ScriptEngineShellTable.java

/**
 * Licensed to jclouds, Inc. (jclouds) under one or more
 * contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  jclouds 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.jclouds.karaf.commands.table.internal;

import org.jclouds.karaf.commands.table.BasicShellTable;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

/**
 * A shell table implementation that works with groovy expressions.
 */
public class ScriptEngineShellTable<D extends Object> extends BasicShellTable<D> {

  private final String engine;
  private final ScriptEngineManager scriptEngineFactory = new ScriptEngineManager();
  private final ScriptEngine scriptEngine;

  /**
   * Constructor
   * @param engine
   */
  public ScriptEngineShellTable(String engine) {
    this.engine = engine;
    this.scriptEngine = scriptEngineFactory.getEngineByName(engine);
  }

  /**
   * Evaluates an expression.
   * @param obj
   * @param expression
   * @return
   */
  public String evaluate(Object obj, String expression) {
    String result = "";
    try {
      scriptEngine.put(getType(), obj);
      result = String.valueOf(scriptEngine.eval(expression));
    } catch (Exception ex) {
      //Ignore
    }
    return result;
  }
}