by SuperBonBon

Jafs custom FTP commands

Introduction

JAFS allows you to reimplement, add or remove FTP commands for each deployed FTP server instances. This is done with the command xml tag for generic FTP protocol commands and the feat xml tag for FTP features.

For each command or feature configuration entry, you'll need to define a protocol command name ( such as RETR to retreive a file ), a command implementation class name and optionally a class location ( such as http://www.myhost.com/myImpl.jar ). The commands and features config let you also provide a set of settings.

Commands implementation

To create your own command, you'll have to implement the net.sbbi.jafs.commands.CommandInterface. Here is a small class who will return an "Hello world" to the FTP client :

      package com.myCompany;
      
      import java.net.InetAddress;

      import org.apache.avalon.framework.parameters.Parameters;
        
      import net.sbbi.jafs.session.SessionContext;
      import net.sbbi.jafs.session.SessionInstructionProcessor;
        
      public class HelloWorld implements CommandInterface {
        
        public void execute( StringBuffer responseBuffer, String commandParameter, 
                             SessionContext sessionContext, 
                             SessionInstructionProcessor processor ) throws Exception {
        
          // let's retreive some info from the sesion context
          InetAddress piAdr = (InetAddress)sessionContext.get( SessionContext.PI_INET_ADDRESS );
          // use the StringBuffer if you have large output or multiple concats
          responseBuffer.append( "Helloworld to IP " ).append( piAdr.getHostAddress() );
          // the commandParameter String contains all the params provided by the client.
          if ( commandParameter.length() > 0 ) {
            responseBuffer.append( " you param is " ).append( commandParameter );
          }
          // if you need to stor or retreive custom data from the context use the 
          // getCustomObject() and putCustomObject() methods
          if ( sessionContext.getCustomObject( "myCustomKey" ) == null ) {
            sessionContext.putCustomObject( "MyCustomKey", "myUselessValue" );
          }
          // ok now write the response to the client
          processor.getPIrw().writePI( "200", responseBuffer.toString() );
          // no need to cleanup the buffer this is done automatically
        }

        public void parameterize( Parameters parameters ) {
          // contains the params defined in the config file for the command
        }
      }
      

If your command receives a file path as command parameter, you can use the net.sbbi.jafs.commands.AbstractPathCommand ( for a directory as param ) class or the net.sbbi.jafs.commands.AbstractFileCommand ( for a file as param ) class to easily access the file passed into param and make some automatic security checks.

Features implementation

The features are quite the same than the commands, they have to implement the FeatCommandInterface interface which consists of 2 new methods :

• getVersion() : returns the version of the feature.
• getUse() : to retreive the usage text that will be returned when the FEAT command is called.

      package com.myCompany;
        
      import java.net.InetAddress;
        
      import org.apache.avalon.framework.parameters.ParameterException;
      import org.apache.avalon.framework.parameters.Parameters;
        
      import net.sbbi.jafs.session.SessionContext;
      import net.sbbi.jafs.session.SessionInstructionProcessor;
        
      public class HelloWorld implements FeatCommandInterface {
        
        private String myParam;
        
        public void execute( StringBuffer responseBuffer, String commandParameter, 
                             SessionContext sessionContext, 
                             SessionInstructionProcessor processor ) throws Exception {

          // let's retreive some info from the sesion context
          InetAddress piAdr = (InetAddress)sessionContext.get( SessionContext.PI_INET_ADDRESS );
          // use the StringBuffer if you have large output or multiple concats
          responseBuffer.append( "Helloworld to IP " ).append( piAdr.getHostAddress() );
          // the commandParameter String contains all the params provided by the client.
          if ( commandParameter.length() > 0 ) {
            responseBuffer.append( " you param is " ).append( commandParameter );
          }
          if ( myParam != null ) {
            responseBuffer.append( " feature params is " ).append( myParam );
          }
          // if you need to stor or retreive custom data from the context use the 
          // getCustomObject() and putCustomObject() methods
          if ( sessionContext.getCustomObject( "myCustomKey" ) == null ) {
            sessionContext.putCustomObject( "MyCustomKey", "myUselessValue" );
          }
        
          // ok now write the response to the client
          processor.getPIrw().writePI( "200", responseBuffer.toString() );
          // no need to cleanup the buffer this is done automatically
        }
        
        public String getUse( SessionInstructionProcessor processor ) {
          return "someHelloWorldParam";
        }
        
        public byte getVersion() {
          return 1;
        }
        
        public void parameterize( Parameters params ) throws ParameterException {
          myParam = params.getParameter( "myHelloWorldParam", null );
        }
      }
      

Once you're done simply compile the code, put the jar into the libs dir and add the feature the the server configuration entry, start jafs and you're done :

      
      <server xmlns="http://www.sbbi.net/jafs/1.0/jafs-server"
              ...>
        ...
        <feats>
          ...
          <feat className="com.myCompany.HelloWorld" name="HELLOWORLD">
            <setting name="myHelloWorldParam">Additional myHelloWorldParam param</setting>
          </feat>
          ...
        </feats>
        ...
      </server>
      
      

When the FTP client will send an HELLOWORLD command the code above will be executed.