Structural Reflection by Java Bytecode Instrumentation

Transcription

1 Vol. 42 No. 11 Nov Java, Java API introspection API Javassist Java JVM Javassist JVM Javassist Structural Reflection by Java Bytecode Instrumentation Shigeru Chiba, and Michiaki Tatsubori The standard reflection API of Java provides the ability to introspect a program but not to alter program behavior. This paper presents an extension to the reflection API for addressing this limitation. Unlike other extensions enabling behavioral reflection, our extension called Javassist enables structural reflection in Java. For using a standard Java virtual machine (JVM) and avoiding a performance problem, Javassist allows structural reflection only before a class is loaded into the JVM. This paper presents the design principles of Javassist, which distinguish Javassist from related work. 1. Java API Application Programming Interface introspection Java behavioral reflection Graduate School of Information Science and Engineering, Tokyo Institute of Technology 21 PRESTO, Japan Science and Technology Corporation Doctral Program in Engineering, University of Tsukuba structural reflection Javassist Javassist Java Java Java 2752

2 Vol. 42 No. 11 Java 2753 Javassist 3 Javassist 4 Javassist API Java Java Java P P C P P C P P D m() D m() D m() Reflective Java 18) Kava 17) MetaXa 9),14) Java 3. Java Javassist

3 2754 Nov Smalltalk 8) ObjVlisp 4) CLOS 11) API Application Programming Interface API C++ C++ API Javassist Java JVM Java JVM JIT final final final Java 15) 3.2 Java JVM Javassist Java Javassist Javassist JVM Javassist JVM 4. Javassist API Javassist API Application Programming Interface 4.1 Javassist Java JVM byte Javassist byte Javassist 1 JVM CtClass compile-time class reify stream InputStream CtClass c = new CtClass(stream); CtClass CtClass Input- Stream String Javassist CtClass

4 Vol. 42 No. 11 Java CtClass Table 1 Methods in CtClass for introspection. String getname() int getmodifiers() ( public ) boolean isinterface() CtClass getsuperclass() CtClass[] getinterfaces() CtField[] getdeclaredfields() CtMethod[] getdeclaredmethods() CtMethod[] getconstructors() byte[] bcode = c.tobytecode(); bcode JVM CtClass reflect Class tobytecode() Javassist JVM Javassist CtClass c2 = new CtNewClass(); CtClass c2 4.2 introspection introspection Javassist Java API newinstance() 1 CtClass getsuperclass() getinterfaces() Ct- Class JVM CtClass new URL 2 Table 2 Methods for alteration. CtClass void bepublic() public void notfinal() final void setname(string name) void setsuperclass(ctclass) void addinterfaces(ctclass[]) void addconstructor(...) void addmethod(...) void addfield(...) CtField void bepublic() public void notfinal() final CtMethod void bepublic() public void notfinal() final void instrument(...) void setbody(...) void makewrapped(...) Glue code getdeclaredfields() CtField getdeclaredmethods() Ct- Method Java API Field Method CtMethod 4.3 alteration Javassist Java API Javassist Javassist 2 3 (1) Java (2) (3) 1 Javassist API Java Javassist API Java Javassist

5 2756 Nov Java Javassist this this Javassist Java Java setname() 2 Javassist API Javassist Javassist 7) Java 10) Javassist final Javassist Java 6) Javassist 4.4 Javassist 3 N Javassist Javassist Javassist 5.2 Javassist CtMethod 1 CtMethod glue code Glue code Object

6 Vol. 42 No. 11 Java 2757 Object lookup(object[] args) { return hashtable.get(args[0]); } hashtable java.util. Hashtable glue code String String String stringlookup(string key) { Object[] args = { key }; return (String)hashtable.get(args[0]); } String Object Javassist CtField int 4.5 Java Javassist C++ new. CodeConverter Javassist Javassist 3 CodeConverter Table 3 Methods in CodeConverter. void replacenew() new void replacefieldread() void replacefieldwrite() void redirectfieldaccess() void redirectfieldaccess() Javassist Kava 17) Javassist 750 Java Javassist Kava 2) Javassist API GUI Graphical User Interface Addistant Javassist 16) 2 Javassist Javassist Addistant Javassist 19)

7 2758 Nov Java JavaClass API 5) JOIE 3) Javassist Java Javassist API JVM 12) OpenC++ 1) OpenJava 20) Javassist Javassist Java Kirby 13) linguistic reflection 5.2 OpenJava OpenJava 20) Java 1) Javassist OpenJava OpenJava public OpenJava Javassist Javassist OpenJava Javassist OpenJava Javassist SPECjvm TM Java Open- Java JVM OpenJava OpenJava Sun Ultra10 UltraSPARC IIi 440 MHz Solaris 7 JVM Sun JDK HotSpot TM Client VM Sun JDK javac IBM Jikes javac Java Jikes 1 OpenJava Javassist Javassist Java 34 KB 0.7 1KB 0.03 OpenJava

8 Vol. 42 No. 11 Java 2759 Fig. 1 1 Execution time of reification and reflection. Javassist 6. Java API Javassist Javassist Javassist Javassist Javassist JVM Javassist Java Javassist Javassist OpenJava 20) Javassist Javassist Javassist Javassist Javassist Javassist 1) Chiba, S.: A Metaobject Protocol for C++, Proc. ACM Conf. on Object-Oriented Programming Systems, Languages, and Applications, SIGPLAN Notices, Vol.30, No.10, pp , ACM (1995). 2) Chiba, S.: Load-time structural reflection in Java, ECOOP 2000, LNCS 1850, pp , Springer-Verlag (2000). 3) Cohen, G.A., Chase, J.S. and Kaminsky, D.L.: Automatic Program Transformation with JOIE, USENIX Annual Technical Conference 98 (1998). 4) Cointe, P.: Metaclasses are first class: The ObjVlisp model, Proc. ACM Conf. on Object-

9 2760 Nov Oriented Programming Systems, Languages, and Applications, pp (1987). 5) Dahm, M.: Byte Code Engineering with the JavaClass API, Techincal Report B-17-98, Institut für Informatik, Freie Universität Berlin (1999). 6) Drossopoulou, S., Wragg, D. and Eisenbach, S.: What is Java Binary Compatibility?, Proc. ACM Conf. on Object-Oriented Programming Systems, Languages, and Applications, pp (1998). 7) Forman, I., Conner, M., Danforth, S. and Raper, L.: Release-to-Release Binary Compatibility in SOM, Proc. ACM Conf. on Object- Oriented Programming Systems, Languages, and Applications, pp (1995). 8) Goldberg, A. and Robson, D.: Smalltalk- 80: The Language and Its Implementation, Addison-Wesley (1983). 9) Golm, M. and Kleinöder, J.: Jumping to the Meta Level, Behavioral Reflection Can Be Fast and Flexible, Proc. Reflection 99, LNCS 1616, pp.22 39, Springer (1999). 10) Gosling, J., Joy, B., Steele, G. and Bracha, G.: The Java Language Specification, 2nd edition, Addison-Wesley (2000). 11) Kiczales, G., des Rivières, J. and Bobrow, D.G.: The Art of the Metaobject Protocol, The MIT Press (1991). 12) Kiczales, G.: Foil for the Workshop on Open Implementation, internet publication ( Xerox PARC (1994). 13) Kirby, G., Morrison, R. and Stemple, D.: Linguistic Reflection in Java, Software Practice and Experience, Vol.28, No.10, pp (1998). 14) Kleinöder, J. and Golm, M.: MetaJava: An Efficient Run-Time Meta Architecture for Java, Proc. International Workshop on Object Orientation in Operating Systems (IWOOS 96 ), IEEE (1996). 15) Malabarba, S., Pandey, R., Gragg, J., Barr, E. and Barnes, J.F.: Runtime Support for Type-Safe Dynamic Java Classes, ECOOP 2000, LNCS 1850, pp , Springer-Verlag (2000). 16) Tatsubori, M., Sasaki, T., Chiba, S. and Itano, K.: A Bytecode Translator for Distributed Execution of Legacy Java Software, ECOOP 2001, LNCS 2072, pp , Springer-Verlag (2001). 17) Welch, I. and Stroud, R.: From Dalang to Kava The Evolution of a Reflective Java Extension, Proc.Reflection 99, LNCS 1616, pp.2 21, Springer (1999). 18) Wu, Z.: Reflective Java and A Reflective- Component-Based Transaction Architecture, Proc.OOPSLA 98 Workshop on Reflective Programming in C++ and Java, Fabre, J.-C. and Chiba, S. (Eds.) (1998). 19) Vol.17, No.2, pp (2000). 20) Java Vol.41, No.8, pp (2000). ( ) ( ) ACM ACM