Java source code must be embedded between a java and end java instruction.

Example:

java
   System.out.println("Hello from Java");
end java

Java source code can appear at different locations in Obix source:

Variables, constants, input arguments and output arguments declared in Obix can be accessed in embedded Java by simply specifying the prefixed identifier of the variable, constant, input argument or output argument.

See following rule for an example.

Scalar values in Obix can be converted to their corresponding primitive Java values by applying the getValue().java_value() methods to the object.

The following example demonstrates how to access primitive Java values stored in Obix variables, constants, input arguments and output arguments:

service java_examples

   command example_4
      in i1 type:string end
      in i2 type:positive32 end

      out result type:string end

      script
         var string name = "Albert"
         const string friday = "Friday"

         // at this point we have 2 input arguments, one output argument, a variable, and a constant declared in Obix
         // we will now access them in embedded Java code:
         java
            System.out.println ( "values in Java:" );
            
            // access Obix input argument
            System.out.println ( "i1: " + i_i1.getValue().java_value() );

            // store Obix scalar value into Java primitive value
            int i2 = i_i2.getValue().java_value();
            System.out.println ( "i2: " + i2 );

            // access Obix variable
            System.out.println ( "name: " + v_name.getValue().java_value() );

            // access Obix constant
            System.out.println ( "friday: " + c_friday.getValue().java_value() );
            
            // assign Obix variable to Obix output argument
            o_result = v_name;
            System.out.println ( "result: " + o_result.getValue().java_value());

            System.out.println();
         end java

         // o_result has been set in Java code; now display it with Obix
         system.console.write_line ( "result in Obix: " & result )
      end
   end


end

Executing

se_java_examples.co_example_4 ( i1 = "foo"; i2 = 17 )

will produce the following output on the system console:

values in Java:
i1: foo
i2: 17
name: Albert
friday: Friday
result: Albert

result in Obix: Albert

Scalar values in Obix can be created from primitive Java values by using specific Java constructors.

The following example shows the different Java constructors that can be used to create scalar values:

service java_examples

   command example_5
      script
         // declare some scalars in Obix
         var string first_name
         var positive32 i
         var character char
         var yes_no flag

         // now create Obix objects in Java and assign them to the above variables
         java
            v_first_name = new fa_string ( "Albert" );
            v_i = new fa_positive32 ( 17 );
            v_char = new fa_character ( 'A' );
            v_flag = new fa_yes_no ( true );
         end java

         // check values in Obix:
         check script first_name =v "Albert"
         check script i =v 17
         check script char =v 'A'
         check script flag =v yes
      end
   end

end

Other scalar values (zero_positive32, non_empty_string, etc.) are created analogously to the examples above.

The value of an attribute can be accessed in Java by using the Java Beans syntax for accessing properties, i.e. get{unprefixed_and_capitalized_attribute_identifier}().

Suppose the following type exists in Obix, and a factory has also been defined to create dogs:

type dog
   attribute name type:string end
   command bark end
end type

We can then create a dog and access its name in Java as shown below:

service java_examples

   command example_6
      script
         // create dog in Obix
         var dog lassie = fa_dog.co_create ( "Lassie" )

         // now access the dog's name in Java
         java
            System.out.println ( "dog's name: " + v_lassie.getName().getValue().java_value() );
         end java
      end
   end

end

Here is the result displayed:

dog's name: Lassie
dog's name: Lassie

The value of an attribute can be set in Java by using the Java Beans syntax for setting properties, i.e. set{unprefixed_and_capitalized_attribute_identifier}({value}).

Let's reuse the following type defined in the section called “Attribute property setable”:

type person_2 default_factory:yes

   attribute_list type:string

      attribute first_name end             // attribute is immutable. it can only be set in the creator.
                                           // (property 'kind' defaults to 'constant', in which case
                                           // property 'setable' defaults to 'creator')
      attribute last_name &
         kind:variable setable:factory end // only scripts in the factory that creates the object can change 'last_name'

      attribute city &
         kind:variable setable:all end     // any script can change the value

   end attribute_list

end type

We can now create a person and change the city through embedded Java as follows:

service java_examples

   command example_7
      script
         // create person in Obix
         var person_2 paganini = fa_person_2.co_create ( &
            first_name = "Nicolas" &
            last_name = "Paganini" &
            city = "unknown" )

         // now set attribute 'city' in Java
         java
            v_paganini.setCity ( new fa_string("Genoa, Italy") );
         end java

         // check in Obix
         check script paganini.city =v "Genoa, Italy"
      end
   end

end

Whenever a method of a type, factory or service is called in Java, the package path must be specified if no import statements are defined between java_header and end java_header. The package path consists of the library path defined in Obix. For each library, the prefixed library identifier must be used (i.e. li_bar for library bar)

Example:

If a service foo exists in library bar.zar, then the service is accessed in Java with li_bar.li_zar.se_foo.

See also the following rule for an additional example.

An object or service command (including object creators) can be executed in Java by calling the method {prefixed_command_identifier}_command({input_values}), where {prefixed_command_identifier} denotes the actual prefixed identifier of the command, and {input_values} denotes the list of actual input arguments passed to the command.

Example:

service java_examples

   command example_8
      script
         // use Obix service command to display "Hello" on system console
         system.console.write_line ( "Hello from Obix" )

         java
            // now use same command in Java
            org.obix.obix_core.system.se_system.getConsole().co_write_line_command ( new fa_string("Hello from Java") );
            // the same result can of course also be achieved with the following statement:
            System.out.println ("Hello from Java");
         end java

         // create dog in Obix
         var dog bello = fa_dog.co_create ( "Bello" )
         // use Java to make him bark
         java
            v_bello.co_bark_command();
         end java

         // we can also make the inverse: create the dog in Java and make him bark in Obix:
         java
            v_bello = manual_examples.li_basics.li_RSE.fa_dog.co_create_command(new fa_string("Bello"));
         end java
         system.console.write_line ( "Hello from Obix again" )
         bello.bark
      end
   end


end

The result on the system console will be:

Hello from Obix
Hello from Java
Hello from Java
bark bark
Hello from Obix again
bark bark