jdbcstatement.java

hsqldb是100％java实现的数据库,是一个开放源代码的JAVA数据库 l 具有标准的SQL语法和JAVA接口 l HSQLDB可以自由使用和分发 l 非常简洁和快速的

/* Copyright (c) 2001-2005, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
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 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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package org.hsqldb.jdbc;

//#ifdef JAVA2
import java.sql.BatchUpdateException;

//#endif JAVA2
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.Statement;

import org.hsqldb.HsqlException;
import org.hsqldb.Result;
import org.hsqldb.ResultConstants;
import org.hsqldb.Trace;
import org.hsqldb.Types;

// fredt@users 20020320 - patch 1.7.0 - JDBC 2 support and error trapping
// JDBC 2 methods can now be called from jdk 1.1.x - see javadoc comments
// SCROLL_INSENSITIVE and FORWARD_ONLY types for ResultSet are now supported
// boucherb@users 20020509 - added "throws SQLException" to all methods where
// it was missing here but specified in the java.sql.Statement interface,
// updated generic documentation to JDK 1.4, and added JDBC3 methods and docs
// boucherb@users and fredt@users - 20020505 extensive review and update
// of docs and behaviour to comply with java.sql specification
// fredt@users 20030620 - patch 1.7.2 - rewritten and simplified
// boucherb@users 200404xx - javadoc updates toward 1.7.2 final

/**
 * <!-- start generic documentation -->
 * The object used for executing a static SQL statement
 * and returning the results it produces.
 * <P>
 * By default, only one <code>ResultSet</code> object per <code>Statement</code>
 * object can be open at the same time. Therefore, if the reading of one
 * <code>ResultSet</code> object is interleaved
 * with the reading of another, each must have been generated by
 * different <code>Statement</code> objects. All execution methods in the
 * <code>Statement</code> interface implicitly close a statment's current
 * <code>ResultSet</code> object if an open one exists.<p>
 * <!-- end generic documentation-->
 *
 * <!-- start release-specific documentation -->
 * <div class="ReleaseSpecificDocumentation">
 * <h3>HSQLDB-Specific Information:</h3><p>
 *
 * <b>JRE 1.1.x Notes:</b> <p>
 *
 * In general, JDBC 2 support requires Java 1.2 and above, and JDBC3 requires
 * Java 1.4 and above. In HSQLDB, support for methods introduced in different
 * versions of JDBC depends on the JDK version used for compiling and building
 * HSQLDB.<p>
 *
 * Since 1.7.0, all JDBC 2 methods can be called while executing under the
 * version 1.1.x
 * <em>Java Runtime Environment</em><sup><font size="-2">TM</font></sup>.
 * However, in addition to this technique requiring explicit casts to the
 * org.hsqldb.jdbcXXX classes, some of these method calls require
 * <code>int</code> values that are defined only in the JDBC 2 or greater
 * version of the {@link java.sql.ResultSet ResultSet} interface.  For this
 * reason these values are defined in {@link jdbcResultSet jdbcResultSet}.<p>
 *
 * In a JRE 1.1.x environment, calling JDBC 2 methods that take or return the
 * JDBC2-only <code>ResultSet</code> values can be achieved by referring
 * to them in parameter specifications and return value comparisons,
 * respectively, as follows: <p>
 *
 * <pre class="JavaCodeExample">
 * jdbcResultSet.FETCH_FORWARD
 * jdbcResultSet.TYPE_FORWARD_ONLY
 * jdbcResultSet.TYPE_SCROLL_INSENSITIVE
 * jdbcResultSet.CONCUR_READ_ONLY
 * //etc.
 * </pre> <p>
 *
 * However, please note that code written to use HSQLDB JDBC 2 features under
 * JDK 1.1.x will not be compatible for use with other JDBC 2 drivers. Please
 * also note that this feature is offered solely as a convenience to developers
 * who must work under JDK 1.1.x due to operating constraints, yet wish to
 * use some of the more advanced features available under the JDBC 2
 * specification. <p>
 *
 * (fredt@users)<br>
 * (boucherb@users)<p>
 *
 * </div>
 * <!-- end release-specific documentation -->
 *
 * @author boucherb@users
 * @author fredt@user
 * @version 1.8.0
 * @see jdbcConnection#createStatement
 * @see jdbcResultSet
 */
public class jdbcStatement implements Statement {

    /**
     * Whether this Statement has been explicitly closed.  A jdbcConnection
     * object now explicitly closes all of its open jdbcXXXStatement objects
     * when it is closed.
     */
    volatile boolean isClosed;

    /** Is escape processing enabled? */
    private boolean isEscapeProcessing = true;

    /** The connection used to execute this statement. */
    protected jdbcConnection connection;

    /** The maximum number of rows to generate when executing this statement. */
    protected int maxRows;

    /** The result of executing this statement. */
    protected Result resultIn;

    /** The result set type obtained by executing this statement. */
    protected int rsType = jdbcResultSet.TYPE_FORWARD_ONLY;

    /** Used by this statement to communicate non-batched requests. */
    protected Result resultOut = new Result(ResultConstants.SQLEXECDIRECT);

    /** Use by this statement to communicate batched execution requests */
    protected Result batchResultOut = null;

    // boucherb@users
    // NOTE:
    // This method is synchronized since resultIn is an instance attribute
    // and thus it is theoretically possible that a race condition occurs
    // in which a different thread executes fetchResult(sql), replacing
    // resultIn before it gets assigned propery to the new result set.
    // fredt - this class is not supposed to be called multi-threaded -
    // For example, if two threads call execute() then both call getResult() in
    // the wrong order, the ResultSet object for one call could actually belong
    // to the other call.

    /**
     * <!-- start generic documentation -->
     * Executes the given SQL statement, which returns a single
     * <code>ResultSet</code> object. <p>
     * <!-- end generic documentation -->
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * This method should not be used for statements other than SELECT queries.<p>
     *
     * Including 1.7.2, HSQLDB does not throw an exception when the statement
     * is a DDL statement or an UPDATE or DELETE statement. This will certainly
     * change in future version.
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @param sql an SQL statement to be sent to the database, typically a
     *      static SQL <code>SELECT</code> statement
     * @return a <code>ResultSet</code> object that contains the data produced
     *       by the given query; never <code>null</code>
     * @exception SQLException if a database access error occurs or the given
     *          SQL statement produces anything other than a single
     *          <code>ResultSet</code> object
     */
    public ResultSet executeQuery(String sql) throws SQLException {

        checkClosed();
        connection.clearWarningsNoCheck();
        fetchResult(sql);

        return new jdbcResultSet(this, resultIn, connection.connProperties,
                                 connection.isNetConn);
    }

    /**
     * <!-- start generic documentation -->
     * Executes the given SQL statement, which may be an <code>INSERT</code>,
     * <code>UPDATE</code>, or <code>DELETE</code> statement or an
     * SQL statement that returns nothing, such as an SQL DDL statement. <p>
     * <!-- end generic documentation -->
     *
     * @param sql an SQL <code>INSERT</code>, <code>UPDATE</code> or
     * <code>DELETE</code> statement or an SQL statement that returns nothing
     * @return either the row count for <code>INSERT</code>, <code>UPDATE</code>
     * or <code>DELETE</code> statements, or <code>0</code> for SQL statements
     * that return nothing
     * @exception SQLException if a database access error occurs or the given
     *          SQL statement produces a <code>ResultSet</code> object
     */
    public int executeUpdate(String sql) throws SQLException {

        checkClosed();
        connection.clearWarningsNoCheck();
        fetchResult(sql);

        if (resultIn == null || resultIn.isData()) {

            /**
             * @todo: - fredt@users - check for type of statement _must_ be done
             * in the engine and error returned _without_ executing
             */
            throw new SQLException(
                Trace.getMessage(Trace.jdbcStatement_executeUpdate));
        } else if (resultIn.isError()) {
            Util.throwError(resultIn);
        }

        return resultIn.getUpdateCount();
    }

    /**
     * <!-- start generic documentation -->
     * Releases this <code>Statement</code> object's database
     * and JDBC resources immediately instead of waiting for
     * this to happen when it is automatically closed.
     * It is generally good practice to release resources as soon as
     * you are finished with them to avoid tying up database
     * resources.
     * <P>
     * Calling the method <code>close</code> on a <code>Statement</code>
     * object that is already closed has no effect.
     * <P>
     * <B>Note:</B> A <code>Statement</code> object is automatically closed
     * when it is garbage collected. When a <code>Statement</code> object is
     * closed, its current <code>ResultSet</code> object, if one exists, is
     * also closed. <p>
     * <!-- end generic documentation -->
     *
     * @exception SQLException if a database access error occurs
     */
    public synchronized void close() throws SQLException {

        if (isClosed) {
            return;
        }

        batchResultOut = null;
        connection     = null;
        resultIn       = null;
        resultOut      = null;
        isClosed       = true;
    }

    //----------------------------------------------------------------------

    /**
     * <!-- start generic documentation -->
     * Retrieves the maximum number of bytes that can be
     * returned for character and binary column values in a <code>ResultSet</code>
     * object produced by this <code>Statement</code> object.
     * This limit applies only to <code>BINARY</code>,
     * <code>VARBINARY</code>, <code>LONGVARBINARY</code>, <code>CHAR</code>,
     * <code>VARCHAR</code>, and <code>LONGVARCHAR</code>
     * columns.  If the limit is exceeded, the excess data is silently
     * discarded. <p>
     * <!-- end generic documentation -->
     *
     * <!-- start release-specific documentation -->
     * <div class="ReleaseSpecificDocumentation">
     * <h3>HSQLDB-Specific Information:</h3> <p>
     *
     * Including 1.7.2, HSQLDB always returns zero, meaning there
     * is no limit.
     * </div>
     * <!-- end release-specific documentation -->
     *
     * @return the current column size limit for columns storing character and
     *       binary values; zero means there is no limit
     * @exception SQLException if a database access error occurs
     * @see #setMaxFieldSize
     */
    public int getMaxFieldSize() throws SQLException {

        checkClosed();

        return 0;
    }

    /**
     * <!-- start generic documentation -->
     * Sets the limit for the maximum number of bytes in a <code>ResultSet</code>
     * column storing character or binary values to
     * the given number of bytes.  This limit applies
     * only to <code>BINARY</code>, <code>VARBINARY</code>,
     * <code>LONGVARBINARY</code>, <code>CHAR</code>, <code>VARCHAR</code>, and
     * <code>LONGVARCHAR</code> fields.  If the limit is exceeded, the excess data
     * is silently discarded. For maximum portability, use values
     * greater than 256. <p>
     * <!-- emd generic documentation -->