/*
 * 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.support;

import javax.sql.DataSource;

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

import org.springframework.beans.factory.InitializingBean;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Base class for {@link org.springframework.jdbc.core.JdbcTemplate} and
 * other JDBC-accessing DAO helpers, defining common properties such as
 * DataSource and exception translator.
 *
 * <p>Not intended to be used directly.
 * See {@link org.springframework.jdbc.core.JdbcTemplate}.
 *
 * @author Juergen Hoeller
 * @since 28.11.2003
 * @see org.springframework.jdbc.core.JdbcTemplate
 */
public abstract class JdbcAccessor implements InitializingBean {

        /** Logger available to subclasses. */
        protected final Log logger = LogFactory.getLog(getClass());

        @Nullable
        private DataSource dataSource;

        @Nullable
        private volatile SQLExceptionTranslator exceptionTranslator;

        private boolean lazyInit = true;


        /**
         * Set the JDBC DataSource to obtain connections from.
         */
        public void setDataSource(@Nullable DataSource dataSource) {
                this.dataSource = dataSource;
        }

        /**
         * Return the DataSource used by this template.
         */
        @Nullable
        public DataSource getDataSource() {
                return this.dataSource;
        }

        /**
         * Obtain the DataSource for actual use.
         * @return the DataSource (never {@code null})
         * @throws IllegalStateException in case of no DataSource set
         * @since 5.0
         */
        protected DataSource obtainDataSource() {
                DataSource dataSource = getDataSource();
                Assert.state(dataSource != null, "No DataSource set");
                return dataSource;
        }

        /**
         * Specify the database product name for the DataSource that this accessor uses.
         * This allows to initialize an SQLErrorCodeSQLExceptionTranslator without
         * obtaining a Connection from the DataSource to get the meta-data.
         * @param dbName the database product name that identifies the error codes entry
         * @see SQLErrorCodeSQLExceptionTranslator#setDatabaseProductName
         * @see java.sql.DatabaseMetaData#getDatabaseProductName()
         */
        public void setDatabaseProductName(String dbName) {
                this.exceptionTranslator = new SQLErrorCodeSQLExceptionTranslator(dbName);
        }

        /**
         * Set the exception translator for this instance.
         * <p>If no custom translator is provided, a default
         * {@link SQLErrorCodeSQLExceptionTranslator} is used
         * which examines the SQLException's vendor-specific error code.
         * @see org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator
         * @see org.springframework.jdbc.support.SQLStateSQLExceptionTranslator
         */
        public void setExceptionTranslator(SQLExceptionTranslator exceptionTranslator) {
                this.exceptionTranslator = exceptionTranslator;
        }

        /**
         * Return the exception translator for this instance.
         * <p>Creates a default {@link SQLErrorCodeSQLExceptionTranslator}
         * for the specified DataSource if none set, or a
         * {@link SQLStateSQLExceptionTranslator} in case of no DataSource.
         * @see #getDataSource()
         */
        public SQLExceptionTranslator getExceptionTranslator() {
                SQLExceptionTranslator exceptionTranslator = this.exceptionTranslator;
                if (exceptionTranslator != null) {
                        return exceptionTranslator;
                }
                synchronized (this) {
                        exceptionTranslator = this.exceptionTranslator;
                        if (exceptionTranslator == null) {
                                DataSource dataSource = getDataSource();
                                if (dataSource != null) {
                                        exceptionTranslator = new SQLErrorCodeSQLExceptionTranslator(dataSource);
                                }
                                else {
                                        exceptionTranslator = new SQLStateSQLExceptionTranslator();
                                }
                                this.exceptionTranslator = exceptionTranslator;
                        }
                        return exceptionTranslator;
                }
        }

        /**
         * Set whether to lazily initialize the SQLExceptionTranslator for this accessor,
         * on first encounter of an SQLException. Default is "true"; can be switched to
         * "false" for initialization on startup.
         * <p>Early initialization just applies if {@code afterPropertiesSet()} is called.
         * @see #getExceptionTranslator()
         * @see #afterPropertiesSet()
         */
        public void setLazyInit(boolean lazyInit) {
                this.lazyInit = lazyInit;
        }

        /**
         * Return whether to lazily initialize the SQLExceptionTranslator for this accessor.
         * @see #getExceptionTranslator()
         */
        public boolean isLazyInit() {
                return this.lazyInit;
        }

        /**
         * Eagerly initialize the exception translator, if demanded,
         * creating a default one for the specified DataSource if none set.
         */
        @Override
        public void afterPropertiesSet() {
                if (getDataSource() == null) {
                        throw new IllegalArgumentException("Property 'dataSource' is required");
                }
                if (!isLazyInit()) {
                        getExceptionTranslator();
                }
        }

}