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Provides JDBC integration mechanism for Bootique without implementing a specific DataSource. Requires an extra implementor module in runtime, such as 'bootique-jdbc-tomcat", etc.
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/*
 * Licensed to ObjectStyle LLC under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ObjectStyle LLC licenses
 * this file to you 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 io.bootique.jdbc;

import javax.sql.DataSource;
import java.io.PrintWriter;
import java.sql.*;
import java.util.Objects;
import java.util.function.Supplier;
import java.util.logging.Logger;

/**
 * A DataSource wrapper delegating to another DataSource that is created lazily on first access.
 *
 * @since 3.0
 */
public class LazyDataSource implements DataSource, AutoCloseable {

    private final Supplier supplier;
    private volatile DataSource delegate;

    public LazyDataSource(Supplier supplier) {
        this.supplier = supplier;
    }

    protected DataSource getDelegate() {
        if (delegate == null) {
            synchronized (this) {
                if (delegate == null) {
                    delegate = Objects.requireNonNull(supplier.get());
                }
            }
        }

        return delegate;
    }

    @Override
    public void close() throws Exception {
        DataSource local = this.delegate;
        if (local instanceof AutoCloseable) {
            ((AutoCloseable) local).close();
        }
    }

    @Override
    public Connection getConnection() throws SQLException {
        return getDelegate().getConnection();
    }

    @Override
    public Connection getConnection(String username, String password) throws SQLException {
        return getDelegate().getConnection(username, password);
    }

    @Override
    public PrintWriter getLogWriter() throws SQLException {
        return getDelegate().getLogWriter();
    }

    @Override
    public void setLogWriter(PrintWriter out) throws SQLException {
        getDelegate().setLogWriter(out);
    }

    @Override
    public void setLoginTimeout(int seconds) throws SQLException {
        getDelegate().setLoginTimeout(seconds);
    }

    @Override
    public int getLoginTimeout() throws SQLException {
        return getDelegate().getLoginTimeout();
    }

    @Override
    public ConnectionBuilder createConnectionBuilder() throws SQLException {
        return getDelegate().createConnectionBuilder();
    }

    @Override
    public Logger getParentLogger() throws SQLFeatureNotSupportedException {
        return getDelegate().getParentLogger();
    }

    @Override
    public ShardingKeyBuilder createShardingKeyBuilder() throws SQLException {
        return getDelegate().createShardingKeyBuilder();
    }

    @Override
    public  T unwrap(Class iface) throws SQLException {
        return iface.isInstance(this) ? (T) this : getDelegate().unwrap(iface);
    }

    @Override
    public boolean isWrapperFor(Class iface) throws SQLException {
        return iface.isInstance(this) ? true : getDelegate().isWrapperFor(iface);
    }
}