部署</h2><hr>";html += "<div>name："+ name +"<div>";// 修改的东西html += "update.....";resp.write(html);}
}

3.6 文件修改监听日志

------------ start 热部署 --------------
源码文件进行编译：code-netty-tomcat/src/main/java/com/catalina/servlet/TestServlet.java
------------- end 热部署 --------------

3.7 测试结果

希望给路过的朋友们可以解决一些疑惑，走过路过，不用错过，感兴趣就关注一波吧，感谢…