libraries/sql/src/main/java/org/qi4j/library/sql/datasource/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()
    {
    }

}