tomcat简单实现（how tomcat work第一章内容）

       学习tomcat的时候，我们只是编写一个实现Servlet（间接实现）简单的java类。但是容器却能把他变成一个服务，在这之前他还是一个普通的类，并不能接受http请求。只有容器加载类并调用init方法才会把他变成一个真正的servlet，这时候他才能接受请求返回响应。



        那么容器究竟是怎么实现的呢，从上一篇文章我们利用socket编程实现了远程操作文件夹，同样的。tomcat也是封装了socket从而实现将servlet类变成servlet服务。只是最终的业务逻辑传到我们编写的servlet类来处理。下面我们来实现一个简单的web服务器，效果就是可以接受http请求并响应,先看效果图：网址中输入http:\\localhost:8080



后台打印信息，也就是请求信息



下面是源代码，共有三个类

HttServer：提供服务

Resquest：得到请求信息并解析

Response：返回信息（需要加入http响应头部，不然浏览器无法解析）

import java.io.*;
import java.net.*;

/**
*我们的服务类，当运行这个类时会监听指定的端口
*/
public class HttpServer {

// 关闭标识
private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";

// 是否关闭监听，根据URI判定
private boolean shutdown = false;

public static void main(String[] args) {
HttpServer server = new HttpServer();
server.await();
}

public void await() {
ServerSocket serverSocket = null;
int port = 8080;
try {
//监听本地8080端口
serverSocket =  new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));
}
catch (IOException e) {
e.printStackTrace();
System.exit(1);
}

//死循环，监听端口
while (!shutdown) {
Socket socket = null;
InputStream input = null;
OutputStream output = null;
try {
socket = serverSocket.accept();
input = socket.getInputStream();
output = socket.getOutputStream();

// 读取请求内容，包括http请求头，以及请求内容
Request request = new Request(input);
request.parse();

// 做出响应
Response response = new Response(output);
response.setRequest(request);
response.sendStaticResource();

// 关闭socket
socket.close();

//检查是否要关闭监听
shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
}
catch (Exception e) {
e.printStackTrace();
continue;
}
}
}
}

import java.io.*;

/**
* 解析请求内容
*/
public class Request {

private InputStream input;
private String uri;

public Request(InputStream input) {
this.input = input;
}

public void parse() {
StringBuffer request = new StringBuffer(2048);
int i;
byte[] buffer = new byte[2048];
try {
i = input.read(buffer);
}
catch (IOException e) {
e.printStackTrace();
i = -1;
}
for (int j=0; j<i; j++) {
request.append((char) buffer[j]);
}
System.out.println("请求信息"+request.toString());
uri = parseUri(request.toString());
System.out.println("URI"+uri);
}

private String parseUri(String requestString) {
int index1, index2;
index1 = requestString.indexOf(' ');
if (index1 != -1) {
index2 = requestString.indexOf(' ', index1 + 1);
if (index2 > index1)
return requestString.substring(index1 + 1, index2);
}
return null;
}

public String getUri() {
return uri;
}

}

import java.io.*;

/**
* 响应类
*/
public class Response {

private static final int BUFFER_SIZE = 1024;
Request request;
OutputStream output;

public Response(OutputStream output) {
this.output = output;
}

public void setRequest(Request request) {
this.request = request;
}

public void sendStaticResource() throws IOException {
byte[] bytes = new byte[BUFFER_SIZE];
FileInputStream fis = null;
try {
//File file = new File(HttpServer.WEB_ROOT, request.getUri());
System.out.println(request.getUri());
File file = new File("F:\\howtomcatworks\\HowTomcatWorks\\webroot\\index.html");
System.out.println("文件已找到");
if (file.exists()) {
String errorMessage = "HTTP/1.1 200 File Found\r\n" +
"Content-Type: text/html\r\n" +
"\r\n"+
"<h1>File Found</h1>";
output.write(errorMessage.getBytes());
}
else {
// file not found
String errorMessage = "HTTP/1.1 404 File Not Found\r\n" +
"Content-Type: text/html\r\n" +
"Content-Length: 23\r\n" +
"\r\n" +
"<h1>File Not Found</h1>";
output.write(errorMessage.getBytes());
}
}
catch (Exception e) {
// thrown if cannot instantiate a File object
System.out.println(e.toString() );
}
finally {
if (fis!=null)
fis.close();
}
}
}