voteimpl.java

java web services how to program

// VoteImpl.java
// VoteImpl implements the Vote remote interface to provide
// a VoteService remote object.
package com.deitel.jws1.jaxrpc.service.vote;

// Java core packages
import java.rmi.*;
import java.sql.*;

// Java XML packages
import javax.xml.rpc.server.*;
import javax.xml.rpc.JAXRPCException;
import javax.servlet.ServletContext;

public class VoteImpl implements ServiceLifecycle, Vote {

   private Connection connection;
   private PreparedStatement sqlUpdate, sqlSelect;
   
   // set up database connection and prepare SQL statement
   public void init( Object context )
      throws JAXRPCException
   {
      // attempt database connection and 
      // create PreparedStatements
      try {

         // cast context to ServletEndpointContext
         ServletEndpointContext endpointContext = 
            ( ServletEndpointContext ) context;

         // get ServletContext
         ServletContext servletContext = 
            endpointContext.getServletContext();

         // get database driver from servlet context
         String dbDriver = 
            servletContext.getInitParameter( "dbDriver" );
   
         // get database name from servlet context
         String voteDB = 
            servletContext.getInitParameter( "voteDB" );

         // load database driver
         Class.forName( dbDriver );

         // connect to database
         connection = DriverManager.getConnection( voteDB );

         // PreparedStatement to increment vote total for a
         // specific language
         sqlUpdate = 
            connection.prepareStatement(
               "UPDATE surveyresults SET vote = vote + 1 " +
               "WHERE name = ?"
            );

         // PreparedStatement to obtain surveyresults table's data
         sqlSelect =
            connection.prepareStatement( "SELECT name, vote " +
               "FROM surveyresults ORDER BY vote DESC"
            );

      } // end try

      // for any exception, throw an JAXRPCException to
      // indicate that the servlet is not currently available
      catch ( Exception exception ) {
         exception.printStackTrace();

         throw new JAXRPCException( exception.getMessage() );
      }

   } // end method init

   // implementation for interface Vote method addVote
   public String addVote( String name ) throws RemoteException
   {
      // get votes count from database and update it
      try {

         // set parameter in sqlUpdate
         sqlUpdate.setString( 1, name );

         // execute sqlUpdate statement
         sqlUpdate.executeUpdate();

         // execute sqlSelect statement
         ResultSet results = sqlSelect.executeQuery();
         StringBuffer voteInfo = new StringBuffer();

         // iterate ResultSet and prepare return string
         while ( results.next() ) {

            // append results to String voteInfo
            voteInfo.append( " " + results.getString( 1 ) );
            voteInfo.append( " " + results.getInt( 2 ) );
         }

         return voteInfo.toString();

      } // end try

      // handle exceptions during database connection
      catch ( Exception exception ) {
         exception.printStackTrace();

         return exception.getMessage();
      }

   } // end method addVote

   // close SQL statements and database when servlet terminates
   public void destroy()
   {
      // attempt to close statements and database connection
      try {
         sqlUpdate.close();
         sqlSelect.close();
         connection.close();
      }

      // handle database exception
      catch ( Exception exception ) {
         exception.printStackTrace();
      }

   } // end method destroy

} // end class VoteImpl


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 * (C) Copyright 2001 by Deitel & Associates, Inc. and Prentice Hall.     *
 * All Rights Reserved.                                                   *
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