Java 5 Language PSM for DDS: Final Submission

Java 5 PSM for DDS:Revised Submission 2MARS – Santa Clara, CA – December 2010

Presenter: Rick Warren, RTI

Submitting POCs: Rick Warren, RTI:

[email protected] Angelo Corsaro, PrismTech:

[email protected]

document number: mars/2010-12-22

1Tuesday, December 7, 2010

Copyright © 2010 RTI - All rights Reserved

Agenda

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Agenda

Specification Overview Goals and Principles Process

Better Living Through Source Code License Bootstrapping Publishing Data Reading Data Getting and Setting QoS Java Type Representation

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Goals & Design Principles

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Improve user experience standardNamingConvention Standard containers (e.g. java.util.List) Standard enumerations Error conditions reported with exceptions Serializable, Cloneable value types Simplified method overloads

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Improve type safety Generics

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Improve performance Loanable memory No critical-path memory allocation (unlike IDL PSM)

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Improve performance Loanable memory No critical-path memory allocation (unlike IDL PSM)

Improve portability Build apps against standard interfaces; decide at run time which impl to use Host multiple implementations (or versions) within same JVM Dynamic loading and unloading

Play nicely with containers, e.g. Java EE and OSGi Don’t require non-constant static state

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State of the Proposal

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State of the Proposal

Ready for implementation All mandatory requirements satisfied User vetting process begun

Private conversations with Java power users Publicly available code repository at http://

code.google.com/p/datadistrib4j/ So far, reviewers enthusiastic

Positive AB review Doug Tolbert: content Sridhar Iyengar: license

Will ask for vote to recommend adoption this week

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Source Code License & Copyright

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Principles Every vendor, user will receive code from OMG

Need to know their rights Need free access to spec, according to OMG principles

OMG must not dictate vendors’ business models Open source, shared source, closed source must be allowed ...under variety of licenses

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License Apache 2.0 (permissive but GPL-compatible) Use is royalty-free, unlike BSD (proposed last time) Requires acknowledgement of license, copyright holders

from redistributors

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License Apache 2.0 (permissive but GPL-compatible) Use is royalty-free, unlike BSD (proposed last time) Requires acknowledgement of license, copyright holders

from redistributors

Copyright OMG, RTI, PrismTech hold copyright

i.e. OMG + submitters, per OMG conventions

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Bootstrapping a DDS Java Application

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Design pattern: API is abstract, stateless Interfaces when possible; stateless abstract classes when not Doesn’t dictate state or other implementation to vendors

Design pattern: multiple DDS’s coexist in JVM i.e. Even “singletons” are not

Challenge: How do you create the first object?

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Design pattern: API is abstract, stateless Interfaces when possible; stateless abstract classes when not Doesn’t dictate state or other implementation to vendors

Design pattern: multiple DDS’s coexist in JVM i.e. Even “singletons” are not

Challenge: How do you create the first object?

Solution: Bootstrap class Represents DDS implementation Step 1: Bootstrap.createInstance(/*system property*/) Singletons: DomainParticipantFactory.getInstance(myBstrap) If no PIM factory: Duration.newDuration(myBstrap) Get back there from anywhere: myDuration.getBootstrap() * Note: API change since previous submission

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Example: Publishing Dataimport org.omg.dds.domain.*; import …;

// Join domain:DomainParticipantFactory factory = DomainParticipantFactory.getInstance( Bootstrap.createInstance());DomainParticipant dp = factory.createParticipant();

// Create topic with implicit type registration:Topic<Greeting> tp = dp.createTopic( "My Topic", Greeting.class);

// Create publishing entities:Publisher pub = dp.createPublisher();DataWriter<Greeting> dw = pub.createDataWriter(tp);

// Publish data:try { dw.write(new Greeting("Hello, World"));} catch (TimeoutException tx) { tx.printStackTrace();}

// Dispose of all entities:dp.close();

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Example: Publishing Dataimport org.omg.dds.domain.*; import …;

// Join domain:DomainParticipantFactory factory = DomainParticipantFactory.getInstance( Bootstrap.createInstance());DomainParticipant dp = factory.createParticipant();

// Create topic with implicit type registration:Topic<Greeting> tp = dp.createTopic( "My Topic", Greeting.class);

// Create publishing entities:Publisher pub = dp.createPublisher();DataWriter<Greeting> dw = pub.createDataWriter(tp);

// Publish data:try { dw.write(new Greeting("Hello, World"));} catch (TimeoutException tx) { tx.printStackTrace();}

// Dispose of all entities:dp.close();

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// Explicit TypeSupport w/ default name:Topic<Greeting> tp = dp.createTopic( "My Topic", TypeSupport.newTypeSupport( Greeting.class, dp.getBootstrap()));

// Explicit TypeSupport w/ custom name:Topic<Greeting> tp = dp.createTopic( "My Topic", TypeSupport.newTypeSupport( Greeting.class, "MyType", dp.getBootstrap()));

}or



Example: Reading Data

...// Create subscribing entities:Subscriber sub = dp.createSubscriber();DataReader<Greeting> dr = sub.createDataReader( topic, sub.getDefaultDataReaderQos(), listener, null /* all status changes */);

...

class MyListener extends DataReaderAdapter<Greeting> { @Override public void onDataAvailable(DataAvailableStatus<Greeting> status) { DataReader<Greeting> dr = status.getSource(); Sample.Iterator<Greeting> it = dr.take(/* loan, or pass List to copy */); try { while (it.hasNext()) { Sample<Greeting> smp = it.next(); // SampleInfo stuff is built into Sample: InstanceHandle inst = smp.getInstanceHandle(); // Data accessible from Sample; null if invalid: Greeting dt = smp.getData(); // ... } } finally { it.returnLoan(); } }}

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...


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“Listener” is interface: implement all.

“Adapter” is no-op class: override what

you want.





...


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“Listener” is interface: implement all.

“Adapter” is no-op class: override what

you want.

Statuses extend java.util.EventObject



Example: Get QoS

// QoS is a bean-style property of the entity:DataReaderQos qos = myReader.getQos();

// Get specific policy:ReliabilityQosPolicy.Kind rKind = qos.getReliability().getKind();

// EntityQos is a Map from QosPolicy.Id to QosPolicy:for (QosPolicy policy : qos.values()) { // Iterate over all policies, standard or not. // ...}

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Example: Set QoS

// Call modify() to get a mutable copy of the QoS:ModifiableDataReaderQos qos = myReader.getQos().modify();

// Modifiable version provides setters:qos.getReliability().setKind( ReliabilityQosPolicy.Kind.RELIABLE);

// QoS setter accepts modifiable or unmodifiable objects:myReader.setQos(qos);myReader.setQos(myOtherReader.getQos());

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Why the modifiable/unmodifiable pattern?

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Easy to use correctly qos = entity.getQos();

Hard to get wrong qos = new DataReaderQos(); // ERROR!

// What state does ‘qos’ have before the next line?entity.getQos(qos);

What does this mean:myDataReader.getQos().setReliability(…)

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Easy to use correctly qos = entity.getQos();

Hard to get wrong qos = new DataReaderQos(); // ERROR!

// What state does ‘qos’ have before the next line?entity.getQos(qos);

What does this mean:myDataReader.getQos().setReliability(…)

Fast to get Just return a pointer No allocation or deep copy needed

Good for concurrency Share immutable objects freely without locking

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Java Type Representation

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Goal: Write the following code:

public class MyPojo /*extends/implements…*/ { private int foo; private Bar[] baz; public void doStuff() { … }}…Topic<MyPojo> t = dp.createTopic( "My Topic", MyPojo.class);

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Leverage the knowledge of Java developersLeverage the code they already have

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Leverage the knowledge of Java developersLeverage the code they already have

Observations: JRE already provides type definition constructs

Primitive types, strings, lists (sequences), classes (structures), enumerations, annotations

Types to be sent over network already indicate that …by implementing java.io.Serializable

…including which fields should not be sent …with the transient keyword

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Approach: Define DDS type on the fly based on run-time introspection of Java class

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Approach: Define DDS type on the fly based on run-time introspection of Java class

Convenience feature for non-real-time Java systems Reflection slower than compiled generated code If other languages are used, type definitions must

be “duplicated”

Does not: ...replace, modify other Language Bindings ...impact serialization, therefore is interoperable

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Java Type Representation: What It Does

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Java Type Representation: What It Does

Defines mappings JRE concepts DDS concepts int Int32 (IDL long) double Float64 (IDL double) java.util.List Sequence Serializable class Structure

Allows customization to support non-Java DDS concepts e.g. unsigned primitives, narrow vs. wide strings, unions Mechanism: @SerializeAs and other annotations

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Java Type Representation: Example

Java IDL

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Javapackage com.acme;

IDLmodule com { module acme {

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class Fooimplements Serializable {


struct Foo {

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class Fooimplements Serializable { @Key int theInt;


struct Foo { @Key long theInt;

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class Fooimplements Serializable { @Key int theInt; transient float theFlt;



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class Fooimplements Serializable { @Key int theInt; transient float theFlt; String theStr;



string theStr;

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class Fooimplements Serializable { @Key int theInt; transient float theFlt; String theStr; @SerializeAs(UINT_64) BigInteger theUInt;



string theStr;

unsigned long theUInt;

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class Fooimplements Serializable { @Key int theInt; transient float theFlt; String theStr; @SerializeAs(UINT_64) BigInteger theUInt; String[] theArr;}



string theStr;

unsigned long theUInt; sequence<string> theArr;};

}}

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Summary

Proposed specification is complete Provides (the first) run-time-portable API for DDS Improves performance over IDL-based API Improves type safety over IDL-based API Simplifies type handling Satisfies all mandatory requirements

We will ask for your vote on Thursday Vote to vote Vote to recommend adoption

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Q & A

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Appendix: Changes Since Cambridge

Changed license from BSD to Apache

Modified package organization Modifiable value type variants in parallel packages

to simplify package lists Moved contents of org.omg.dds.type.annotation to

org.omg.dds.type Consolidated statuses in org.omg.dds.core.status

package to match C++ proposal Moved built-in topic data interfaces to

org.omg.dds.topic package to match C++ proposal

All new unchecked exceptions now extend common base class

Improvements to value types All setters return enclosing object to facilitate

method chaining Improvements to Time and Duration

Leverage TimeUnit Address Y2038 problem

Renamed Qos to EntityQos to match C++ proposal

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Simplified object creation Renamed Context to Bootstrap to avoid confusion with

JNDI Reduced number of entity and condition factory

method overloads Pass Bootstrap as argument to factories; don’t make it

the factory for everything (required changing some interfaces into abstract classes)

Improved DDS-XTypes APIs, aligned with FTF Simplified Dynamic Language Binding by removing

unneeded methods Improved overloads in built-in type writers Fixed method names in TypeLibraryElement “union”

Added JavaDoc Added JavaDoc building to packaging script Included some documentation from DDS specification

(not done yet)

Made some “enumerations” more extensible by vendors Replaced status kind mask with collection of status

classes Made QosPolicy.Id an abstract class, not an

enumeration


Technology

Java 5 Language PSM for DDS: Final Submission