Since the Java language uses a different set of data types than Virtuoso a type mapping system has been established to allow the passage of data to and from Java. All Java simple types are mapped to a corresponding Virtuoso type as follows:

All other Java objects are represented as a special Virtuoso value, which contains a reference to the Java object in the VM memory space. When such a value is returned as a Virtuoso/PL return value or as a result set column, it calls the java.lang.Object.toString() method for the Java VM object it refers to and that result is returned to the calling client.

Arrays are mapped to a Virtuoso vector of their elements. The array handling routines are recursive, so each element may be a Java array or a scalar type.

The above mappings are applied when converting Virtuoso/PL data to Java data as follows:

• method parameter values in java_call_method VSE
• method parameter values in java_new_object VSE
• property values in java_set_property VSE
• the instance parameters in java_call_method/java_get_property/java_set_property VSEs

The above mappings are applied in the opposite direction (Java Data -> Virtuoso/PL data) as follows:

• method return values in java_call_method VSE
• return value of the java_new_object VSE
• property values returned from java_get_property VSE