Package org.objectweb.asm.util

Class CheckClassAdapter

  • public class CheckClassAdapter
extends org.objectweb.asm.ClassVisitor
    A 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.

    • Field Summary

      • Fields inherited from class org.objectweb.asm.ClassVisitor

        api, cv

    • 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​(org.objectweb.asm.ClassReader classReader, boolean printResults, java.io.PrintWriter printWriter)
      Checks the given class.
      static void verify​(org.objectweb.asm.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)  
      org.objectweb.asm.AnnotationVisitor visitAnnotation​(java.lang.String descriptor, boolean visible)  
      void visitAttribute​(org.objectweb.asm.Attribute attribute)  
      void visitEnd()  
      org.objectweb.asm.FieldVisitor visitField​(int access, java.lang.String name, java.lang.String descriptor, java.lang.String signature, java.lang.Object value)  
      void visitInnerClass​(java.lang.String name, java.lang.String outerName, java.lang.String innerName, int access)  
      org.objectweb.asm.MethodVisitor visitMethod​(int access, java.lang.String name, java.lang.String descriptor, java.lang.String signature, java.lang.String[] exceptions)  
      org.objectweb.asm.ModuleVisitor visitModule​(java.lang.String name, int access, java.lang.String version)  
      void visitNestHost​(java.lang.String nestHost)  
      void visitNestMember​(java.lang.String nestMember)  
      void visitOuterClass​(java.lang.String owner, java.lang.String name, java.lang.String descriptor)  
      void visitPermittedSubclass​(java.lang.String permittedSubclass)  
      org.objectweb.asm.RecordComponentVisitor visitRecordComponent​(java.lang.String name, java.lang.String descriptor, java.lang.String signature)  
      void visitSource​(java.lang.String file, java.lang.String debug)  
      org.objectweb.asm.AnnotationVisitor visitTypeAnnotation​(int typeRef, org.objectweb.asm.TypePath typePath, java.lang.String descriptor, boolean visible)  

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • CheckClassAdapter

        public CheckClassAdapter​(org.objectweb.asm.ClassVisitor classVisitor)
        Constructs a new CheckClassAdapter. Subclasses must not use this constructor. Instead, they must use the CheckClassAdapter(int, ClassVisitor, boolean) version.
        Parameters:
        classVisitor - the class visitor to which this adapter must delegate calls.

      • CheckClassAdapter

        public CheckClassAdapter​(org.objectweb.asm.ClassVisitor classVisitor,
                         boolean checkDataFlow)
        Constructs a new CheckClassAdapter. Subclasses must not use this constructor. Instead, they must use the CheckClassAdapter(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.

      • CheckClassAdapter

        protected CheckClassAdapter​(int api,
                            org.objectweb.asm.ClassVisitor classVisitor,
                            boolean checkDataFlow)
        Constructs a new CheckClassAdapter.
        Parameters:
        api - the ASM API version implemented by this visitor. Must be one of the ASMx values in Opcodes.
        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 (see CheckMethodAdapter).

    • Method Detail

      • visit

        public void visit​(int version,
                  int access,
                  java.lang.String name,
                  java.lang.String signature,
                  java.lang.String superName,
                  java.lang.String[] interfaces)
        Overrides:
        visit in class org.objectweb.asm.ClassVisitor

      • visitSource

        public void visitSource​(java.lang.String file,
                        java.lang.String debug)
        Overrides:
        visitSource in class org.objectweb.asm.ClassVisitor

      • visitModule

        public org.objectweb.asm.ModuleVisitor visitModule​(java.lang.String name,
                                                   int access,
                                                   java.lang.String version)
        Overrides:
        visitModule in class org.objectweb.asm.ClassVisitor

      • visitNestHost

        public void visitNestHost​(java.lang.String nestHost)
        Overrides:
        visitNestHost in class org.objectweb.asm.ClassVisitor

      • visitNestMember

        public void visitNestMember​(java.lang.String nestMember)
        Overrides:
        visitNestMember in class org.objectweb.asm.ClassVisitor

      • visitPermittedSubclass

        public void visitPermittedSubclass​(java.lang.String permittedSubclass)
        Overrides:
        visitPermittedSubclass in class org.objectweb.asm.ClassVisitor

      • visitOuterClass

        public void visitOuterClass​(java.lang.String owner,
                            java.lang.String name,
                            java.lang.String descriptor)
        Overrides:
        visitOuterClass in class org.objectweb.asm.ClassVisitor

      • visitInnerClass

        public void visitInnerClass​(java.lang.String name,
                            java.lang.String outerName,
                            java.lang.String innerName,
                            int access)
        Overrides:
        visitInnerClass in class org.objectweb.asm.ClassVisitor

      • visitRecordComponent

        public org.objectweb.asm.RecordComponentVisitor visitRecordComponent​(java.lang.String name,
                                                                     java.lang.String descriptor,
                                                                     java.lang.String signature)
        Overrides:
        visitRecordComponent in class org.objectweb.asm.ClassVisitor

      • visitField

        public org.objectweb.asm.FieldVisitor visitField​(int access,
                                                 java.lang.String name,
                                                 java.lang.String descriptor,
                                                 java.lang.String signature,
                                                 java.lang.Object value)
        Overrides:
        visitField in class org.objectweb.asm.ClassVisitor

      • visitMethod

        public org.objectweb.asm.MethodVisitor visitMethod​(int access,
                                                   java.lang.String name,
                                                   java.lang.String descriptor,
                                                   java.lang.String signature,
                                                   java.lang.String[] exceptions)
        Overrides:
        visitMethod in class org.objectweb.asm.ClassVisitor

      • visitAnnotation

        public org.objectweb.asm.AnnotationVisitor visitAnnotation​(java.lang.String descriptor,
                                                           boolean visible)
        Overrides:
        visitAnnotation in class org.objectweb.asm.ClassVisitor

      • visitTypeAnnotation

        public org.objectweb.asm.AnnotationVisitor visitTypeAnnotation​(int typeRef,
                                                               org.objectweb.asm.TypePath typePath,
                                                               java.lang.String descriptor,
                                                               boolean visible)
        Overrides:
        visitTypeAnnotation in class org.objectweb.asm.ClassVisitor

      • visitAttribute

        public void visitAttribute​(org.objectweb.asm.Attribute attribute)
        Overrides:
        visitAttribute in class org.objectweb.asm.ClassVisitor

      • visitEnd

        public void visitEnd()
        Overrides:
        visitEnd in class org.objectweb.asm.ClassVisitor

      • checkClassSignature

        public static void checkClassSignature​(java.lang.String signature)
        Checks a class signature.
        Parameters:
        signature - a string containing the signature that must be checked.

      • checkMethodSignature

        public static void checkMethodSignature​(java.lang.String signature)
        Checks a method signature.
        Parameters:
        signature - a string containing the signature that must be checked.

      • checkFieldSignature

        public static void checkFieldSignature​(java.lang.String signature)
        Checks a field signature.
        Parameters:
        signature - a string containing the signature that must be checked.

      • 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.

      • verify

        public static void verify​(org.objectweb.asm.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.

      • verify

        public static void verify​(org.objectweb.asm.ClassReader classReader,
                          java.lang.ClassLoader loader,
                          boolean printResults,
                          java.io.PrintWriter printWriter)
        Checks the given class.
        Parameters:
        classReader - the class to be checked.
        loader - a ClassLoader 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.