Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.commons.dbutils; import java.io.PrintWriter; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; /** * A collection of JDBC helper methods. This class is thread safe. */ public final class DbUtils { /** * Default constructor. * * Utility classes should not have a public or default constructor, * but this one preserves retro-compatibility. * * @since 1.4 */ public DbUtils() { // do nothing } /** * Close a <code>Connection</code>, avoid closing if null. * * @param conn Connection to close. * @throws SQLException if a database access error occurs */ public static void close(Connection conn) throws SQLException { if (conn != null) { conn.close(); } } /** * Close a <code>ResultSet</code>, avoid closing if null. * * @param rs ResultSet to close. * @throws SQLException if a database access error occurs */ public static void close(ResultSet rs) throws SQLException { if (rs != null) { rs.close(); } } /** * Close a <code>Statement</code>, avoid closing if null. * * @param stmt Statement to close. * @throws SQLException if a database access error occurs */ public static void close(Statement stmt) throws SQLException { if (stmt != null) { stmt.close(); } } /** * Close a <code>Connection</code>, avoid closing if null and hide * any SQLExceptions that occur. * * @param conn Connection to close. */ public static void closeQuietly(Connection conn) { try { close(conn); } catch (SQLException e) { // NOPMD // quiet } } /** * Close a <code>Connection</code>, <code>Statement</code> and * <code>ResultSet</code>. Avoid closing if null and hide any * SQLExceptions that occur. * * @param conn Connection to close. * @param stmt Statement to close. * @param rs ResultSet to close. */ public static void closeQuietly(Connection conn, Statement stmt, ResultSet rs) { try { closeQuietly(rs); } finally { try { closeQuietly(stmt); } finally { closeQuietly(conn); } } } /** * Close a <code>ResultSet</code>, avoid closing if null and hide any * SQLExceptions that occur. * * @param rs ResultSet to close. */ public static void closeQuietly(ResultSet rs) { try { close(rs); } catch (SQLException e) { // NOPMD // quiet } } /** * Close a <code>Statement</code>, avoid closing if null and hide * any SQLExceptions that occur. * * @param stmt Statement to close. */ public static void closeQuietly(Statement stmt) { try { close(stmt); } catch (SQLException e) { // NOPMD // quiet } } /** * Commits a <code>Connection</code> then closes it, avoid closing if null. * * @param conn Connection to close. * @throws SQLException if a database access error occurs */ public static void commitAndClose(Connection conn) throws SQLException { if (conn != null) { try { conn.commit(); } finally { conn.close(); } } } /** * Commits a <code>Connection</code> then closes it, avoid closing if null * and hide any SQLExceptions that occur. * * @param conn Connection to close. */ public static void commitAndCloseQuietly(Connection conn) { try { commitAndClose(conn); } catch (SQLException e) { // NOPMD // quiet } } /** * Loads and registers a database driver class. * If this succeeds, it returns true, else it returns false. * * @param driverClassName of driver to load * @return boolean <code>true</code> if the driver was found, otherwise <code>false</code> */ public static boolean loadDriver(String driverClassName) { return loadDriver(DbUtils.class.getClassLoader(), driverClassName); } /** * Loads and registers a database driver class. * If this succeeds, it returns true, else it returns false. * * @param classLoader the class loader used to load the driver class * @param driverClassName of driver to load * @return boolean <code>true</code> if the driver was found, otherwise <code>false</code> * @since 1.4 */ public static boolean loadDriver(ClassLoader classLoader, String driverClassName) { try { classLoader.loadClass(driverClassName).newInstance(); return true; } catch (IllegalAccessException e) { // Constructor is private, OK for DriverManager contract return true; } catch (Exception e) { return false; } } /** * Print the stack trace for a SQLException to STDERR. * * @param e SQLException to print stack trace of */ public static void printStackTrace(SQLException e) { printStackTrace(e, new PrintWriter(System.err)); } /** * Print the stack trace for a SQLException to a * specified PrintWriter. * * @param e SQLException to print stack trace of * @param pw PrintWriter to print to */ public static void printStackTrace(SQLException e, PrintWriter pw) { SQLException next = e; while (next != null) { next.printStackTrace(pw); next = next.getNextException(); if (next != null) { pw.println("Next SQLException:"); } } } /** * Print warnings on a Connection to STDERR. * * @param conn Connection to print warnings from */ public static void printWarnings(Connection conn) { printWarnings(conn, new PrintWriter(System.err)); } /** * Print warnings on a Connection to a specified PrintWriter. * * @param conn Connection to print warnings from * @param pw PrintWriter to print to */ public static void printWarnings(Connection conn, PrintWriter pw) { if (conn != null) { try { printStackTrace(conn.getWarnings(), pw); } catch (SQLException e) { printStackTrace(e, pw); } } } /** * Rollback any changes made on the given connection. * @param conn Connection to rollback. A null value is legal. * @throws SQLException if a database access error occurs */ public static void rollback(Connection conn) throws SQLException { if (conn != null) { conn.rollback(); } } /** * Performs a rollback on the <code>Connection</code> then closes it, * avoid closing if null. * * @param conn Connection to rollback. A null value is legal. * @throws SQLException if a database access error occurs * @since DbUtils 1.1 */ public static void rollbackAndClose(Connection conn) throws SQLException { if (conn != null) { try { conn.rollback(); } finally { conn.close(); } } } /** * Performs a rollback on the <code>Connection</code> then closes it, * avoid closing if null and hide any SQLExceptions that occur. * * @param conn Connection to rollback. A null value is legal. * @since DbUtils 1.1 */ public static void rollbackAndCloseQuietly(Connection conn) { try { rollbackAndClose(conn); } catch (SQLException e) { // NOPMD // quiet } } }