COMMONS_JEXL_2_0/src/main/java/org/apache/commons/jexl2/Main.java

/*
 * 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.commons.jexl2;

import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;

/**
 * Test application for JEXL.
 *
 * @since 2.0
 */
public class Main {
    /**
     * Test application for JEXL
     * 
     * If a single argument is present, it is treated as a filename of a JEXL
     * script to be executed as a script. Any exceptions terminate the application.
     * 
     * Otherwise, lines are read from standard input and evaluated.
     * ParseExceptions and JexlExceptions are logged, and do not cause the application to exit.
     * This is done so that interactive testing is easier.
     * 
     * @param args (optional) filename to execute. Stored in the args variable.
     * 
     * @throws Exception if parsing or IO fail
     */
    public static void main(String[] args) throws Exception {
        JexlEngine engine = new JexlEngine();
        JexlContext context = new MapContext();
        context.set("args", args);
        if (args.length == 1) {
            Script script = engine.createScript(new File(args[0]));
            Object value = script.execute(context);
            System.out.println("Return value: " + value);
        } else {
            BufferedReader console = new BufferedReader(new InputStreamReader(System.in));
            String line;
            System.out.print("> ");
            while (null != (line = console.readLine())) {
                try {
                    Expression expression = engine.createExpression(line);
                    Object value = expression.evaluate(context);
                    System.out.println("Return value: " + value);
                } catch (JexlException e) {
                    System.out.println(e.getLocalizedMessage());
                }
                System.out.print("> ");
            }
        }
    }
}