Package org.objectweb.asm.util
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 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 theCheckClassAdapter
. 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 byILOAD 1
instruction at position00071
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 usingSimpleVerifier
.- Author:
- Eric Bruneton
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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 cv, boolean checkDataFlow)
Constructs a newCheckClassAdapter
.CheckClassAdapter(ClassVisitor cv)
Constructs a newCheckClassAdapter
.CheckClassAdapter(ClassVisitor cv, 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(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 classstatic 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.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.
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Constructor Detail
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CheckClassAdapter
public CheckClassAdapter(ClassVisitor cv)
Constructs a newCheckClassAdapter
. Subclasses must not use this constructor. Instead, they must use theCheckClassAdapter(int, ClassVisitor, boolean)
version.- Parameters:
cv
- the class visitor to which this adapter must delegate calls.
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CheckClassAdapter
public CheckClassAdapter(ClassVisitor cv, boolean checkDataFlow)
Constructs a newCheckClassAdapter
. Subclasses must not use this constructor. Instead, they must use theCheckClassAdapter(int, ClassVisitor, boolean)
version.- Parameters:
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 (seeCheckMethodAdapter
). This option requires valid maxLocals and maxStack values.- Throws:
IllegalStateException
- If a subclass calls this constructor.
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CheckClassAdapter
protected CheckClassAdapter(int api, ClassVisitor cv, boolean checkDataFlow)
Constructs a newCheckClassAdapter
.- Parameters:
api
- the ASM API version implemented by this visitor. Must be one ofOpcodes.ASM4
orOpcodes.ASM5
.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 (seeCheckMethodAdapter
). This option requires valid maxLocals and maxStack values.
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Method Detail
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main
public static void main(String[] args) throws Exception
Checks a given class.Usage: CheckClassAdapter <binary class name or class file name>
- Parameters:
args
- the command line arguments.- Throws:
Exception
- if the class cannot be found, or if an IO exception occurs.
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verify
public static void verify(ClassReader cr, ClassLoader loader, boolean dump, PrintWriter pw)
Checks a given class.- Parameters:
cr
- aClassReader
that contains bytecode for the analysis.loader
- aClassLoader
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 printed
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verify
public static void verify(ClassReader cr, boolean dump, PrintWriter pw)
Checks a given class- Parameters:
cr
- aClassReader
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 printed
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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.access
- the class's access flags (seeOpcodes
). This parameter also indicates if the class is deprecated.name
- the internal name of the class (seegetInternalName
).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 (seegetInternalName
). For interfaces, the super class isObject
. May be null, but only for theObject
class.interfaces
- the internal names of the class's interfaces (seegetInternalName
). May be null.
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visitSource
public void visitSource(String file, 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 correspondance between source and compiled elements of the class. May be null.
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visitOuterClass
public void visitOuterClass(String owner, String name, String desc)
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.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.
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visitInnerClass
public void visitInnerClass(String name, String outerName, 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 (seegetInternalName
).outerName
- the internal name of the class to which the inner class belongs (seegetInternalName
). 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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visitField
public FieldVisitor visitField(int access, String name, String desc, 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.desc
- 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
(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.- 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 desc, 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.desc
- 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 (seegetInternalName
). 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(String desc, boolean visible)
Description copied from class:ClassVisitor
Visits an annotation of the class.- Overrides:
visitAnnotation
in classClassVisitor
- Parameters:
desc
- 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 desc, 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 beCLASS_TYPE_PARAMETER
,CLASS_TYPE_PARAMETER_BOUND
orCLASS_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.desc
- 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 attr)
Description copied from class:ClassVisitor
Visits a non standard attribute of the class.- Overrides:
visitAttribute
in classClassVisitor
- Parameters:
attr
- 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(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(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(String signature)
Checks a field signature.- Parameters:
signature
- a string containing the signature that must be checked.
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