Java tutorial
/* * RHQ Management Platform * Copyright (C) 2005-2008 Red Hat, Inc. * All rights reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License, version 2, as * published by the Free Software Foundation, and/or the GNU Lesser * General Public License, version 2.1, also as published by the Free * Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License and the GNU Lesser General Public License * for more details. * * You should have received a copy of the GNU General Public License * and the GNU Lesser General Public License along with this program; * if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ package org.rhq.core.util.jdbc; import java.io.InputStream; import java.io.OutputStream; import java.io.Reader; import java.io.Writer; import java.sql.Connection; import java.sql.DatabaseMetaData; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; /** * Take care of some JDBC related stuff. Mostly closing resources * * @author Heiko W. Rupp */ public class JDBCUtil { private static final Log log = LogFactory.getLog(JDBCUtil.class); private static final String SQL_ERROR = "Error closing a resource: "; /* * The next constants specify how to generate the next value in a sequence for * table %s */ private static final String POSTGRES_NEXTVAL_SQL = "(SELECT nextval('%s_id_seq'::text))"; private static final String ORACLE_NEXTVAL_SQL = "%s_id_seq.nextval"; private static final String H2_NEXTVAL_SQL = "(SELECT nextval('%s_id_seq'))"; public static void safeClose(Statement stm, ResultSet rs) { safeClose(rs); safeClose(stm); } public static void safeClose(Connection conn, Statement stm, ResultSet rs) { safeClose(rs); safeClose(stm); safeClose(conn); } public static void safeClose(Connection con) { if (con != null) { try { con.close(); } catch (Exception e) { log.error(SQL_ERROR, e); } } } public static void safeClose(ResultSet rs) { if (rs != null) { try { rs.close(); } catch (Exception e) { log.error(SQL_ERROR, e); } } } public static void safeClose(Statement statement) { if (statement != null) { try { statement.close(); } catch (Exception e) { log.error(SQL_ERROR, e); } } } /** * Bind the passed values to the parameters of the {@link PreparedStatement}, starting at position startBinding * * @param ps PreparedStatement to use * @param values the array of int values to fill in * @param startingBinding the starting position of the parameter to fill in * * @throws SQLException if the {@link Statement}.setInt() call fails */ public static void bindNTimes(PreparedStatement ps, int[] values, int startingBinding) throws SQLException { for (int i = 0; i < values.length; i++) { ps.setInt(startingBinding + i, values[i]); } } /** * Populate the passed query with bindCount number of placeholders '?'. The method will not put necessary parenteses * around the placeholders. * * @param query the original query including text to replace * @param replaceable the part of the original query that should be replaced by '?'s. * @param bindCount how many placeholders '?' should be generated * * @return The modified query */ public static String transformQueryForMultipleInParameters(String query, String replaceable, int bindCount) { String replacement = generateInBinds(bindCount); return query.replace(replaceable, replacement); } /** * Generate count '? separated by comma */ public static String generateInBinds(int count) { StringBuilder b = new StringBuilder(); for (int i = 0; i < count; i++) { if (i > 0) { b.append(","); } b.append("?"); } return b.toString(); } /** * Generate the correct SQL statement to obtain the next value from a sequence/table * generator for the passed table. The passed connection gets closed in case of an error. * @param conn A valid database connection * @param tableName The name of the table to use * @return A statement that obtains the next value for the passed table */ public static String getNextValSql(Connection conn, String tableName) { String nextvalSql; try { DatabaseMetaData meta = conn.getMetaData(); String name = meta.getDatabaseProductName().toLowerCase(); if (name.contains("postgres")) { nextvalSql = POSTGRES_NEXTVAL_SQL; } else if (name.contains("oracle")) { nextvalSql = ORACLE_NEXTVAL_SQL; } else if (name.contains("h2")) { nextvalSql = H2_NEXTVAL_SQL; } else { JDBCUtil.safeClose(conn); throw new IllegalStateException("Unsupported database type: " + name); } } catch (Exception e) { JDBCUtil.safeClose(conn); throw new IllegalStateException("Failed to determine database type."); } nextvalSql = String.format(nextvalSql, tableName); return nextvalSql; } /** * @deprecated This should correctly be handled at the place where the stream is about to be closed JBNADM-2600 */ @Deprecated public static void safeClose(InputStream in) { if (in != null) { try { in.close(); } catch (Exception e) { log.error(SQL_ERROR, e); } } } /** * @deprecated This should correctly be handled at the place where the stream is about to be closed JBNADM-2600 */ @Deprecated public static void safeClose(OutputStream out) { if (out != null) { try { out.close(); } catch (Exception e) { log.error(SQL_ERROR, e); } } } /** * @deprecated This should correctly be handled at the place where the stream is about to be closed JBNADM-2600 */ @Deprecated public static void safeClose(Reader reader) { if (reader != null) { try { reader.close(); } catch (Exception e) { log.error(SQL_ERROR, e); } } } /** * @deprecated This should correctly be handled at the place where the stream is about to be closed JBNADM-2600 */ @Deprecated public static void safeClose(Writer writer) { if (writer != null) { try { writer.close(); } catch (Exception e) { log.error(SQL_ERROR, e); } } } public static String convertSQLExceptionToString(SQLException e) { StringBuilder result = new StringBuilder(e.toString()); if (e.getNextException() != null) { result.append(" - causes:"); SQLException cause = e; while ((cause = cause.getNextException()) != null) { result.append("\n\t").append(e); } } return result.toString(); } }