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java.lang.Objectorg.objectweb.asm.ClassAdapter
org.objectweb.asm.util.CheckClassAdapter
A ClassAdapter
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.In the above output you can see that variable 1 loaded by(I)V ...
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
.
Field Summary |
Fields inherited from class org.objectweb.asm.ClassAdapter |
cv |
Constructor Summary | |
CheckClassAdapter(ClassVisitor cv)
Constructs a new CheckClassAdapter . |
Method Summary | |
static void |
main(String[] args)
Checks a given class. |
static void |
verify(ClassReader cr,
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. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public CheckClassAdapter(ClassVisitor cv)
CheckClassAdapter
.
cv
- the class visitor to which this adapter must delegate calls.Method Detail |
public static void main(String[] args) throws Exception
Usage: CheckClassAdapter <fully qualified 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, 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 interface ClassVisitor
visit
in class ClassAdapter
public void visitSource(String file, String debug)
ClassVisitor
visitSource
in interface ClassVisitor
visitSource
in class ClassAdapter
public void visitOuterClass(String owner, String name, String desc)
ClassVisitor
visitOuterClass
in interface ClassVisitor
visitOuterClass
in class ClassAdapter
public void visitInnerClass(String name, String outerName, String innerName, int access)
ClassVisitor
visitInnerClass
in interface ClassVisitor
visitInnerClass
in class ClassAdapter
public FieldVisitor visitField(int access, String name, String desc, String signature, Object value)
ClassVisitor
visitField
in interface ClassVisitor
visitField
in class ClassAdapter
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 interface ClassVisitor
visitMethod
in class ClassAdapter
public AnnotationVisitor visitAnnotation(String desc, boolean visible)
ClassVisitor
visitAnnotation
in interface ClassVisitor
visitAnnotation
in class ClassAdapter
public void visitAttribute(Attribute attr)
ClassVisitor
visitAttribute
in interface ClassVisitor
visitAttribute
in class ClassAdapter
public void visitEnd()
ClassVisitor
visitEnd
in interface ClassVisitor
visitEnd
in class ClassAdapter
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