实现一个简单的Tomcat

Tomcat Servlet · 發表 2018-11-06 20:30:23

摘要：实现一个简单的Tomcat 1. Tomcat作用我们的web应用会运行在Tomcat中，那么显然请求必定是先到达Tomcat的，Tomcat对于请求实际上会进行如下的处理：提供Socket服务：Tomcat的启动，必然是Socket服务，支持ht...

实现一个简单的Tomcat

1. Tomcat作用

我们的web应用会运行在Tomcat中，那么显然请求必定是先到达Tomcat的，Tomcat对于请求实际上会进行如下的处理：

提供Socket服务：Tomcat的启动，必然是Socket服务，支持http协议。
进行请求的分发：一个Tomcat可以为多个web应用提供服务，那么就需要把url下发到不同的web应用。
需要将请求和响应封装成request和response：我们在写后端代码的时候都是直接使用request和response的，这是因为Tomcat已经做好了。

下面我们就自己来实现这三步。

2. 实现代码

项目结构：

src
└─mytomcat
BookServlet.java
CarServlet.java
MyRequest.java
MyResponse.java
MyServlet.java
MyTomcat.java
ServletMapping.java
ServletMappingConfig.java

2.1 封装http请求和响应

package mytomcat;

import java.io.IOException;
import java.io.InputStream;

/**
 * 封装http请求
 */
public class MyRequest {

private String url;
private String method;

public MyRequest(InputStream inputStream) throws IOException {

String httpRequest = "";
byte[] httpRequestBytes = new byte[1024];
int length = 0;
if((length = inputStream.read(httpRequestBytes)) > 0) {
httpRequest = new String(httpRequestBytes, 0, length);
}

String httpHead = httpRequest.split("\n")[0];
url = httpHead.split("\\s")[1];
method = httpHead.split("\\s")[0];

System.out.println(this.toString());
}

public String getUrl() {
return url;
}

public void setUrl(String url) {
this.url = url;
}

public String getMethod() {
return method;
}

public void setMethod(String method) {
this.method = method;
}

@Override
public String toString() {
return "MyRequest -- url:" + url + ",method:" + method;
}

}

package mytomcat;

import java.io.IOException;
import java.io.OutputStream;

/**
 * 封装http响应
 */
public class MyResponse {

private OutputStream outputStream;

public MyResponse (OutputStream outputStream) {
this.outputStream = outputStream;
}

public void write(String content) throws IOException {
StringBuffer httpResponse = new StringBuffer();
httpResponse.append("HTTP/1.1 200 OK\n")
.append("Content-Type: text/html\n")
.append("\r\n")
.append(content);

outputStream.write(httpResponse.toString().getBytes());
outputStream.close();
}

}

2.2 实现不同的Servlet

package mytomcat;
/**
 * Servlet抽象类
 */
public abstract class MyServlet {

public abstract void doGet(MyRequest myRequest, MyResponse myResponse);

public abstract void doPost(MyRequest myRequest, MyResponse myResponse);

public void service(MyRequest myRequest, MyResponse myResponse) {
if(myRequest.getMethod().equalsIgnoreCase("POST")) {
doPost(myRequest, myResponse);
}else if(myRequest.getMethod().equalsIgnoreCase("GET")) {
doGet(myRequest, myResponse);
}
}
}

package mytomcat;

import java.io.IOException;

/**
 * 处理操作'书'的http请求
 */
public class BookServlet extends MyServlet {

@Override
public void doGet(MyRequest myRequest, MyResponse myResponse) {
try {
myResponse.write("[get] book...");
}catch(IOException e) {
e.printStackTrace();
}
}

@Override
public void doPost(MyRequest myRequest, MyResponse myResponse) {
try {
myResponse.write("[post] book...");
}catch(IOException e) {
e.printStackTrace();
}
}

}

package mytomcat;

import java.io.IOException;

/**
 * 处理操作'车'的http请求
 */
public class CarServlet extends MyServlet {

@Override
public void doGet(MyRequest myRequest, MyResponse myResponse) {
try {
myResponse.write("[get] car...");
}catch(IOException e) {
e.printStackTrace();
}

}

@Override
public void doPost(MyRequest myRequest, MyResponse myResponse) {
try {
myResponse.write("[post] car...");
}catch(IOException e) {
e.printStackTrace();
}
}

}

2.3 定义Servlet映射POJO类

package mytomcat;

public class ServletMapping {

private String servletName;
private String url;
private String className;

public ServletMapping(String servletName, String url, String className) {
super();
this.servletName = servletName;
this.url = url;
this.className = className;
}

public String getServletName() {
return servletName;
}

public void setServletName(String servletName) {
this.servletName = servletName;
}

public String getUrl() {
return url;
}

public void setUrl(String url) {
this.url = url;
}

public String getClassName() {
return className;
}

public void setClassName(String className) {
this.className = className;
}

}

2.4 配置Servlet映射关系

package mytomcat;

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

/**
 * 配置请求url和处理的servlet的对应关系
 */
public class ServletMappingConfig {

public static List<ServletMapping> servletMappingList = new ArrayList<>();;

static {
servletMappingList.add(new ServletMapping("Book", "/book", "mytomcat.BookServlet"));
servletMappingList.add(new ServletMapping("Car", "/car", "mytomcat.CarServlet"));
}

}

2.5 主类

package mytomcat;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashMap;
import java.util.Map;

public class MyTomcat {
private int port;
//保存请求url和处理请求servlet的对应关系
private Map<String, String> urlServletMap = new HashMap<String, String>();

public MyTomcat(int port) {
this.port = port;
}

public void start() {
initServletMapping();

ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(port);
System.out.println("MyTomcat is start...\n监听端口：" + port);

while(true) {
System.out.println("等待请求...");
Socket socket = serverSocket.accept();
InputStream inputStream = socket.getInputStream();
OutputStream outputStream = socket.getOutputStream();

MyRequest myRequest = new MyRequest(inputStream);
MyResponse myResponse = new MyResponse(outputStream);

//请求分发
disPatch(myRequest, myResponse);
socket.close();
}
}catch(IOException e) {
e.printStackTrace();
}finally {
if(serverSocket != null) {
try {
serverSocket.close();
}catch(IOException e) {
e.printStackTrace();
}
}
}
}

//初始化url和处理的servlet的对应关系
private void initServletMapping() {
for(ServletMapping servletMapping: ServletMappingConfig.servletMappingList) {
urlServletMap.put(servletMapping.getUrl(), servletMapping.getClassName());
}
}

//分发处理请求
private void disPatch(MyRequest myRequest, MyResponse myResponse) {
String className = urlServletMap.get(myRequest.getUrl());

//反射
try {
Class<MyServlet> myServletClass = (Class<MyServlet>) Class.forName(className);
MyServlet myServlet = myServletClass.newInstance();

myServlet.service(myRequest, myResponse);
}catch(Exception e) {
e.printStackTrace();
}
}

public static void main(String[] args) {
MyTomcat myTomcat = new MyTomcat(8080);
myTomcat.start();
}
}

3. 测试

运行MyTomcat主类，然后在浏览器输入http://localhost:8080/car ，可以看到返回[get] car... ，大功告成。

源码地址：

ofollow,noindex">https://github.com/WangJun-SCU/mytomcat

实现一个简单的Tomcat

实现一个简单的Tomcat

1. Tomcat作用

2. 实现代码

2.1 封装http请求和响应

2.2 实现不同的Servlet

2.3 定义Servlet映射POJO类

2.4 配置Servlet映射关系

2.5 主类

3. 测试

源码地址：

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