queryrunner.java

实现了从Google

/*
 * $Header: /home/cvs/jakarta-commons/dbutils/src/java/org/apache/commons/dbutils/QueryRunner.java,v 1.6 2003/11/12 01:00:55 dgraham Exp $
 * $Revision: 1.6 $
 * $Date: 2003/11/12 01:00:55 $
 * 
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
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 * Copyright (c) 2002-2003 The Apache Software Foundation.  All rights
 * reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
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 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    distribution.
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 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
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 *    Foundation" must not be used to endorse or promote products derived
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 * 5. Products derived from this software may not be called "Apache"
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package org.apache.commons.dbutils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.util.Arrays;

import javax.sql.DataSource;

/**
 * Executes SQL queries with pluggable strategies for handling 
 * <code>ResultSet</code>s.  This class is thread safe.
 * 
 * @see ResultSetHandler
 * 
 * @author Henri Yandell
 * @author Juozas Baliuka
 * @author Steven Caswell
 * @author David Graham
 */
public class QueryRunner {

    /**
     * The DataSource to retrieve connections from.
     */
    protected DataSource ds = null;

    /**
     * Constructor for QueryRunner.
     */
    public QueryRunner() {
        super();
    }

    /**
     * Constructor for QueryRunner.  Methods that do not take a 
     * <code>Connection</code> parameter will retrieve connections from this
     * <code>DataSource</code>.
     * 
     * @param ds The <code>DataSource</code> to retrieve connections from.
     */
    public QueryRunner(DataSource ds) {
        super();
        this.ds = ds;
    }

    /**
     * Fill the <code>PreparedStatement</code> replacement parameters with 
     * the given objects.
     * @param stmt
     * @param params Query replacement parameters; <code>null</code> is a valid
     * value to pass in.
     * @throws SQLException
     */
    protected void fillStatement(PreparedStatement stmt, Object[] params)
        throws SQLException {

        if (params == null) {
            return;
        }

        for (int i = 0; i < params.length; i++) {
            if (params[i] != null) {
                stmt.setObject(i + 1, params[i]);
            } else {
                stmt.setNull(i + 1, Types.OTHER);
            }
        }
    }

    /**
     * Returns the <code>DataSource</code> this runner is using.
     */
    public DataSource getDataSource() {
        return this.ds;
    }

    /**
     * Factory method that creates and initializes a 
     * <code>PreparedStatement</code> object for the given SQL.  
     * <code>QueryRunner</code> methods always call this method to prepare 
     * statements for them.  Subclasses can override this method to provide 
     * special PreparedStatement configuration if needed.  This implementation
     * simply calls <code>conn.prepareStatement(sql)</code>.
     *  
     * @param conn The <code>Connection</code> used to create the 
     * <code>PreparedStatement</code>
     * @param sql The SQL statement to prepare.
     * @return An initialized <code>PreparedStatement</code>.
     * @throws SQLException
     */
    protected PreparedStatement prepareStatement(Connection conn, String sql)
        throws SQLException {
            
        return conn.prepareStatement(sql);
    }

    /**
     * Execute an SQL SELECT query with a single replacement parameter.  The
     * caller is responsible for connection cleanup.
     * 
     * @param conn The connection to execute the query in.
     * @param sql The query to execute.
     * @param param The replacement parameter.
     * @param rsh The handler that converts the results into an object.
     * @return The object returned by the handler.
     * @throws SQLException
     */
    public Object query(
        Connection conn,
        String sql,
        Object param,
        ResultSetHandler rsh)
        throws SQLException {

        return this.query(conn, sql, new Object[] { param }, rsh);
    }

    /**
     * Execute an SQL SELECT query with replacement parameters.  The
     * caller is responsible for connection cleanup.
     * 
     * @param conn The connection to execute the query in.
     * @param sql The query to execute.
     * @param params The replacement parameters.
     * @param rsh The handler that converts the results into an object.
     * @return The object returned by the handler.
     * @throws SQLException
     */
    public Object query(
        Connection conn,
        String sql,
        Object[] params,
        ResultSetHandler rsh)
        throws SQLException {

        PreparedStatement stmt = null;
        ResultSet rs = null;
        Object result = null;

        try {
            stmt = this.prepareStatement(conn, sql);
            this.fillStatement(stmt, params);

            rs = this.wrap(stmt.executeQuery());

            result = rsh.handle(rs);

        } catch (SQLException e) {
            this.rethrow(e, sql, params);

        } finally {
            DbUtils.close(rs);
            DbUtils.close(stmt);
        }

        return result;
    }

    /**
     * Execute an SQL SELECT query without any replacement parameters.  The
     * caller is responsible for connection cleanup.
     * 
     * @param conn The connection to execute the query in.
     * @param sql The query to execute.
     * @param rsh The handler that converts the results into an object.
     * @return The object returned by the handler.
     * @throws SQLException
     */
    public Object query(Connection conn, String sql, ResultSetHandler rsh)
        throws SQLException {

        return this.query(conn, sql, (Object[]) null, rsh);
    }

    /**
     * Executes the given SELECT SQL with a single replacement parameter.
     * The <code>Connection</code> is retrieved from the
     * <code>DataSource</code> set in the constructor.