How to use while loop statements to process key links in Java

Java code

<ol class=" list-paddingleft-2">
<li><p>public void handleConnection(Socket connectionToHandle) {   </p></li>
<li><p>new Thread(new ConnectionHandler(connectionToHandle)).<br>start();   </p></li>
<li><p>}   </p></li>
<li><p>public void handleConnection(Socket connectionToHandle) {  </p></li>
<li><p>new Thread(new ConnectionHandler(connectionToHandle)).<br>start();  </p></li>
<li><p>} </p></li>
</ol>

The big changes we made to RemoteFileServer are reflected in this method. We still call handleConnection() after the server accepts a connection, but now we pass the Socket to an instance of ConnectionHandler, which is Runnable. We create a new Thread with ConnectionHandler and start it. The run() method of ConnectionHandler contains the code for Socket reading/writing and reading File, which is originally in handleConnection() of RemoteFileServer.

4. Handling Connections: Part 2

Here is the structure of the ConnectionHandler class:

Java code

import java.io.*;   import java.net.*;   public class ConnectionHandler implements Runnable{   Socket socketToHandle;   public ConnectionHandler(Socket aSocketToHandle) {   socketToHandle = aSocketToHandle;   }   public void run() {   }   }   import java.io.*;  import java.net.*;  public class ConnectionHandler implements Runnable{  Socket socketToHandle;  public ConnectionHandler(Socket aSocketToHandle) {  socketToHandle = aSocketToHandle;  }  public void run() {  }

This helper class is quite simple. Like our other classes so far, we import java.net and java.io . This class has only one instance variable, socketToHandle, which holds the Socket handled by this instance. The class's constructor takes a Socket instance as a parameter and assigns it to socketToHandle.

Please note that this class implements the Runnable interface. Classes that implement this interface must implement the run() method, which is what our class does. We'll explore the details of run() later. Now just know that it will actually handle the connection, using the same code we saw earlier in the RemoteFileServer class.

Implement run()

Here we implement the run() method, which will grab the stream of our connection, use it to read and write the connection, and close it after the task is completed:

Java code

public void run() {   try {   PrintWriter streamWriter = new PrintWriter(socketToHandle.getOutputStream());   BufferedReader streamReader =   new BufferedReader(new InputStreamReader(socketToHandle.getInputStream()));   String fileToRead = streamReader.readLine();   BufferedReader fileReader = new BufferedReader(new FileReader(fileToRead));   String line = null;   while ((line = fileReader.readLine()) != null)   streamWriter.println(line);   fileReader.close();   streamWriter.close();   streamReader.close();   } catch (Exception e) {   System.out.println("Error handling a client: " + e);   }   }   public void run() {  try {  PrintWriter streamWriter = new PrintWriter(socketToHandle.getOutputStream());  BufferedReader streamReader =  new BufferedReader(new InputStreamReader(socketToHandle.getInputStream()));  String fileToRead = streamReader.readLine();  BufferedReader fileReader = new BufferedReader(new FileReader(fileToRead));  String line = null;  while ((line = fileReader.readLine()) != null)  streamWriter.println(line);  fileReader.close();  streamWriter.close();  streamReader.close();  } catch (Exception e) {  System.out.println("Error handling a client: " + e);  }  }

What the run() method of ConnectionHandler does is what handleConnection() on RemoteFileServer does. First, we wrap InputStream and OutputStream (using Socket's getOutputStream() and getInputStream()) into BufferedReader and PrintWriter respectively. Then we use this code to read the target file line by line:

Java code

FileReader fileReader = new FileReader(new File(streamReader.readLine()));   BufferedReader bufferedFileReader = new BufferedReader(fileReader);   String line = null;   while ((line = bufferedFileReader.readLine()) != null) {   streamWriter.println(line);   }   FileReader fileReader = new FileReader(new File(streamReader.readLine()));  BufferedReader bufferedFileReader = new BufferedReader(fileReader);  String line = null;  while ((line = bufferedFileReader.readLine()) != null) {  streamWriter.println(line);  }

Please remember that we should get a valid file path from the client, so that we can construct a new file with that path name File , wrap it into a FileReader to handle reading the file, and then wrap it into a BufferedReader to let us read the file line by line. We call readLine() on the BufferedReader in a Java while loop statement until there are no more lines to read. Please note that the call to readLine() will block until a byte comes. After we get some bytes, we put them into the local line variable and write them out to the client.

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