问题描述
我正在尝试使用 ByteBuddy (v1.7.9) java 代理记录在方法和构造函数中抛出的每个调用、返回的对象和异常，而不干扰检测代码的正常运行.
I'm trying to log every call, returned objects and exceptions thrown in methods and constructors using a ByteBuddy (v1.7.9) java agent, without iterfering with the normal functioning of the instrumented code.
我当前的代理实例是
new AgentBuilder.Default()
.with(AgentBuilder.Listener.StreamWriting.toSystemOut())
.type((typeDescription, classLoader, module, classBeingRedefined, protectionDomain) ->
matcher.matchesIncoming(typeDescription.getTypeName()))
.transform((builder, typeDescription, classLoader, javaModule) -> builder
.visit(Advice.to(CustomAdvicer.class).on(ElementMatchers.any())))
.installOn(inst);
我从最简单的顾问"开始，
I have started with the simplest "advicer",
public class CustomAdvicer {
@Advice.OnMethodEnter
public static void enter(@Advice.Origin String origin) {
System.out.println("Entering " + origin);
}
@Advice.OnMethodExit(onThrowable = Throwable.class)
public static void exit(
@Advice.Return(typing = Assigner.Typing.DYNAMIC) @RuntimeType Object value,
@Advice.Origin String origin,
@Advice.Thrown Throwable thrown) {
System.out.println("Exiting " + origin);
}
}
但是，当我运行程序时，我收到了来自 bytebuddy 的异常:
However when I run the program I get an exception from bytebuddy:
[Byte Buddy] ERROR some.pack.Thrower [sun.misc.Launcher$AppClassLoader@18b4aac2, null, loaded=false]
java.lang.IllegalStateException: Cannot catch exception during constructor call for public some.pack.Thrower() throws java.lang.Exception
at net.bytebuddy.asm.Advice.doWrap(Advice.java:515)
at net.bytebuddy.asm.Advice.wrap(Advice.java:470)
at net.bytebuddy.asm.AsmVisitorWrapper$ForDeclaredMethods$Entry.wrap(AsmVisitorWrapper.java:481)
at net.bytebuddy.asm.AsmVisitorWrapper$ForDeclaredMethods$DispatchingVisitor.visitMethod(AsmVisitorWrapper.java:562)
at net.bytebuddy.jar.asm.ClassVisitor.visitMethod(ClassVisitor.java:327)
at net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForInlining$RedefinitionClassVisitor.visitMethod(TypeWriter.java:3801)
at net.bytebuddy.jar.asm.ClassReader.readMethod(ClassReader.java:1020)
at net.bytebuddy.jar.asm.ClassReader.accept(ClassReader.java:698)
at net.bytebuddy.jar.asm.ClassReader.accept(ClassReader.java:500)
at net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForInlining.create(TypeWriter.java:2941)
at net.bytebuddy.dynamic.scaffold.TypeWriter$Default.make(TypeWriter.java:1633)
at net.bytebuddy.dynamic.scaffold.inline.RebaseDynamicTypeBuilder.make(RebaseDynamicTypeBuilder.java:200)
at net.bytebuddy.agent.builder.AgentBuilder$Default$Transformation$Simple$Resolution.apply(AgentBuilder.java:8905)
at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.doTransform(AgentBuilder.java:9306)
at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.transform(AgentBuilder.java:9269)
at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.access$1300(AgentBuilder.java:9047)
at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$LegacyVmDispatcher.run(AgentBuilder.java:9625)
at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$LegacyVmDispatcher.run(AgentBuilder.java:9575)
at java.security.AccessController.doPrivileged(Native Method)
at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.transform(AgentBuilder.java:9194)
at sun.instrument.TransformerManager.transform(Unknown Source)
at sun.instrument.InstrumentationImpl.transform(Unknown Source)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at Main.main(Main.java:23)
那么，我应该怎么做才能记录构造函数中抛出的异常，记住它不能干扰原始代码?
So, what should I do in order to log the exceptions thrown inside constructors, bearing in mind that it must not interfere with the original code?
顺便说一下，Thrower 类是我为了测试这个案例而写的一个愚蠢的类:
By the way, the Thrower class is a silly class I wrote to test this case:
package some.pack;
public class Thrower {
public Thrower() throws Exception {
throw new Exception("By courtesy of thrower! ;)");
}
}
推荐答案
问题是构造函数有一个隐式的第一条指令，它是另一个或超级构造函数的调用.你的 Thrower 类实际上是这样的:
The problem is that a constructor has an implicit first instruction which is the invocation of another or a super constructor. Your Thrower class really looks like this:
public class Thrower {
public Thrower() throws Exception {
super();
throw new Exception("By courtesy of thrower! ;)");
}
}
如果你想将整个调用包装在一个 try-catch 块中，这将产生:
If you wanted to wrap the entire call in a try-catch block, this would yield this:
public class Thrower {
public Thrower() throws Exception {
try {
super();
throw new Exception("By courtesy of thrower! ;)");
} catch (Exception e) {
...
}
}
}
但这在 JVM 中是不合法的，因此 Byte Buddy 不允许这样做.没有一种好方法可以排除超级构造函数调用，因为这是第一次调用只是 Java 语言约定，但字节码允许更多任意组合.因为你不知道一个类来自什么语言，Byte Buddy在这里没有尝试任何技巧，只是不允许它.
But this is not legal in the JVM and therefore, Byte Buddy does not allow it. There is neither a good way to exclude the super constructor call as this being the first call is only a Java language convention but byte code allows more arbitrary combinations. As you cannot know what language a class comes from, Byte Buddy does not try any tricks here and simply does not allow it.
这篇关于如何使用 ByteBuddy 代理处理构造函数抛出的异常?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！