Java Connectivity with J-Integra® Espresso

J-Integra® Espresso offers an easy and high performance solution to establish interoperability between .NET and Java. You can access EJB or Java objects implementing RMI remote interfaces. It is also possible to use and exchange Java serializable objects, catch exceptions thrown in Java, or throw exceptions in .NET. If you have a running Java system all this can be done without any changes on the Java side. Many Java types are directly mapped to .NET types (e.g. java.util.Hashtable is mapped to System.Collections.Hashtable).

The mapping is performed in two steps. During the first step Java is mapped to IDL (Interface Definition Language) and during the secound step IDL is mapped to .NET. IDL is a specification published by the Object Management Group (OMG). In the examples listed below we show how the mappings between .NET and Java work with a focus on the Java language types.

In all of the following examples we use Java as the server language and .NET as the client language. The Java server is written as an RMI server. The mappings are the same no matter which environment you are using (RMI on a Java server or EJBs on a J2EE server).

Contents

• Requirements
• Remarks
• Mappings for Java Primitive Types
• Mappings for Java Types

• First Steps
  • Getting started - A simple "Hello" example
  • A simple "Hello" example -- .NET Server & Java Client

• Language Mapping
  • Attributes - Java Attributes (set/get/is)
  • JavaNames - Java Names starting with $, _, ...
  • OverloadMethods - Method Signatures overloaded in Java
  • ObjectByValue - Java Serializables
  • Arrays - Multi Dimensional Array
  • Collections - HashTable, ArrayList,...
  • InnerClasses - A Java Serializable with an Inner Class
  • Exceptions - Java User Exceptions
  • SqlTypes - Sql.Date and Sql.Time mapping

• Common Patterns
  • Callback - Callbacks from Java to .NET

Requirements

• Sun J2SE JDK 1.4.2 (http://java.sun.com/)
• Naming Service: use the batch '\DemoJava\startNameService.bat' to start the Java Naming Service (orbd)
• Libraries: add '[install dir]\bin\Jintegra.Espresso.dll' and '[install dir]\bin\JavaBuildTypes.Dll' as references to your .NET projects.

Remarks

• Each example is located in a separate folder named '\DemoJava\<NameOfExample>'. Each folder comprises three subdirectories:
  1. JavaServer: contains 2 batches:
     • 'buildServer.bat' - creates 'server.jar', the IDL files, and the .NET stub/skeleton code
     • 'startServer.bat' - starts the server (ensure that the Sun Naming Service is running first)
  2. DotNetClient: contains the .NET client project
  3. IDL: contains the IDL files created by the 'buildServer.bat' batch

Mappings for Java Primitive Types

Java	OMG IDL	.NET
void	void	void
boolean	boolean	bool
char	wchar	char
byte	octet	byte
short	short	short
int	long	int
long	long long	long
float	float	float
double	double	double
string	WStringValue	string