JexlNamingStrategy.java

/**
 * The MIT License
 * Copyright © 2010 JmxTrans team
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package com.googlecode.jmxtrans.model.naming;

import com.googlecode.jmxtrans.model.NamingStrategy;
import com.googlecode.jmxtrans.model.Result;
import com.googlecode.jmxtrans.model.naming.typename.TypeNameValue;
import lombok.EqualsAndHashCode;
import org.apache.commons.jexl2.Expression;
import org.apache.commons.jexl2.JexlContext;
import org.apache.commons.jexl2.JexlEngine;
import org.apache.commons.jexl2.JexlException;
import org.apache.commons.jexl2.MapContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Map;

/**
 * Naming strategy which uses an JEXL expression to format the name from the result, its class name, attribute name,
 * and more.  Note the resulting name can be used for any of a number of purposes.  For example, with OpenTSDB it could
 * be the metric name or a tag name.
 * <p/>
 * In the expression, all of the following may be used:
 * <b>Variables</b>
 * <dl>
 * <dt>alias</dt>
 * <dd>the classname alias of the MBean.</dd>
 * <dt>attribute</dt>
 * <dd>the name of the attribute of the MBean queried.</dd>
 * <dt>class</dt>
 * <dd>the effective classname of the MBean (uses #alias is not null, otherwise uses #realclass).</dd>
 * <dt>realclass</dt>
 * <dd>the class name of the MBean.</dd>
 * <dt>result</dt>
 * <dd>the full Result object.</dd>
 * </dl>
 */

@EqualsAndHashCode
public class JexlNamingStrategy implements NamingStrategy {
	private static final Logger LOG = LoggerFactory.getLogger(JexlNamingStrategy.class);

	public static final String DEFAULT_EXPRESSION = "class + \".\" + attribute";
	public static final String VAR_CLASSNAME = "realclass";
	public static final String VAR_ATTRIBUTE_NAME = "attribute";
	public static final String VAR_CLASSNAME_ALIAS = "alias";
	public static final String VAR_EFFECTIVE_CLASSNAME = "class";
	public static final String VAR_TYPENAME = "typename";
	public static final String VAR_RESULT = "result";

	protected JexlEngine jexl;
	protected Expression parsedExpr;


	/**
	 * Create a new naming strategy using an JEXL expression and the default expression.
	 */
	public JexlNamingStrategy() throws JexlException {
		jexl = new JexlEngine();
		this.parsedExpr = jexl.createExpression(DEFAULT_EXPRESSION);
	}

	/**
	 * Create a new naming strategy using an JEXL expression and the given expression.
	 *
	 * @param expr - the JEXL expression to use to create names.
	 */
	public JexlNamingStrategy(String expr) throws JexlException {
		jexl = new JexlEngine();
		this.parsedExpr = jexl.createExpression(expr);
	}

	/**
	 * Format the name for the given result.
	 *
	 * @param result - the result of a JMX query.
	 * @return String - the formatted string resulting from the expression, or null if the formatting fails.
	 */
	@Override
	public String formatName(Result result) {
		String formatted;
		JexlContext context = new MapContext();

		this.populateContext(context, result);
		try {
			formatted = (String) this.parsedExpr.evaluate(context);
		} catch (JexlException jexlExc) {
			LOG.error("error applying JEXL expression to query results", jexlExc);
			formatted = null;
		}

		return formatted;
	}

	public void setExpression(String expr) throws JexlException {
		this.parsedExpr = this.jexl.createExpression(expr);
	}

	/**
	 * Populate the context with values from the result.
	 *
	 * @param context - the expression context used when evaluating JEXL expressions.
	 * @param result  - the result of a JMX query.
	 */
	protected void populateContext(JexlContext context, Result result) {
		context.set(VAR_CLASSNAME, result.getClassName());
		context.set(VAR_ATTRIBUTE_NAME, result.getAttributeName());
		context.set(VAR_CLASSNAME_ALIAS, result.getKeyAlias());

		Map<String, String> typeNameMap = TypeNameValue.extractMap(result.getTypeName());
		context.set(VAR_TYPENAME, typeNameMap);

		String effectiveClassname = result.getKeyAlias();
		if (effectiveClassname == null) {
			effectiveClassname = result.getClassName();
		}
		context.set(VAR_EFFECTIVE_CLASSNAME, effectiveClassname);

		context.set(VAR_RESULT, result);
	}
}