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.nettygroupId>
<artifactId>netty-allartifactId>
<version>4.1.31.Finalversion>
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>() {
@Override
protected 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wait
f.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();
}
}
}
}
}
@Override
public 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 discarded
continue;
}
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 = "自己手写Netty实现Tomcat&热部署
";
html += "name："+ name +"";
// 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…