简单实现Java web服务器

一个简单的Java web服务器实现，比较简单，基于java.net.Socket和java.net.ServerSocket实现；
一、程序执行步骤
 1.创建一个ServerSocket对象；
 2.调用ServerSocket对象的accept方法，等待连接，连接成功会返回一个Socket对象，否则一直阻塞等待；
 3.从Socket对象中获取InputStream和OutputStream字节流，这两个流分别对应request请求和response响应；
 4.处理请求：读取InputStream字节流信息，转成字符串形式，并解析，这里的解析比较简单，仅仅获取uri(统一资源标识符)信息;
 5.处理响应：根据解析出来的uri信息，从WEB_ROOT目录中寻找请求的资源资源文件, 读取资源文件，并将其写入到OutputStream字节流中；
 6.关闭Socket对象；
 7.转到步骤2，继续等待连接请求； 

二、代码实现

 服务器实现： 

package ex01.pyrmont;

import java.net.Socket;
import java.net.ServerSocket;
import java.net.InetAddress;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;
import java.io.File;

public class HttpServer {

/**
* WEB_ROOT是HTML和其它文件存放的目录. 这里的WEB_ROOT为工作目录下的webroot目录
*/
public static final String WEB_ROOT = System.getProperty("user.dir") + File.separator + "webroot";

// 关闭服务命令
private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";

public static void main(String[] args) {
HttpServer server = new HttpServer();
//等待连接请求
server.await();
}

public void await() {
ServerSocket serverSocket = null;
int port = 8080;
try {
 //服务器套接字对象
 serverSocket = new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));
} catch (IOException e) {
 e.printStackTrace();
 System.exit(1);
}

// 循环等待一个请求
while (true) {
 Socket socket = null;
 InputStream input = null;
 OutputStream output = null;
 try {
 //等待连接，连接成功后，返回一个Socket对象
 socket = serverSocket.accept();
 input = socket.getInputStream();
 output = socket.getOutputStream();

// 创建Request对象并解析
 Request request = new Request(input);
 request.parse();
 // 检查是否是关闭服务命令
 if (request.getUri().equals(SHUTDOWN_COMMAND)) {
  break;
 }

// 创建 Response 对象
 Response response = new Response(output);
 response.setRequest(request);
 response.sendStaticResource();

// 关闭 socket 对象
 socket.close();

} catch (Exception e) {
 e.printStackTrace();
 continue;
 }
}
}
}

Request类： 

package ex01.pyrmont;

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

public class Request {

private InputStream input;
private String uri;

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

//从InputStream中读取request信息，并从request中获取uri值
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.print(request.toString());
uri = parseUri(request.toString());
}

/**
*
* requestString形式如下：
* GET /index.html HTTP/1.1
* Host: localhost:8080
* Connection: keep-alive
* Cache-Control: max-age=0
* ...
* 该函数目的就是为了获取/index.html字符串
*/
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;
}

}

Response类：

package ex01.pyrmont;

import java.io.OutputStream;
import java.io.IOException;
import java.io.FileInputStream;
import java.io.File;

/*
HTTP Response = Status-Line
*(( general-header | response-header | entity-header ) CRLF)
CRLF
[ message-body ]
Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
*/

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 {
 //将web文件写入到OutputStream字节流中
 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 {
 // 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();
}
}
}

三、结果测试

访问存在的资源文件(注意存放在工程目录的webroot文件夹里)：

访问不存在的资源文件：

关闭服务器：

参考资料：《深入剖析Tomcat》

@author   风一样的码农

来源：http://www.cnblogs.com/chenpi/archive/2016/06/20/5602171.html