org.objectweb.asm.util
Class DumpClassVisitor
java.lang.Object
|
+--org.objectweb.asm.util.PrintClassVisitor
|
+--org.objectweb.asm.util.DumpClassVisitor
- All Implemented Interfaces:
- ClassVisitor
- public class DumpClassVisitor
- extends PrintClassVisitor
A PrintClassVisitor
that prints the ASM code that
generates the classes it visits. This class visitor can be used to quickly
write ASM code to generate some given bytecode:
- write the Java source code equivalent to the bytecode you want to
generate;
- compile it with javac;
- make a
DumpClassVisitor
visit this compiled
class (see the main
method);
- edit the generated source code, if necessary.
The source code printed when visiting the Hello class is the
following:
import org.objectweb.asm.*;
import java.io.FileOutputStream;
public class Dump implements Constants {
public static void main (String[] args) throws Exception {
ClassWriter cw = new ClassWriter(false);
CodeVisitor cv;
cw.visit(ACC_PUBLIC + ACC_SUPER, "Hello", "java/lang/Object", null, "Hello.java");
{
cv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "main", "([Ljava/lang/String;)V", null);
cv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
cv.visitLdcInsn("hello");
cv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V");
cv.visitInsn(RETURN);
cv.visitMaxs(2, 1);
}
{
cv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null);
cv.visitVarInsn(ALOAD, 0);
cv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V");
cv.visitInsn(RETURN);
cv.visitMaxs(1, 1);
}
cw.visitEnd();
FileOutputStream os = new FileOutputStream("Dumped.class");
os.write(cw.toByteArray());
os.close();
}
}
where Hello is defined by:
public class Hello {
public static void main (String[] args) {
System.out.println("hello");
}
}
Method Summary |
static void |
main(String[] args)
Prints the ASM source code to generate the given class to the standard
output.
|
PrintCodeVisitor |
printMethod(int access,
String name,
String desc,
String[] exceptions)
|
void |
visit(int access,
String name,
String superName,
String[] interfaces,
String sourceFile)
Visits the header of the class. |
void |
visitEnd()
Visits the end of the class. |
void |
visitField(int access,
String name,
String desc,
Object value)
Visits a field of the class. |
void |
visitInnerClass(String name,
String outerName,
String innerName,
int access)
Visits information about an inner class. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
DumpClassVisitor
public DumpClassVisitor(PrintWriter pw)
- Constructs a new
DumpClassVisitor
object.
- Parameters:
pw
- the print writer to be used to print the trace.
main
public static void main(String[] args)
throws Exception
- Prints the ASM source code to generate the given class to the standard
output.
Usage: DumpClassVisitor <fully qualified class name>
visit
public void visit(int access,
String name,
String superName,
String[] interfaces,
String sourceFile)
- Description copied from interface:
ClassVisitor
- Visits the header of the class.
- Following copied from interface:
org.objectweb.asm.ClassVisitor
- Parameters:
access
- the class's access flags (see Constants
). This
parameter also indicates if the class is deprecated.name
- the internal name of the class (see getInternalName
).superName
- the internal of name of the super class (see getInternalName
). For interfaces, the super
class is Object
.interfaces
- the internal names of the class's interfaces (see getInternalName
). May be null.sourceFile
- the name of the source file from which this class was
compiled. May be null.
visitInnerClass
public void visitInnerClass(String name,
String outerName,
String innerName,
int access)
- Description copied from interface:
ClassVisitor
- Visits information about an inner class. This inner class is not
necessarily a member of the class being visited.
- Following copied from interface:
org.objectweb.asm.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.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.
visitField
public void visitField(int access,
String name,
String desc,
Object value)
- Description copied from interface:
ClassVisitor
- Visits a field of the class.
- Following copied from interface:
org.objectweb.asm.ClassVisitor
- Parameters:
access
- the field's access flags (see Constants
). This
parameter also indicates if the field is synthetic and/or deprecated.name
- the field's name.desc
- the field's descriptor (see Type
).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
.
printMethod
public PrintCodeVisitor printMethod(int access,
String name,
String desc,
String[] exceptions)
- Overrides:
printMethod
in class PrintClassVisitor
visitEnd
public void visitEnd()
- Description copied from interface:
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 class PrintClassVisitor