Eiffel2Java Sample

This example shows how to create an instance of the Java Virtual Machine and the creation of an object of type test, a java class reproduced below: 

(Java Code)
 
class test 
{
	test () 
	{
		my_integer = 10;
	}
 
	public int my_integer;
	public static int my_static_integer;
	public void my_method (int arg_int, String arg_string) 
	{		
		my_static_integer = arg_int;
		my_integer = arg_int;
	}
}

In order to run properly you need to read the library requirement .

Compiling the example

Since the example is using the `test.java' class, the first step is to compile the java class using the `javac' command line utility from the JDK. Once it is done, copy the `test.class' either into $ISE_EIFFEL\examples\Eiffel2Java\EIFGENs\classic\W_code or else into $ISE_EIFFEL\examples\Eiffel2Java\EIFGENs\classic\F_code, depending on your compilation mode (freezing vs. finalizing).

Running the example

Once the example is compiled, you can run it and here is the expected output: 

$ sample
Creating instance of class `test'
Value of `my_integer' is 10
Value of `my_static_integer' is 0
Calling `my_method' with (2, "String test")
Value of `my_integer' after call to `my_method' is 2

Code description

(Eiffel Code)
 
class
    EIFFEL_TO_JAVA
inherit
    SHARED_JNI_ENVIRONMENT
 
create
    make
 
feature -- Creation
 
    make
        local
            class_test: JAVA_CLASS
            instance_of_class_test: JAVA_OBJECT	
            fid: POINTER
            value: INTEGER
            j_args: JAVA_ARGS
        do
                --| Creation of the Java object
            class_test := jni.find_class ("test")
            create instance_of_class_test.create_instance (class_test, "()V", Void)
 
                --| Access to a public attribute
            fid := instance_of_class_test.field_id ("my_integer", "I")
 
                -- 'fid' contains the id of the field 'my_integer'
                -- 'value' contains the value of the field referenced	
                -- by 'fid'
 
            value := instance_of_class_test.integer_attribute (fid)
 
                --| Access to a static attribute using directly the JAVA_CLASS
            fid := class_test.field_id ("my_static_integer", "I")
            value := class_test.integer_attribute (fid)
 
 
                --| Access to a static attribute using the attribute 'jclass'
            fid := instance_of_class_test.jclass.field_id ("my_static_integer", "I")
            value := instance_of_class_test.jclass.integer_attribute (fid)
 
                --| Access to the method 'my_method'
                -- Get the id of 'my_method'
            fid := instance_of_class_test.method_id ("my_method", "(ILjava/lang/String;)V")	
 
                -- Create the set of arguments for 'my_method'
            create j_args.make(2)
            j_args.push_int (2)
            j_args.push_string("String test")
 
                -- Create the set of arguments for 'my_method'
                -- Call to the void method referenced by 'fid'
            instance_of_class_test.void_method (fid, j_args)
        end -- make
 
end -- class EIFFEL_TO_JAVA


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