transactioncontext.java

《Developing Applications with Java and UML》一书的源代码。

package com.jacksonreed;

import java.io.*;
import java.sql.*;
import java.text.*;
import java.util.*;
import javax.sql.*;

/**
 * This class is a transaction context object which maintains the
 * state of the connection including the ability to close it as well
 * as support of transaction management
 *
 * @author Paul R. Reed, Jr., Jackson-Reed, Inc. <[e-mail]>
 */
public class TransactionContext implements Serializable {
    private Connection dbConnection = null;
    private DataSource datasource   = null;
    private CustomerValue custVal   = null;
    private boolean unitOfWork = false;

    /**
     * Class constructor with no arguments
    */
    public TransactionContext() {
      try {
        log("TransactionContext: setup JDBC Driver");
        // This is where we load the driver for sun and used
        // with MS Access
        //Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
		// This is where we load the driver for hypersonicSQL
        Class.forName("org.hsql.jdbcDriver");
        // This is where we load the driver for Cloudscape
        // JDBC Driver
        //Class.forName("COM.cloudscape.core.JDBCDriver");
        // This is where we load the driver for Cloudscape
        // RmiJdbc Driver
        //Class.forName("COM.cloudscape.core.RmiJdbcDriver");
        log("TransactionContext: setup JDBC loaded ok");
      }
      catch (ClassNotFoundException e) {
        System.out.println("class not found");
        throw new TranSysException(e.getMessage());
      }
    }

    public Connection getDBConnection() {
          log("TransactionContext: in get connection");
          if (dbConnection == null)
              throw new TranSysException ("no database connection established yet");
          return dbConnection;
    }

    public void beginTran(boolean supportTran) throws TranBeginException, TranSysException {

      unitOfWork = supportTran;
      getConnection();
      try {
          if (supportTran) {
          log("TransactionContext: auto off");
              dbConnection.setAutoCommit(false);
          }
          else {
          log("TransactionContext: auto on");
              dbConnection.setAutoCommit(true);
          }

      }
      catch (SQLException e) {
          throw new TranBeginException(e.getMessage());
          }

    }

    public void commitTran()
      throws TranCommitException, TranSysException, TranRollBackException {

      log("TransactionContext: in commit");
      if (unitOfWork) {
        try {
            dbConnection.commit();
            log("TransactionContext: afterCommit");
             closeConnection();

            }
        catch (SQLException e) {
            rollBackTran();
            throw new TranCommitException("Cant commit transaction");
            }
      }

      closeConnection();

    }

     public boolean rollBackTran() throws TranRollBackException, TranSysException {
      boolean returnValue = false;
      try {
          dbConnection.rollback();
          log("TransactionContext: afterRollback");
          closeConnection();
          returnValue = true;
      }
      catch (SQLException e) {
          throw new TranRollBackException("Cant rollback transaction");
      }
      return returnValue;
    }

    public void closeResultSet(ResultSet result) throws TranSysException {
        try {
            if (result != null) {
                result.close();
            }
         }
         catch (SQLException se) {
            throw new TranSysException("SQL Exception while closing " +
                                        "Result Set : \n" + se);
        }
    }

    public void closeStatement(Statement stmt) throws TranSysException {
        try {
            if (stmt != null) {
                stmt.close();
            }
        } catch (SQLException se) {
            throw new TranSysException("SQL Exception while closing " +
                                        "Statement : \n" + se);
        }
    }

    public void closeConnection() throws TranSysException {
        try {
            if (dbConnection != null && !dbConnection.isClosed()) {
                dbConnection.close();
                log("TransactionContext: closing connection");
            }
        } catch (SQLException se) {
            throw new TranSysException("SQLExcpetion while closing" +
                                    " DB Connection : \n" + se);
        }
    }

    public void getConnection() throws TranSysException {
        try {
        log("TransactionContext: before get connection");
		// connection string for the HypersonicSQL Database implementation
        dbConnection = DriverManager.getConnection("jdbc:HypersonicSQL:hsql://localhost", "sa", "");
        // connection string for the MS Access Database implementation
        //dbConnection = DriverManager.getConnection("jdbc:odbc:remulak-bea", "", "");
        // connection string for the Cloudscape JDBC implementation
        //dbConnection = DriverManager.getConnection("jdbc:cloudscape:data", "", "");
        // connection string for the Cloudscape RmiJdbc implementation
        //dbConnection = DriverManager.getConnection("jdbc:cloudscape:rmi://localhost:1099/c:/tomcat/jakarta-tomcat-3.2.1/webapps/RemulakWebApp/data","", "");
        log("TransactionContext: after get connection");
        } catch (SQLException se) {
        log("TransactionContext: SQL Exception");
            se.printStackTrace();
            throw new TranSysException("SQLExcpetion while getting" +
                                        " DB Connection : \n" + se);
        }
    }

    private void log(String s) {
        System.out.println(s);
    }
}