/*
 * 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.jexl.scripting;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.InputStreamReader;

import javax.script.ScriptEngine;

import org.apache.commons.jexl.JexlException;

/**
 * Test application for JexlScriptEngine (JSR-223 implementation).
 * @since 2.0
 */
public class Main {

    /**
     * Test application for JexlScriptEngine (JSR-223 implementation).
     * 
     * If a single argument is present, it is treated as a filename of a JEXL
     * script to be executed.
     * Otherwise, lines are read from standard input and evaluated.
     * 
     * @param args (optional) filename to evaluate. Stored in the args variable.
     * 
     * @throws Exception if parsing or IO fail
     */
    public static void main(String[] args) throws Exception {
        JexlScriptEngineFactory fac = new JexlScriptEngineFactory();
        ScriptEngine engine = fac.getScriptEngine();
        engine.put("args", args);
        if (args.length == 1){
            Object value = engine.eval(new FileReader(args[0]));
            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 {
                    Object value = engine.eval(line);
                    System.out.println("Return value: "+value);
                    System.out.print("> ");
                } catch (JexlException e) {
                    System.out.println(e.getLocalizedMessage());
                }
            }
        }
    }
}

/*
 * 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.jexl.scripting;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.InputStreamReader;

import javax.script.ScriptEngine;
import javax.script.ScriptException;

/**
 * Test application for JexlScriptEngine (JSR-223 implementation).
 * @since 2.0
 */
public class Main {

    /**
     * Test application for JexlScriptEngine (JSR-223 implementation).
     * 
     * If a single argument is present, it is treated as a filename of a JEXL
     * script to be evaluated. Any exceptions terminate the application.
     * 
     * Otherwise, lines are read from standard input and evaluated.
     * ScriptExceptions are logged, and do not cause the application to exit.
     * This is done so that interactive testing is easier.
     * 
     * @param args (optional) filename to evaluate. Stored in the args variable.
     * 
     * @throws Exception if parsing or IO fail
     */
    public static void main(String[] args) throws Exception {
        JexlScriptEngineFactory fac = new JexlScriptEngineFactory();
        ScriptEngine engine = fac.getScriptEngine();
        engine.put("args", args);
        if (args.length == 1){
            Object value = engine.eval(new FileReader(args[0]));
            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 {
                    Object value = engine.eval(line);
                    System.out.println("Return value: "+value);
                } catch (ScriptException e) {
                    System.out.println(e.getLocalizedMessage());
                }
                System.out.print("> ");
            }
        }
    }
}

Document expected behaviour when Exceptions occur. Don't exit interactive session on ScriptException. Print prompt after exception as well.