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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,124 @@ | ||
| --- | ||
| layout: default | ||
| title: jvm-sadnbox-1.4.0版本不支持增强业务模块的类 | ||
| parent: Sandbox | ||
| --- | ||
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| # 原因分析 | ||
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| ## 分析1 | ||
| 对比了1.4.0和1.3.0的代码，有以下代码，看着像是把业务类与sandbox类分离，后来发现在搞错了，这个是为了增强一类native本地方法的 | ||
| ```java | ||
| // 如果未开启unsafe开关，是不允许增强来自BootStrapClassLoader的类 | ||
| if (!isEnableUnsafe | ||
| && null == loader) { | ||
| logger.debug("transform ignore {}, class from bootstrap but unsafe.enable=false.", internalClassName); | ||
| return null; | ||
| } | ||
| ``` | ||
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| ## 分析2 | ||
| 对比了1.4.0和1.3.0的代码，发现BusinessClassLoaderHolder类被移除了，因为每次增强被触发后，是以事件监听器来处理的，所以1.3.3版本是 | ||
| 在EventListenerHandler类中以如下代码。这串代码在1.4.0中移除了。所以在EventListenerHandler（这个类处在sandbox.core包下）执行时， | ||
| 线程的上下文不是业务类加载器，是jvm-sandbox的类加载器。 | ||
| ```java | ||
| package com.alibaba.jvm.sandbox.core.classloader; | ||
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| /** | ||
| * @author zhuangpeng | ||
| * @since 2020/1/15 | ||
| */ | ||
| public class BusinessClassLoaderHolder { | ||
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| private static final ThreadLocal<DelegateBizClassLoader> holder = new ThreadLocal<DelegateBizClassLoader>(); | ||
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| public static void setBussinessClassLoader(ClassLoader classLoader){ | ||
| if(null == classLoader){ | ||
| return; | ||
| } | ||
| DelegateBizClassLoader delegateBizClassLoader = new DelegateBizClassLoader(classLoader); | ||
| holder.set(delegateBizClassLoader); | ||
| } | ||
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| public static void removeBussinessClassLoader(){ | ||
| holder.remove(); | ||
| } | ||
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| public static DelegateBizClassLoader getBussinessClassLoader(){ | ||
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| return null != holder ? holder.get() : null; | ||
| } | ||
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| public static class DelegateBizClassLoader extends ClassLoader{ | ||
| public DelegateBizClassLoader(ClassLoader parent){ | ||
| super(parent); | ||
| } | ||
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| @Override | ||
| public Class<?> loadClass(final String javaClassName, final boolean resolve) throws ClassNotFoundException { | ||
| return super.loadClass(javaClassName,resolve); | ||
| } | ||
| } | ||
| } | ||
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| ``` | ||
| 在类加载中，在事件处置中，将参数的类加载器，置入,代码如下： | ||
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| ```sql | ||
| final ClassLoader javaClassLoader = ObjectIDs.instance.getObject(targetClassLoaderObjectID); | ||
| //放置业务类加载器 | ||
| BusinessClassLoaderHolder.setBussinessClassLoader(javaClassLoader); | ||
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| ``` | ||
| 这个加载器使用，类加载的时机 | ||
| ```java | ||
| @Override | ||
| protected Class<?> loadClass(final String javaClassName, final boolean resolve) throws ClassNotFoundException { | ||
| synchronized (getClassLoadingLock0(javaClassName)){ | ||
| // 优先查询类加载路由表,如果命中路由规则,则优先从路由表中的ClassLoader完成类加载 | ||
| if (ArrayUtils.isNotEmpty(routingArray)) { | ||
| for (final Routing routing : routingArray) { | ||
| if (!routing.isHit(javaClassName)) { | ||
| continue; | ||
| } | ||
| final ClassLoader routingClassLoader = routing.classLoader; | ||
| try { | ||
| return routingClassLoader.loadClass(javaClassName); | ||
| } catch (Exception cause) { | ||
| // 如果在当前routingClassLoader中找不到应该优先加载的类(应该不可能，但不排除有就是故意命名成同名类) | ||
| // 此时应该忽略异常，继续往下加载 | ||
| // ignore... | ||
| } | ||
| } | ||
| } | ||
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| // 先走一次已加载类的缓存，如果没有命中，则继续往下加载 | ||
| final Class<?> loadedClass = findLoadedClass(javaClassName); | ||
| if (loadedClass != null) { | ||
| return loadedClass; | ||
| } | ||
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| try { | ||
| Class<?> aClass = findClass(javaClassName); | ||
| if (resolve) { | ||
| resolveClass(aClass); | ||
| } | ||
| return aClass; | ||
| } catch (Exception cause) { | ||
| DelegateBizClassLoader delegateBizClassLoader = BusinessClassLoaderHolder.getBussinessClassLoader(); | ||
| try { | ||
| if(null != delegateBizClassLoader){ | ||
| return delegateBizClassLoader.loadClass(javaClassName,resolve); | ||
| } | ||
| } catch (Exception e) { | ||
| //忽略异常，继续往下加载 | ||
| } | ||
| return RoutingURLClassLoader.super.loadClass(javaClassName, resolve); | ||
| } | ||
| } | ||
| } | ||
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| ``` | ||
| 问题可以定位是因为分析2。 |