/*
 * 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 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.apache.jasper.runtime;

import javax.servlet.ServletConfig;

import org.apache.jasper.compiler.Localizer;
import org.apache.tomcat.InstanceManager;

/**
 * Factory for obtaining {@link InstanceManager} instances from a JSP {@link ServletConfig}.
 */
public class InstanceManagerFactory {

    private InstanceManagerFactory() {
    }

    /**
     * Get the InstanceManager from the given ServletConfig.
     *
     * @param config the ServletConfig
     * @return the InstanceManager
     */
    public static InstanceManager getInstanceManager(ServletConfig config) {
        InstanceManager instanceManager =
                (InstanceManager) config.getServletContext().getAttribute(InstanceManager.class.getName());
        if (instanceManager == null) {
            throw new IllegalStateException(Localizer.getMessage("jsp.error.noInstanceManager"));
        }
        return instanceManager;
    }

}
