# Patent

## Title
Method and a software product for adapting a .Net framework compliant reflection mechanism to a java environment

## Abstract

A method for adapting a .Net framework compliant reflection mechanism to a JavaTM environment, wherein the reflection mechanism allows a user to discover class information and invoke data members solely at runtime. The method includes gathering reflection related metadata from a .Net assembly class of a respective .Net class that comprises the metadata. The method also includes the steps of generating an attributes class comprising at least the reflection related metadata and a plurality of conversion methods and integrating the attributes class in a JavaTM class file of the respective .Net class, such that the reflection mechanism is capable of adapting the reflection mechanism as defined in the .Net framework to the JavaTM environment. Also disclosed is a plurality of conversion methods. The attributes class is included in a JavaTM class file rendered by a compiler capable of compiling a .Net class to a JavaTM compliant programming code.

## Background
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FIELD OF THE INVENTION
The present invention relates generally to software compilers, and more particularly to a method for adapting a reflection mechanism compliant with the .Net framework to the Java environment.
BACKGROUND OF THE INVENTION
Sun, Sun Microsystems, JVM, Java, are trademarks or registered trademarks of Sun Microsystems, Inc. in the United States and other countries. Microsoft® .NET is a brand associated with Microsoft technology. Microsoft® .NET is software for connecting people, information, systems, and devices. Visual Basic is a registered trademark of Microsoft in the United States and other countries.
The Microsoft® .NET framework is a new platform for building integrated, service-oriented, applications to meet the needs of today's and future Internet businesses. The .Net platform allows developers to take better advantage of technologies than any earlier Microsoft platform. Specifically, the .NET platform provides for code reuse, code specialization, resource management, multi-language development, security, deployment and administration.
A .NET application can be executed on any platform that supports the .NET common language runtime (CLR). The .Net platform allows different programming languages to be integrated with one another. For example, it is possible to create a class in C++ that is derived from a class implemented in Visual Basic. The programming languages supported by the .Net platform include, but are not limited to, C++ with managed extensions, C# (C-Sharp), Visual Basic, Pascal, COBOL, JavaScript and many others. Notably, the source code written in these languages requires the CLR engine in order to execute.
The Java programming environment has recently gained significant popularity. The Java programming language is a language that is designed to be portable enough so that it can be executed on a wide range of computers, ranging from small devices, such as a personal digital assistant (PDA), cell phone, and smart cards, all the way to high-end supercomputers. Computer programs written in the Java programming language are compiled into Java bytecode instructions that are suitable for execution by a Java virtual machine (JVM).
Applications designed with the .Net platform cannot execute on a JVM. As a result, developers cannot integrate the advantages inherent to .Net with the capabilities provided by the Java runtime environments. To overcome this limitation, compilers that enable the execution of .Net applications on JVM have been introduced. These compilers (hereinafter the “IL2J compilers”) decode Microsoft intermediate language (MSIL) instructions and produce Java bytecodes instructions. An example of such a compiler is disclosed in U.S. patent application Ser. No. 10/437,518 entitled “Compiler and Software Product for Compiling Intermediate Language Bytecodes into Java Bytecodes,” assigned to common assignee and incorporated herein by reference for all that it contains.
Besides the need to compile MSIL instructions into Java bytecodes, there is also a necessity to compile other software mechanisms introduced by the .Net platform, to allow a full adaptation to Java. One of these mechanisms is the reflection, used to discover class information solely at runtime. Specifically, the reflection allows invoking data members at runtime, determining the class of an object, finding what constants and method declarations belong to an interface, creating an instance of a class whose name is not known until runtime, and retrieving as well as setting a value of a data member, even if the data member name is unknown until runtime.
There are many differences between the reflection mechanisms, or application programming interfaces (API's), provided by the Java and .Net frameworks. These differences are mainly related to handling semantic gaps between the programming languages supported by the .Net and the Java programming language and to the fact that attributes in a Java framework are only a subset of those defined in the .Net framework. Furthermore, the two frameworks use different API's to invoke data members at runtime.
It would be therefore advantageous to provide a method and software product capable of adapting the reflection mechanism as defined in the .Net framework to the Java environment.
SUMMARY OF THE INVENTION
Accordingly, it is a principal object of the present invention to provide a method and software product capable of adapting a reflection mechanism as defined in the .Net framework to the Java environment.
It is another object of the present invention to provide a plurality of conversion methods for use with a reflection mechanism as defined in the .Net framework to the Java environment.
It is a further object of the present invention to provide means for generating an attributes class for inclusion in a Java class file rendered by a compiler capable of compiling a .Net class to a Java compliant programming code.
A method is disclosed for adapting a .Net framework compliant reflection mechanism to a Java environment, wherein the reflection mechanism allows a user to discover class information and invoke data members solely at runtime. The method includes gathering reflection related metadata from a .Net assembly class of a respective .Net class that comprises the metadata. The method also includes the steps of generating an attributes class comprising at least the reflection related metadata and a plurality of conversion methods and integrating the attributes class in a Java class file of the respective .Net class, such that the reflection mechanism is capable of adapting the reflection mechanism as defined in the .Net framework to the Java environment. Also disclosed is a plurality of conversion methods. The attributes class is included in a Java class file rendered by a compiler capable of compiling a .Net class to a Java compliant programming code.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows hereinafter may be better understood. Additional details and advantages of the invention will be set forth in the detailed description, and in part will be appreciated from the description, or may be learned by practice of the invention.



BRIEF DESCRIPTION OF THE DRAWINGS
In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:
FIG. 1 is an illustration of a non-limiting process flow for adapting a reflection mechanism in accordance with an exemplary embodiment of the present invention;
FIG. 2A is the software coding for a non-limiting example of a .Net class that includes reflection definitions that can be handled by the reflection analyzer of the present invention;
FIG. 2B is the software coding for a non-limiting example of an attributes class file generated by the reflection analyzer of the present invention;
FIG. 2C is the software coding for a non-limiting example of a Java class file generated in accordance with the present invention;
FIG. 3A is the software coding for a .Net class that includes definition of a custom attribute, wherein the .Net class can be handled by the reflection analyzer of the present invention;
FIG. 3B is the software coding for a non-limiting example of a Java class file that includes a custom attribute definition and generated in accordance with the present invention; and
FIG. 4 is a non-limiting and exemplary flowchart describing the operation of the present invention.



DETAILED DESCRIPTION OF THE INVENTION
The principles and operation of a method and a software product according to the present invention may be better understood with reference to the drawings and the accompanying description, it being understood that these drawings are given for illustrative purposes only and are not meant to be limiting.
Hereinafter there is disclosed a method for adapting a reflection mechanism, compliant with the .Net framework, to the Java environment. The method includes gathering reflection related metadata, and thereafter generating an attributes class that comprises the metadata. In addition there are disclosed a plurality of conversion methods. The attributes class is included in a Java class file rendered by a compiler capable of compiling a .Net class to a Java compliant programming code.
Reference is now made to FIG. 1, which is an illustration of a non-limiting process flow 100 for adapting a reflection mechanism, in accordance with an exemplary embodiment of the present invention. Reflection is a mechanism that allows a user to discover class information and invoke data members solely at runtime. Reflection functions are part of the reflection namespace defined in the .Net framework. For example, a list of data members for a given data type can be retrieved using a group of “Info” objects, each representing a different set of members. For instance, the “MethodInfo” object represents information about a method. As another example, the developer can further include reflection functions for retrieving information on a type declaration, such as constructors, properties, methods and events. For that purpose the reflection namespace comprises a set of “GetTypes” functions, e.g., GetConstructors( ), GetProperties( ), GetMethods( ), GetEvents( ) and others. To invoke data members the developer creates an instance of a class including the data member to be invoked.
Initially, a software developer creates a .Net class 110 that comprises a source code written in any programming language supported by the .Net platform. The programming languages supported by the .Net platform may be, but are not limited to, C++ with managed extensions, C# (C-Sharp), Visual Basic, Pascal, COBOL, JavaScript and many others. The .Net Class 110 may include at least a reflection function (or definition) of the type of information desired to be retrieved, viewed, set and/or invoked at runtime.
FIG. 2A shows the software coding for an exemplary .Net class, written in C# and named “TestClass.” TestClass includes several definitions of data members, such a field (line 1007), a property (lines 1009-1019), constructors (lines 1022-1029) and methods (lines 1031-1048).
Referring again to FIG. 1, Net class 110 is compiled into a .Net assembly file 130 using a .Net compiler 120. .Net compiler 120 consists of several compilers, each targeted to a different programming language supported by the .Net platform. Assembly file 130 includes at least MSIL instructions, which are provided as an input to an intermediate language to Java (IL2J) compiler 140 and a reflection analyzer 150. IL2J compiler 140 compiles the MSIL instructions into Java bytecodes and outputs Java class files that can be executed over any Java runtime environment, e.g., the Java Virtual Machine (JVM). A detailed example for the operation of IL2J compiler 140 is found in U.S. patent application Ser. No. 10/437,518 referenced above. In an alternative embodiment of the present invention, reflection analyzer 150 may be part of IL2J compiler 140.
Reflection analyzer 150 enables the utilization of the .Net reflection mechanism in the Java environment. Specifically, reflection analyzer 150 analyzes each class and method defined in .Net assembly file 130 and gathers reflection related information that may be used during runtime. This information includes parameter names, parameter types, modifiers, custom attributes, flags and any other data relevant to data members. Data members may be fields, constructers, methods, properties or events defined in .Net class 110. In addition, reflection analyzer 150 generates conversion methods enabling the use by the Java environment of each reflection function in .Net class 110. Specifically, these methods allow getting, setting and invoking data members when the resultant Java class is executed over the Java runtime environment. The conversion methods and the metadata, i.e., the gathered information, are saved in an attributes class 160 produced by reflection analyzer 150. Attributes class 160 is a Java class file 170 that extends the Java file “TypeInfo,” for which the software coding is listed in FIG. 2B
FIG. 2B shows the software coding for a non-limiting and exemplary attributes class 160 produced by reflection analyzer 150, and is related to the .Net class shown in FIG. 2A. The TypeInfo file contains at least one abstract method that attributes classes generated by reflection analyzer 150 can inherit. The attributes class provided in FIG. 2B includes a set of conversion methods called “Create Methods,” each of which is associated with a single type of data member. The Create Methods convert the .Net reflection related information to a Java compliant format. For example, an implementation of the conversion method, createMethodData( ), is shown in lines 2003-2023. This method uses the “addMethodData” function defined in TypeInfo, and is listed below, followed by a detailed explanation of the addMethodData function. This function gets seven arguments as follows:












addMethodData(String methodName,









String mangledName,



int flags,



int attributes,



String customAttribMethod,



String returnAttribMethod,



ParameterInfo[ ] parameters){









String javaMethodName = (mangledName == null) ? methodName :







mangledName;









Class[ ] javaParams = getJavaParameterClasses(parameters);



try



{









Method m =_clazz.getDeclaredMethod(javaMethodName,



javaParams);



MethodInfo mi = new MethodInfo(m, _clazz,



methodName, flags,







attributes,









parameters, customAttribMethod,



returnAttribMethod);









mi.setOrderNum(_methodOrder++);



_methods.add(mi);









}



catch(Exception e)



{









System.out.println(“Cannot find method ” +



javaMethodName + “ in class







” + _reflectedClassName);









e.printStackTrace( );









}









}










The first argument, “methodName,” is the name of the method as defined in .Net class 110. The second argument, “mangledName,” is the method name in a resultant Java class file 170. If the method's name has not been modified, this argument receives a null value. The third argument, “flags,” is an integer value that represents the flags assigned for the method. The fourth argument, “attributes,” contains general attributes defined for that method. Attributes are descriptive declarations that allow annotation of data members. Attributes can be extracted using runtime reflection services. The fifth argument, “customAttribMethod,” includes user-defined attributes for that method. Handling custom attributes is exemplified in one embodiment of the present invention and will be described in greater detailed below. The sixth argument includes attributes that are attached to return types. The seventh argument is a parameter array that includes the representation of the method's parameters and its return value. For each return value or parameter, an element in the parameter array holds its .Net specific modifiers, name, custom attributes and so on. The values of the flags, attributes, customs attributes and parameters are set according to the content of the metadata gathered by reflection analyzer 150. For example, in line 2018, the method “GetIntField” defined in the TestClass (line 1031-1034) is handled. The addMethodData function is called with the following values:
addMethodData (“GetIntField”, null, 454, 0, null, null, aparameterinfo2)
The mangledName has a null value, since the method name was not modified when converted to Java. The “aparameterinfo2” is an array that holds only one component which is the return value of the “GetIntField” method. The array is set in line 2017, with a 32-bit integer, which is the type of the return value of the “GetIntField” method.
As depicted in FIG. 2B the “TestClassArrtib” class includes other types of create methods used for converting field data (see lines 2041-2044), property data (lines 2035-2039), constructors data (lines 2025-2033) and events data (line 2040). The createEventData( ) method is an empty method, as no events were defined in the .Net class “TestClass” shown in FIG. 2A.
Attributes class 160 is combined with Java class file 170 generated by IL2J compiler 140. Namely, Java class file 170 includes the Java bytecodes and the attributes class. The production of Java class file 170 includes generating a single Java class for each MSIL class in assembly file 130, mapping methods as well as variable names.
FIG. 2C shows the software coding for a non-limiting and exemplary de-compiled Java class file 170. As can be noted lines 3011-3071 are the nested attributes class described in greater detail above. Lines 3073-3137 include Java code lines of methods, constructors, and properties defined in the TestClass shown in FIG. 2A. As the Java programming language does not explicitly support the Property function, as defined in the .Net framework, the Property function (lines 1009-1019 of FIG. 2A) is implemented using two methods “get_IntFieldProperty” and “set_IntFieldProperty” (see lines 3073-3081 of FIG. 2C). The prefixes “set_” and “get_” are used for converting Property functions. The same problem is faced with Event functions, and the prefixes used in this case are “add_” and “remove_.”
When retrieving information related to data members there is also a need to support semantic differences between the programming languages supported by the .Net platform and the Java programming language. For example, conversion of .Net proprietary variable and data structure types (e.g., Enum) to Java variable types is required. Specifically, when invoking a data member, this data member is first converted to a format compliant with the Java programming language, invoked and then converted back to a format compliant with one of the .Net programming languages.
In one exemplary embodiment, the present invention is capable of handling custom attributes. Custom attributes are user-defined attributes that provide additional information about data members. For example, a custom security attribute that specifies the permissions required by a caller function to execute a procedure. In the .Net framework, custom attributes are defined in attribute classes based on the System.Attribute class.
FIG. 3A shows the software coding to provide a .Net class that includes, in line 4015, a custom attribute definition “ObsoleteAttrubute.” This attribute is defined for the method “foo.”
In the earliest version of the Java development environment a program element similar to the custom attributes does not exist. In order to allow the full adaptation of .Net framework to Java environment, the present invention enables the retrieval of custom attributes when executing the Java code. With that aim, reflection analyzer 150 creates a special conversion method “custom attribute handler,” that manages the retrieval of the custom attributes. In addition, reflection analyzer 150 passes to “Info” objects (e.g., MethodInfo, TypeInfo, FieldInfo and others) the name of the custom attribute handler.
FIG. 3B shows the software coding for an exemplary Java class that includes the attributes class and related to FIG. 3A. The conversion method createDataMethod( ), in lines 5015-5027, handles methods defined in the .Net class (e.g., “main” and “foo”). As shown in line 5019, the call to the addMethodData function includes in the fifth argument the parameter “methodAttr—1.” This parameter is the name of the custom attribute handler. The implementation of the custom attribute handler “methodAttr—1” is provided in lines 5046-5062. The array “aobj” holds the custom attribute “ObsoleteAttribute” defined for the method “foo.”
At runtime, when a user invokes GetCustomAttribute( ) method, the attributes are retrieved through the “foo” method, as illustrated in the following exemplary code:
Type t=foo;
MethodInfo m=t. GetMethod(“foo”);
A[ ] CustomAttribs=m. GetCustomAttribute( );
The array A holds the custom attributes “ObsoleteAttribute” defined for the method “foo.”
Additionally, during run-time, the user may request to instantiate one of the “Info” objects. In that case the name of the custom attributes handler (e.g., methodAttr—1) is passed to the “Info” object's constructor.
FIG. 4 is a non-limiting and exemplary flowchart 400, describing the overall operation of the present invention. The reflection analyzer receives as its input an assembly file created by a .Net compiler. At step S410, the received assembly file is scanned for the purpose of extracting reflection-related information included in the file. Namely, information associated with data members defined in the .Net class (e.g., .Net class 110) is gathered. At step S420, one or more conversion methods are generated to handle reflection functions defined in the .Net class. Examples of the conversion methods are the createMethodData( ) and methodAttr—1( ) described in greater detail above. At step S430, the conversion methods, together with the extracted information (i.e., metadata), are saved in an attributes class (e.g., attributes class 160 shown in FIG. 1). At step S440, the assembly files are compiled into a Java class, i.e., to Java bytecodes by means of the IL2J compiler. At step S450, the generated attributes class and the Java class, respectively produced by the reflection analyzer and IL2J, are merged into a single Java file that can be executed over any Java runtime environment.
It is to be understood that the phraseology and terminology employed herein are for the purpose of description, and should not be regarded as limiting.
It is important, therefore, that the scope of the invention is not construed as being limited by the illustrative embodiments set forth herein. Other variations are possible within the scope of the present invention as defined in the appended claims and their equivalents.

## Claims

1. A method for adapting a .Net framework compliant reflection mechanism to a Java runtime environment, wherein said reflection mechanism discovering class information and invoking data members solely at runtime, said method comprising:
gathering reflection related metadata from a .Net assembly class of a respective .Net class;
generating a plurality of conversion methods, wherein each of the conversion methods enables the use of at least a reflection function defined in said .Net class by said Java run, time environment;
generating an attributes class comprising at least said reflection related metadata and said plurality of conversion methods; and
integrating said attributes class in a Java class file of said respective .Net class,
such that said reflection mechanism is adapted as defined in the .Net framework to the Java environment;
wherein the reflection functions are for retrieving information on a type data declaration; for creating an instance of a class and for invoking a data member of a class.

2. The method of claim 1, wherein said reflection related metadata comprises at least one of: a parameter name; a parameter type; a modifier; a custom attribute; and flags of at least one data member defined in said .Net class.

3. The method of claim 2, wherein said data member is at least one of: a nested type; a field, a constructer; a method; a property; and an event.

4. The method of claim 1, wherein said reflection function is at least one of: get a data member; invoke a data member; and set a data member.

5. The method of claim 1, wherein each of said plurality of conversion methods comprises a create method, wherein said create method is capable of converting said reflection related metadata from .Net compliant format to a Java compliant format.

6. The method of claim 1, wherein each of said plurality of conversion methods comprises a custom attribute handler, wherein said custom attribute handler is capable of enabling the use of custom attributes defined in said .Net class of said Java environment.

7. The method of claim 1, wherein said .Net class comprises a programming code written in at least one of the following programming languages: C++ with managed extensions; C-Sharp (C#); Visual Basic; Pascal; COBOL; Java-Sharp (J#); and Jscript.

8. The method of claim 7, wherein said assembly .Net class is generated by a .Net compiler.

9. The method of claim 1, wherein said Java class file is generated by a compiler capable of compiling said .Net class to a Java compliant programming code.

10. The method of claim 1, wherein said attributes class is a Java class.

11. The method of claim 1, wherein said attributes class inherits a TypeInfo class.

12. The method of claim 11, wherein said TypeInfo class comprises implementation of said plurality of conversion methods.

13. A computer software product, comprising computer-readable media with instructions to enable a computer to implement a process for adapting a .Net framework compliant reflection mechanism to a Java runtime environment, wherein said reflection mechanism for discovering class information and for invoking data members solely at runtime, said process comprising:
gathering reflection related metadata from a .Net assembly class of a respective .Net class that is configured to comprise said metadata;
generating a plurality of conversion methods, wherein each of the conversion methods enables the use of at least a reflection function defined in said .Net class by said Java runtime environment;
generating an attributes class comprising at least said reflection related metadata and said plurality of conversion methods; and
integrating said attributes class in a Java class file of said respective .Net class,
such that said reflection mechanism is adapted as defined in the .Net framework to the Java environment;
wherein reflection functions are for retrieving information on a type data declaration; for creating an instance of a class and for invoking a data member of a class.

14. The computer software product of claim 13, wherein said reflection related metadata comprises at least one of: a parameter name; a parameter type; a modifier; a custom attribute; and flags of at least one data member defined in said .Net class.

15. The computer software product of claim 14, wherein said data member is at least one of: a nested type; a field; a constructer; a method; a property; and an event.

16. The computer software product of claim 13, wherein said at least one reflection function is at least one of: get a data member; invoke a data member; and set a data member.

17. The computer software product of claim 13, wherein each of said plurality of conversion methods comprises a create method, wherein said create method is being capable of converting said reflection related metadata from .Net compliant format to a Java compliant format.

18. The computer software product of claim 13, wherein each of said plurality of conversion methods comprises a custom attribute handler, wherein said custom attribute handler is being capable of enabling the use of custom attributes defined in said .Net class in said Java environment.

19. The computer software product of claim 13, wherein said .Net class comprises a programming code writing in at least one of the following programming languages: C++ with managed extensions, C-Sharp (C#), Visual Basic, Pascal, COBOL, Java-Sharp (J#), Jscript.

20. The computer software product of claim 19, wherein said assembly .Net class is generated by a .Net compiler.

21. The computer software product of claim 13, wherein said Java class file is generated by a compiler capable of compiling said .Net class to a Java compliant programming code.

22. The computer software product of claim 13, wherein said attributes class is a Java class.

23. The computer software product of claim 13, wherein said attributes class inherits a TypeInfo class.

24. The computer software product of claim 23, wherein said TypeInfo class comprises implementation of said plurality of conversion methods.