如何使用Javassist进行字节码操作以解决链接错误？

我已经发布了几个与javassit链接错误相关的问题。现在，在围绕这个主题和错误进行了一些研究工作之后，我获得了一些关于使用Javassist处理字节码以解决链接错误的有用信息

供您参考（已在此处的其他问题中发布此堆栈跟踪）

在线

cc.toClass（）上，我收到此异常。我在WebSphere上尝试了不同的类加载器方法来解决此异常，并得到了相同的错误

现在我明白了当试图修改引用类加载器已经加载的类时会出现链接问题。

为了解决这个错误，我应该首先从引用类加载器中卸载该类，我认为这很困难

所以我认为解决这个问题的唯一方法是在任何类装入器装入类之前实现字节码操作。不是吗

如何使用java代理将现有代码更改为字节码操作？有什么想法和建议吗？请不要重复提问。这只是上一个问题的参考工作 您需要动态地编写和附加它，以便在加载时转换类。你可以找到一个很酷的教程，解释如何做到这一点

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请注意，此方法允许您在JVM加载类时拦截该类，并在实际加载完成后对其进行修改

有什么建议吗？这个检测过程将解决“由于类加载器导致的链接错误”？我认为可能是这样的，因为这将在类加载时修改类，而不是在类已经加载时修改类。通过这个过程，我构建了一个软件，该软件对目标软件的每个库的每个类进行检测，我从来没有遇到过您的错误。试试看，谢谢。我想在我现有的代码上添加这个工具支持。我正在/WEB\u INF/lib path上使用Javassit库。因为我已经有了我的代码，我想知道我是否应该只添加java代理代码，还是添加其他代码

  [10/13/17 ] 00000089 webapp        E com.ibm.ws.webcontainer.webapp.WebApp logServletError SRVE0293E: [Servlet                                                                       Error]-[weblge]: java.lang.ExceptionInInitializerError
        at java.lang.J9VMInternals.ensureError(J9VMInternals.java:134)
        at java.lang.J9VMInternals.recordInitializationFailure(J9VMInternals.java:123)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:83)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:57)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:437)
        at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:163)
        at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:120)
        at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:345)
        at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:278)
        at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:103)
        at com.ibm.ws.webcontainer.webapp.WebApp.notifyServletContextCreated(WebApp.java:1826)
        at com.ibm.ws.webcontainer.webapp.WebAppImpl.initialize(WebAppImpl.java:442)
        at com.ibm.ws.webcontainer.webapp.WebGroupImpl.addWebApplication(WebGroupImpl.java:88)
        at com.ibm.ws.webcontainer.VirtualHostImpl.addWebApplication(VirtualHostImpl.java:171)
        at com.ibm.ws.webcontainer.WSWebContainer.addWebApp(WSWebContainer.java:904)
        at com.ibm.ws.webcontainer.WSWebContainer.addWebApplication(WSWebContainer.java:789)
        at com.ibm.ws.webcontainer.component.WebContainerImpl.install(WebContainerImpl.java:427)
        at com.ibm.ws.webcontainer.component.WebContainerImpl.start(WebContainerImpl.java:719)
        at com.ibm.ws.runtime.component.ApplicationMgrImpl.start(ApplicationMgrImpl.java:1247)
        at com.ibm.ws.runtime.component.DeployedApplicationImpl.fireDeployedObjectStart(DeployedApplicationImpl.java:1514)
        at com.ibm.ws.runtime.component.DeployedModuleImpl.start(DeployedModuleImpl.java:704)
        at com.ibm.ws.runtime.component.DeployedApplicationImpl.start(DeployedApplicationImpl.java:1096)
        at com.ibm.ws.runtime.component.ApplicationMgrImpl.startApplication(ApplicationMgrImpl.java:799)
        at com.ibm.ws.runtime.component.ApplicationMgrImpl$5.run(ApplicationMgrImpl.java:2315)
        at com.ibm.ws.security.auth.ContextManagerImpl.runAs(ContextManagerImpl.java:5488)
        at com.ibm.ws.security.auth.ContextManagerImpl.runAsSystem(ContextManagerImpl.java:5614)
        at com.ibm.ws.security.core.SecurityContext.runAsSystem(SecurityContext.java:255)
        at com.ibm.ws.runtime.component.ApplicationMgrImpl.start(ApplicationMgrImpl.java:2320)
        at com.ibm.ws.runtime.component.CompositionUnitMgrImpl.start(CompositionUnitMgrImpl.java:436)
        at com.ibm.ws.runtime.component.CompositionUnitImpl.start(CompositionUnitImpl.java:123)
        at com.ibm.ws.runtime.component.CompositionUnitMgrImpl.start(CompositionUnitMgrImpl.java:379)
        at com.ibm.ws.runtime.component.CompositionUnitMgrImpl.access$500(CompositionUnitMgrImpl.java:127)
        at com.ibm.ws.runtime.component.CompositionUnitMgrImpl$CUInitializer.run(CompositionUnitMgrImpl.java:985)
        at com.ibm.wsspi.runtime.component.WsComponentImpl$_AsynchInitializer.run(WsComponentImpl.java:524)
        at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1909)
Caused by: java.lang.IllegalStateException: javassist.CannotCompileException: by java.lang.LinkageError: org.springframework.aop.framework.ProxyCreatorSupport
        at org.springframework.aop.framework.JavassistApplicationContext.<clinit>(JavassistApplicationContext.java:36)
        ... 34 more
Caused by: javassist.CannotCompileException: by java.lang.LinkageError: org.springframework.aop.framework.ProxyCreatorSupport
        at javassist.ClassPool.toClass(ClassPool.java:1170)
        at javassist.ClassPool.toClass(ClassPool.java:1113)
        at javassist.ClassPool.toClass(ClassPool.java:1071)
        at javassist.CtClass.toClass(CtClass.java:1275)
        at org.springframework.aop.framework.JavassistApplicationContext.<clinit>(JavassistApplicationContext.java:34)
        ... 34 more
Caused by: java.lang.LinkageError: org.springframework.aop.framework.ProxyCreatorSupport
        at java.lang.ClassLoader.defineClassImpl(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:357)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:293)
        at sun.reflect.GeneratedMethodAccessor17.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:55)
        at java.lang.reflect.Method.invoke(Method.java:508)
        at javassist.ClassPool.toClass2(ClassPool.java:1183)
        at javassist.ClassPool.toClass(ClassPool.java:1164)
        ... 38 more

package org.spring.aop.framework;

import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtConstructor;
import javassist.LoaderClassPath;
import org.springframework.web.context.support.XmlWebApplicationContext;

public class JavassistApplicationContext extends XmlWebApplicationContext {

    static {
        ClassPool classPool = ClassPool.getDefault();
        try {
            ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
            classPool.appendClassPath(new LoaderClassPath(classLoader));

            CtClass cc = classPool.get("org.spring.aop.framework.ProxyCreatorSupport");
            CtConstructor c = cc.getConstructors()[0];
            c.insertAfter("$0.aopProxyFactory = new org.spring.aop.framework.JavassistAopProxyFactory();");
            cc.toClass();
        } catch (Exception e) {
            throw new IllegalStateException(e);
        }
    }
}