手动实现Tomcat底层机制+自己设计Servlet

1.Tomcat整体架构分析

自己理解

pdf下载

2.第一阶段

1.实现功能

编写自己的Tomcat能接受浏览器的请求并返回结果

2.代码

1.TomcatV1.java

package Tomcat;import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;/*** @author 孙显圣* @version 1.0* 第一个版本的，可以接收浏览器的请求并返回信息*/
public class TomcatV1 {public static void main(String[] args) throws Exception {//在8080端口监听ServerSocket serverSocket = new ServerSocket(8081);System.out.println("Tomcat在8080端口监听");//只要不是手动关闭服务，则循环获取连接while (!serverSocket.isClosed()) {//获取连接Socket accept = serverSocket.accept();//获取输入流InputStream inputStream = accept.getInputStream();//使用转换流转为bufferedreader可以读取一行BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "utf-8"));//字符串缓冲区String buff = null;while ((buff = bufferedReader.readLine()) != null) {//readline()在网络编程中，只有客户端的连接关闭了才会返回null,所以如果不设置别的判定条件退出，则会阻塞//由于请求信息最后有一个\r\n，读到这个\r\n会返回一个""，就可以退出了if (buff.equals("")) {break;}System.out.println(buff);}//tomcat向浏览器发送http响应，\r\n是换行String respHead ="HTTP/1.1 200 OK\r\n" +"Content-Type: text/html;charset=utf-8\r\n\r\n"; //响应头下面要空一行才能写响应体所以两个换行String resp = respHead + "<h1>hello world!</h1>";//获取输出流OutputStream outputStream = accept.getOutputStream();//输出outputStream.write(resp.getBytes());//关闭outputStream.flush();outputStream.close();inputStream.close();accept.close();}}
}

3.调试阶段

1.阻塞在readLine导致无法返回结果

1. 最开始我并没有添加，如果readLine()读到""就退出循环的逻辑
2. 后来发现readLine()在网络编程中，只有浏览器端关闭连接才会返回null
3. 当读到了请求的\r\n的时候就会返回一个""字符串，然后阻塞在这里等待输入
4. 所以在循环中添加当读到\r\n即返回""的时候退出即可

4.结果演示

3.第二阶段

1.实现功能

BIO线程模型支持多线程

2.代码

1.RequestHander.java

package Tomcat.handler;import java.io.*;
import java.net.Socket;/*** @author 孙显圣* @version 1.0* 处理http请求的线程类*/
public class RequestHander implements Runnable{//定义一个socket属性private Socket socket = null;public RequestHander(Socket socket) {this.socket = socket;}public void run() {//可以对客户端或浏览器进行交互try {//获取输入流InputStream inputStream = socket.getInputStream();//转换成BufferedReader,方便按行读取BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "utf-8"));System.out.println("tomcatV2接受到浏览器的数据如下：");//接受数据//设置缓冲String buff = null;//循环读取while ((buff = bufferedReader.readLine()) != null) {//判断是否读取到了\r\nif (buff.equals("")) {break; //读取完毕则退出循环，避免readLine阻塞}System.out.println(buff);}//获取输出流，返回信息到浏览器OutputStream outputStream = socket.getOutputStream();String respHead ="HTTP/1.1 200 OK\r\n" +"Content-Type: text/html;charset=utf-8\r\n\r\n"; //响应头下面要空一行才能写响应体所以两个换行String resp = respHead + "<h1>hello 孙显圣!</h1>";outputStream.write(resp.getBytes());//关闭outputStream.flush();outputStream.close();inputStream.close();socket.close();} catch (IOException e) {throw new RuntimeException(e);} finally {//确保关闭if (socket != null) {try {socket.close();} catch (IOException e) {throw new RuntimeException(e);}}}}
}

2.TomcatV2.java

package Tomcat;import Tomcat.handler.RequestHander;import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;/*** @author 孙显圣* @version 1.0*/
public class TomcatV2 {public static void main(String[] args) throws IOException {//在8080端口监听ServerSocket serverSocket = new ServerSocket(8080);System.out.println("TomcatV2在8080端口监听");//只要没有手动关闭则服务一直开启，循环监听while (!serverSocket.isClosed()) {Socket socket = serverSocket.accept();//将获取的socket交给线程类来处理RequestHander requestHander = new RequestHander(socket);Thread thread = new Thread(requestHander);thread.start(); //启动线程}}
}

3.调试阶段

1.发现每次按回车会接受到两次请求

原因就是每次请求还要请求一下页面的小图标

4.结果演示

4.第三阶段

1.实现功能

2.总体框架

3.代码实现

===1.封装Request

1.Request.java

package Tomcat.http;/*** @author 孙显圣* @version 1.0*/import java.io.*;
import java.util.HashMap;/*** 1.Request的作用就是封装http请求的数据 GET /tomcatv2?a=9&b=3 HTTP/1.1* 2.比如method（get）， uri（/tomcat/cal），还有参数列表（num1&num2）* 3.相当于原生的HttpServletRequest*/
public class Request {private String method;private String uri;//存放参数列表private HashMap<String, String> parametersMapping = new HashMap<String, String>();//构造方法获取inputStream来封装信息public Request(InputStream inputStream) throws IOException {//转换成BufferedReaderBufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "utf-8"));//读取第一行String s = bufferedReader.readLine();//将内容封装到属性String[] split = s.split(" ");method = split[0];//判断是否有参数列表int index = split[1].indexOf("?");if (index == -1) { //没有参数列表uri = split[1];}else { //有参数列表uri = split[1].substring(0,index);String parameters = split[1].substring(index + 1, split[1].length());String[] split1 = parameters.split("&"); //分割参数//判断？后面是否有东西if (split1 != null && !"".equals(split1)) {//遍历参数for (String parameterPair : split1) {String[] split2 = parameterPair.split("=");parametersMapping.put(split2[0],split2[1]);}}}//不能关闭，否则socket也就关闭了
//        inputStream.close();}public String getMethod() {return method;}public String getUri() {return uri;}public String getParameter(String name) {if (parametersMapping.containsKey(name)) {return parametersMapping.get(name);}else {return null;}}}

2.RequestHander.java

package Tomcat.handler;import Tomcat.http.Request;import java.io.*;
import java.net.Socket;/*** @author 孙显圣* @version 1.0* 处理http请求的线程类*/
public class RequestHander implements Runnable {//定义一个socket属性private Socket socket = null;public RequestHander(Socket socket) {this.socket = socket;}public void run() {//可以对客户端或浏览器进行交互try {//获取输入流InputStream inputStream = socket.getInputStream();//封装到Request里Request request = new Request(inputStream);//获取数据System.out.println(request.getUri() + " " + request.getMethod());System.out.println(request.getParameter("num1") + " " + request.getParameter("num2")+ " " + request.getParameter("num3"));//获取输出流，返回信息到浏览器OutputStream outputStream = socket.getOutputStream();String respHead ="HTTP/1.1 200 OK\r\n" +"Content-Type: text/html;charset=utf-8\r\n\r\n"; //响应头下面要空一行才能写响应体所以两个换行String resp = respHead + "<h1>hello 孙显圣!</h1>";outputStream.write(resp.getBytes());//关闭outputStream.flush();outputStream.close();inputStream.close();socket.close();} catch (IOException e) {throw new RuntimeException(e);} finally {//确保关闭if (socket != null) {try {socket.close();} catch (IOException e) {throw new RuntimeException(e);}}}}
}

单元测试报错Sock is closed

原因

在Request.java中获取完参数顺便把inputStream关闭了，导致了Socket也一起关闭了，使得主线程在使用socket的时候出现了已经关闭的错误

修改之后

===2.封装Response

3.Response.java

package Tomcat.http;/*** @author 孙显圣* @version 1.0*/import java.io.OutputStream;/*** 1.这个response对象可以封装OutputSream* 2.即可以通过这个对象返回http响应给浏览器* 3.相当于原生的HttpServletResponse*/
public class Response {private OutputStream outputStream = null;//封装一个响应头public static final String respHeader = "HTTP/1.1 200 OK\r\n" +"Content-Type: text/html;charset=utf-8\r\n\r\n"; //响应头下面要空一行才能写响应体所以两个换行public Response(OutputStream outputStream) {this.outputStream = outputStream;}//以后再Servlet里面获取输出流public OutputStream getOutputStream() {return outputStream;}
}

4.RequestHander.java

package Tomcat.handler;import Tomcat.http.Request;
import Tomcat.http.Response;import java.io.*;
import java.net.Socket;/*** @author 孙显圣* @version 1.0* 处理http请求的线程类*/
public class RequestHander implements Runnable {//定义一个socket属性private Socket socket = null;public RequestHander(Socket socket) {this.socket = socket;}public void run() {//可以对客户端或浏览器进行交互try {//获取输入流InputStream inputStream = socket.getInputStream();//封装到Request里Request request = new Request(inputStream);//获取数据System.out.println(request.getUri() + " " + request.getMethod());System.out.println(request.getParameter("num1") + " " + request.getParameter("num2")+ " " + request.getParameter("num3"));//获取输出流，返回信息到浏览器OutputStream outputStream = socket.getOutputStream();//封装到Response对象中Response response = new Response(outputStream);//获取输出流输出信息OutputStream outputStream1 = response.getOutputStream();outputStream1.write((response.respHeader + "<h1>response响应：你好，孙显圣</h1>").getBytes());//关闭outputStream.flush();outputStream.close();inputStream.close();socket.close();} catch (IOException e) {throw new RuntimeException(e);} finally {//确保关闭if (socket != null) {try {socket.close();} catch (IOException e) {throw new RuntimeException(e);}}}}
}

单元测试无误

===3.设计servlet规范

5.Servlet.java

package Tomcat.servlet;import Tomcat.http.Request;
import Tomcat.http.Response;import java.io.IOException;/*** @author 孙显圣* @version 1.0* 保留三个核心方法*/
public interface Servlet {void init() throws Exception;void service(Request request, Response response) throws IOException;void destroy();
}

6.HttpServlet.java

package Tomcat.servlet;import Tomcat.http.Request;
import Tomcat.http.Response;import java.io.IOException;/*** @author 孙显圣* @version 1.0*/
public abstract class HttpServlet implements Servlet {public void service(Request request, Response response) throws IOException {//抽象模板设计模式，判断类型来决定调用什么方法if ("GET".equalsIgnoreCase(request.getMethod())) {//以后会反射创建子类实例，调用子类的service方法，子类没有，就从父类找，然后再使用动态绑定到子类的doGet方法this.doGet(request, response);} else if ("POST".equalsIgnoreCase(request.getMethod())) {this.doPost(request, response);}}public abstract void doGet(Request request, Response response);public abstract void doPost(Request request, Response response);}

7.CalServlet.java

package Tomcat.servlet;import Tomcat.http.Request;
import Tomcat.http.Response;
import Tomcat.utils.WebUtils;import java.io.IOException;
import java.io.OutputStream;/*** @author 孙显圣* @version 1.0*/
public class CalServlet extends HttpServlet {public void doGet(Request request, Response response) {//完成计算任务int num1 = WebUtils.parseInt(request.getParameter("num1"), 0);int num2 = WebUtils.parseInt(request.getParameter("num2"), 0);int sum = num1 + num2;//返回计算结果给浏览器OutputStream outputStream = response.getOutputStream();String resp = Response.respHeader + "<h1>" + num1 + " + " + num2 + " = " + sum + "</h1>";try {outputStream.write(resp.getBytes());//关闭outputStream.flush();outputStream.close();} catch (IOException e) {throw new RuntimeException(e);}}public void doPost(Request request, Response response) {this.doGet(request, response);}public void init() throws Exception {}public void destroy() {}
}

8.WebUtils.java

package Tomcat.utils;/*** @author 孙显圣* @version 1.0*/
public class WebUtils {//把String类型转换成int类型，如果是非整数则返回默认值public static int parseInt(String str, int defaultVal) {try {return Integer.parseInt(str);} catch (NumberFormatException e) {System.out.println("转换失败");}return defaultVal;}}

9.RequestHander.java

package Tomcat.handler;import Tomcat.http.Request;
import Tomcat.http.Response;
import Tomcat.servlet.CalServlet;import java.io.*;
import java.net.Socket;/*** @author 孙显圣* @version 1.0* 处理http请求的线程类*/
public class RequestHander implements Runnable {//定义一个socket属性private Socket socket = null;public RequestHander(Socket socket) {this.socket = socket;}public void run() {//可以对客户端或浏览器进行交互try {//获取输入流InputStream inputStream = socket.getInputStream();//封装到Request里Request request = new Request(inputStream);//获取输出流，返回信息到浏览器OutputStream outputStream = socket.getOutputStream();//封装到Response对象中Response response = new Response(outputStream);CalServlet calServlet = new CalServlet();calServlet.service(request,response); //这个会调用他抽象父类的service方法inputStream.close();socket.close();} catch (IOException e) {throw new RuntimeException(e);} finally {//确保关闭if (socket != null) {try {socket.close();} catch (IOException e) {throw new RuntimeException(e);}}}}
}

单元测试无误

===4.xml + 反射初始化容器

10.web.xml

11.TomcatV3.java

package Tomcat;import Tomcat.handler.RequestHander;
import Tomcat.servlet.HttpServlet;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;/*** @author 孙显圣* @version 1.0*/
public class TomcatV3 {//设置两个hashmap容器，在启动的Tomcat的时候就初始化//存放名字和实例public static final ConcurrentHashMap<String, HttpServlet>servletMapping = new ConcurrentHashMap<String, HttpServlet>();//存放路径和名字public static final ConcurrentHashMap<String, String>servletUrlMapping = new ConcurrentHashMap<String, String>();public static void main(String[] args) throws MalformedURLException, DocumentException, ClassNotFoundException, InstantiationException, IllegalAccessException {TomcatV3 tomcatV3 = new TomcatV3();tomcatV3.init();tomcatV3.run();}//启动TomcatV3容器public void run() {try {ServerSocket serverSocket = new ServerSocket(8080);System.out.println("TomcatV3在8080端口监听");while (!serverSocket.isClosed()) { //只要没有手动关闭服务，就循环获取连接Socket socket = serverSocket.accept();//将socket交给线程处理RequestHander requestHander = new RequestHander(socket);new Thread(requestHander).start(); //启动线程}} catch (IOException e) {throw new RuntimeException(e);}}private void init() throws MalformedURLException, DocumentException, ClassNotFoundException, InstantiationException, IllegalAccessException {//获取该类的路径String path = TomcatV3.class.getResource("/").getPath();//使用dom4j读取web.xml文件//获取解析器SAXReader saxReader = new SAXReader();//读取文件Document read = saxReader.read(new File(path + "web.xml"));//获取根元素Element rootElement = read.getRootElement();//获取所有二级元素List<Element> servlet = rootElement.elements();//遍历所有二级元素，根据不同类型做处理for (Element element : servlet) {if ("servlet".equalsIgnoreCase(element.getName())) {//获取名字和全类名Element servletName = element.element("servlet-name");Element servletClass = element.element("servlet-class");//通过反射创建实例Class<?> aClass = Class.forName(servletClass.getText().trim()); //trim是清除空格HttpServlet httpServlet = (HttpServlet) aClass.newInstance();//将其放到容器中去servletMapping.put(servletName.getText(), httpServlet);} else if ("servlet-mapping".equalsIgnoreCase(element.getName())) {//获取名字和urlElement servletName = element.element("servlet-name");Element servletUrl = element.element("url-pattern");//将其放到容器中去servletUrlMapping.put("/tomcat" + servletUrl.getText(), servletName.getText());}}}}

12.RequestHander.java

package Tomcat.handler;import Tomcat.TomcatV3;
import Tomcat.http.Request;
import Tomcat.http.Response;
import Tomcat.servlet.CalServlet;
import Tomcat.servlet.HttpServlet;import java.io.*;
import java.net.Socket;/*** @author 孙显圣* @version 1.0* 处理http请求的线程类*/
public class RequestHander implements Runnable {//定义一个socket属性private Socket socket = null;public RequestHander(Socket socket) {this.socket = socket;}public void run() {//可以对客户端或浏览器进行交互try {//获取输入流InputStream inputStream = socket.getInputStream();//封装到Request里Request request = new Request(inputStream);//获取输出流，返回信息到浏览器OutputStream outputStream = socket.getOutputStream();//封装到Response对象中Response response = new Response(outputStream);String uri = request.getUri();String servletName = TomcatV3.servletUrlMapping.get(uri);if (servletName == null) {servletName = "";}HttpServlet httpServlet = TomcatV3.servletMapping.get(servletName);//判断是否得到了这个对象if (httpServlet != null) {httpServlet.service(request, response);} else {//没有得到则返回404String resp = Response.respHeader + "<h1>404 not found</h1>";response.getOutputStream().write(resp.getBytes());}inputStream.close();socket.close();} catch (IOException e) {throw new RuntimeException(e);} finally {//确保关闭if (socket != null) {try {socket.close();} catch (IOException e) {throw new RuntimeException(e);}}}}
}

4.总体调试阶段

1.空指针异常

5.结果演示

5.课后作业

1.更新WebUtils.java

添加方法

    //判断是不是html格式的文件，如果是就直接读取文件内容并且返回truepublic static boolean isHtml(String uri, Response response) {//使用正则表达式匹配html文件String regStr = "(/.*)*/(.*\\.html)";Pattern compile = Pattern.compile(regStr);Matcher matcher = compile.matcher(uri);if (!matcher.find()) { //没匹配到就直接返回falsereturn false;}//得到html文件的路径String path = "D:\\Intelij IDEA Project\\java_web\\tomcat\\target\\classes\\" + matcher.group(2);System.out.println(path);//根据路径读取文件并存放到StringBuilder中StringBuilder stringBuilder = new StringBuilder();try {BufferedReader bufferedReader = new BufferedReader(new FileReader(path));String buf = null;while ((buf = bufferedReader.readLine()) != null) {stringBuilder.append(buf); //存放到stringBuilder中}//将stringBuilder的内容响应给浏览器String resp = Response.respHeader + stringBuilder.toString();response.getOutputStream().write(resp.getBytes());}catch (Exception e) {System.out.println("文件找不到！");return false; //返回false之后就会继续进行原来的逻辑，弹出404}//如果不出异常则说明响应成功return true;}

2.修改RequestHander.java

3.cal.html

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title>
</head>
<body>
<form action="/tomcat/CalServlet" method="get">num1:<input type="text" name="num1">num2:<input type="text" name="num2"><input type="submit" value="提交">
</form>
</body>
</html>

4.调试阶段

1. 一直显示我的cal.html文件找不到，调了半个小时
2. 原因是String path = TomcatV3.class.getResource("/").getPath();使用这个来获取的路径没有空格，而我的资源路径是这个D:\\Intelij IDEA Project\\java_web\\tomcat\\target\\classes\\，中间带了空格，真的是醉了，深刻体会到文件夹起名不要带空格的重要性了

5.结果展示