ACS Course Transparent XML DeSerialization in Java H

ACS Course Transparent XML De-/Serialization in Java H. Sommer ESO - Garching 23 June – 02 July, 2003

XML Invisible ALMA Project Flat-XML API seen from outside: Xml. Entity. Struct 19. November 2002 Comp Transparent-XML API implemented by component: Sched. Block Comp De-/Serialization layer (dynamic) XML container Comp XML container 2

XML Invisible easy programming ALMA Project • Java component implementation code can work with binding classes directly, without having to convert parameters in the functional interface methods • Same for (Java) clients of the component: they see the component with an interface that takes binding classes, rather than flat XML (i. e. Xml. Entity. Struct) • It’s still possible to use the plain CORBA component interface, e. g. from a client that’s not written in Java 19. November 2002 3

XML Invisible how it works ALMA Project • Custom IDL compiler recognizes XML-entity typedefs in IDL and constructs “inner” interface that uses binding classes instead of Xml. Entity. Structs. • Container can map between the CORBA-IF and the inner IF at runtime, by serializing and deserializing binding objects to/from Xml. Entity. Structs • Communication between components inside a container can be optimized to cut out XML serialization completely – binding objects are passed in memory. 19. November 2002 4

Schema + IDL Implementation code sees only binding classes ALMA Project Complex data type defined as XML schema “Sched. Block. xsd” typedef Xml. Entity. Struct Sched. Block; <xsd: element name=“Sched. Block”> ref 0. . 1 void take. Sched. Block( Sched. Block sb ) 1. . n instance level 19. November 2002 Sched. Block XML document implements meta level Client component Operation defined in CORBA IDL Server component 5

Custom IDL compiler ALMA Project Flat-XML “My. Interface” IDL IF typedef xmlstring Obs. Project; … Obs. Project get. Obs. Project() CORBA IDL compiler ACS IDL compiler Xml. Entity. Struct get. Obs. Project() Transparent-XML “My. Interface. J” alma. data. Obs. Project get. Obs. Project() Makefile mapping info: “Obs. Project” -> alma. data. Obs. Project 19. November 2002 together in one JAR file 6

Example: IDL from jcontexmpl/idl/Xml. Component. idl ALMA Project typedef xmlentity: : Xml. Entity. Struct Obs. Proposal; typedef xmlentity: : Xml. Entity. Struct Sched. Block; typedef sequence <Sched. Block> Sched. Block. Seq; interface Xml. Component { Obs. Proposal create. Obs. Proposal(); Sched. Block. Seq get. All. Sched. Blocks(); void xml. In. Out. Method(in Obs. Proposal ops. Prop. In, out Sched. Block sched. Block. Out); … } Garching, 23 June – 02 July 2003 ALMA Common Software course 7

Example: Xml. Component IF created by the CORBA IDL compiler ALMA Project public interface Xml. Component. Operations { alma. xmlentity. Xml. Entity. Struct create. Obs. Proposal(); alma. xmlentity. Xml. Entity. Struct[] get. All. Sched. Blocks(); void xml. In. Out. Method(alma. xmlentity. Xml. Entity. Struct ops. Prop. In, alma. xmlentity. Xml. Entity. Struct. Holder sched. Block. Out); } Garching, 23 June – 02 July 2003 ALMA Common Software course 8

Example: Xml. Component IF created by the ACS IDL compiler ALMA Project ACS IDL compiler public interface Xml. Component. J adds a “J” { public alma. xmljbind. test. obsproposal. Obs. Proposal create. Obs. Proposal(); public alma. xmljbind. test. schedblock. Sched. Block[] get. All. Sched. Blocks(); public void xml. In. Out. Method(alma. xmljbind. test. obsproposal. Obs. Prop osal ops. Prop. In, alma. demo. Sched. Block. Holder sched. Block. Out); Garching, 23 June – 02 July 2003 ALMA Common Software course 9

ALMA Project Example: Component Implementation package alma. demo. Xml. Component. Impl; public class Xml. Component. Impl extends Component. Impl. Base implements Xml. Component. J { public Obs. Proposal create. Obs. Proposal() { Obs. Proposal obs. Prop = new Obs. Proposal(); obs. Prop. set. Performance. Goals(“whatever. "); return obs. Prop; } Garching, 23 June – 02 July 2003 ALMA Common Software course 10

Client side (components acting as clients, or non-component clients) ALMA Project Container. Services#get. Component returns the „flat-XML“ interface org. omg. CORBA. Object comp. Obj = serv. get. Component("XMLCOMP 1"); Xml. Component xml. Comp = alma. demo. Xml. Component. Helper. narrow(comp. Obj); Wrap it using Container. Services#create. Xml. Binding. Wrapper(. . ): Xml. Component. J xml. Comp. J = (Xml. Component. J) cserv. create. Xml. Binding. Wrapper( Xml. Component. J. class, xml. Comp, Xml. Component. Operations. class); component reference 19. November 2002 “flat-XML” IF “transparent. XML” IF 11

Example: Makefile ALMA Project IDL compilation (as usual) IDL_FILES = Hello. Lamp Xml. Component Triggers ACS-IDL compiler and maps IDL-typedefs to Java-XML binding classes XML_IDL= "Obs. Proposal=alma. xmljbind. test. obsproposal. Obs. Proposal; Sched. Block=alma. xmljbind. test. schedblock. Sched. Block“ No need for any XSDBIND since we reuse the binding classes from the module acstestentities, which are on the classpath. Garching, 23 June – 02 July 2003 ALMA Common Software course 12

define systementities. xml Common. Entity. xsd General. Includes. xsd xmlentity. idl systementities. jar Project lib ALMA xmlentity. jar define/src/Makefile idl Inter-module referencing through INTROOT, ACSROOT idl lib <xsd: import > acstestentities acs. Test. Entities. xml Test. Obs. Project. xsd Test. Obs. Proposal. xsd Test. Sched. Block acs. Test. Entities. jar Schema-to-Java class mappings for imported schemas XSDBIND = systementities IDL_FILES = xmlentity acstestentities/src/Makefile XSDBIND = acs. Test. Entities XSDBIND_INCLUDE = systementities jcontexmpl idl Hello. Lamp. idl Xml. Component. idl lib Hello. Lamp. jar Xml. Component. jar IDL #include Inter-module referencing through INTROOT, ACSROOT jcontexmpl/src/Makefile IDL_FILES = Hello. Lamp Xml. Component XML_IDL = "Obs. Proposal=alma. xmljbind. test. obsproposal. Obs. Proposal; Sched. Block=alma. xmljbind. test. schedblock. Sched. Block” Connects IDL entity class references, e. g. the “Sched. Block” typedef xmlentity: : Xml. Entity. Struct Sched. Block; with the corresponding Java binding classes. 19. November 2002 13

Remarks ALMA Project • Transparent de-/serialisation works also for Java clients or components when the other part is not Java; • Transport is done using plain CORBA – Stability – Accessible by any software even if it‘s not aware of binding classes • Using this transparent-XML mechanism is not mandatory. On both the client and server side of a component call, the entire interface or even individual methods can use unparsed XML: – Always if there‘s no binding class support for that language – To use a specific XML parser, or to just forward XML without parsing it at all 19. November 2002 14