samples/javashell.js

#// Usage: jjs -scripting javashell.js

/*
 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

// Simple Java "shell" with which you can try out
// your few liner Java code leaving imports, main etc.
// And you can leave even compilation as this script
// takes care boilerplate+compile step for you.

// Java types used
var Arrays = Java.type("java.util.Arrays");
var BufferedReader = Java.type("java.io.BufferedReader");
var FileWriter = Java.type("java.io.FileWriter");
var LocalDateTime = Java.type("java.time.LocalDateTime");
var InputStreamReader = Java.type("java.io.InputStreamReader");
var PrintWriter = Java.type("java.io.PrintWriter");
var ProcessBuilder = Java.type("java.lang.ProcessBuilder");
var System = Java.type("java.lang.System");

// read multiple lines of input from stdin till user
// enters an empty line
function input(endMarker, prompt) {
    if (!endMarker) {
        endMarker = "";
    }

    if (!prompt) {
        prompt = " >> ";
    }

    var str = "";
    var reader = new BufferedReader(new InputStreamReader(System.in));
    var line;
    while (true) {
        System.out.print(prompt);
        line = reader.readLine();
        if (line == null || line == endMarker) {
            break;
        }
        str += line + "\n";
    }
    return str;
}

// write the string to the given file
function writeTo(file, str) {
    var w = new PrintWriter(new FileWriter(file));
    try {
        w.print(str);
    } finally {
        w.close();
    }
}

// generate Java code with user's input
// put inside generated main method
function generate(className) {
    var usercode = input();
    if (usercode == "") {
        return false;
    }

    var fullcode = <<EOF
// userful imports, add more here if you want
// more imports.
import static java.lang.System.*;
import java.io.*;
import java.net.*;
import java.math.*;
import java.nio.file.*;
import java.time.*;
import java.time.chrono.*;
import java.time.format.*;
import java.time.temporal.*;
import java.time.zone.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.stream.*;

public class ${className} {
   public static void main(String[] args) throws Exception {
       ${usercode}
   }
}
EOF

    writeTo("${className}.java", fullcode);
    return true;
}

// execute code command
function exec(args) {
    // build child process and start it!
    new ProcessBuilder(Arrays.asList(args.split(' ')))
         .inheritIO()
         .start()
         .waitFor();
}

// generate unique name
function uniqueName() {
    var now = LocalDateTime.now().toString();
    // replace unsafe chars with '_'
    return "JavaShell" + now.replace(/-|:|\./g, '_');
}

// read-compile-run loop
while(true) {
    var className = uniqueName();
    if (generate(className)) {
        exec("javac ${className}.java");
        exec("java ${className}");
    } else {
        break;
    }
}