resultset.java

java数据库源代码 请看看啊 提点宝贵的意见

/*
 * @(#)ResultSet.java	1.44 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.sql;

import java.math.BigDecimal;
import java.util.Calendar;

/**
 * A table of data representing a database result set, which
 * is usually generated by executing a statement that queries the database. 
 * 
 * <P>A <code>ResultSet</code> object  maintains a cursor pointing
 * to its current row of data.  Initially the cursor is positioned 
 * before the first row. The <code>next</code> method moves the 
 * cursor to the next row, and because it returns <code>false</code>
 * when there are no more rows in the <code>ResultSet</code> object,
 * it can be used in a <code>while</code> loop to iterate through 
 * the result set.
 * <P>
 * A default <code>ResultSet</code> object is not updatable and
 * has a cursor that moves forward only.  Thus, you can
 * iterate through it only once and only from the first row to the
 * last row. It is possible to
 * produce <code>ResultSet</code> objects that are scrollable and/or
 * updatable.  The following code fragment, in which <code>con</code>
 * is a valid <code>Connection</code> object, illustrates how to make 
 * a result set that is scrollable and insensitive to updates by others, and 
 * that is updatable. See <code>ResultSet</code> fields for other
 * options.
 * <PRE>
 *
 *       Statement stmt = con.createStatement(
 *                                      ResultSet.TYPE_SCROLL_INSENSITIVE,
 *                                      ResultSet.CONCUR_UPDATABLE);
 *       ResultSet rs = stmt.executeQuery("SELECT a, b FROM TABLE2");
 *       // rs will be scrollable, will not show changes made by others,
 *       // and will be updatable
 *
 * </PRE>
 * The <code>ResultSet</code> interface provides 
 * <i>getter</i> methods (<code>getBoolean</code>, <code>getLong</code>, and so on)
 * for retrieving column values from the current row.
 * Values can be retrieved using either the index number of the
 * column or the name of the column.  In general, using the 
 * column index will be more efficient.  Columns are numbered from 1.
 * For maximum portability, result set columns within each row should be
 * read in left-to-right order, and each column should be read only once.
 *
 * <P>For the getter methods, a JDBC driver attempts
 * to convert the underlying data to the Java type specified in the
 * getter method and returns a suitable Java value.  The JDBC specification 
 * has a table showing the allowable mappings from SQL types to Java types
 * that can be used by the <code>ResultSet</code> getter methods.
 * <P>
 * <P>Column names used as input to getter methods are case
 * insensitive.  When a getter method is called  with
 * a column name and several columns have the same name, 
 * the value of the first matching column will be returned. 
 * The column name option is
 * designed to be used when column names are used in the SQL
 * query that generated the result set.
 * For columns that are NOT explicitly named in the query, it
 * is best to use column numbers. If column names are used, there is
 * no way for the programmer to guarantee that they actually refer to
 * the intended columns.
 * <P>
 * A set of updater methods were added to this interface
 * in the JDBC 2.0 API (Java<sup><font size=-2>TM</font></sup> 2 SDK,
 * Standard Edition, version 1.2). The comments regarding parameters
 * to the getter methods also apply to parameters to the
 * updater methods.
 *<P>
 * The updater methods may be used in two ways:
 * <ol>
 * <LI>to update a column value in the current row.  In a scrollable
 *     <code>ResultSet</code> object, the cursor can be moved backwards
 *     and forwards, to an absolute position, or to a position
 *     relative to the current row.
 *     The following code fragment updates the <code>NAME</code> column
 *     in the fifth row of the <code>ResultSet</code> object
 *     <code>rs</code> and then uses the method <code>updateRow</code>
 *     to update the data source table from which <code>rs</code> was derived.
 * <PRE>
 *
 *       rs.absolute(5); // moves the cursor to the fifth row of rs
 *       rs.updateString("NAME", "AINSWORTH"); // updates the 
 *          // <code>NAME</code> column of row 5 to be <code>AINSWORTH</code>
 *       rs.updateRow(); // updates the row in the data source
 *
 * </PRE>
 * <LI>to insert column values into the insert row.  An updatable
 *     <code>ResultSet</code> object has a special row associated with
 *     it that serves as a staging area for building a row to be inserted.
 *     The following code fragment moves the cursor to the insert row, builds
 *     a three-column row, and inserts it into <code>rs</code> and into
 *     the data source table using the method <code>insertRow</code>.
 * <PRE>
 *
 *       rs.moveToInsertRow(); // moves cursor to the insert row
 *       rs.updateString(1, "AINSWORTH"); // updates the 
 *          // first column of the insert row to be <code>AINSWORTH</code>
 *       rs.updateInt(2,35); // updates the second column to be <code>35</code>
 *       rs.updateBoolean(3, true); // updates the third column to <code>true</code>
 *       rs.insertRow();
 *       rs.moveToCurrentRow();
 *
 * </PRE>
 * </ol>
 * <P>A <code>ResultSet</code> object is automatically closed when the
 * <code>Statement</code> object that
 * generated it is closed, re-executed, or used
 * to retrieve the next result from a sequence of multiple results.
 * 
 * <P>The number, types and properties of a <code>ResultSet</code>
 * object's columns are provided by the <code>ResulSetMetaData</code>
 * object returned by the <code>ResultSet.getMetaData</code> method.
 *
 * @see Statement#executeQuery 
 * @see Statement#getResultSet 
 * @see ResultSetMetaData 
 */

public interface ResultSet {

    /**
     * Moves the cursor down one row from its current position.
     * A <code>ResultSet</code> cursor is initially positioned
     * before the first row; the first call to the method
     * <code>next</code> makes the first row the current row; the
     * second call makes the second row the current row, and so on. 
     *
     * <P>If an input stream is open for the current row, a call
     * to the method <code>next</code> will
     * implicitly close it. A <code>ResultSet</code> object's
     * warning chain is cleared when a new row is read.
     *
     * @return <code>true</code> if the new current row is valid; 
     * <code>false</code> if there are no more rows 
     * @exception SQLException if a database access error occurs
     */
    boolean next() throws SQLException;


    /**
     * Releases this <code>ResultSet</code> object's database and
     * JDBC resources immediately instead of waiting for
     * this to happen when it is automatically closed.
     *
     * <P><B>Note:</B> A <code>ResultSet</code> object
     * is automatically closed by the
     * <code>Statement</code> object that generated it when
     * that <code>Statement</code> object is closed,
     * re-executed, or is used to retrieve the next result from a
     * sequence of multiple results. A <code>ResultSet</code> object
     * is also automatically closed when it is garbage collected.  
     *
     * @exception SQLException if a database access error occurs
     */
    void close() throws SQLException;

    /**
     * Reports whether
     * the last column read had a value of SQL <code>NULL</code>.
     * Note that you must first call one of the getter methods
     * on a column to try to read its value and then call
     * the method <code>wasNull</code> to see if the value read was
     * SQL <code>NULL</code>.
     *
     * @return <code>true</code> if the last column value read was SQL
     *         <code>NULL</code> and <code>false</code> otherwise
     * @exception SQLException if a database access error occurs
     */
    boolean wasNull() throws SQLException;
    
    //======================================================================
    // Methods for accessing results by column index
    //======================================================================

    /**
     * Retrieves the value of the designated column in the current row
     * of this <code>ResultSet</code> object as
     * a <code>String</code> in the Java programming language.
     *
     * @param columnIndex the first column is 1, the second is 2, ...
     * @return the column value; if the value is SQL <code>NULL</code>, the
     * value returned is <code>null</code>
     * @exception SQLException if a database access error occurs
     */
    String getString(int columnIndex) throws SQLException;

    /**
     * Retrieves the value of the designated column in the current row
     * of this <code>ResultSet</code> object as
     * a <code>boolean</code> in the Java programming language.
     *
     * @param columnIndex the first column is 1, the second is 2, ...
     * @return the column value; if the value is SQL <code>NULL</code>, the
     * value returned is <code>false</code>
     * @exception SQLException if a database access error occurs
     */
    boolean getBoolean(int columnIndex) throws SQLException;

    /**
     * Retrieves the value of the designated column in the current row
     * of this <code>ResultSet</code> object as
     * a <code>byte</code> in the Java programming language.
     *
     * @param columnIndex the first column is 1, the second is 2, ...
     * @return the column value; if the value is SQL <code>NULL</code>, the
     * value returned is <code>0</code>
     * @exception SQLException if a database access error occurs
     */
    byte getByte(int columnIndex) throws SQLException;

    /**
     * Retrieves the value of the designated column in the current row
     * of this <code>ResultSet</code> object as
     * a <code>short</code> in the Java programming language.
     *
     * @param columnIndex the first column is 1, the second is 2, ...
     * @return the column value; if the value is SQL <code>NULL</code>, the
     * value returned is <code>0</code>
     * @exception SQLException if a database access error occurs
     */
    short getShort(int columnIndex) throws SQLException;

    /**
     * Retrieves the value of the designated column in the current row
     * of this <code>ResultSet</code> object as
     * an <code>int</code> in the Java programming language.
     *
     * @param columnIndex the first column is 1, the second is 2, ...
     * @return the column value; if the value is SQL <code>NULL</code>, the
     * value returned is <code>0</code>
     * @exception SQLException if a database access error occurs
     */
    int getInt(int columnIndex) throws SQLException;

    /**
     * Retrieves the value of the designated column in the current row
     * of this <code>ResultSet</code> object as
     * a <code>long</code> in the Java programming language.
     *
     * @param columnIndex the first column is 1, the second is 2, ...
     * @return the column value; if the value is SQL <code>NULL</code>, the
     * value returned is <code>0</code>
     * @exception SQLException if a database access error occurs
     */
    long getLong(int columnIndex) throws SQLException;

    /**
     * Retrieves the value of the designated column in the current row
     * of this <code>ResultSet</code> object as
     * a <code>float</code> in the Java programming language.
     *
     * @param columnIndex the first column is 1, the second is 2, ...
     * @return the column value; if the value is SQL <code>NULL</code>, the
     * value returned is <code>0</code>
     * @exception SQLException if a database access error occurs
     */
    float getFloat(int columnIndex) throws SQLException;

    /**
     * Retrieves the value of the designated column in the current row
     * of this <code>ResultSet</code> object as
     * a <code>double</code> in the Java programming language.
     *
     * @param columnIndex the first column is 1, the second is 2, ...
     * @return the column value; if the value is SQL <code>NULL</code>, the
     * value returned is <code>0</code>
     * @exception SQLException if a database access error occurs
     */
    double getDouble(int columnIndex) throws SQLException;

    /**
     * Retrieves the value of the designated column in the current row
     * of this <code>ResultSet</code> object as
     * a <code>java.sql.BigDecimal</code> in the Java programming language.
     *
     * @param columnIndex the first column is 1, the second is 2, ...
     * @param scale the number of digits to the right of the decimal point
     * @return the column value; if the value is SQL <code>NULL</code>, the
     * value returned is <code>null</code>
     * @exception SQLException if a database access error occurs
     * @deprecated
     */
    BigDecimal getBigDecimal(int columnIndex, int scale) throws SQLException;

    /**
     * Retrieves the value of the designated column in the current row
     * of this <code>ResultSet</code> object as
     * a <code>byte</code> array in the Java programming language.
     * The bytes represent the raw values returned by the driver.
     *
     * @param columnIndex the first column is 1, the second is 2, ...
     * @return the column value; if the value is SQL <code>NULL</code>, the
     * value returned is <code>null</code>
     * @exception SQLException if a database access error occurs
     */