java - 使用编译器 API 的程序中的内存泄漏

Question

我在一段用于在运行时编译和运行 Java 代码的代码中检测到严重的内存泄漏。我已经创建了堆转储，看来 com.sun.tools.javac.util.SharedNameTable$NameImpL 是罪魁祸首。

我想知道如何防止 SharedNameTable 占用如此多的空间。有没有办法强制释放 SharedNameTable ？

编译器代码:

public static Object compile(String code) throws IOException, InvocationTargetException, IllegalAccessException, ClassNotFoundException, NoSuchMethodException, java.lang.InstantiationException {
    String uuid = UUID.randomUUID().toString();
    File theDir = new File(uuid);

    if (!theDir.exists()) {
        System.out.println("creating directory: " + uuid);
        boolean result = false;

        try{
            theDir.mkdir();
            result = true;
        }
        catch(SecurityException se){
            System.out.println(se);
        }
        if(result) {
            System.out.println("DIR created");
        }
    }
    //Compile
    JavaCompiler jc = ToolProvider.getSystemJavaCompiler();
    StandardJavaFileManager sjfm = jc.getStandardFileManager(null, null, null);
    JavaFileObject javaObjectFromString = getJavaFileContentsAsString(new StringBuilder(code));
    System.out.println(javaObjectFromString.getName());
    Iterable fileObjects = Arrays.asList(javaObjectFromString);
    String[] options = new String[]{"-d", "/src/"+uuid};
    DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
    if (jc.getTask(null, null, diagnostics, Arrays.asList(options), null, fileObjects).call()) {
        sjfm.close();
        System.out.println("Class has been successfully compiled");
        //Load
        URL[] urls = new URL[]{new URL("file:///src/"+uuid+"/")};
        URLClassLoader ucl = new URLClassLoader(urls);
        Class cl = ucl.loadClass("TestClass");
        System.out.println("Class has been successfully loaded");
        //Run
        final Method method = cl.getDeclaredMethod("testMethod");
        final Object object = cl.newInstance();
        ExecutorService executor = Executors.newFixedThreadPool(1);
        Callable<Object> task = new Callable<Object>() {
            public Object call() throws IllegalAccessException, InvocationTargetException {
                return method.invoke(object);
            }
        };
        Future<Object> future = executor.submit(task);
        try {
            Object result = future.get(20, TimeUnit.SECONDS);
            return result;
        } catch (TimeoutException ex) {
            return "Method timed out (20 seconds). Please review your code.";
        } catch (InterruptedException e) {
            return "Method interrupted.";
        } catch (ExecutionException e) {
            e.printStackTrace();
            return String.format("ExecutionException thrown! %s", e.getMessage());
        } finally {
            future.cancel(true);
            executor.shutdown();
        }
    }
    sjfm.close();
    System.out.println("Class compilation failed!");
    //Create diagnostics and return them
    List<String> errors = new ArrayList<>();
    for (Diagnostic diagnostic : diagnostics.getDiagnostics()){
        String s = String.format("[Code:%s] %s on line %d / column % d in %s",
                diagnostic.getCode(),
                diagnostic.getKind().toString(),
                diagnostic.getLineNumber(),
                diagnostic.getColumnNumber(),
                diagnostic.getSource());
        errors.add(s);
        errors.add(diagnostic.toString());
    }
    return errors.toArray();
}

编辑:

我找到了similar question其中指出 SoftReference 是问题的原因。强制发生 OutOfMemoryException 应该强制清除这些异常。不过，我使用“node-java”npm 包在 node.js 应用程序中运行此代码。当我尝试强制 OoM 时，我的 node.js 应用程序将在抛出异常之前被终止。

Answer 1

正如我在 my answer 到 this question 中所写的那样，有一个编译器选项可以完全阻止使用 SharedNameTable。您可以将其添加为附加编译器选项:

String[] options = new String[]{"-d", "/src/"+uuid, "-XDuseUnsharedTable"};