AbstractMetricHandler.java

/*
 * Copyright 2014 the original author or authors.
 *
 * 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.springframework.xd.analytics.metrics.integration;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.integration.context.IntegrationContextUtils;
import org.springframework.messaging.Message;
import org.springframework.util.Assert;


/**
 * Abstract support class for authoring metrics oriented handlers. Provides support for
 * dynamically choosing the name of the counter to contribute to.
 *
 * @author Eric Bottard
 */
abstract class AbstractMetricHandler implements BeanFactoryAware, InitializingBean {

	protected final Expression nameExpression;

	protected final SpelExpressionParser spelExpressionParser = new SpelExpressionParser();

	protected EvaluationContext evaluationContext = new StandardEvaluationContext();

	private boolean evalationContextSet;

	private BeanFactory beanFactory;

	protected AbstractMetricHandler(String nameExpression) {
		Assert.notNull(nameExpression, "Metric name expression can not be null");
		this.nameExpression = spelExpressionParser.parseExpression(nameExpression);
	}

	protected String computeMetricName(Message<?> message) {
		return nameExpression.getValue(evaluationContext, message, CharSequence.class).toString();
	}

	public void setIntegrationEvaluationContext(EvaluationContext evaluationContext) {
		Assert.notNull(evaluationContext, "'evaluationContext' cannot be null");
		this.evaluationContext = evaluationContext;
		this.evalationContextSet = true;
	}

	@Override
	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
		this.beanFactory = beanFactory;
	}

	@Override
	public void afterPropertiesSet() throws Exception {
		if (!this.evalationContextSet) {
			this.evaluationContext = IntegrationContextUtils.getEvaluationContext(this.beanFactory);
		}
	}

}