jpa-container/src/main/java/org/apache/aries/jpa/container/weaving/impl/DummyDataSource.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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 WARRANTIESOR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.aries.jpa.container.weaving.impl;

import java.io.PrintWriter;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.sql.Statement;

import javax.sql.DataSource;

/**
 * DummyDataSource to be able to create the EMF before DataSource is ready
 */
public final class DummyDataSource implements DataSource {
    
    /**
     * Simply tries to avoid that calling code runs into NPE
     */
    private final class DummyHandler implements InvocationHandler {
        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            ClassLoader classLoader = this.getClass().getClassLoader();
            Class<?> type = method.getReturnType();
            if (type == int.class) {
                return new Integer(0);
            }
            if (type == boolean.class) {
                return new Boolean(false);
            }
            if (type == String.class) {
                return "";
            }
            return proxyClasses(classLoader, type);
        }

        private Object proxyClasses(ClassLoader classLoader, Class<?> type) {
            if (type == DatabaseMetaData.class) {
                return createProxy(classLoader, DatabaseMetaData.class);
            }
            if (type == ResultSet.class) {
                return createProxy(classLoader, ResultSet.class);
            }
            if (type == Statement.class) {
                return createProxy(classLoader, PreparedStatement.class);
            }
            return null;
        }

        private Object createProxy(ClassLoader classLoader, Class<?> iface) {
            Class<?>[] ifAr = new Class[] { iface };
            return Proxy.newProxyInstance(classLoader, ifAr, this);
        }
    }
    
    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        return false;
    }

    @Override
    public void setLoginTimeout(int seconds) throws SQLException {
        // Ignore
    }

    @Override
    public void setLogWriter(PrintWriter out) throws SQLException {
        // Ignore
    }

    @Override
    public java.util.logging.Logger getParentLogger() throws SQLFeatureNotSupportedException {
        return null;
    }

    @Override
    public int getLoginTimeout() throws SQLException {
        return 0;
    }

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

    @Override
    public Connection getConnection(String username, String password) throws SQLException {
        InvocationHandler handler = new DummyHandler();
        ClassLoader classLoader = this.getClass().getClassLoader();
        return (Connection)Proxy.newProxyInstance(classLoader, new Class[] {
            Connection.class
        }, handler);
    }

    @Override
    public Connection getConnection() throws SQLException {
        return getConnection(null, null);
    }
}