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    * distributed with this work for additional information        *
    * regarding copyright ownership.  The ASF licenses this file   *
    * to you under the Apache License, Version 2.0 (the            *
    * "License"); you may not use this file except in compliance   *
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  package org.apache.james.transport.mailets;
  
  import org.apache.avalon.cornerstone.services.datasources.DataSourceSelector;
  import org.apache.avalon.excalibur.datasource.DataSourceComponent;
  import org.apache.avalon.framework.service.ServiceManager;
  import org.apache.james.Constants;
  import org.apache.james.util.sql.JDBCUtil;
  import org.apache.mailet.base.GenericMailet;
  import org.apache.mailet.Mail;
  import org.apache.mailet.MailAddress;
  import org.apache.mailet.MailetException;
  
  import javax.mail.MessagingException;
  import javax.mail.internet.ParseException;
  
  import java.sql.Connection;
  import java.sql.DatabaseMetaData;
  import java.sql.PreparedStatement;
  import java.sql.ResultSet;
  import java.sql.SQLException;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.Vector;
  
  /**
   * Rewrites recipient addresses based on a database table.  The connection
   * is configured by passing the URL to a conn definition.  You need to set
   * the table name to check (or view) along with the source and target columns
   * to use.  For example,
   * <mailet match="All" class="JDBCAlias">
   *   <mappings>db://maildb/Aliases</mappings>
   *   <source_column>source_email_address</source_column>
   *   <target_column>target_email_address</target_column>
   * </mailet>
   *
   */
  public class JDBCAlias extends GenericMailet {
  
      protected DataSourceComponent datasource;
      protected String query = null;
  
      // The JDBCUtil helper class
      private final JDBCUtil theJDBCUtil =
              new JDBCUtil() {
                  protected void delegatedLog(String logString) {
                      log("JDBCAlias: " + logString);
                  }
              };
  
      /**
       * Initialize the mailet
       */
      public void init() throws MessagingException {
          String mappingsURL = getInitParameter("mappings");
  
          String datasourceName = mappingsURL.substring(5);
          int pos = datasourceName.indexOf("/");
          String tableName = datasourceName.substring(pos + 1);
          datasourceName = datasourceName.substring(0, pos);
  
          Connection conn = null;
          if (getInitParameter("source_column") == null) {
              throw new MailetException("source_column not specified for JDBCAlias");
          }
          if (getInitParameter("target_column") == null) {
              throw new MailetException("target_column not specified for JDBCAlias");
          }
          try {
              ServiceManager componentManager = (ServiceManager)getMailetContext().getAttribute(Constants.AVALON_COMPONENT_MANAGER);
              // Get the DataSourceSelector service
              DataSourceSelector datasources = (DataSourceSelector)componentManager.lookup(DataSourceSelector.ROLE);
              // Get the data-source required.
              datasource = (DataSourceComponent)datasources.select(datasourceName);
  
              conn = datasource.getConnection();
  
              // Check if the required table exists. If not, complain.
              DatabaseMetaData dbMetaData = conn.getMetaData();
             // Need to ask in the case that identifiers are stored, ask the DatabaseMetaInfo.
             // Try UPPER, lower, and MixedCase, to see if the table is there.
             if (!(theJDBCUtil.tableExists(dbMetaData, tableName)))  {
                 StringBuffer exceptionBuffer =
                     new StringBuffer(128)
                             .append("Could not find table '")
                             .append(tableName)
                             .append("' in datasource '")
                             .append(datasourceName)
                             .append("'");
                 throw new MailetException(exceptionBuffer.toString());
             }
 
             //Build the query
             StringBuffer queryBuffer =
                 new StringBuffer(128)
                         .append("SELECT ")
                         .append(getInitParameter("target_column"))
                         .append(" FROM ")
                         .append(tableName)
                         .append(" WHERE ")
                         .append(getInitParameter("source_column"))
                         .append(" = ?");
             query = queryBuffer.toString();
         } catch (MailetException me) {
             throw me;
         } catch (Exception e) {
             throw new MessagingException("Error initializing JDBCAlias", e);
         } finally {
             theJDBCUtil.closeJDBCConnection(conn);
         }
     }
 
     public void service(Mail mail) throws MessagingException {
         //Then loop through each address in the recipient list and try to map it according to the alias table
 
         Connection conn = null;
         PreparedStatement mappingStmt = null;
         ResultSet mappingRS = null;
 
         Collection recipients = mail.getRecipients();
         Collection recipientsToRemove = new Vector();
         Collection recipientsToAdd = new Vector();
         try {
             conn = datasource.getConnection();
             mappingStmt = conn.prepareStatement(query);
 
 
             for (Iterator i = recipients.iterator(); i.hasNext(); ) {
                 try {
                     MailAddress source = (MailAddress)i.next();
                     mappingStmt.setString(1, source.toString());
                     mappingRS = mappingStmt.executeQuery();
                     if (!mappingRS.next()) {
                         //This address was not found
                         continue;
                     }
                     try {
                         String targetString = mappingRS.getString(1);
                         MailAddress target = new MailAddress(targetString);
 
                         //Mark this source address as an address to remove from the recipient list
                         recipientsToRemove.add(source);
                         recipientsToAdd.add(target);
                     } catch (ParseException pe) {
                         //Don't alias this address... there's an invalid address mapping here
                         StringBuffer exceptionBuffer =
                             new StringBuffer(128)
                                     .append("There is an invalid alias from ")
                                     .append(source)
                                     .append(" to ")
                                     .append(mappingRS.getString(1));
                         log(exceptionBuffer.toString());
                         continue;
                     }
                 } finally {
                     ResultSet localRS = mappingRS;
                     // Clear reference to result set
                     mappingRS = null;
                     theJDBCUtil.closeJDBCResultSet(localRS);
                 }
             }
         } catch (SQLException sqle) {
             throw new MessagingException("Error accessing database", sqle);
         } finally {
             theJDBCUtil.closeJDBCStatement(mappingStmt);
             theJDBCUtil.closeJDBCConnection(conn);
         }
 
         recipients.removeAll(recipientsToRemove);
         recipients.addAll(recipientsToAdd);
     }
 
     /**
      * Return a string describing this mailet.
      *
      * @return a string describing this mailet
      */
     public String getMailetInfo() {
         return "JDBC aliasing mailet";
     }
 
 }