https://github.com/spring-projects/spring-framework: Spring JDBC (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2018 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
 *
 *      https://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.datasource;

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

import org.springframework.core.Constants;
import org.springframework.lang.Nullable;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.support.DefaultTransactionDefinition;
import org.springframework.transaction.support.TransactionSynchronizationManager;


An adapter for a target DataSource, applying the current Spring transaction's isolation level (and potentially specified user credentials) to every getConnection call. Also applies the read-only flag, if specified. 
Can be used to proxy a target JNDI DataSource that does not have the
desired isolation level (and user credentials) configured. Client code
can work with this DataSource as usual, not worrying about such settings.

Inherits the capability to apply specific user credentials from its superclass UserCredentialsDataSourceAdapter; see the latter's javadoc for details on that functionality (e.g. UserCredentialsDataSourceAdapter.setCredentialsForCurrentThread). 
WARNING: This adapter simply calls Connection.setTransactionIsolation and/or Connection.setReadOnly for every Connection obtained from it. It does, however, not reset those settings; it rather expects the target
DataSource to perform such resetting as part of its connection pool handling.
Make sure that the target DataSource properly cleans up such transaction state.

Author:Juergen Hoeller
See Also:
Since:2.0.3
/**
 * An adapter for a target {@link javax.sql.DataSource}, applying the current
 * Spring transaction's isolation level (and potentially specified user credentials)
 * to every {@code getConnection} call. Also applies the read-only flag,
 * if specified.
 *
 * <p>Can be used to proxy a target JNDI DataSource that does not have the
 * desired isolation level (and user credentials) configured. Client code
 * can work with this DataSource as usual, not worrying about such settings.
 *
 * <p>Inherits the capability to apply specific user credentials from its superclass
 * {@link UserCredentialsDataSourceAdapter}; see the latter's javadoc for details
 * on that functionality (e.g. {@link #setCredentialsForCurrentThread}).
 *
 * <p><b>WARNING:</b> This adapter simply calls
 * {@link java.sql.Connection#setTransactionIsolation} and/or
 * {@link java.sql.Connection#setReadOnly} for every Connection obtained from it.
 * It does, however, <i>not</i> reset those settings; it rather expects the target
 * DataSource to perform such resetting as part of its connection pool handling.
 * <b>Make sure that the target DataSource properly cleans up such transaction state.</b>
 *
 * @author Juergen Hoeller
 * @since 2.0.3
 * @see #setIsolationLevel
 * @see #setIsolationLevelName
 * @see #setUsername
 * @see #setPassword
 */
public class IsolationLevelDataSourceAdapter extends UserCredentialsDataSourceAdapter {

	
Constants instance for TransactionDefinition. 
/** Constants instance for TransactionDefinition. */
	private static final Constants constants = new Constants(TransactionDefinition.class);

	@Nullable
	private Integer isolationLevel;


	
Set the default isolation level by the name of the corresponding constant in TransactionDefinition, e.g. "ISOLATION_SERIALIZABLE". 
If not specified, the target DataSource's default will be used.
Note that a transaction-specific isolation value will always override
any isolation setting specified at the DataSource level.

Params:
  • constantName – name of the constant
See Also:
/**
	 * Set the default isolation level by the name of the corresponding constant
	 * in {@link org.springframework.transaction.TransactionDefinition}, e.g.
	 * "ISOLATION_SERIALIZABLE".
	 * <p>If not specified, the target DataSource's default will be used.
	 * Note that a transaction-specific isolation value will always override
	 * any isolation setting specified at the DataSource level.
	 * @param constantName name of the constant
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_READ_UNCOMMITTED
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_READ_COMMITTED
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_REPEATABLE_READ
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_SERIALIZABLE
	 * @see #setIsolationLevel
	 */
	public final void setIsolationLevelName(String constantName) throws IllegalArgumentException {
		if (!constantName.startsWith(DefaultTransactionDefinition.PREFIX_ISOLATION)) {
			throw new IllegalArgumentException("Only isolation constants allowed");
		}
		setIsolationLevel(constants.asNumber(constantName).intValue());
	}

	
Specify the default isolation level to use for Connection retrieval, according to the JDBC Connection constants (equivalent to the corresponding Spring TransactionDefinition constants). 
If not specified, the target DataSource's default will be used.
Note that a transaction-specific isolation value will always override
any isolation setting specified at the DataSource level.

See Also:
/**
	 * Specify the default isolation level to use for Connection retrieval,
	 * according to the JDBC {@link java.sql.Connection} constants
	 * (equivalent to the corresponding Spring
	 * {@link org.springframework.transaction.TransactionDefinition} constants).
	 * <p>If not specified, the target DataSource's default will be used.
	 * Note that a transaction-specific isolation value will always override
	 * any isolation setting specified at the DataSource level.
	 * @see java.sql.Connection#TRANSACTION_READ_UNCOMMITTED
	 * @see java.sql.Connection#TRANSACTION_READ_COMMITTED
	 * @see java.sql.Connection#TRANSACTION_REPEATABLE_READ
	 * @see java.sql.Connection#TRANSACTION_SERIALIZABLE
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_READ_UNCOMMITTED
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_READ_COMMITTED
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_REPEATABLE_READ
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_SERIALIZABLE
	 * @see org.springframework.transaction.TransactionDefinition#getIsolationLevel()
	 * @see org.springframework.transaction.support.TransactionSynchronizationManager#getCurrentTransactionIsolationLevel()
	 */
	public void setIsolationLevel(int isolationLevel) {
		if (!constants.getValues(DefaultTransactionDefinition.PREFIX_ISOLATION).contains(isolationLevel)) {
			throw new IllegalArgumentException("Only values of isolation constants allowed");
		}
		this.isolationLevel = (isolationLevel != TransactionDefinition.ISOLATION_DEFAULT ? isolationLevel : null);
	}

	
Return the statically specified isolation level, or null if none. 
/**
	 * Return the statically specified isolation level,
	 * or {@code null} if none.
	 */
	@Nullable
	protected Integer getIsolationLevel() {
		return this.isolationLevel;
	}


	
Applies the current isolation level value and read-only flag
to the returned Connection.

See Also:
/**
	 * Applies the current isolation level value and read-only flag
	 * to the returned Connection.
	 * @see #getCurrentIsolationLevel()
	 * @see #getCurrentReadOnlyFlag()
	 */
	@Override
	protected Connection doGetConnection(@Nullable String username, @Nullable String password) throws SQLException {
		Connection con = super.doGetConnection(username, password);
		Boolean readOnlyToUse = getCurrentReadOnlyFlag();
		if (readOnlyToUse != null) {
			con.setReadOnly(readOnlyToUse);
		}
		Integer isolationLevelToUse = getCurrentIsolationLevel();
		if (isolationLevelToUse != null) {
			con.setTransactionIsolation(isolationLevelToUse);
		}
		return con;
	}

	
Determine the current isolation level: either the transaction's
isolation level or a statically defined isolation level.

See Also:
Returns:the current isolation level, or null if none
/**
	 * Determine the current isolation level: either the transaction's
	 * isolation level or a statically defined isolation level.
	 * @return the current isolation level, or {@code null} if none
	 * @see org.springframework.transaction.support.TransactionSynchronizationManager#getCurrentTransactionIsolationLevel()
	 * @see #setIsolationLevel
	 */
	@Nullable
	protected Integer getCurrentIsolationLevel() {
		Integer isolationLevelToUse = TransactionSynchronizationManager.getCurrentTransactionIsolationLevel();
		if (isolationLevelToUse == null) {
			isolationLevelToUse = getIsolationLevel();
		}
		return isolationLevelToUse;
	}

	
Determine the current read-only flag: by default,
the transaction's read-only hint.

See Also:
Returns:whether there is a read-only hint for the current scope
/**
	 * Determine the current read-only flag: by default,
	 * the transaction's read-only hint.
	 * @return whether there is a read-only hint for the current scope
	 * @see org.springframework.transaction.support.TransactionSynchronizationManager#isCurrentTransactionReadOnly()
	 */
	@Nullable
	protected Boolean getCurrentReadOnlyFlag() {
		boolean txReadOnly = TransactionSynchronizationManager.isCurrentTransactionReadOnly();
		return (txReadOnly ? Boolean.TRUE : null);
	}

}