/*
 * Copyright 2002-2008 the original author or authors.
 *
 * Licensed 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.springframework.jdbc.support;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.math.BigDecimal;
import java.sql.Blob;
import java.sql.Clob;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Types;

import javax.sql.DataSource;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.jdbc.CannotGetJdbcConnectionException;
import org.springframework.jdbc.datasource.DataSourceUtils;

/**
 * Generic utility methods for working with JDBC. Mainly for internal use
 * within the framework, but also useful for custom JDBC access code.
 *
 * @author Thomas Risberg
 * @author Juergen Hoeller
 */
public abstract class JdbcUtils {

	/**
	 * Constant that indicates an unknown (or unspecified) SQL type.
	 * @see java.sql.Types
	 */
	public static final int TYPE_UNKNOWN = Integer.MIN_VALUE;


	private static final Log logger = LogFactory.getLog(JdbcUtils.class);


	/**
	 * Close the given JDBC Connection and ignore any thrown exception.
	 * This is useful for typical finally blocks in manual JDBC code.
	 * @param con the JDBC Connection to close (may be <code>null</code>)
	 */
	public static void closeConnection(Connection con) {
		if (con != null) {
			try {
				con.close();
			}
			catch (SQLException ex) {
				logger.debug("Could not close JDBC Connection", ex);
			}
			catch (Throwable ex) {
				// We don't trust the JDBC driver: It might throw RuntimeException or Error.
				logger.debug("Unexpected exception on closing JDBC Connection", ex);
			}
		}
	}

	/**
	 * Close the given JDBC Statement and ignore any thrown exception.
	 * This is useful for typical finally blocks in manual JDBC code.
	 * @param stmt the JDBC Statement to close (may be <code>null</code>)
	 */
	public static void closeStatement(Statement stmt) {
		if (stmt != null) {
			try {
				stmt.close();
			}
			catch (SQLException ex) {
				logger.trace("Could not close JDBC Statement", ex);
			}
			catch (Throwable ex) {
				// We don't trust the JDBC driver: It might throw RuntimeException or Error.
				logger.trace("Unexpected exception on closing JDBC Statement", ex);
			}
		}
	}

	/**
	 * Close the given JDBC ResultSet and ignore any thrown exception.
	 * This is useful for typical finally blocks in manual JDBC code.
	 * @param rs the JDBC ResultSet to close (may be <code>null</code>)
	 */
	public static void closeResultSet(ResultSet rs) {
		if (rs != null) {
			try {
				rs.close();
			}
			catch (SQLException ex) {
				logger.trace("Could not close JDBC ResultSet", ex);
			}
			catch (Throwable ex) {
				// We don't trust the JDBC driver: It might throw RuntimeException or Error.
				logger.trace("Unexpected exception on closing JDBC ResultSet", ex);
			}
		}
	}

	/**
	 * Retrieve a JDBC column value from a ResultSet, using the specified value type.
	 * <p>Uses the specifically typed ResultSet accessor methods, falling back to
	 * {@link #getResultSetValue(java.sql.ResultSet, int)} for unknown types.
	 * <p>Note that the returned value may not be assignable to the specified
	 * required type, in case of an unknown type. Calling code needs to deal
	 * with this case appropriately, e.g. throwing a corresponding exception.
	 * @param rs is the ResultSet holding the data
	 * @param index is the column index
	 * @param requiredType the required value type (may be <code>null</code>)
	 * @return the value object
	 * @throws SQLException if thrown by the JDBC API
	 */
	public static Object getResultSetValue(ResultSet rs, int index, Class requiredType) throws SQLException {
		if (requiredType == null) {
			return getResultSetValue(rs, index);
		}

		Object value = null;
		boolean wasNullCheck = false;

		// Explicitly extract typed value, as far as possible.
		if (String.class.equals(requiredType)) {
			value = rs.getString(index);
		}
		else if (boolean.class.equals(requiredType) || Boolean.class.equals(requiredType)) {
			value = rs.getBoolean(index);
			wasNullCheck = true;
		}
		else if (byte.class.equals(requiredType) || Byte.class.equals(requiredType)) {
			value = rs.getByte(index);
			wasNullCheck = true;
		}
		else if (short.class.equals(requiredType) || Short.class.equals(requiredType)) {
			value = rs.getShort(index);
			wasNullCheck = true;
		}
		else if (int.class.equals(requiredType) || Integer.class.equals(requiredType)) {
			value = rs.getInt(index);
			wasNullCheck = true;
		}
		else if (long.class.equals(requiredType) || Long.class.equals(requiredType)) {
			value = rs.getLong(index);
			wasNullCheck = true;
		}
		else if (float.class.equals(requiredType) || Float.class.equals(requiredType)) {
			value = rs.getFloat(index);
			wasNullCheck = true;
		}
		else if (double.class.equals(requiredType) || Double.class.equals(requiredType) ||
				Number.class.equals(requiredType)) {
			value = rs.getDouble(index);
			wasNullCheck = true;
		}
		else if (byte[].class.equals(requiredType)) {
			value = rs.getBytes(index);
		}
		else if (java.sql.Date.class.equals(requiredType)) {
			value = rs.getDate(index);
		}
		else if (java.sql.Time.class.equals(requiredType)) {
			value = rs.getTime(index);
		}
		else if (java.sql.Timestamp.class.equals(requiredType) || java.util.Date.class.equals(requiredType)) {
			value = rs.getTimestamp(index);
		}
		else if (BigDecimal.class.equals(requiredType)) {
			value = rs.getBigDecimal(index);
		}
		else if (Blob.class.equals(requiredType)) {
			value = rs.getBlob(index);
		}
		else if (Clob.class.equals(requiredType)) {
			value = rs.getClob(index);
		}
		else {
			// Some unknown type desired -> rely on getObject.
			value = getResultSetValue(rs, index);
		}

		// Perform was-null check if demanded (for results that the
		// JDBC driver returns as primitives).
		if (wasNullCheck && value != null && rs.wasNull()) {
			value = null;
		}
		return value;
	}

	/**
	 * Retrieve a JDBC column value from a ResultSet, using the most appropriate
	 * value type. The returned value should be a detached value object, not having
	 * any ties to the active ResultSet: in particular, it should not be a Blob or
	 * Clob object but rather a byte array respectively String representation.
	 * <p>Uses the <code>getObject(index)</code> method, but includes additional "hacks"
	 * to get around Oracle 10g returning a non-standard object for its TIMESTAMP
	 * datatype and a <code>java.sql.Date</code> for DATE columns leaving out the
	 * time portion: These columns will explicitly be extracted as standard
	 * <code>java.sql.Timestamp</code> object.
	 * @param rs is the ResultSet holding the data
	 * @param index is the column index
	 * @return the value object
	 * @throws SQLException if thrown by the JDBC API
	 * @see java.sql.Blob
	 * @see java.sql.Clob
	 * @see java.sql.Timestamp
	 */
	public static Object getResultSetValue(ResultSet rs, int index) throws SQLException {
		Object obj = rs.getObject(index);
		String className = null;
		if (obj != null) {
			className = obj.getClass().getName();
		}
		if (obj instanceof Blob) {
			obj = rs.getBytes(index);
		}
		else if (obj instanceof Clob) {
			obj = rs.getString(index);
		}
		else if (className != null &&
				("oracle.sql.TIMESTAMP".equals(className) ||
				"oracle.sql.TIMESTAMPTZ".equals(className))) {
			obj = rs.getTimestamp(index);
		}
		else if (className != null && className.startsWith("oracle.sql.DATE")) {
			String metaDataClassName = rs.getMetaData().getColumnClassName(index);
			if ("java.sql.Timestamp".equals(metaDataClassName) ||
					"oracle.sql.TIMESTAMP".equals(metaDataClassName)) {
				obj = rs.getTimestamp(index);
			}
			else {
				obj = rs.getDate(index);
			}
		}
		else if (obj != null && obj instanceof java.sql.Date) {
			if ("java.sql.Timestamp".equals(rs.getMetaData().getColumnClassName(index))) {
				obj = rs.getTimestamp(index);
			}
		}
		return obj;
	}

	/**
	 * Extract database meta data via the given DatabaseMetaDataCallback.
	 * <p>This method will open a connection to the database and retrieve the database metadata.
	 * Since this method is called before the exception translation feature is configured for
	 * a datasource, this method can not rely on the SQLException translation functionality.
	 * <p>Any exceptions will be wrapped in a MetaDataAccessException. This is a checked exception
	 * and any calling code should catch and handle this exception. You can just log the
	 * error and hope for the best, but there is probably a more serious error that will
	 * reappear when you try to access the database again.
	 * @param dataSource the DataSource to extract metadata for
	 * @param action callback that will do the actual work
	 * @return object containing the extracted information, as returned by
	 * the DatabaseMetaDataCallback's <code>processMetaData</code> method
	 * @throws MetaDataAccessException if meta data access failed
	 */
	public static Object extractDatabaseMetaData(DataSource dataSource, DatabaseMetaDataCallback action)
			throws MetaDataAccessException {

		Connection con = null;
		try {
			con = DataSourceUtils.getConnection(dataSource);
			if (con == null) {
				// should only happen in test environments
				throw new MetaDataAccessException("Connection returned by DataSource [" + dataSource + "] was null");
			}
			DatabaseMetaData metaData = con.getMetaData();
			if (metaData == null) {
				// should only happen in test environments
				throw new MetaDataAccessException("DatabaseMetaData returned by Connection [" + con + "] was null");
			}
			return action.processMetaData(metaData);
		}
		catch (CannotGetJdbcConnectionException ex) {
			throw new MetaDataAccessException("Could not get Connection for extracting meta data", ex);
		}
		catch (SQLException ex) {
			throw new MetaDataAccessException("Error while extracting DatabaseMetaData", ex);
		}
		catch (AbstractMethodError err) {
			throw new MetaDataAccessException(
					"JDBC DatabaseMetaData method not implemented by JDBC driver - upgrade your driver", err);
		}
		finally {
			DataSourceUtils.releaseConnection(con, dataSource);
		}
	}

	/**
	 * Call the specified method on DatabaseMetaData for the given DataSource,
	 * and extract the invocation result.
	 * @param dataSource the DataSource to extract meta data for
	 * @param metaDataMethodName the name of the DatabaseMetaData method to call
	 * @return the object returned by the specified DatabaseMetaData method
	 * @throws MetaDataAccessException if we couldn't access the DatabaseMetaData
	 * or failed to invoke the specified method
	 * @see java.sql.DatabaseMetaData
	 */
	public static Object extractDatabaseMetaData(DataSource dataSource, final String metaDataMethodName)
			throws MetaDataAccessException {

		return extractDatabaseMetaData(dataSource,
				new DatabaseMetaDataCallback() {
					public Object processMetaData(DatabaseMetaData dbmd) throws SQLException, MetaDataAccessException {
						try {
							Method method = DatabaseMetaData.class.getMethod(metaDataMethodName, (Class[]) null);
							return method.invoke(dbmd, (Object[]) null);
						}
						catch (NoSuchMethodException ex) {
							throw new MetaDataAccessException("No method named '" + metaDataMethodName +
									"' found on DatabaseMetaData instance [" + dbmd + "]", ex);
						}
						catch (IllegalAccessException ex) {
							throw new MetaDataAccessException(
									"Could not access DatabaseMetaData method '" + metaDataMethodName + "'", ex);
						}
						catch (InvocationTargetException ex) {
							if (ex.getTargetException() instanceof SQLException) {
								throw (SQLException) ex.getTargetException();
							}
							throw new MetaDataAccessException(
									"Invocation of DatabaseMetaData method '" + metaDataMethodName + "' failed", ex);
						}
					}
				});
	}

	/**
	 * Return whether the given JDBC driver supports JDBC 2.0 batch updates.
	 * <p>Typically invoked right before execution of a given set of statements:
	 * to decide whether the set of SQL statements should be executed through
	 * the JDBC 2.0 batch mechanism or simply in a traditional one-by-one fashion.
	 * <p>Logs a warning if the "supportsBatchUpdates" methods throws an exception
	 * and simply returns <code>false</code> in that case.
	 * @param con the Connection to check
	 * @return whether JDBC 2.0 batch updates are supported
	 * @see java.sql.DatabaseMetaData#supportsBatchUpdates()
	 */
	public static boolean supportsBatchUpdates(Connection con) {
		try {
			DatabaseMetaData dbmd = con.getMetaData();
			if (dbmd != null) {
				if (dbmd.supportsBatchUpdates()) {
					logger.debug("JDBC driver supports batch updates");
					return true;
				}
				else {
					logger.debug("JDBC driver does not support batch updates");
				}
			}
		}
		catch (SQLException ex) {
			logger.debug("JDBC driver 'supportsBatchUpdates' method threw exception", ex);
		}
		catch (AbstractMethodError err) {
			logger.debug("JDBC driver does not support JDBC 2.0 'supportsBatchUpdates' method", err);
		}
		return false;
	}

	/**
	 * Extract a common name for the database in use even if various drivers/platforms provide varying names.
	 * @param source the name as provided in database metedata
	 * @return the common name to be used
	 */
	public static String commonDatabaseName(String source) {
		String name = source;
		if (source != null && source.startsWith("DB2")) {
			name = "DB2";
		}
		else if ("Sybase SQL Server".equals(source) ||
				"Adaptive Server Enterprise".equals(source) || 
				"ASE".equals(source) || 
				"sql server".equalsIgnoreCase(source) ) {
			name = "Sybase";
		}
		return name;
	}

	/**
	 * Check whether the given SQL type is numeric.
	 * @param sqlType the SQL type to be checked
	 * @return whether the type is numeric
	 */
	public static boolean isNumeric(int sqlType) {
		return Types.BIT == sqlType || Types.BIGINT == sqlType || Types.DECIMAL == sqlType ||
				Types.DOUBLE == sqlType || Types.FLOAT == sqlType || Types.INTEGER == sqlType ||
				Types.NUMERIC == sqlType || Types.REAL == sqlType || Types.SMALLINT == sqlType ||
				Types.TINYINT == sqlType;
	}

	/**
	 * Determine the column name to use. The column name is determined based on a
	 * lookup using ResultSetMetaData.
	 * <p>This method implementation takes into account recent clarifications
	 * expressed in the JDBC 4.0 specification:
	 * <p><i>columnLabel - the label for the column specified with the SQL AS clause.
	 * If the SQL AS clause was not specified, then the label is the name of the column</i>.
	 * @return the column name to use
	 * @param resultSetMetaData the current meta data to use
	 * @param columnIndex the index of the column for the look up
	 * @throws SQLException in case of lookup failure
	 */
	public static String lookupColumnName(ResultSetMetaData resultSetMetaData, int columnIndex) throws SQLException {
		String name = resultSetMetaData.getColumnLabel(columnIndex);
		if (name == null || name.length() < 1) {
			name = resultSetMetaData.getColumnName(columnIndex);
		}
		return name;
	}

	/**
	 * Convert a column name with underscores to the corresponding property name using "camel case".  A name
	 * like "customer_number" would match a "customerNumber" property name.
	 * @param name the column name to be converted
	 * @return the name using "camel case"
	 */
	public static String convertUnderscoreNameToPropertyName(String name) {
		StringBuilder result = new StringBuilder();
		boolean nextIsUpper = false;
		if (name != null && name.length() > 0) {
			if (name.length() > 1 && name.substring(1,2).equals("_")) {
				result.append(name.substring(0, 1).toUpperCase());
			}
			else {
				result.append(name.substring(0, 1).toLowerCase());
			}
			for (int i = 1; i < name.length(); i++) {
				String s = name.substring(i, i + 1);
				if (s.equals("_")) {
					nextIsUpper = true;
				}
				else {
					if (nextIsUpper) {
						result.append(s.toUpperCase());
						nextIsUpper = false;
					}
					else {
						result.append(s.toLowerCase());
					}
				}
			}
		}
		return result.toString();
	}

}
