public class CheckClassAdapter extends ClassVisitor
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 transformed bytecode is sane. For
example:
InputStream is = ...; // get bytes for the source class ClassReader cr = new ClassReader(is); ClassWriter cw = new ClassWriter(cr, ClassWriter.COMPUTE_MAXS); ClassVisitor cv = new MyClassAdapter(new CheckClassAdapter(cw)); cr.accept(cv, 0); StringWriter sw = new StringWriter(); PrintWriter pw = new PrintWriter(sw); CheckClassAdapter.verify(new ClassReader(cw.toByteArray()), false, pw); assertTrue(sw.toString(), sw.toString().length()==0);Above code runs transformed bytecode trough the
CheckClassAdapter
. It won't be exactly the same verification as
JVM does, but it run data flow analysis for the code of each method and
checks that expectations are met for each method instruction.
If method bytecode has errors, assertion text will show the erroneous instruction number and dump of the failed method with information about locals and stack slot 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:289) at org.objectweb.asm.util.CheckClassAdapter.verify(CheckClassAdapter.java:135) ... 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 ...In the above output you can see that variable 1 loaded by
ILOAD 1
instruction at position 00071
is not
initialized. You can also see that at the beginning of the method (code
inserted by the transformation) variable 2 is initialized.
Note that when used like that, CheckClassAdapter.verify()
can
trigger additional class loading, because it is using
SimpleVerifier
.
api, cv
Modifier | Constructor and Description |
---|---|
|
CheckClassAdapter(ClassVisitor cv)
Constructs a new
CheckClassAdapter . |
|
CheckClassAdapter(ClassVisitor cv,
boolean checkDataFlow)
Constructs a new
CheckClassAdapter . |
protected |
CheckClassAdapter(int api,
ClassVisitor cv,
boolean checkDataFlow)
Constructs a new
CheckClassAdapter . |
Modifier and Type | Method and Description |
---|---|
static void |
checkClassSignature(String signature)
Checks a class signature.
|
static void |
checkFieldSignature(String signature)
Checks a field signature.
|
static void |
checkMethodSignature(String signature)
Checks a method signature.
|
static void |
main(String[] args)
Checks a given class.
|
static void |
verify(ClassReader cr,
boolean dump,
PrintWriter pw)
Checks a given class
|
static void |
verify(ClassReader cr,
ClassLoader loader,
boolean dump,
PrintWriter pw)
Checks a given class.
|
void |
visit(int version,
int access,
String name,
String signature,
String superName,
String[] interfaces)
Visits the header of the class.
|
AnnotationVisitor |
visitAnnotation(String desc,
boolean visible)
Visits an annotation of the class.
|
void |
visitAttribute(Attribute attr)
Visits a non standard attribute of the class.
|
void |
visitEnd()
Visits the end of the class.
|
FieldVisitor |
visitField(int access,
String name,
String desc,
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.
|
MethodVisitor |
visitMethod(int access,
String name,
String desc,
String signature,
String[] exceptions)
Visits a method of the class.
|
ModuleVisitor |
visitModule()
Visit the module corresponding to the class.
|
void |
visitOuterClass(String owner,
String name,
String desc)
Visits the enclosing class of the class.
|
void |
visitSource(String file,
String debug)
Visits the source of the class.
|
AnnotationVisitor |
visitTypeAnnotation(int typeRef,
TypePath typePath,
String desc,
boolean visible)
Visits an annotation on a type in the class signature.
|
public CheckClassAdapter(ClassVisitor cv)
CheckClassAdapter
. Subclasses must not use
this constructor. Instead, they must use the
CheckClassAdapter(int, ClassVisitor, boolean)
version.cv
- the class visitor to which this adapter must delegate calls.public CheckClassAdapter(ClassVisitor cv, boolean checkDataFlow)
CheckClassAdapter
. Subclasses must not use
this constructor. Instead, they must use the
CheckClassAdapter(int, ClassVisitor, boolean)
version.cv
- 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 (see
CheckMethodAdapter
). This option requires valid
maxLocals and maxStack values.IllegalStateException
- If a subclass calls this constructor.protected CheckClassAdapter(int api, ClassVisitor cv, boolean checkDataFlow)
CheckClassAdapter
.api
- the ASM API version implemented by this visitor. Must be one
of Opcodes.ASM4
, Opcodes.ASM5
or Opcodes.ASM6
.cv
- 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 (see
CheckMethodAdapter
). This option requires valid
maxLocals and maxStack values.public static void main(String[] args) throws Exception
Usage: CheckClassAdapter <binary class name or class file name>
args
- the command line arguments.Exception
- if the class cannot be found, or if an IO exception occurs.public static void verify(ClassReader cr, ClassLoader loader, boolean dump, PrintWriter pw)
cr
- a ClassReader
that contains bytecode for the
analysis.loader
- a ClassLoader
which will be used to load
referenced classes. This is useful if you are verifiying
multiple interdependent classes.dump
- true if bytecode should be printed out not only when errors
are found.pw
- write where results going to be printedpublic static void verify(ClassReader cr, boolean dump, PrintWriter pw)
cr
- a ClassReader
that contains bytecode for the
analysis.dump
- true if bytecode should be printed out not only when errors
are found.pw
- write where results going to be printedpublic void visit(int version, int access, String name, String signature, String superName, String[] interfaces)
ClassVisitor
visit
in class ClassVisitor
version
- the class version.access
- the class's access flags (see Opcodes
). This parameter
also indicates if the class is deprecated.name
- the internal name of the class (see
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 (see
getInternalName
). For
interfaces, the super class is Object
. May be
null, but only for the Object
class.interfaces
- the internal names of the class's interfaces (see
getInternalName
). May be
null.public void visitSource(String file, String debug)
ClassVisitor
visitSource
in class ClassVisitor
file
- the name of the source file from which the class was compiled.
May be null.debug
- additional debug information to compute the correspondance
between source and compiled elements of the class. May be
null.public ModuleVisitor visitModule()
ClassVisitor
visitModule
in class ClassVisitor
public void visitOuterClass(String owner, String name, String desc)
ClassVisitor
visitOuterClass
in class ClassVisitor
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.desc
- the descriptor of the method that contains the class, or
null if the class is not enclosed in a method of its
enclosing class.public void visitInnerClass(String name, String outerName, String innerName, int access)
ClassVisitor
visitInnerClass
in class ClassVisitor
name
- the internal name of an inner class (see
getInternalName
).outerName
- the internal name of the class to which the inner class
belongs (see 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.public FieldVisitor visitField(int access, String name, String desc, String signature, Object value)
ClassVisitor
visitField
in class ClassVisitor
access
- the field's access flags (see Opcodes
). This parameter
also indicates if the field is synthetic and/or deprecated.name
- the field's name.desc
- the field's descriptor (see Type
).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 an Integer
, a Float
, a Long
, a
Double
or a String
(for int,
float, long or String 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.public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions)
ClassVisitor
MethodVisitor
instance (or null) each time it is called,
i.e., it should not return a previously returned visitor.visitMethod
in class ClassVisitor
access
- the method's access flags (see Opcodes
). This
parameter also indicates if the method is synthetic and/or
deprecated.name
- the method's name.desc
- the method's descriptor (see Type
).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 (see
getInternalName
). May be
null.public AnnotationVisitor visitAnnotation(String desc, boolean visible)
ClassVisitor
visitAnnotation
in class ClassVisitor
desc
- the class descriptor of the annotation class.visible
- true if the annotation is visible at runtime.public AnnotationVisitor visitTypeAnnotation(int typeRef, TypePath typePath, String desc, boolean visible)
ClassVisitor
visitTypeAnnotation
in class ClassVisitor
typeRef
- a reference to the annotated type. The sort of this type
reference must be CLASS_TYPE_PARAMETER
,
CLASS_TYPE_PARAMETER_BOUND
or
CLASS_EXTENDS
. See
TypeReference
.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.desc
- the class descriptor of the annotation class.visible
- true if the annotation is visible at runtime.public void visitAttribute(Attribute attr)
ClassVisitor
visitAttribute
in class ClassVisitor
attr
- an attribute.public void visitEnd()
ClassVisitor
visitEnd
in class ClassVisitor
public static void checkClassSignature(String signature)
signature
- a string containing the signature that must be checked.public static void checkMethodSignature(String signature)
signature
- a string containing the signature that must be checked.public static void checkFieldSignature(String signature)
signature
- a string containing the signature that must be checked.