org.objectweb.asm.util

Class TraceClassVisitor

Implemented Interfaces:
ClassVisitor

public class TraceClassVisitor
extends TraceAbstractVisitor
implements ClassVisitor

A ClassVisitor that prints a disassembled view of the classes it visits. This class visitor can be used alone (see the main method) to disassemble a class. It can also be used in the middle of class visitor chain to trace the class that is visited at a given point in this chain. This may be uselful for debugging purposes.

The trace printed when visiting the Hello class is the following:

 // class version 49.0 (49)
 // access flags 33
 public class Hello {

  // compiled from: Hello.java

   // access flags 1
   public <init> ()V
     ALOAD 0
     INVOKESPECIAL java/lang/Object <init> ()V
     RETURN
     MAXSTACK = 1
     MAXLOCALS = 1

   // access flags 9
   public static main ([Ljava/lang/String;)V
     GETSTATIC java/lang/System out Ljava/io/PrintStream;
     LDC "hello"
     INVOKEVIRTUAL java/io/PrintStream println (Ljava/lang/String;)V
     RETURN
     MAXSTACK = 2
     MAXLOCALS = 1
 }
 
where Hello is defined by:

 public class Hello {

     public static void main(String[] args) {
         System.out.println("hello");
     }
 }
 
Authors:
Eric Bruneton
Eugene Kuleshov

Field Summary

protected ClassVisitor
cv
The ClassVisitor to which this visitor delegates calls.
protected PrintWriter
pw
The print writer to be used to print the class.

Fields inherited from class org.objectweb.asm.util.TraceAbstractVisitor

CLASS_DECLARATION, CLASS_SIGNATURE, FIELD_DESCRIPTOR, FIELD_SIGNATURE, INTERNAL_NAME, METHOD_DESCRIPTOR, METHOD_SIGNATURE, PARAMETERS_DECLARATION, TYPE_DECLARATION, tab

Fields inherited from class org.objectweb.asm.util.AbstractVisitor

OPCODES, TYPES, buf, text

Constructor Summary

TraceClassVisitor(PrintWriter pw)
Constructs a new TraceClassVisitor.
TraceClassVisitor(ClassVisitor cv, PrintWriter pw)
Constructs a new TraceClassVisitor.

Method Summary

protected TraceFieldVisitor
createTraceFieldVisitor()
protected TraceMethodVisitor
createTraceMethodVisitor()
static void
main(String[] args)
Prints a disassembled view of the given class to the standard output.
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 org.objectweb.asm.util.TraceAbstractVisitor

appendDescriptor, createTraceAnnotationVisitor, visitAnnotation, visitAttribute, visitEnd

Methods inherited from class org.objectweb.asm.util.AbstractVisitor

appendString, getDefaultAttributes, getText, print

Field Details

cv

protected final ClassVisitor cv
The ClassVisitor to which this visitor delegates calls. May be null.

pw

protected final PrintWriter pw
The print writer to be used to print the class.

Constructor Details

TraceClassVisitor

public TraceClassVisitor(PrintWriter pw)
Parameters:
pw - the print writer to be used to print the class.

TraceClassVisitor

public TraceClassVisitor(ClassVisitor cv,
                         PrintWriter pw)
Constructs a new TraceClassVisitor.
Parameters:
cv - the ClassVisitor to which this visitor delegates calls. May be null.
pw - the print writer to be used to print the class.

Method Details

createTraceFieldVisitor

protected TraceFieldVisitor createTraceFieldVisitor()

createTraceMethodVisitor

protected TraceMethodVisitor createTraceMethodVisitor()

main

public static void main(String[] args)
            throws Exception
Prints a disassembled view of the given class to the standard output.

Usage: TraceClassVisitor [-debug] <fully qualified class name or class file name >

Parameters:
args - the command line arguments.

visit

public void visit(int version,
                  int access,
                  String name,
                  String signature,
                  String superName,
                  String[] interfaces)
Visits the header of the class.
Specified by:
visit in interface ClassVisitor
Parameters:
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.

visitAnnotation

public AnnotationVisitor visitAnnotation(String desc,
                                         boolean visible)
Visits an annotation of the class.
Specified by:
visitAnnotation in interface ClassVisitor
Overrides:
visitAnnotation in interface TraceAbstractVisitor
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.

visitAttribute

public void visitAttribute(Attribute attr)
Visits a non standard attribute of the class.
Specified by:
visitAttribute in interface ClassVisitor
Overrides:
visitAttribute in interface TraceAbstractVisitor
Parameters:
attr - an attribute.

visitEnd

public void visitEnd()
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.
Specified by:
visitEnd in interface ClassVisitor
Overrides:
visitEnd in interface TraceAbstractVisitor

visitField

public FieldVisitor visitField(int access,
                               String name,
                               String desc,
                               String signature,
                               Object value)
Visits a field of the class.
Specified by:
visitField in interface ClassVisitor
Parameters:
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.
Returns:
a visitor to visit field annotations and attributes, or null if this class visitor is not interested in visiting these annotations and attributes.

visitInnerClass

public void visitInnerClass(String name,
                            String outerName,
                            String innerName,
                            int access)
Visits information about an inner class. This inner class is not necessarily a member of the class being visited.
Specified by:
visitInnerClass in interface ClassVisitor
Parameters:
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.

visitMethod

public MethodVisitor visitMethod(int access,
                                 String name,
                                 String desc,
                                 String signature,
                                 String[] exceptions)
Visits a method of the class. This method must return a new MethodVisitor instance (or null) each time it is called, i.e., it should not return a previously returned visitor.
Specified by:
visitMethod in interface ClassVisitor
Parameters:
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.
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.

visitOuterClass

public void visitOuterClass(String owner,
                            String name,
                            String desc)
Visits the enclosing class of the class. This method must be called only if the class has an enclosing class.
Specified by:
visitOuterClass in interface ClassVisitor
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.

visitSource

public void visitSource(String file,
                        String debug)
Visits the source of the class.
Specified by:
visitSource in interface ClassVisitor
Parameters:
debug - additional debug information to compute the correspondance between source and compiled elements of the class. May be null.