Class CheckClassAdapter
- java.lang.Object
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- org.objectweb.asm.ClassVisitor
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- org.objectweb.asm.util.CheckClassAdapter
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public class CheckClassAdapter extends ClassVisitor
AClassVisitor
that checks that its methods are properly used. More precisely this class adapter checks each method call individually, based only on its arguments, but does not check the sequence of method calls. For example, the invalid sequencevisitField(ACC_PUBLIC, "i", "I", null)
visitField(ACC_PUBLIC, "i", "D", null)
will not be detected by this class adapter.CheckClassAdapter
can be also used to verify bytecode transformations in order to make sure that the transformed bytecode is sane. For example:InputStream inputStream = ...; // get bytes for the source class ClassReader classReader = new ClassReader(inputStream); ClassWriter classWriter = new ClassWriter(classReader, ClassWriter.COMPUTE_MAXS); ClassVisitor classVisitor = new MyClassAdapter(new CheckClassAdapter(classWriter, true)); classReader.accept(classVisitor, 0); StringWriter stringWriter = new StringWriter(); PrintWriter printWriter = new PrintWriter(stringWriter); CheckClassAdapter.verify(new ClassReader(classWriter.toByteArray()), false, printWriter); assertTrue(stringWriter.toString().isEmpty());
The above code pass the transformed bytecode through a
CheckClassAdapter
, with data flow checks enabled. These checks are not exactly the same as the JVM verification, but provide some basic type checking for each method instruction. If the bytecode has errors, the output text shows the erroneous instruction number, and a dump of the failed method with information about the type of the local variables and of the operand stack slots for each instruction. For example (format is - insnNumber locals : stack):org.objectweb.asm.tree.analysis.AnalyzerException: Error at instruction 71: Expected I, but found . at org.objectweb.asm.tree.analysis.Analyzer.analyze(Analyzer.java:...) at org.objectweb.asm.util.CheckClassAdapter.verify(CheckClassAdapter.java:...) ... remove()V 00000 LinkedBlockingQueue$Itr . . . . . . . . : ICONST_0 00001 LinkedBlockingQueue$Itr . . . . . . . . : I ISTORE 2 00001 LinkedBlockingQueue$Itr . I . . . . . . : ... 00071 LinkedBlockingQueue$Itr . I . . . . . . : ILOAD 1 00072 ? INVOKESPECIAL java/lang/Integer.<init> (I)V ...
The above output shows that the local variable 1, loaded by the
ILOAD 1
instruction at position00071
is not initialized, whereas the local variable 2 is initialized and contains an int value.
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Field Summary
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Fields inherited from class org.objectweb.asm.ClassVisitor
api, cv
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Constructor Summary
Constructors Modifier Constructor Description protected
CheckClassAdapter(int api, ClassVisitor classVisitor, boolean checkDataFlow)
Constructs a newCheckClassAdapter
.CheckClassAdapter(ClassVisitor classVisitor)
Constructs a newCheckClassAdapter
.CheckClassAdapter(ClassVisitor classVisitor, boolean checkDataFlow)
Constructs a newCheckClassAdapter
.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description static void
checkClassSignature(java.lang.String signature)
Checks a class signature.static void
checkFieldSignature(java.lang.String signature)
Checks a field signature.static void
checkMethodSignature(java.lang.String signature)
Checks a method signature.static void
main(java.lang.String[] args)
Checks the given class.static void
verify(ClassReader classReader, boolean printResults, java.io.PrintWriter printWriter)
Checks the given class.static void
verify(ClassReader classReader, java.lang.ClassLoader loader, boolean printResults, java.io.PrintWriter printWriter)
Checks the given class.void
visit(int version, int access, java.lang.String name, java.lang.String signature, java.lang.String superName, java.lang.String[] interfaces)
Visits the header of the class.AnnotationVisitor
visitAnnotation(java.lang.String descriptor, boolean visible)
Visits an annotation of the class.void
visitAttribute(Attribute attribute)
Visits a non standard attribute of the class.void
visitEnd()
Visits the end of the class.FieldVisitor
visitField(int access, java.lang.String name, java.lang.String descriptor, java.lang.String signature, java.lang.Object value)
Visits a field of the class.void
visitInnerClass(java.lang.String name, java.lang.String outerName, java.lang.String innerName, int access)
Visits information about an inner class.MethodVisitor
visitMethod(int access, java.lang.String name, java.lang.String descriptor, java.lang.String signature, java.lang.String[] exceptions)
Visits a method of the class.ModuleVisitor
visitModule(java.lang.String name, int access, java.lang.String version)
Visit the module corresponding to the class.void
visitNestHost(java.lang.String nestHost)
Visits the nest host class of the class.void
visitNestMember(java.lang.String nestMember)
Visits a member of the nest.void
visitOuterClass(java.lang.String owner, java.lang.String name, java.lang.String descriptor)
Visits the enclosing class of the class.void
visitPermittedSubclass(java.lang.String permittedSubclass)
Visits a permitted subclasses.RecordComponentVisitor
visitRecordComponent(java.lang.String name, java.lang.String descriptor, java.lang.String signature)
Visits a record component of the class.void
visitSource(java.lang.String file, java.lang.String debug)
Visits the source of the class.AnnotationVisitor
visitTypeAnnotation(int typeRef, TypePath typePath, java.lang.String descriptor, boolean visible)
Visits an annotation on a type in the class signature.
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Constructor Detail
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CheckClassAdapter
public CheckClassAdapter(ClassVisitor classVisitor)
Constructs a newCheckClassAdapter
. Subclasses must not use this constructor. Instead, they must use theCheckClassAdapter(int, ClassVisitor, boolean)
version.- Parameters:
classVisitor
- the class visitor to which this adapter must delegate calls.
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CheckClassAdapter
public CheckClassAdapter(ClassVisitor classVisitor, boolean checkDataFlow)
Constructs a newCheckClassAdapter
. Subclasses must not use this constructor. Instead, they must use theCheckClassAdapter(int, ClassVisitor, boolean)
version.- Parameters:
classVisitor
- the class visitor to which this adapter must delegate calls.checkDataFlow
- whether to perform basic data flow checks.- Throws:
java.lang.IllegalStateException
- If a subclass calls this constructor.
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CheckClassAdapter
protected CheckClassAdapter(int api, ClassVisitor classVisitor, boolean checkDataFlow)
Constructs a newCheckClassAdapter
.- Parameters:
api
- the ASM API version implemented by this visitor. Must be one of theASM
x values inOpcodes
.classVisitor
- the class visitor to which this adapter must delegate calls.checkDataFlow
- true to perform basic data flow checks, or false to not perform any data flow check (seeCheckMethodAdapter
).
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Method Detail
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visit
public void visit(int version, int access, java.lang.String name, java.lang.String signature, java.lang.String superName, java.lang.String[] interfaces)
Description copied from class:ClassVisitor
Visits the header of the class.- Overrides:
visit
in classClassVisitor
- Parameters:
version
- the class version. The minor version is stored in the 16 most significant bits, and the major version in the 16 least significant bits.access
- the class's access flags (seeOpcodes
). This parameter also indicates if the class is deprecatedOpcodes.ACC_DEPRECATED
or a recordOpcodes.ACC_RECORD
.name
- the internal name of the class (seeType.getInternalName()
).signature
- the signature of this class. May be null if the class is not a generic one, and does not extend or implement generic classes or interfaces.superName
- the internal of name of the super class (seeType.getInternalName()
). For interfaces, the super class isObject
. May be null, but only for theObject
class.interfaces
- the internal names of the class's interfaces (seeType.getInternalName()
). May be null.
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visitSource
public void visitSource(java.lang.String file, java.lang.String debug)
Description copied from class:ClassVisitor
Visits the source of the class.- Overrides:
visitSource
in classClassVisitor
- Parameters:
file
- the name of the source file from which the class was compiled. May be null.debug
- additional debug information to compute the correspondence between source and compiled elements of the class. May be null.
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visitModule
public ModuleVisitor visitModule(java.lang.String name, int access, java.lang.String version)
Description copied from class:ClassVisitor
Visit the module corresponding to the class.- Overrides:
visitModule
in classClassVisitor
- Parameters:
name
- the fully qualified name (using dots) of the module.access
- the module access flags, amongACC_OPEN
,ACC_SYNTHETIC
andACC_MANDATED
.version
- the module version, or null.- Returns:
- a visitor to visit the module values, or null if this visitor is not interested in visiting this module.
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visitNestHost
public void visitNestHost(java.lang.String nestHost)
Description copied from class:ClassVisitor
Visits the nest host class of the class. A nest is a set of classes of the same package that share access to their private members. One of these classes, called the host, lists the other members of the nest, which in turn should link to the host of their nest. This method must be called only once and only if the visited class is a non-host member of a nest. A class is implicitly its own nest, so it's invalid to call this method with the visited class name as argument.- Overrides:
visitNestHost
in classClassVisitor
- Parameters:
nestHost
- the internal name of the host class of the nest.
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visitNestMember
public void visitNestMember(java.lang.String nestMember)
Description copied from class:ClassVisitor
Visits a member of the nest. A nest is a set of classes of the same package that share access to their private members. One of these classes, called the host, lists the other members of the nest, which in turn should link to the host of their nest. This method must be called only if the visited class is the host of a nest. A nest host is implicitly a member of its own nest, so it's invalid to call this method with the visited class name as argument.- Overrides:
visitNestMember
in classClassVisitor
- Parameters:
nestMember
- the internal name of a nest member.
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visitPermittedSubclass
public void visitPermittedSubclass(java.lang.String permittedSubclass)
Description copied from class:ClassVisitor
Visits a permitted subclasses. A permitted subclass is one of the allowed subclasses of the current class.- Overrides:
visitPermittedSubclass
in classClassVisitor
- Parameters:
permittedSubclass
- the internal name of a permitted subclass.
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visitOuterClass
public void visitOuterClass(java.lang.String owner, java.lang.String name, java.lang.String descriptor)
Description copied from class:ClassVisitor
Visits the enclosing class of the class. This method must be called only if the class has an enclosing class.- Overrides:
visitOuterClass
in classClassVisitor
- Parameters:
owner
- internal name of the enclosing class of the class.name
- the name of the method that contains the class, or null if the class is not enclosed in a method of its enclosing class.descriptor
- the descriptor of the method that contains the class, or null if the class is not enclosed in a method of its enclosing class.
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visitInnerClass
public void visitInnerClass(java.lang.String name, java.lang.String outerName, java.lang.String innerName, int access)
Description copied from class:ClassVisitor
Visits information about an inner class. This inner class is not necessarily a member of the class being visited.- Overrides:
visitInnerClass
in classClassVisitor
- Parameters:
name
- the internal name of an inner class (seeType.getInternalName()
).outerName
- the internal name of the class to which the inner class belongs (seeType.getInternalName()
). May be null for not member classes.innerName
- the (simple) name of the inner class inside its enclosing class. May be null for anonymous inner classes.access
- the access flags of the inner class as originally declared in the enclosing class.
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visitRecordComponent
public RecordComponentVisitor visitRecordComponent(java.lang.String name, java.lang.String descriptor, java.lang.String signature)
Description copied from class:ClassVisitor
Visits a record component of the class.- Overrides:
visitRecordComponent
in classClassVisitor
- Parameters:
name
- the record component name.descriptor
- the record component descriptor (seeType
).signature
- the record component signature. May be null if the record component type does not use generic types.- Returns:
- a visitor to visit this record component annotations and attributes, or null if this class visitor is not interested in visiting these annotations and attributes.
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visitField
public FieldVisitor visitField(int access, java.lang.String name, java.lang.String descriptor, java.lang.String signature, java.lang.Object value)
Description copied from class:ClassVisitor
Visits a field of the class.- Overrides:
visitField
in classClassVisitor
- Parameters:
access
- the field's access flags (seeOpcodes
). This parameter also indicates if the field is synthetic and/or deprecated.name
- the field's name.descriptor
- the field's descriptor (seeType
).signature
- the field's signature. May be null if the field's type does not use generic types.value
- the field's initial value. This parameter, which may be null if the field does not have an initial value, must be anInteger
, aFloat
, aLong
, aDouble
or aString
(forint
,float
,long
orString
fields respectively). This parameter is only used for static fields. Its value is ignored for non static fields, which must be initialized through bytecode instructions in constructors or methods.- Returns:
- a visitor to visit field annotations and attributes, or null if this class visitor is not interested in visiting these annotations and attributes.
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visitMethod
public MethodVisitor visitMethod(int access, java.lang.String name, java.lang.String descriptor, java.lang.String signature, java.lang.String[] exceptions)
Description copied from class:ClassVisitor
Visits a method of the class. This method must return a newMethodVisitor
instance (or null) each time it is called, i.e., it should not return a previously returned visitor.- Overrides:
visitMethod
in classClassVisitor
- Parameters:
access
- the method's access flags (seeOpcodes
). This parameter also indicates if the method is synthetic and/or deprecated.name
- the method's name.descriptor
- the method's descriptor (seeType
).signature
- the method's signature. May be null if the method parameters, return type and exceptions do not use generic types.exceptions
- the internal names of the method's exception classes (seeType.getInternalName()
). May be null.- Returns:
- an object to visit the byte code of the method, or null if this class visitor is not interested in visiting the code of this method.
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visitAnnotation
public AnnotationVisitor visitAnnotation(java.lang.String descriptor, boolean visible)
Description copied from class:ClassVisitor
Visits an annotation of the class.- Overrides:
visitAnnotation
in classClassVisitor
- Parameters:
descriptor
- the class descriptor of the annotation class.visible
- true if the annotation is visible at runtime.- Returns:
- a visitor to visit the annotation values, or null if this visitor is not interested in visiting this annotation.
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visitTypeAnnotation
public AnnotationVisitor visitTypeAnnotation(int typeRef, TypePath typePath, java.lang.String descriptor, boolean visible)
Description copied from class:ClassVisitor
Visits an annotation on a type in the class signature.- Overrides:
visitTypeAnnotation
in classClassVisitor
- Parameters:
typeRef
- a reference to the annotated type. The sort of this type reference must beTypeReference.CLASS_TYPE_PARAMETER
,TypeReference.CLASS_TYPE_PARAMETER_BOUND
orTypeReference.CLASS_EXTENDS
. SeeTypeReference
.typePath
- the path to the annotated type argument, wildcard bound, array element type, or static inner type within 'typeRef'. May be null if the annotation targets 'typeRef' as a whole.descriptor
- the class descriptor of the annotation class.visible
- true if the annotation is visible at runtime.- Returns:
- a visitor to visit the annotation values, or null if this visitor is not interested in visiting this annotation.
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visitAttribute
public void visitAttribute(Attribute attribute)
Description copied from class:ClassVisitor
Visits a non standard attribute of the class.- Overrides:
visitAttribute
in classClassVisitor
- Parameters:
attribute
- an attribute.
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visitEnd
public void visitEnd()
Description copied from class:ClassVisitor
Visits the end of the class. This method, which is the last one to be called, is used to inform the visitor that all the fields and methods of the class have been visited.- Overrides:
visitEnd
in classClassVisitor
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checkClassSignature
public static void checkClassSignature(java.lang.String signature)
Checks a class signature.- Parameters:
signature
- a string containing the signature that must be checked.
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checkMethodSignature
public static void checkMethodSignature(java.lang.String signature)
Checks a method signature.- Parameters:
signature
- a string containing the signature that must be checked.
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checkFieldSignature
public static void checkFieldSignature(java.lang.String signature)
Checks a field signature.- Parameters:
signature
- a string containing the signature that must be checked.
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main
public static void main(java.lang.String[] args) throws java.io.IOException
Checks the given class.Usage: CheckClassAdapter <binary class name or class file name>
- Parameters:
args
- the command line arguments.- Throws:
java.io.IOException
- if the class cannot be found, or if an IO exception occurs.
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verify
public static void verify(ClassReader classReader, boolean printResults, java.io.PrintWriter printWriter)
Checks the given class.- Parameters:
classReader
- the class to be checked.printResults
- whether to print the results of the bytecode verification.printWriter
- where the results (or the stack trace in case of error) must be printed.
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verify
public static void verify(ClassReader classReader, java.lang.ClassLoader loader, boolean printResults, java.io.PrintWriter printWriter)
Checks the given class.- Parameters:
classReader
- the class to be checked.loader
- aClassLoader
which will be used to load referenced classes. May be null.printResults
- whether to print the results of the bytecode verification.printWriter
- where the results (or the stack trace in case of error) must be printed.
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