模拟tomcat进行http请求及响应处理：BufferedReader类的readLine在socket网络编程应用时发生阻塞

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最近写一个简单的程序模拟tomcat进行http请求及响应处理时，发现使用BufferedReader类的readLine在socket网络编程应用时发生阻塞。

启动服务类：

package com.lwf.server;

import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;

public class WebServer {

	public static void main(String[] args) {
		int port = 8080;
		if(args != null && args.length == 1){
			port = Integer.parseInt(args[0]);
		}
		new WebServer().startServer(port);
		
	}
	
	public void startServer(int port){
		ServerSocket serverSocket = null;
		try {
			serverSocket = new ServerSocket(port);
			int i = 0;
			while(true){
				System.out.println("server started " + i++);
				Socket socket = serverSocket.accept();
				new Processor(socket).start();
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

请求处理类：

package com.lwf.server;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintStream;
import java.net.Socket;

public class Processor extends Thread{
	Socket socket = null;
	InputStream in = null;
	PrintStream out = null;
	OutputStream out1 = null;
	public static final String filePath = "F:";
	public Processor(){	}
	
	public Processor(Socket socket){
		this.socket = socket;
		try {
			in = socket.getInputStream();
			out = new PrintStream(socket.getOutputStream());
			out1 = socket.getOutputStream();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	public void run() {
		try {
			String fileNamePath = parse(in);
			OutPrintFile(fileNamePath);
			Thread current = Thread.currentThread();
			System.out.println("当前线程：" + current.getName());
			socket.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	public String parse(InputStream in){
		String retVal = "";
		try {
			BufferedReader bf = new BufferedReader(new InputStreamReader(in));
			retVal = getRequestPath(bf);
			//printParseContent(bf);
			
//			bf.close();  //不能关闭输入流，如果关闭则socket将重置

		} catch (IOException e) {
			e.printStackTrace();
		}
		return retVal;
		
	}

	/** 
	* @Title: getRequestPath 
	* @Description: 获得http请求的资源路径
	* @param @param bf
	* @param @return
	* @param @throws IOException   
	* @return String  
	* @throws 
	*/ 
	private String getRequestPath(BufferedReader bf) throws IOException {
		String retVal;
		String httpMsg = bf.readLine();
		String[] contents = httpMsg.split(" ");
		if(contents.length != 3){
			sendErrorMsg(400, "Client Send Error");
		}
		System.out.println("Method:" + contents[0] + " Resource:" + contents[1] + " Protocol:" + contents[2]);
		retVal = contents[1];
		return retVal;
	}
	
	/** 
	* @Title: printParseContent 
	* @Description: 输出解析出来的http请求信息
	* @param @param bf
	* @param @throws IOException   
	* @return void  
	* @throws 
	*/ 
	private void printParseContent(BufferedReader bf) throws IOException {
		StringBuffer requestStr = new StringBuffer();
		String data = null;
		while((data = bf.readLine()) != null){
			requestStr.append(data + "\n");
		}
		System.out.println(requestStr.toString());
	}

	public void sendErrorMsg(int errCode,String errMsg){
		out.println("HTTP/1.1 " + errCode + " " + errMsg);
		out.println("Content-Type: text/html");
		out.println();
		out.println("<html>");
		out.println("<title>ErrMsg");	
		out.println("</title>");
		out.println("<body>");
		out.println("<h1>ErrorCode:" +  errCode + "ErrMsg:" + errMsg + "</h1>");
		out.println("</body>");
		out.println("</html>");
	}
	
	public void OutPrintFile(String fileName){	
		File file = new File(filePath + fileName);
		if(!file.exists()){
			sendErrorMsg(404, "File Not Found !!");
			return;
		}
		
		try {
			outWriteByPrintStream(file);
		  //outWriteByOutPutStream(file);
			System.out.println("OutPrintFile finish -- " );
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}

	private void outWriteByPrintStream(File file) throws FileNotFoundException,
			IOException {
		InputStream in = new FileInputStream(file);
		byte b [] = new byte[(int)file.length()];
		in.read(b);
		out.println("HTTP/1.1 200 OK");
		out.println("Content-Type: text/html");
		out.println("Content-Length:"+ b.length);
		out.println();
		out.write(b);
		in.close();
	}

	@SuppressWarnings("unused")
	private void outWriteByOutPutStream(File file) throws FileNotFoundException, IOException {
		byte[] bytes = new byte[1024];
		InputStream in = new FileInputStream(file);
		int ch = in.read(bytes, 0, 1024);
		
		while (ch != -1) {
			out1.write(bytes, 0, ch);
			ch = in.read(bytes, 0, 1024);
		}
		in.close();
	}
}

将上类的parse方法的printParseContent(bf);取消注释，调试：

如在浏览器输入地址：http://本机IP:8080/Noname1.html （我这里将Noname1.html放在F盘根目录）

当程序运行到printParseContent的while循环时读取几行后程序不再运行。。

跟踪bf来源，BufferedReader bf = new BufferedReader(new InputStreamReader(in));

in = socket.getInputStream();

可见最终来源于socket得到的输入流。。经查

readLine()是一个阻塞函数，当没有数据读取时，就一直会阻塞在那，而不是返回null。

readLine()只有在数据流发生异常或者另一端被close()掉时，才会返回null值。

使用socket之类的数据流时，要避免使用readLine()，以免为了等待一个换行/回车符而一直阻塞

参考文章：http://blog.csdn.net/swingline/article/details/5357581

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2016-05-11 15:04
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