ASM - How can I convert Java class name from Java bytecode name?

Question

I'm using ASM (a bytecode modification library) and it provides access to type names in the bytecode naming format, for example a String field is reported to have the description: Ljava/lang/String

I need to invoke Class.forName for some classes, but I need the source code form of the type names for that, e.g. java.lang.String.

Is there a way of converting from internal name to Java source format?

Haozhun · Accepted Answer · 2015-09-16 17:58:55Z

8

I don't know any API method, but the conversion is quite simple. You cand find details in JVM spec here. Primitive types are represented by one character:

B = byte
C = char
D = double
F = float
I = int
J = long
S = short
Z = boolean

Class and interface types are represented by the fully qualified name, with an 'L' prefix and a ';' suffix. The dots '.' in the fully qualified class name are replaced by '/' (for inner classes, the '.' separating the outer class name from the inner class name is replaced by a '$'). So the internal name of the String class would be "Ljava/lang/String;" and the internal name of the inner class "java.awt.geom.Arc2D.Float" would be "Ljava/awt/geom/Arc2D$Float;".

Array names begin with an opening bracket '[' followed by the component type name (primitive or reference). An "int[]" thus becomes "[I" and a "javax.swing.JFrame[][]" becomes "[[Ljavax.swing.JFrame;".

edited Sep 16, 2015 at 17:58

Haozhun

6,5313 gold badges32 silver badges51 bronze badges

answered Jul 22, 2011 at 13:22

zacheusz

8,8604 gold badges39 silver badges61 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Perception Over a year ago

With the caveat that you cannot actually instantiate an inner class dynamically using its FQN. You need to use the same name as would be returned by Class.getName() instead - in this case java.awt.geom.Arc2D$Float.

mahonya Over a year ago

Thanks, I was hoping for some api, but I'll do it manually in this case.

Chandra Sekhar K · Accepted Answer · 2012-05-15 02:32:08Z

1

You can use org.objectweb.asm.Type.getInternalName(java.lang.Class).

edited May 15, 2012 at 2:32

Chandra Sekhar K

16.6k11 gold badges71 silver badges91 bronze badges

answered May 15, 2012 at 2:05

Slonopotamus

2011 silver badge5 bronze badges

3 Comments

Stephen C Over a year ago

This is wrong in 2 ways. 1) The OP wants to convert from the internal form to the source code form. This method goes the other way. 2) The OP wants to convert a String so that he can pass it as an argument to Class.forName(). Obviously, he doesn't have the Class object at this point.

FlightOfStairs Over a year ago

A correct way would be Type.getObject(className).getClassName().

apetrelli Over a year ago

FlightOfStairs, why don't you add it as an answer?

Avallach · Accepted Answer · 2020-10-21 10:53:08Z

1

Use

org.objectweb.asm.Type.getType(typeDescriptor).getClassName()

Example: for Ljava/lang/Deprecated; returns java.lang.Deprecated. Found this thanks to hint from @FlightOfStairs who pointed at right class.

answered Oct 21, 2020 at 10:53

Avallach

111 bronze badge

Collectives™ on Stack Overflow

ASM - How can I convert Java class name from Java bytecode name?

3 Answers 3

2 Comments

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related