长话短说:
- 我需要转换程序中的每个类(甚至是 java
在我的代理之前加载的库)。
- 我已经找到办法了
但还没有完全发挥作用。我对新想法持开放态度。
- 我的实际方法表现得很奇怪:它应该在文件和控制台中打印相同的名称,但事实并非如此。我确信这些类能够达到我的转换方法,因为如果我尝试对它们进行检测
我收到一个错误。
完整故事:我创建了一个代理,以便在加载到我的项目中的每个类中注入一些自定义代码。我在运行时使用选项 -javaagent 添加此代理,并且效果很好。
问题是,当我的代理连接到 JVM 时,已经加载了很多类(例如 java.io.* 类),因此我的转换丢失了一大堆类。
所以我的问题是:有一种方法可以让我缺失的所有课程都可用吗?每一个建议都非常受欢迎。
现在我已经尝试过这样的:
public class MyTransformer implements ClassFileTransformer {
public static void premain(String agentArgs, Instrumentation inst) {
final MyTransformer t = MyTransformer .getInstance();
inst.addTransformer(t, true);
MyTransformer .log.info(t + " registered via JVM option -javaagent");
// TEST
// by the time we are attached, the classes to be
// dumped may have been loaded already. So, check
// for candidates in the loaded classes.
Class[] classes = inst.getAllLoadedClasses();
List<Class> candidates = new ArrayList<Class>();
for (Class c : classes) {
if (inst.isModifiableClass(c) && inst.isRetransformClassesSupported()){
candidates.add(c);
}
}
System.out.println("There are "+candidates.size()+" classes");
try {
// if we have matching candidates, then
// retransform those classes so that we
// will get callback to transform.
if (! candidates.isEmpty()) {
Iterator it = candidates.iterator();
while(it.hasNext()){
Class c = (Class)it.next();
if(!c.getName().startsWith("javassist")){
System.out.println(" ========================> In Progress:"+c.getName());
inst.retransformClasses(c);
}
}
}else{
System.out.println("candidates.isEmpty()");
}
} catch (Exception e) {
e.printStackTrace();
}
}
public byte[] transform(ClassLoader loader, String className,
Class<?> classBeingRedefined, ProtectionDomain protectionDomain,
byte[] classfileBuffer) throws IllegalClassFormatException {
byte[] byteCode = classfileBuffer;
final String dot_classname = className.replace('/', '.');
// log classes that are going throug the instrumentor
// just log if the java.io. is coming here
try {
PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(path, true)));
out.println(dot_classname);
out.close();
} catch (IOException ex) {
Logger.getLogger(MyTransformer.class.getName()).log(Level.SEVERE, null, ex);
}
return byteCode;
}
}
因此,我的第一次尝试是采用每个已加载的类的“premain”方法,如果可能的话,使用“retransfromClasses”方法重新转换它。
现在,在我的转换方法中,我只有一个日志,它将每个要转换的类写入文件中。现在我的测试结果是:
There are 1486 classes
==> In Progress:com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser
==> In Progress:java.lang.Enum
==> In Progress:java.lang.ThreadGroup
==> In Progress:java.nio.file.FileSystem
==> In Progress:java.util.regex.Pattern$Prolog
==> In Progress:com.sun.org.apache.xerces.internal.dom.AttributeMap
==> In Progress:java.util.regex.Matcher
==> In Progress:org.apache.commons.beanutils.converters.ShortConverter
==> In Progress:com.google.gson.JsonNull
==> In Progress:java.util.concurrent.CopyOnWriteArrayList$COWIterator
==> In Progress:java.util.concurrent.locks.ReentrantLock
==> In Progress:java.lang.NoSuchMethodError
==> In Progress:org.apache.commons.lang.BooleanUtils
==> In Progress:java.lang.reflect.WeakCache$CacheValue
==> In Progress:com.google.gson.internal.bind.TypeAdapters$33
==> In Progress:java.lang.reflect.Type
==> In Progress:sun.reflect.generics.scope.AbstractScope
==> In Progress:org.apache.log4j.helpers.DateTimeDateFormat
==> In Progress:sun.nio.cs.MS1252
==> In Progress:java.lang.Integer$IntegerCache
==> In Progress:com.sun.org.apache.xerces.internal.utils.SecuritySupport$3
==> In Progress:org.apache.commons.configuration.MapConfiguration
==> In Progress:org.apache.commons.beanutils.IntrospectionContext
==> In Progress:java.io.Reader
==> In Progress:java.util.WeakHashMap$Holder
==> In Progress:java.util.ServiceLoader$LazyIterator
==> In Progress:java.util.regex.Pattern$Branch
==> In Progress:java.lang.IllegalMonitorStateException
==> In Progress:java.util.regex.Pattern$Curly
==> In Progress:org.apache.commons.configuration.resolver.EntityRegistry
==> In Progress:java.io.IOException
==> In Progress:java.io.FilterOutputStream
==> In Progress:org.apache.log4j.LogManager
==> In Progress:sun.util.logging.PlatformLogger$Level
==> In Progress:java.nio.charset.CoderResult$1
==> In Progress:com.google.gson.FieldNamingPolicy$5
==> In Progress:com.google.gson.internal.ObjectConstructor
==> In Progress:sun.util.calendar.BaseCalendar$Date
所以你可以注意到我可以找到我感兴趣的每个类(甚至是 java.io)。现在,如果我们看一下应该包含 MyTransformer 尝试转换的每个类的文件,我们会注意到没有公共条目,这真的很奇怪。
org.apache.commons.beanutils.converters.ShortConverter
com.google.gson.JsonNull
org.apache.commons.lang.BooleanUtils
com.google.gson.internal.bind.TypeAdapters$33
org.apache.log4j.helpers.DateTimeDateFormat
org.apache.commons.configuration.MapConfiguration
org.apache.commons.beanutils.IntrospectionContext
org.apache.commons.configuration.resolver.EntityRegistry
org.apache.log4j.LogManager
com.google.gson.FieldNamingPolicy$5
com.google.gson.internal.ObjectConstructor
org.apache.log4j.Layout
com.google.gson.internal.bind.TypeAdapters
org.apache.log4j.PropertyConfigurator
com.sap.psr.vulas.java.JavaEnumId
org.apache.commons.collections.collection.AbstractSerializableCollectionDecorator
org.apache.commons.logging.impl.LogFactoryImpl
org.apache.commons.lang.text.StrTokenizer
我发现的另一个问题是,如果我尝试在 Mytransformer.transform(..) 方法中插入一些字节码篡改,它将破坏我的执行。我的意思是我正在使用的转换操作非常好,因为我在附加代理后加载的每个类上都使用它。但不知何故,如果我尝试在那些“重新转换”的类中使用它,我会出现此错误:
==> In Progress:org.apache.commons.lang.text.StrMatcher$TrimMatcher java.lang.UnsupportedOperationException: class redefinition failed: attempted to change the schema (add/remove fields)
at sun.instrument.InstrumentationImpl.retransformClasses0(Native Method)
at sun.instrument.InstrumentationImpl.retransformClasses(InstrumentationImpl.java:144)
我知道本机类的转换存在限制,但我不认为我的转换操作正在尝试更改架构。我将调查这一点并发布更新。