# DataSources.java

    /*
     * Copyright (c) 2011, Rickard Öberg. All Rights Reserved.
     * Copyright (c) 2012, Paul Merlin. All Rights Reserved.
     *
     * 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.qi4j.library.sql.datasource;

    import java.lang.reflect.InvocationHandler;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    import java.lang.reflect.Proxy;
    import java.net.ConnectException;
    import javax.sql.DataSource;
    import org.qi4j.api.service.ServiceImporterException;
    import org.qi4j.functional.Specification;
    import org.qi4j.library.circuitbreaker.CircuitBreaker;

    import static org.qi4j.functional.Specifications.not;
    import static org.qi4j.library.circuitbreaker.CircuitBreakers.in;
    import static org.qi4j.library.circuitbreaker.CircuitBreakers.rootCause;

    public class DataSources
    {

        public static CircuitBreaker newDataSourceCircuitBreaker()
        {
            return newDataSourceCircuitBreaker( 5, 1000 * 60 * 5 );
        }

        public static CircuitBreaker newDataSourceCircuitBreaker( int threshold, long timeout )
        {
            @SuppressWarnings( "unchecked" )
            Specification<Throwable> in = in( ConnectException.class );
            return new CircuitBreaker( threshold, timeout, not( rootCause( in ) ) );
        }

        public static DataSource wrapWithCircuitBreaker( final String dataSourceIdentity, final DataSource pool, final CircuitBreaker circuitBreaker )
        {
            // Create wrapper
            InvocationHandler handler = new InvocationHandler()
            {
                @Override
                public Object invoke( Object proxy, Method method, Object[] args )
                        throws Throwable
                {
                    if ( !circuitBreaker.isOn() ) {
                        Throwable throwable = circuitBreaker.lastThrowable();
                        if ( throwable != null ) {
                            throw throwable;
                        } else {
                            throw new ServiceImporterException( "Circuit breaker for DataSource " + dataSourceIdentity + " is not on" );
                        }
                    }

                    try {
                        Object result = method.invoke( pool, args );
                        circuitBreaker.success();
                        return result;
                    } catch ( IllegalAccessException e ) {
                        circuitBreaker.throwable( e );
                        throw e;
                    } catch ( IllegalArgumentException e ) {
                        circuitBreaker.throwable( e );
                        throw e;
                    } catch ( InvocationTargetException e ) {
                        circuitBreaker.throwable( e.getCause() );
                        throw e.getCause();
                    }
                }

            };

            // Create proxy with circuit breaker
            return ( DataSource ) Proxy.newProxyInstance( DataSource.class.getClassLoader(), new Class[]{ DataSource.class }, handler );
        }

        private DataSources()
        {
        }

    }