模型热交换后,Freemarker removeIntrospectionInfo不能与DCEVM一起使用

Question

我正在使用Freemarker和DCEVM + HotSwapManager代理.这基本上允许我即使在添加/删除方法时也可以热交换类.

一切都像魅力一样,直到Freemarker使用hotswapped类作为模型.它正在抛出freemarker.ext.beans.InvalidPropertyException:即使反射显示该方法存在(在调试会话期间检查),我也没有这样的bean属性.

我在用

final Method clearInfoMethod = beanWrapper.getClass().getDeclaredMethod("removeIntrospectionInfo", Class.class);
clearInfoMethod.setAccessible(true);
clearInfoMethod.invoke(clazz);

清除缓存,但它不起作用.我甚至尝试获取classCache成员字段并使用反射清除它,但它也不起作用.

我究竟做错了什么？我只需要强制freemarker抛弃他已经获得的模型类/类的任何内省.

有什么办法吗？

UPDATE

示例代码

Application.java

// Application.java
public class Application
{
    public static final String TEMPLATE_PATH = "TemplatePath";
    public static final String DEFAULT_TEMPLATE_PATH = "./";

    private static Application INSTANCE;
    private Configuration freemarkerConfiguration;
    private BeansWrapper beanWrapper;

    public static void main(String[] args)
    {
        final Application application = new Application();
        INSTANCE = application;
        try
        {
            application.run(args);
        }
        catch (InterruptedException e)
        {
            System.out.println("Exiting");
        }
        catch (IOException e)
        {
            System.out.println("IO Error");
            e.printStackTrace();
        }
    }

    public Configuration getFreemarkerConfiguration()
    {
        return freemarkerConfiguration;
    }

    public static Application getInstance()
    {
        return INSTANCE;
    }

    private void run(String[] args) throws InterruptedException, IOException
    {
        final String templatePath = System.getProperty(TEMPLATE_PATH) != null
                ? System.getProperty(TEMPLATE_PATH)
                : DEFAULT_TEMPLATE_PATH;

        final Configuration configuration = new Configuration();
        freemarkerConfiguration = configuration;

        beanWrapper = new BeansWrapper();
        beanWrapper.setUseCache(false);
        configuration.setObjectWrapper(beanWrapper);
        try
        {
            final File templateDir = new File(templatePath);
            configuration.setTemplateLoader(new FileTemplateLoader(templateDir));
        }
        catch (IOException e)
        {
            throw new RuntimeException(e);
        }

        final RunnerImpl runner = new RunnerImpl();
        try
        {
            runner.run(args);
        }
        catch (RuntimeException e)
        {
            e.printStackTrace();
        }
    }

    public BeansWrapper getBeanWrapper()
    {
        return beanWrapper;
    }
}

RunnerImpl.java

// RunnerImpl.java
public class RunnerImpl implements Runner
{
    @Override
    public void run(String[] args) throws InterruptedException
    {
        long counter = 0;
        while(true)
        {
            ++counter;
            System.out.printf("Run %d\n", counter);
//          Application.getInstance().getFreemarkerConfiguration().setObjectWrapper(new BeansWrapper());
            Application.getInstance().getBeanWrapper().clearClassIntrospecitonCache();
            final Worker worker = new Worker();
            worker.doWork();
            Thread.sleep(1000);
        }
    }

Worker.java

// Worker.java
public class Worker
{
    void doWork()
    {
        final Application application = Application.getInstance();
        final Configuration freemarkerConfiguration = application.getFreemarkerConfiguration();

        try
        {
            final Template template = freemarkerConfiguration.getTemplate("test.ftl");
            final Model model = new Model();
            final PrintWriter printWriter = new PrintWriter(System.out);

            printObjectInto(model);
            System.out.println("-----TEMPLATE MACRO PROCESSING-----");
            template.process(model, printWriter);
            System.out.println();
            System.out.println("-----END OF PROCESSING------");
            System.out.println();
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        catch (TemplateException e)
        {
            e.printStackTrace();
        }
    }

    private void printObjectInto(Object o)
    {
        final Class<?> aClass = o.getClass();
        final Method[] methods = aClass.getDeclaredMethods();
        for (final Method method : methods)
        {
            System.out.println(String.format("Method name: %s, public: %s", method.getName(), Modifier.isPublic(method.getModifiers())));
        }
    }
}

Model.java

// Model.java    
public class Model
{
    public String getMessage()
    {
        return "Hello";
    }

    public String getAnotherMessage()
    {
        return "Hello World!";
    }
}

这个例子根本不起作用.即使在运行时更改BeansWrapper也不会产生任何影响.

Answer 1

BeansWrapper（和DefaultObjectWrapper等）内省缓存依赖于java.beans.Introspector.getBeanInfo(aClass)，而不是反射。（这是因为它将对象视为 JavaBean。）java.beans.Introspector有自己的内部缓存，因此它可以返回过时的信息，在这种情况下，它BeansWrapper只会根据该过时的信息重新创建自己的类自省数据。至于 的java.beans.Introspector缓存，它实际上是正确的，因为它建立在 Java 中的类是不可变的假设之上。如果有什么东西违反了这个基本规则，它应该确保java.beans.Introspector它的缓存被清除（以及许多其他缓存......），否则不仅仅是 FreeMarker 会被破坏。例如，在 JRebel，他们付出了很多努力来清除所有类型的缓存。我猜 DCEVM 没有这方面的资源。那么看来你得给Introspector.flushCaches()自己打电话了。

更新：有一段时间（Java 7，也许是 6）java.beans.Introspector每个线程组有一个缓存，因此您可以flushCaches()从所有线程组进行调用。这一切实际上都是实现细节，原则上可以随时更改。遗憾的是，JavaDocIntrospector.flushCaches()没有警告您......