tomcat学习(一)----HTTP服务器是怎么工作的(一个简单的tomcat)

清风听雨

1.Request类(模拟HttpServletRequest)
package ex01.pyrmont;
import java.io.IOException;
import java.io.InputStream;
public class Request {
private InputStream input;
private String uri;
public Request(InputStream input) {
this.input = input;
}
public String getUri() {
return uri;
}
/**
* 读取InputStream中内容，转化成字符串，调用解析字符串方法解析
*/
public void parse() {
//从socket中读取字符
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("HTTP Request:");
System.out.print(request.toString());
uri = parseURI(request.toString());
}
/**
*截取requestString第一个空格和第二个空格之间的内容返回
*/
private String parseURI(String requestString) {
int index1;
int index2;
index1 = requestString.indexOf(' ');
if(index1 != -1) {
index2 = requestString.indexOf(' ', index1 + 1);
if (index2 > index1) {
return requestString.substring(index1 + 1, index2);
}
}
return "";
}
}

2.Response类(模拟HttpServletResponse)
package ex01.pyrmont;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
/**
*HTTP Response =
*   状态行 Status-Line=HTTP-Version SP Status-Code SP Reason-Phrase CRLF
*   响应头部字段 ((general-header | response-header | entity-header) CRLF)
*   空行 CRLF
*   响应主体 message-body
*/
public class Response {
private static final int BUFFER_SIZE = 1024;
Request request;
OutputStream output;
public Response(OutputStream output) {
this.output = output;
}
public void setRequset(Request request) {
this.request = request;
}
public void sendStaticResource() {
byte[] bytes = new byte[BUFFER_SIZE];
FileInputStream fis = null;
try {
File file = new File(HttpServer.WEB_ROOT, request.getUri());
if(file.exists()) {
fis = new FileInputStream(file);
int ch = fis.read(bytes, 0, BUFFER_SIZE);
while(ch != -1) {
output.write(bytes, 0, ch);
ch = fis.read(bytes, 0, BUFFER_SIZE);
}
} else {
//文件不存在
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) {
e.printStackTrace();
} finally {
if(fis != null) {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}

3.HttpServer类(模拟主服务)
package ex01.pyrmont;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
public class HttpServer {
/**
* WEB_ROOT是html文件和其他文件所存放的目录 System.getProperty("user.dir")获得的是该文件编译后存放的目录
* 对于这个包，WEB_ROOT是在工作目录下的"webroot"
* 工作目录是在系统中java命令被执行的地方
*/
public static final String WEB_ROOT = System.getProperty("user.dir") + File.separator + "webroot";
// shutdown command
private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";
// 判断是否关闭服务器标志
private boolean shutdown = false;
public void await() {
ServerSocket server = null;
int port = 9999;
try {
server = new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
//循环等待请求
while(!shutdown) {
Socket socket = null;
InputStream input = null;
OutputStream output = null;
try {
socket = server.accept();
input = socket.getInputStream();
output = socket.getOutputStream();
//创建一个Requset对象并解析
Request request = new Request(input);
request.parse();
//创建一个Response对象来输出内容
Response response = new Response(output);
response.setRequset(request);
response.sendStaticResource();
//关闭socket
socket.close();
//检查URI是否是关闭命令
shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
} catch (IOException e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) {
HttpServer server = new HttpServer();
server.await();
}
}


4.运行程序
在浏览器输入：localhost:9999/aaa.txt等会返回相应文件，或找不到提示
这三个类实现了一个简单的web服务器是如何工作的