genericdatasource.java

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/*
 * $Header: /sfroot/cvs/esimple/src/core/org/apache/struts/legacy/GenericDataSource.java,v 1.1.1.1 2004/09/08 06:38:35 lava Exp $
 * $Revision: 1.1.1.1 $
 * $Date: 2004/09/08 06:38:35 $
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
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 * reserved.
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 * modification, are permitted provided that the following conditions
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 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
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package org.apache.struts.legacy;


import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.LinkedList;
import java.util.Properties;
import javax.sql.DataSource;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;


/**
 * <p>Generic data source implementation of the <code>DataSource</code>
 * interface.  <b>WARNING</b> - This implementation does not know how to
 * provide connections with different username/password combinations.
 * Calling this version of the implementation using the
 * getConnection(username,password) signature will throw an exception.</p>
 *
 * <p>The following properties are supported by the standard
 * <code>GenericDataSource</code> implementation:</p>
 * <table>
 * <tr>
 *   <th width="15%">Property</th>
 *   <th width="85%">Description</th>
 * </tr>
 * <tr>
 *   <td align="center">autoCommit</td>
 *   <td>Set to <code>true</code> if you want the connections returned to you
 *       by calling <code>getConnection()</code> to be configured in
 *       "auto-commit after every statement" mode.  The default value is
 *       <code>true</code>, to conform to JDBC standard conventions.</td>
 * </tr>
 * <tr>
 *   <td align="center">description</td>
 *   <td>A short textual description of this data source.  This property is
 *       required by the <code>javax.sql.DataSource</code> interface, but is
 *       not used within this implementation.</td>
 * </tr>
 * <tr>
 *   <td align="center">driverClass</td>
 *   <td>The fully qualified class name of the JDBC driver to be utilized for
 *       the connections created by this data source.  Consult the
 *       documentation for your JDBC driver to identify the value to be
 *       configured for this property.</td>
 * </tr>
 * <tr>
 *   <td align="center">maxCount</td>
 *   <td>The maximum number of JDBC connections that will be created by this
 *       data source.  This value must be greater than or equal to the value
 *       specified for the <code>minCount</count> property.</td>
 * </tr>
 * <tr>
 *   <td align="center">minCount</td>
 *   <td>The minimum number of JDBC connections to establish when this data
 *       source is first opened.  This value must be less than or equal to the
 *       value specified for the <code>maxCount</code> property.</td>
 * </tr>
 * <tr>
 *   <td align="center">password</td>
 *   <td>The database password used to establish the connections created by
 *       this connection pool, in conjunction with the username specified in
 *       the <code>user</code> property.</td>
 * </tr>
 * <tr>
 *   <td align="center">pingCommand</td>
 *   <td>A non-query SQL command that, if specified, will be executed before
 *       a connection is returned by a call to <code>getConnection()</code>.
 *       If any SQLException is thrown by the execution of this statement,
 *       it is assumed that this connection is stale and it will be discarded.
 *       Because this happens on every connection allocation, you should ensure
 *       that the statement executes very quickly.</td>
 * </tr>
 * <tr>
 *   <td align="center">pingQuery</td>
 *   <td>A query SQL command (i.e. a SELECT) that, if specified, will be
 *       executed before a connection is returned by a call to
 *       <code>getConnection()</code>.  If any SQLException is thrown by the
 *       execution of this query (or by the subsequent processing of the
 *       entire returned <code>ResultSet</code>), it is assumed that this
 *       connection is stale and it will be discarded.  Because this happens
 *       on every connection allocation, you should ensure that the
 *       statement executes very quickly.</td>
 * </tr>
 * <tr>
 *   <td align="center">readOnly</td>
 *   <td>Set to <code>true</code> if you want the connections returned to you
 *       by calling <code>getConnection()</code> to be configured for read only
 *       operations.  This can result in more efficient database access,
 *       because the database will know it does not need to retain undo logs
 *       for rolling back the transaction.  The default value is
 *       <code>false</code>.</td>
 * </tr>
 * <tr>
 *   <td align="center">url</td>
 *   <td>The connection URL to be passed to our JDBC driver when establishing
 *       a new connection.  The value specified typically starts with
 *       <code>jdbc:</code>, and includes a reference to the host (and,
 *       optionally, the port number) at which the database server is listening
 *       for connections, plus the name of the database to be opened.  Consult
 *       the documentation for your JDBC driver to identify the value to be
 *       configured for this property.</td>
 * </tr>
 * <tr>
 *   <td align="center">user</td>
 *   <td>The database username used to establish the connections created by
 *       this connection pool, in conjunction with the password specified in
 *       the <code>password</code> property.</td>
 * </tr>
 * </table>
 *
 * <p>In addition, you can add to the set of <code>Properties</code> passed to
 * the JDBC driver by calling <code>addProperty()</code>.</p>
 * <p>
 * This class was originally maintained in the core Struts util package [revision 1.11].
 * </p>
 *
 * @author Craig R. McClanahan
 * @author Ted Husted
 * @version $Revision: 1.1.1.1 $ $Date: 2004/09/08 06:38:35 $
 */

public class GenericDataSource implements DataSource {

    // ----------------------------------------------------------- Util Methods

    /**
     * Return the <code>Class</code> object for the specified fully qualified
     * class name, from this web application's class loader.
     * <p>
     * See util.RequestUtils.applicationClass for maintained original.
     *
     * @param className Fully qualified class name to be loaded
     * @return Class object
     * @exception ClassNotFoundException if the class cannot be found
     */
    private static Class applicationClass(String className) throws ClassNotFoundException {

        // Look up the class loader to be used
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        if (classLoader == null) {
            classLoader = GenericDataSource.class.getClassLoader();
        }

        // Attempt to load the specified class
        return (classLoader.loadClass(className));

    }

    /**
     * Return a new instance of the specified fully qualified class name,
     * after loading the class from this web application's class loader.
     * The specified class <strong>MUST</strong> have a public zero-arguments
     * constructor.
     * <p>
     * See util.RequestUtils.applicationClass for maintained original.
     *
     * @param className Fully qualified class name to use
     * @return new instance of class
     * @exception ClassNotFoundException if the class cannot be found
     * @exception IllegalAccessException if the class or its constructor
     *  is not accessible
     * @exception InstantiationException if this class represents an
     *  abstract class, an interface, an array class, a primitive type,
     *  or void
     * @exception InstantiationException if this class has no
     *  zero-arguments constructor
     */
    private static Object applicationInstance(String className)
        throws ClassNotFoundException, IllegalAccessException, InstantiationException {

        return (applicationClass(className).newInstance());

    }


    // ----------------------------------------------------- Instance Constants


    private static final String SQLEXCEPTION_GETCONNECTION =
     "getConnection(String username, String password)  Method not supported. Use getConnection() instead.";



    // ----------------------------------------------------- Instance Variables


    /**
     * Has this data source been closed?
     */
    protected boolean closed = false;


    /**
     * The list of Connections (wrapped in our associated wrapper class) that
     * have been created but are not currently in use.
     */
    protected LinkedList connections = new LinkedList();


    /**
     * The JDBC driver that we use as a connection factory.
     */
    protected Driver driver = null;


    /**
     * Commons Logging instance.
     */
    protected Log log = LogFactory.getLog(this.getClass());


    /**
     * The login timeout for this data source.
     */
    protected int loginTimeout = 0;


    /**
     * The log writer for this data source.
     */
    protected PrintWriter logWriter = null;


    // ------------------------------------------------------------- Properties


    /**
     * Add a generic property to the list of connection properties to be used.
     *
     * @param name Name of the generic property
     * @param value Corresponding generic property value
     */
    public void addProperty(String name, String value) {
        properties.put(name, value);
    }


    /**
     * The number of connections that have been created by this data source.
     */
    protected int activeCount = 0;

    public int getActiveCount() {
        return (this.activeCount);
    }


    /**
     * The default auto-commit state for newly created connections.
     */
    protected boolean autoCommit = true;

    public boolean getAutoCommit() {
        return (this.autoCommit);
    }

    public void setAutoCommit(boolean autoCommit) {
        this.autoCommit = autoCommit;
    }


    /**
     * The debugging detail level for this data source.
     */
    protected int debug = 0;

    public int getDebug() {
        return (this.debug);
    }

    public void setDebug(int debug) {
        this.debug = debug;
    }


    /**
     * The description of this data source.
     */
    protected String description = null;

    public String getDescription() {
        return (this.description);
    }

    public void setDescription(String description) {
        this.description = description;
    }


    /**
     * The Java class name of the JDBC driver to use.
     */
    protected String driverClass = null;

    public String getDriverClass() {
        return (this.driverClass);
    }

    public void setDriverClass(String driverClass) {
        this.driverClass = driverClass;
    }


    /**
     * The maximum number of connections to be created.
     */
    protected int maxCount = 2;

    public int getMaxCount() {
        return (this.maxCount);
    }

    public void setMaxCount(int maxCount) {
        this.maxCount = maxCount;
    }


    /**
     * The minimum number of connections to be created.
     */
    protected int minCount = 1;

    public int getMinCount() {
        return (this.minCount);
    }

    public void setMinCount(int minCount) {
        this.minCount = minCount;
    }


    /**
     * The database password for use in establishing a connection.
     */
    protected String password = null;

    public String getPassword() {
        return (this.password);
    }

    public void setPassword(String password) {
        this.password = password;
        addProperty("password", this.password);
    }



    /**
     * The non-query SQL command used to ping an allocated connection.
     */
    protected String pingCommand = null;

    public String getPingCommand() {
        return (this.pingCommand);
    }

    public void setPingCommand(String pingCommand) {
        this.pingCommand = pingCommand;
    }


    /**
     * The query SQL command used to ping an allocated connection.
     */
    protected String pingQuery = null;

    public String getPingQuery() {
        return (this.pingQuery);
    }

    public void setPingQuery(String pingQuery) {
        this.pingQuery = pingQuery;
    }


    /**
     * The connection properties for use in establishing connections.
     */
    protected Properties properties = new Properties();


    /**
     * The default read-only state for newly created connections.
     */
    protected boolean readOnly = false;

    public boolean getReadOnly() {
        return (this.readOnly);
    }

    public void setReadOnly(boolean readOnly) {
        this.readOnly = readOnly;
    }


    /**
     * The JDBC URL for the database connection to be opened.
     */
    protected String url = null;

    public String getUrl() {
        return (this.url);
    }

    public void setUrl(String url) {
        this.url = url;
    }