从零手动实现简易Tomcat

Hello大家好，本章我们自己实现一个简易版的tomcat 。有问题可以联系我mr_beany@163.com。另求各路大神指点，感谢

程序的运行少不了服务器的支持，而tomcat因其性能稳定，免费等优点，深受 Java 爱好者的喜爱并得到了部分软件开发商的认可，为目前比较流行的 Web 应用服务器。

那么到底它是怎么运行的呢？今天我们来实现一个简化版tomcat来感受一下。

一：导入解析xml的jar包

<dependency><groupId>dom4j</groupId><artifactId>dom4j</artifactId><version>1.6.1</version>
</dependency>复制代码

二：编写XML解析类

package com.example.demo.utils;import java.util.List;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;/*** @author zy*/
public class XmlUtils {/*** 定义解析器和文档对象*/public SAXReader saxReader;public Document document;public XmlUtils(String path) {//获取解析器saxReader = new SAXReader();try {//获取文档对象document = saxReader.read(path);} catch (DocumentException e) {e.printStackTrace();}}/*** 获取节点下的所有节点** @param name* @return*/public List<Element> getNodes(String name) {Element root = document.getRootElement();return root.elements(name);}
}
复制代码

三：实现Request和Response

其中Request是对浏览器的请求的封装，而Response是对浏览器请求的响应，换而言之就是Request 用来取出请求信息，而 Response 则用来添加要返回给浏览器的信息。

创建Request.java

package com.example.demo.http;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;/*** @author zy*/
public class Request {private String method;private String url;public Request(InputStream inputStream) throws IOException {BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));String[] methodAndUrl = bufferedReader.readLine().split(" ");this.method = methodAndUrl[0];this.url = methodAndUrl[1];System.out.println("请求类型："+ method);System.out.println("请求路径："+ url);}public String getMethod() {return method;}public void setMethod(String method) {this.method = method;}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}}复制代码

创建Response.java

package com.example.demo.http;import java.io.OutputStream;/*** @author zy*/
public class Response {private OutputStream outputStream;private String write;public Response(OutputStream outputStream){this.outputStream = outputStream;}public String getWrite() {return write;}public void setWrite(String write) {this.write = write;}}复制代码

四：实现Servlet

先做个接口

package com.example.demo.servlet;import com.example.demo.http.Request;
import com.example.demo.http.Response;/*** @author zy*/
public abstract class AbstractServlet {public abstract void doGet(Request request, Response response);public abstract void doPost(Request request, Response response);
}复制代码

再来实现自己的Servlet

package com.example.demo.servlet;import com.example.demo.http.Request;
import com.example.demo.http.Response;/*** @author zy*/
public class FirstServlet extends AbstractServlet {@Overridepublic void doGet(Request request, Response response) {response.setWrite("我的第一个Servlet");}@Overridepublic void doPost(Request request, Response response) {this.doGet(request, response);}
}复制代码

五：创建web.xml

这里配置了请求路径的servlet的对应关系，文件放在resources文件夹下

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5"><servlet><servlet-name>first.html</servlet-name><servlet-class>com.example.demo.servlet.FirstServlet</servlet-class></servlet><servlet-mapping><servlet-name>first.html</servlet-name><url-pattern>/first.html</url-pattern></servlet-mapping></web-app>复制代码

六，创建tomcat，初始化配置文件

package com.example.demo.tomcat;import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashMap;
import java.util.List;import com.example.demo.utils.XmlUtils;
import org.dom4j.Element;/*** @author zy*/
public class Tomcat {/*** 设置端口号*/private static final int PORT = 8080;public static final HashMap<String, Object> SERVLET_MAPPING = new HashMap<>();public static final HashMap<String, Object> SERVLET = new HashMap<>();/*** 控制服务器启动关闭*/public boolean tomcatStarBool = true;private void init() {InputStream io = null;try {System.out.println("加载配置文件开始");//读取配置文件XmlUtils xml = new XmlUtils(XmlUtils.class.getResource("/")+"web.xml");//将所有的类都存储到容器中List<Element> list = xml.getNodes("servlet");for (Element element : list) {SERVLET.put(element.element("servlet-name").getText(),Class.forName(element.element("servlet-class").getText()).newInstance());}//映射关系创建List<Element> list2 = xml.getNodes("servlet-mapping");for (Element element : list2) {SERVLET_MAPPING.put(element.element("url-pattern").getText(),element.element("servlet-name").getText());}System.out.println("加载配置文件结束");} catch (Exception ex) {ex.printStackTrace();} finally {if (io != null) {try {io.close();} catch (Exception e) {e.printStackTrace();}}}}}复制代码

七：创建处理请求任务的SocketProcess

package com.example.demo.tomcat;import com.example.demo.http.Request;
import com.example.demo.http.Response;
import com.example.demo.servlet.AbstractServlet;import java.io.OutputStream;
import java.net.Socket;/*** @author zy*/
public class SocketProcess extends Thread{protected Socket socket;public SocketProcess(Socket socket){this.socket = socket;}@Overridepublic void run() {try {Request request = new Request(socket.getInputStream());Response response = new Response(socket.getOutputStream());String servletName = (String) Tomcat.SERVLET_MAPPING.get(request.getUrl());if(servletName!=null && !servletName.isEmpty()) {//映射有的话找到对应的对象AbstractServlet servlet = (AbstractServlet) Tomcat.SERVLET.get(servletName);if(servlet!=null) {servlet.doGet(request, response);}else {System.out.println("找不到对应的servlet");}}else {System.out.println("找不到对应的servletMapping");}String res = response.getWrite();OutputStream outputStream = socket.getOutputStream();outputStream.write(res.getBytes("GBK"));outputStream.flush();outputStream.close();}catch (Exception ex){ex.printStackTrace();}finally {if (socket != null) {try {socket.close();} catch (Exception e) {e.printStackTrace();}}}}
}复制代码

八：在tomcat.java中添加启动方法

private void start() {try {ServerSocket serverSocket = new ServerSocket(PORT);System.out.println("Tomcat 服务已启动，地址：localhost ,端口：" + PORT);this.init();//持续监听do {Socket socket = serverSocket.accept();//处理任务Thread thread = new SocketProcess(socket);thread.start();} while (tomcatStarBool);} catch (IOException e) {e.printStackTrace();}
}public static void main(String[] args) {Tomcat tomcat = new Tomcat();tomcat.start();
}复制代码

九：测试

启动在tomcat.java中运行void main方法

出现如下字样代表启动成功，然后地址栏中输入

http://localhost:8080/first.html

？？？？？为什么是这样。。。。。。

啊！原来没有添加响应头信息

Response.java中加入

/*** 响应头信息*/
public static final String RESPONSE_HEADER ="HTTP/1.1 200 \r\n"+ "Content-Type: text/html\r\n"+ "\r\n";复制代码

SocketProcess.java中

String res = response.getWrite();复制代码

改成

String res = Response.RESPONSE_HEADER + response.getWrite();复制代码

重新启动，访问

结尾

祝大家新年快乐。感谢支持！

其他文章：

从零搭建自己的springboot后台框架

码云地址： gitee.com/beany/mySpr…

GitHub地址： github.com/MyBeany/myS…