/*
 * Copyright 2002-2019 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.SQLException;
import java.sql.Savepoint;

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

import org.springframework.lang.Nullable;
import org.springframework.transaction.CannotCreateTransactionException;
import org.springframework.transaction.NestedTransactionNotSupportedException;
import org.springframework.transaction.SavepointManager;
import org.springframework.transaction.TransactionException;
import org.springframework.transaction.TransactionSystemException;
import org.springframework.transaction.TransactionUsageException;
import org.springframework.transaction.support.SmartTransactionObject;
import org.springframework.util.Assert;

/**
 * Convenient base class for JDBC-aware transaction objects. Can contain a
 * {@link ConnectionHolder} with a JDBC {@code Connection}, and implements the
 * {@link SavepointManager} interface based on that {@code ConnectionHolder}.
 *
 * <p>Allows for programmatic management of JDBC {@link java.sql.Savepoint Savepoints}.
 * Spring's {@link org.springframework.transaction.support.DefaultTransactionStatus}
 * automatically delegates to this, as it autodetects transaction objects which
 * implement the {@link SavepointManager} interface.
 *
 * @author Juergen Hoeller
 * @since 1.1
 * @see DataSourceTransactionManager
 */
public abstract class JdbcTransactionObjectSupport implements SavepointManager, SmartTransactionObject {

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


        @Nullable
        private ConnectionHolder connectionHolder;

        @Nullable
        private Integer previousIsolationLevel;

        private boolean readOnly = false;

        private boolean savepointAllowed = false;


        /**
         * Set the ConnectionHolder for this transaction object.
         */
        public void setConnectionHolder(@Nullable ConnectionHolder connectionHolder) {
                this.connectionHolder = connectionHolder;
        }

        /**
         * Return the ConnectionHolder for this transaction object.
         */
        public ConnectionHolder getConnectionHolder() {
                Assert.state(this.connectionHolder != null, "No ConnectionHolder available");
                return this.connectionHolder;
        }

        /**
         * Check whether this transaction object has a ConnectionHolder.
         */
        public boolean hasConnectionHolder() {
                return (this.connectionHolder != null);
        }

        /**
         * Set the previous isolation level to retain, if any.
         */
        public void setPreviousIsolationLevel(@Nullable Integer previousIsolationLevel) {
                this.previousIsolationLevel = previousIsolationLevel;
        }

        /**
         * Return the retained previous isolation level, if any.
         */
        @Nullable
        public Integer getPreviousIsolationLevel() {
                return this.previousIsolationLevel;
        }

        /**
         * Set the read-only status of this transaction.
         * The default is {@code false}.
         * @since 5.2.1
         */
        public void setReadOnly(boolean readOnly) {
                this.readOnly = readOnly;
        }

        /**
         * Return the read-only status of this transaction.
         * @since 5.2.1
         */
        public boolean isReadOnly() {
                return this.readOnly;
        }

        /**
         * Set whether savepoints are allowed within this transaction.
         * The default is {@code false}.
         */
        public void setSavepointAllowed(boolean savepointAllowed) {
                this.savepointAllowed = savepointAllowed;
        }

        /**
         * Return whether savepoints are allowed within this transaction.
         */
        public boolean isSavepointAllowed() {
                return this.savepointAllowed;
        }

        @Override
        public void flush() {
                // no-op
        }


        //---------------------------------------------------------------------
        // Implementation of SavepointManager
        //---------------------------------------------------------------------

        /**
         * This implementation creates a JDBC 3.0 Savepoint and returns it.
         * @see java.sql.Connection#setSavepoint
         */
        @Override
        public Object createSavepoint() throws TransactionException {
                ConnectionHolder conHolder = getConnectionHolderForSavepoint();
                try {
                        if (!conHolder.supportsSavepoints()) {
                                throw new NestedTransactionNotSupportedException(
                                                "Cannot create a nested transaction because savepoints are not supported by your JDBC driver");
                        }
                        if (conHolder.isRollbackOnly()) {
                                throw new CannotCreateTransactionException(
                                                "Cannot create savepoint for transaction which is already marked as rollback-only");
                        }
                        return conHolder.createSavepoint();
                }
                catch (SQLException ex) {
                        throw new CannotCreateTransactionException("Could not create JDBC savepoint", ex);
                }
        }

        /**
         * This implementation rolls back to the given JDBC 3.0 Savepoint.
         * @see java.sql.Connection#rollback(java.sql.Savepoint)
         */
        @Override
        public void rollbackToSavepoint(Object savepoint) throws TransactionException {
                ConnectionHolder conHolder = getConnectionHolderForSavepoint();
                try {
                        conHolder.getConnection().rollback((Savepoint) savepoint);
                        conHolder.resetRollbackOnly();
                }
                catch (Throwable ex) {
                        throw new TransactionSystemException("Could not roll back to JDBC savepoint", ex);
                }
        }

        /**
         * This implementation releases the given JDBC 3.0 Savepoint.
         * @see java.sql.Connection#releaseSavepoint
         */
        @Override
        public void releaseSavepoint(Object savepoint) throws TransactionException {
                ConnectionHolder conHolder = getConnectionHolderForSavepoint();
                try {
                        conHolder.getConnection().releaseSavepoint((Savepoint) savepoint);
                }
                catch (Throwable ex) {
                        logger.debug("Could not explicitly release JDBC savepoint", ex);
                }
        }

        protected ConnectionHolder getConnectionHolderForSavepoint() throws TransactionException {
                if (!isSavepointAllowed()) {
                        throw new NestedTransactionNotSupportedException(
                                        "Transaction manager does not allow nested transactions");
                }
                if (!hasConnectionHolder()) {
                        throw new TransactionUsageException(
                                        "Cannot create nested transaction when not exposing a JDBC transaction");
                }
                return getConnectionHolder();
        }

}