simplenativejdbcextractor.java

一个关于Spring框架的示例应用程序,简单使用,可以参考.

/*
 * Copyright 2002-2004 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.nativejdbc;

import java.sql.Connection;
import java.sql.SQLException;

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

/**
 * Simple implementation of the NativeJdbcExtractor interface.
 * Assumes a pool that wraps Connection handles but not DatabaseMetaData:
 * In this case, the underlying native Connection can be retrieved by simply
 * calling <code>conHandle.getMetaData().getConnection()</code>.
 * All other JDBC objects will be returned as passed in.
 *
 * <p>This extractor should work with any pool that does not wrap DatabaseMetaData,
 * and will also work with any plain JDBC driver. Note that a pool can still wrap
 * Statements, PreparedStatements, etc: The only requirement of this extractor is
 * that java.sql.DatabaseMetaData does not get wrapped, returning the native
 * Connection of the JDBC driver on <code>metaData.getConnection()</code>.
 *
 * <p>Customize this extractor by setting the "nativeConnectionNecessaryForXxx"
 * flags accordingly: If Statements, PreparedStatements, and/or CallableStatements
 * are wrapped by your pool, set the corresponding "nativeConnectionNecessaryForXxx"
 * flags to true. If none of the statement types is wrapped - or you solely need
 * Connection unwrapping in the first place -, the defaults are fine.
 *
 * <p>SimpleNativeJdbcExtractor is a common choice for use with OracleLobHandler,
 * which just needs Connection unwrapping via the
 * <code>getNativeConnectionFromStatement</code> method. This usage will work
 * with almost any connection pool. Known to work are, for example:
 * <ul>
 * <li>Caucho Resin 2.1.x, 3.0.x
 * <li>Sun Java System Application Server 8
 * <li>Oracle OC4J 9.0.3, 9.0.4
 * <li>C3P0 0.8.x
 * <li>Jakarta Commons DBCP 1.0, 1.1, 1.2 (used in Tomcat 4.1.x, 5.0.x)
 * <li>JBoss 3.2.x
 * </ul>
 *
 * <p>For full usage with JdbcTemplate, i.e. to also provide Statement unwrapping:
 * <ul>
 * <li>Use a default SimpleNativeJdbcExtractor for Resin and SJSAS (no JDBC
 * Statement objects are wrapped, therefore no special unwrapping is necessary).
 * <li>Use a SimpleNativeJdbcExtractor with all "nativeConnectionNecessaryForXxx"
 * flags set to true for OC4J and C3P0 (all JDBC Statement objects are wrapped,
 * but none of the wrappers allow for unwrapping).
 * <li>Use a CommonsDbcpNativeJdbcExtractor for Jakarta Commons DBCP respectively
 * a JBossNativeJdbcExtractor for JBoss (all JDBC Statement objects are wrapped,
 * but all of them can be extracted by casting to implementation classes).
 * </ul>
 *
 * @author Juergen Hoeller
 * @since 05.12.2003
 * @see java.sql.DatabaseMetaData#getConnection
 * @see #getNativeConnection
 * @see #setNativeConnectionNecessaryForNativeStatements
 * @see #setNativeConnectionNecessaryForNativePreparedStatements
 * @see #setNativeConnectionNecessaryForNativeCallableStatements
 * @see CommonsDbcpNativeJdbcExtractor
 * @see JBossNativeJdbcExtractor
 * @see org.springframework.jdbc.core.JdbcTemplate#setNativeJdbcExtractor
 * @see org.springframework.jdbc.support.lob.OracleLobHandler#setNativeJdbcExtractor
 */
public class SimpleNativeJdbcExtractor extends NativeJdbcExtractorAdapter {

	protected final Log logger = LogFactory.getLog(getClass());

	private boolean nativeConnectionNecessaryForNativeStatements = false;

	private boolean nativeConnectionNecessaryForNativePreparedStatements = false;

	private boolean nativeConnectionNecessaryForNativeCallableStatements = false;


	/**
	 * Set whether it is necessary to work on the native Connection to
	 * receive native Statements. Default is false. If true, the Connection
	 * will be unwrapped first to create a Statement.
	 * <p>This makes sense if you need to work with native Statements from
	 * a pool that does not allow to extract the native JDBC objects from its
	 * wrappers but returns the native Connection on DatabaseMetaData.getConnection.
	 * <p>The standard SimpleNativeJdbcExtractor is unable to unwrap statements,
	 * so set this to true if your connection pool wraps Statements.
	 * @see java.sql.Connection#createStatement
	 * @see java.sql.DatabaseMetaData#getConnection
	 */
	public void setNativeConnectionNecessaryForNativeStatements(boolean nativeConnectionNecessaryForNativeStatements) {
		this.nativeConnectionNecessaryForNativeStatements = nativeConnectionNecessaryForNativeStatements;
	}

	public boolean isNativeConnectionNecessaryForNativeStatements() {
		return nativeConnectionNecessaryForNativeStatements;
	}

	/**
	 * Set whether it is necessary to work on the native Connection to
	 * receive native PreparedStatements. Default is false. If true,
	 * the Connection will be unwrapped first to create a PreparedStatement.
	 * <p>This makes sense if you need to work with native PreparedStatements from
	 * a pool that does not allow to extract the native JDBC objects from its
	 * wrappers but returns the native Connection on Statement.getConnection.
	 * <p>The standard SimpleNativeJdbcExtractor is unable to unwrap statements,
	 * so set this to true if your connection pool wraps PreparedStatements.
	 * @see java.sql.Connection#prepareStatement
	 * @see java.sql.DatabaseMetaData#getConnection
	 */
	public void setNativeConnectionNecessaryForNativePreparedStatements(boolean nativeConnectionNecessary) {
		this.nativeConnectionNecessaryForNativePreparedStatements = nativeConnectionNecessary;
	}

	public boolean isNativeConnectionNecessaryForNativePreparedStatements() {
		return nativeConnectionNecessaryForNativePreparedStatements;
	}

	/**
	 * Set whether it is necessary to work on the native Connection to
	 * receive native CallableStatements. Default is false. If true,
	 * the Connection will be unwrapped first to create a CallableStatement.
	 * <p>This makes sense if you need to work with native CallableStatements from
	 * a pool that does not allow to extract the native JDBC objects from its
	 * wrappers but returns the native Connection on Statement.getConnection.
	 * <p>The standard SimpleNativeJdbcExtractor is unable to unwrap statements,
	 * so set this to true if your connection pool wraps CallableStatements.
	 * @see java.sql.Connection#prepareCall
	 * @see java.sql.DatabaseMetaData#getConnection
	 */
	public void setNativeConnectionNecessaryForNativeCallableStatements(boolean nativeConnectionNecessary) {
		this.nativeConnectionNecessaryForNativeCallableStatements = nativeConnectionNecessary;
	}

	public boolean isNativeConnectionNecessaryForNativeCallableStatements() {
		return nativeConnectionNecessaryForNativeCallableStatements;
	}


	/**
	 * Retrieve the Connection via the DatabaseMetaData object, which will
	 * result in the native JDBC Connection with many connection pools.
	 * @see java.sql.DatabaseMetaData#getConnection
	 */
	protected Connection doGetNativeConnection(Connection con) throws SQLException {
		Connection nativeCon = con.getMetaData().getConnection();
		if (logger.isDebugEnabled()) {
			logger.debug("Returning native Connection [" + nativeCon + "] for given Connection handle [" + con + "]");
		}
		return nativeCon;
	}

}