java - 从另一个 Java 程序编译并运行一个 Java 程序

Question

我正在编写一个程序，它使用 main 方法获取输入“.java”文件的路径。然后程序应该编译该文件并运行它。

假设我尝试编译和运行的程序如下所示:

Main.java

public class Main {

    public static void main(String[] args) {
        System.out.println("Hello, world!");
    }
}

执行编译并尝试运行它的程序:

Evaluator.java

    /**
     * Matches any .java file.
     */
    private static final PathMatcher matcher = FileSystems.getDefault().getPathMatcher("glob:**.java");

    private static String path;

    /**
     * Program entry point. Obtains the path to the .java file as a command line argument.
     * 
     * @param args One argument from the command line: path to the .java file.
     * @throws Exception 
     */
    public static void main(String[] args) throws Exception {
        if (args.length != 1) {
            throw new IllegalArgumentException(
                    "Expected exactly one argument from the command line.");
        }

        if (!matcher.matches(Paths.get(args[0]))) {
            throw new IllegalArgumentException(
                    String.format("File %s is not a valid java file.", args[0]));
        }

        // path is in a valid format
        path = args[0];

        // compile a program
        compile();

        // run a program
        run();
    }

    /**
     * Compiles a program.
     * 
     * @throws Exception
     */
    private static void compile() throws Exception {
        System.out.println("Compiling the program ...");

        Process p = Runtime.getRuntime().exec("javac " + path);
        output("Std.In", p.getInputStream());
        output("Std.Out", p.getErrorStream());
        p.waitFor();

        System.out.println("Program successfully compiled!\n");
    }

    /**
     * Runs a program.
     * 
     * @throws Exception
     */
    private static void run() throws Exception {
        System.out.println("Executing the program ...");

        Process p = Runtime.getRuntime().exec("java " + getProgramName(path));
        output("Std.In", p.getInputStream());
        output("Std.Out", p.getErrorStream());
        p.waitFor();

        System.out.println("Program finished!");
    }

    private static void output(String stream, InputStream in) throws IOException {      
        BufferedReader reader = new BufferedReader(new InputStreamReader(in, CS));

        for (String line = reader.readLine(); line != null; line = reader.readLine()) {
            System.out.println(String.format("%s: %s", stream, line));
        }
    }

    private static String getProgramName(String path) {
        return path.replace(".java", "");
    }
}

我的“Main.java”文件位于项目根目录中。我正在使用命令行参数“./Main.java”运行该程序。这样做可以正确编译程序并生成一个新文件“Main.class”。但是，run 方法输出如下:

Std.Out:错误:无法找到或加载主类..Main

这里应该出现什么问题？

Answer 1

尝试将您要启动的java进程设置为正确的工作目录，然后设置相关的类路径。

这应该有帮助。

更新

我建议使用方法Runtime.getRuntime().exec(String command, String[] envp, File dir)。

最后一个参数dir是进程工作目录。