jdbcstatement.java

一个用java写的开源的数据库系统

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 * All rights reserved.
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 * list of conditions and the following disclaimer, including earlier
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package org.hsqldb;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.SQLWarning;

// 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 20020409/20020505 extensive review and update
// of docs and behaviour to comply with previous and latest java.sql specification

/**
 * <!-- 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 -->
 * <span class="ReleaseSpecificDocumentation">
 * <b>HSQLDB-Specific Information:</b><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, it is possible to build the product so that
 * 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, some of these method calls require <code>int</code> values that
 * are defined only in the JDBC 2 or greater version of
 * <a href="http://java.sun.com/j2se/1.4/docs/api/java/sql/ResultSet.html">
 * <CODE>ResultSet</CODE></a> interface.  For this reason, when the
 * product is compiled under JDK 1.1.x, 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>
 *
 * <CODE class="JavaCodeExample">
 * jdbcResultSet.FETCH_FORWARD<br>
 * jdbcResultSet.TYPE_FORWARD_ONLY<br>
 * jdbcResultSet.TYPE_SCROLL_INSENSITIVE<br>
 * jdbcResultSet.CONCUR_READ_ONLY<br>
 * </CODE> <p>
 *
 * However, please note that code written in such a manner will not be
 * compatible for use with other JDBC 2 drivers, since they expect and use
 * <code>ResultSet</code>, rather than <code>jdbcResultSet</code>.  Also
 * note, 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>
 *
 * </span>
 * <!-- end release-specific documentation -->
 *
 * @see jdbcConnection#createStatement
 * @see jdbcResultSet
 */
public class jdbcStatement implements java.sql.Statement {

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

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

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

    /**
     * The result of executing this statement.
     */
    private jdbcResultSet rSet;

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

    /**
     * <!-- start generic documentation -->
     * Executes the given SQL statement, which returns a single
     * <code>ResultSet</code> object. <p>
     * <!-- end generic documentation -->
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * </span>
     * <!-- 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();
        fetchResult(sql);

        return rSet;
    }

    /**
     * <!-- 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 -->
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * </span>
     * <!-- end release-specific 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();
        fetchResult(sql);

        if (rSet == null) {
            return -1;
        }

        return rSet.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 -->
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * </span>
     * <!-- end release-specific documentation -->
     *
     * @exception SQLException if a database access error occurs
     */
    public void close() throws SQLException {

        if (Trace.TRACE) {
            Trace.trace();
        }

        closeOldResult();

        rSet = null;
    }

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

    /**
     * <!-- 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 -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</B> <p>
     *
     * Up to and including 1.7.1, HSQLDB always returns zero, meaning there
     * is no limit. <p>
     *
     * </span>
     * <!-- 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 {

        if (Trace.TRACE) {
            Trace.trace();
        }

        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 -->
     *
     * <!-- start release-specific documentation -->
     * <span class="ReleaseSpecificDocumentation">
     * <b>HSQLDB-Specific Information:</b> <p>
     *
     * Calls to this method are simply ignored; HSQLDB always stores the
     * full number of bytes when dealing with any of the field types
     * mentioned above. These types all have an absolute maximum element upper
     * bound determined by the Java array index limit
     * java.lang.Integer.MAX_VALUE.  For XXXBINARY types, this translates to
     * Integer.MAX_VALUE bytes.  For XXXCHAR types, this translates to
     * 2 * Integer.MAX_VALUE bytes (2 bytes / character)
     *
     * </span>
     * <!-- end release-specific documentation -->
     *
     * @param max the new column size limit in bytes; zero means there is no limit
     * @exception SQLException if a database access error occurs
     *          or the condition max >= 0 is not satisfied
     * @see #getMaxFieldSize
     */
    public void setMaxFieldSize(int max) throws SQLException {