commandtemplate.java

java 开发的邮件服务器平台。支持以下协议。 协议可以修改为自己的专门标识

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 * Copyright (c) 2000-2004 The Apache Software Foundation.             *
 * All rights reserved.                                                *
 * ------------------------------------------------------------------- *
 * Licensed under the Apache License, Version 2.0 (the "License"); you *
 * may not use this file except in compliance with the License. You    *
 * may obtain a copy of the License at:                                *
 *                                                                     *
 *     http://www.apache.org/licenses/LICENSE-2.0                      *
 *                                                                     *
 * Unless required by applicable law or agreed to in writing, software *
 * distributed under the License is distributed on an "AS IS" BASIS,   *
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or     *
 * implied.  See the License for the specific language governing       *
 * permissions and limitations under the License.                      *
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package org.apache.james.imapserver.commands;

import org.apache.avalon.framework.logger.AbstractLogEnabled;
import org.apache.james.imapserver.AuthorizationException;
import org.apache.james.imapserver.ImapConstants;
import org.apache.james.imapserver.store.ImapMailbox;
import org.apache.james.imapserver.ImapRequestLineReader;
import org.apache.james.imapserver.ImapResponse;
import org.apache.james.imapserver.ImapSession;
import org.apache.james.imapserver.ImapSessionState;
import org.apache.james.imapserver.store.MailboxException;
import org.apache.james.imapserver.ProtocolException;

/**
 * Base class for all command implementations. This class provides common
 * core functionality useful for all {@link org.apache.james.imapserver.commands.ImapCommand} implementations.
 *
 *
 * @version $Revision: 1.4.2.3 $
 */
abstract class CommandTemplate
        extends AbstractLogEnabled
        implements ImapCommand, ImapConstants
{
    protected CommandParser parser = new CommandParser();

    /**
     * By default, valid in any state (unless overridden by subclass.
     * @see org.apache.james.imapserver.commands.ImapCommand#validForState
     */
    public boolean validForState( ImapSessionState state )
    {
        return true;
    }

    /**
     * Template methods for handling command processing. This method reads
     * argument values (validating them), and checks the request for correctness.
     * If correct, the command processing is delegated to the specific command
     * implemenation.
     *
     * @see ImapCommand#process
     */
    public void process( ImapRequestLineReader request,
                         ImapResponse response,
                         ImapSession session )
    {
        try {
            doProcess( request, response, session );
        }
        catch ( MailboxException e ) {
            response.commandFailed( this, e.getResponseCode(), e.getMessage() );
        }
        catch ( AuthorizationException e ) {
            String msg = "Authorization error: Lacking permissions to perform requested operation.";
            response.commandFailed( this, msg );
        }
        catch ( ProtocolException e ) {
            String msg = e.getMessage() + " Command should be '" +
                    getExpectedMessage() + "'";
            response.commandError( msg );
        }
    }

    /**
     * This is the method overridden by specific command implementations to
     * perform commend-specific processing.
     *
     * @param request The client request
     * @param response The server response
     * @param session The current client session
     */
    protected abstract void doProcess( ImapRequestLineReader request,
                                       ImapResponse response,
                                       ImapSession session )
            throws ProtocolException, MailboxException, AuthorizationException;

    /**
     * Provides a message which describes the expected format and arguments
     * for this command. This is used to provide user feedback when a command
     * request is malformed.
     *
     * @return A message describing the command protocol format.
     */
    protected String getExpectedMessage()
    {
        StringBuffer syntax = new StringBuffer( "<tag> " );
        syntax.append( getName() );

        String args = getArgSyntax();
        if ( args != null && args.length() > 0 ) {
            syntax.append( " " );
            syntax.append( args );
        }

        return syntax.toString();
    }

    /**
     * Provides the syntax for the command arguments if any. This value is used
     * to provide user feedback in the case of a malformed request.
     *
     * For commands which do not allow any arguments, <code>null</code> should
     * be returned.
     *
     * @return The syntax for the command arguments, or <code>null</code> for
     *         commands without arguments.
     */
    protected abstract String getArgSyntax();

    protected ImapMailbox getMailbox( String mailboxName,
                                      ImapSession session,
                                      boolean mustExist )
            throws MailboxException
    {
        return session.getHost().getMailbox( session.getUser(), mailboxName, mustExist );
    }

    protected ImapMailbox getMailbox( String mailboxName,
                                      ImapSession session )
    {
        try {
            return session.getHost().getMailbox( session.getUser(), mailboxName, false );
        }
        catch ( MailboxException e ) {
            throw new RuntimeException( "Unexpected error in CommandTemplate.java" );
        }
    }

    public CommandParser getParser()
    {
        return parser;
    }
}