SpringContextLoaderService.java

package com.thinkbiganalytics.nifi.v2.core.spring;

/*-
 * #%L
 * thinkbig-nifi-core-service
 * %%
 * Copyright (C) 2017 ThinkBig Analytics
 * %%
 * 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.
 * #L%
 */

import com.thinkbiganalytics.nifi.core.api.spring.SpringContextService;

import org.apache.nifi.annotation.lifecycle.OnEnabled;
import org.apache.nifi.components.PropertyDescriptor;
import org.apache.nifi.components.Validator;
import org.apache.nifi.controller.AbstractControllerService;
import org.apache.nifi.controller.ConfigurationContext;
import org.apache.nifi.controller.ControllerService;
import org.apache.nifi.processor.Processor;
import org.apache.nifi.reporting.InitializationException;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.AbstractRefreshableConfigApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import java.util.Collections;
import java.util.List;

/**
 * Creates a Spring {@link ApplicationContext} that can be reused by other {@link ControllerService} and {@link Processor} objects.
 *
 * <p><b>NOTE:</b> The context is only valid within the NAR file containing this service.</p>
 */
public class SpringContextLoaderService extends AbstractControllerService implements SpringContextService {

    public static final PropertyDescriptor CONFIG_CLASSES = new PropertyDescriptor.Builder()
        .name("Configuraton Classes")
        .description("A comma-separated list of fully qualified names of java config classes")
        .addValidator(Validator.VALID)
        .required(false)
        .build();
    private static final List<PropertyDescriptor> properties;

    static {
        properties = Collections.singletonList(CONFIG_CLASSES);
    }

    private volatile AbstractRefreshableConfigApplicationContext context;

    @Override
    protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
        return properties;
    }

    /**
     * Called by the framework to load controller configurations, this method
     * will create a spring context
     *
     * @param context not used in this case
     * @throws InitializationException an except thrown if there are any errors
     */
    @OnEnabled
    public void loadConfiurations(final ConfigurationContext context) throws InitializationException {
        try {
            this.context = new ClassPathXmlApplicationContext();
            this.context.setClassLoader(getClass().getClassLoader());
            this.context.setConfigLocation("application-context.xml");

            getLogger().info("Refreshing spring context");
            this.context.refresh();
            getLogger().info("Spring context refreshed");
        } catch (BeansException | IllegalStateException e) {
            getLogger().error("Failed to load spring configurations", e);
            throw new InitializationException(e);
        }
    }

    /* (non-Javadoc)
     * @see com.thinkbiganalytics.controller.SpringContextService#getBean(java.lang.Class)
     */
    @Override
    public <T> T getBean(Class<T> requiredType) throws BeansException {
        return this.context.getBean(requiredType);
    }

    /* (non-Javadoc)
     * @see com.thinkbiganalytics.controller.SpringContextService#getBean(java.lang.String, java.lang.Class)
     */
    @Override
    public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
        return this.context.getBean(name, requiredType);
    }

}