Class CheckClassAdapter
ClassVisitor
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 sequence
visitField(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 position 00071
is not initialized, whereas the local variable 2 is
initialized and contains an int value.
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate boolean
Whether the bytecode must be checked with a BasicVerifier.private static final String
The index of the instruction designated by each visited label so far.private String
The common package of all the nest members.private static final String
The help message shown when command line arguments are incorrect.private int
The class version number.private boolean
Whether thevisit(int, int, java.lang.String, java.lang.String, java.lang.String, java.lang.String[])
method has been called.private boolean
Whether thevisitEnd()
method has been called.private boolean
Whether thevisitModule(java.lang.String, int, java.lang.String)
method has been called.private boolean
Whether thevisitNestHost(java.lang.String)
method has been called.private boolean
Whether thevisitOuterClass(java.lang.String, java.lang.String, java.lang.String)
method has been called.private boolean
Whether thevisitSource(java.lang.String, java.lang.String)
method has been called.Fields inherited from class org.objectweb.asm.ClassVisitor
api, cv
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Constructor Summary
ConstructorsModifierConstructorDescriptionprotected
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
Modifier and TypeMethodDescription(package private) static void
checkAccess
(int access, int possibleAccess) Checks that the given access flags do not contain invalid flags.private static int
Checks a single character.static void
checkClassSignature
(String signature) Checks a class signature.private static int
checkClassTypeSignature
(String signature, int startPos) Checks a class type signature.static void
checkFieldSignature
(String signature) Checks a field signature.(package private) static void
checkFullyQualifiedName
(int version, String name, String source) Checks that the given name is a fully qualified name, using dots.private static int
checkJavaTypeSignature
(String signature, int startPos) Checks a Java type signature.private static void
checkMethodAccess
(int version, int access, int possibleAccess) Checks that the given access flags do not contain invalid flags for a method.static void
checkMethodSignature
(String signature) Checks a method signature.private static int
checkReferenceTypeSignature
(String signature, int pos) Checks a reference type signature.private static int
checkSignatureIdentifier
(String signature, int startPos) Checks an identifier.private void
Checks that the visit method has been called and that visitEnd has not been called.private static int
checkTypeArgument
(String signature, int startPos) Checks a type argument in a class type signature.private static int
checkTypeArguments
(String signature, int startPos) Checks the type arguments in a class type signature.private static int
checkTypeParameter
(String signature, int startPos) Checks a type parameter of a class or method signature.private static int
checkTypeParameters
(String signature, int startPos) Checks the type parameters of a class or method signature.(package private) static void
checkTypeRef
(int typeRef) Checks the reference to a type in a type annotation.private static int
checkTypeVariableSignature
(String signature, int startPos) Checks a type variable signature.private static char
Returns the string character at the given index, or 0.private static String
getUnqualifiedName
(String name) static void
Checks the given class.(package private) static void
main
(String[] args, PrintWriter logger) Checks the given class.private static String
packageName
(String name) Returns the package name of an internal name.(package private) static void
printAnalyzerResult
(MethodNode method, Analyzer<BasicValue> analyzer, PrintWriter printWriter) static void
verify
(ClassReader classReader, boolean printResults, PrintWriter printWriter) Checks the given class.static void
verify
(ClassReader classReader, ClassLoader loader, boolean printResults, PrintWriter printWriter) Checks the given class.void
visit
(int version, int access, String name, String signature, String superName, String[] interfaces) Visits the header of the class.visitAnnotation
(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.visitField
(int access, String name, String descriptor, String signature, Object value) Visits a field of the class.void
visitInnerClass
(String name, String outerName, String innerName, int access) Visits information about an inner class.visitMethod
(int access, String name, String descriptor, String signature, String[] exceptions) Visits a method of the class.visitModule
(String name, int access, String version) Visit the module corresponding to the class.void
visitNestHost
(String nestHost) Visits the nest host class of the class.void
visitNestMember
(String nestMember) Visits a member of the nest.void
visitOuterClass
(String owner, String name, String descriptor) Visits the enclosing class of the class.void
visitPermittedSubclass
(String permittedSubclass) Visits a permitted subclasses.visitRecordComponent
(String name, String descriptor, String signature) Visits a record component of the class.void
visitSource
(String file, String debug) Visits the source of the class.visitTypeAnnotation
(int typeRef, TypePath typePath, String descriptor, boolean visible) Visits an annotation on a type in the class signature.
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Field Details
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USAGE
The help message shown when command line arguments are incorrect.- See Also:
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ERROR_AT
- See Also:
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checkDataFlow
private boolean checkDataFlowWhether the bytecode must be checked with a BasicVerifier. -
version
private int versionThe class version number. -
visitCalled
private boolean visitCalledWhether thevisit(int, int, java.lang.String, java.lang.String, java.lang.String, java.lang.String[])
method has been called. -
visitModuleCalled
private boolean visitModuleCalledWhether thevisitModule(java.lang.String, int, java.lang.String)
method has been called. -
visitSourceCalled
private boolean visitSourceCalledWhether thevisitSource(java.lang.String, java.lang.String)
method has been called. -
visitOuterClassCalled
private boolean visitOuterClassCalledWhether thevisitOuterClass(java.lang.String, java.lang.String, java.lang.String)
method has been called. -
visitNestHostCalled
private boolean visitNestHostCalledWhether thevisitNestHost(java.lang.String)
method has been called. -
nestMemberPackageName
The common package of all the nest members. Not null if the visitNestMember method has been called. -
visitEndCalled
private boolean visitEndCalledWhether thevisitEnd()
method has been called. -
labelInsnIndices
The index of the instruction designated by each visited label so far.
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Constructor Details
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CheckClassAdapter
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
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:
IllegalStateException
- If a subclass calls this constructor.
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CheckClassAdapter
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 Details
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visit
public void visit(int version, int access, String name, String signature, String superName, 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
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
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
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
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
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
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
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(String name, String descriptor, 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, String name, String descriptor, String signature, 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, String name, String descriptor, String signature, 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
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, 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
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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checkState
private void checkState()Checks that the visit method has been called and that visitEnd has not been called. -
checkAccess
static void checkAccess(int access, int possibleAccess) Checks that the given access flags do not contain invalid flags. This method also checks that mutually incompatible flags are not set simultaneously.- Parameters:
access
- the access flags to be checked.possibleAccess
- the valid access flags.
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checkMethodAccess
private static void checkMethodAccess(int version, int access, int possibleAccess) Checks that the given access flags do not contain invalid flags for a method. This method also checks that mutually incompatible flags are not set simultaneously.- Parameters:
version
- the class version.access
- the method access flags to be checked.possibleAccess
- the valid access flags.
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checkFullyQualifiedName
Checks that the given name is a fully qualified name, using dots.- Parameters:
version
- the class version.name
- the name to be checked.source
- the source of 'name' (e.g 'module' for a module name).
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checkClassSignature
Checks a class signature.- Parameters:
signature
- a string containing the signature that must be checked.
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checkMethodSignature
Checks a method signature.- Parameters:
signature
- a string containing the signature that must be checked.
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checkFieldSignature
Checks a field signature.- Parameters:
signature
- a string containing the signature that must be checked.
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checkTypeParameters
Checks the type parameters of a class or method signature.- Parameters:
signature
- a string containing the signature that must be checked.startPos
- index of first character to be checked.- Returns:
- the index of the first character after the checked part.
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checkTypeParameter
Checks a type parameter of a class or method signature.- Parameters:
signature
- a string containing the signature that must be checked.startPos
- index of first character to be checked.- Returns:
- the index of the first character after the checked part.
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checkReferenceTypeSignature
Checks a reference type signature.- Parameters:
signature
- a string containing the signature that must be checked.pos
- index of first character to be checked.- Returns:
- the index of the first character after the checked part.
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checkClassTypeSignature
Checks a class type signature.- Parameters:
signature
- a string containing the signature that must be checked.startPos
- index of first character to be checked.- Returns:
- the index of the first character after the checked part.
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checkTypeArguments
Checks the type arguments in a class type signature.- Parameters:
signature
- a string containing the signature that must be checked.startPos
- index of first character to be checked.- Returns:
- the index of the first character after the checked part.
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checkTypeArgument
Checks a type argument in a class type signature.- Parameters:
signature
- a string containing the signature that must be checked.startPos
- index of first character to be checked.- Returns:
- the index of the first character after the checked part.
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checkTypeVariableSignature
Checks a type variable signature.- Parameters:
signature
- a string containing the signature that must be checked.startPos
- index of first character to be checked.- Returns:
- the index of the first character after the checked part.
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checkJavaTypeSignature
Checks a Java type signature.- Parameters:
signature
- a string containing the signature that must be checked.startPos
- index of first character to be checked.- Returns:
- the index of the first character after the checked part.
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checkSignatureIdentifier
Checks an identifier.- Parameters:
signature
- a string containing the signature that must be checked.startPos
- index of first character to be checked.- Returns:
- the index of the first character after the checked part.
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checkChar
Checks a single character.- Parameters:
c
- a character.signature
- a string containing the signature that must be checked.pos
- index of first character to be checked.- Returns:
- the index of the first character after the checked part.
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getChar
Returns the string character at the given index, or 0.- Parameters:
string
- a string.pos
- an index in 'string'.- Returns:
- the character at the given index, or 0 if there is no such character.
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checkTypeRef
static void checkTypeRef(int typeRef) Checks the reference to a type in a type annotation.- Parameters:
typeRef
- a reference to an annotated type.
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packageName
Returns the package name of an internal name.- Parameters:
name
- an internal name.- Returns:
- the package name or "" if there is no package.
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main
Checks the given class.Usage: CheckClassAdapter <binary class name or class file name>
- Parameters:
args
- the command line arguments.- Throws:
IOException
- if the class cannot be found, or if an IO exception occurs.
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main
Checks the given class.- Parameters:
args
- the command line arguments.logger
- where to log errors.- Throws:
IOException
- if the class cannot be found, or if an IO exception occurs.
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verify
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, ClassLoader loader, boolean printResults, 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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printAnalyzerResult
static void printAnalyzerResult(MethodNode method, Analyzer<BasicValue> analyzer, PrintWriter printWriter) -
getUnqualifiedName
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