Java 5 PSM for DDS: Revised Submission Overview

Java 5 PSM for DDS:
Revised Submission
MARS – Cambridge, MA – September 2010
Presenter: Rick Warren, RTI
Submitting POCs:
 Rick Warren, RTI:
rick.warren@rti.com
 Angelo Corsaro, PrismTech:
angelo.corsaro@prismtech.com
document number: mars/2010-09-05

Agenda
Specification Overview
 Mostly review from last time
Specification changes since Minneapolis
 Full DDS-XTypes support
 Java Type Representation
 Other minor changes
In depth: Java Type Representation
TODO for the next meeting
 Review: This will impact many of us; needs to be right
Copyright © 2010 RTI - All rights Reserved 2

Goals & Design Principles
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
Improve type safety
 Generics
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

State of the Proposal
First revised submission
Process moving quickly and efficiently
 Submitters have joined
 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
Still to go:
 Review within submission team and with our customers
 Review with your own stakeholders!
 Next submission will be ready for a vote

Hello, World
import org.omg.dds.*;
Topic<Foo> t = …;
DataWriter<Foo> dw =
myPub.createDataWriter(t);
Foo data = …;
dw.write(data);
dw.close();
DataReader<Foo> dr =
mySub.createDataReader(t);
Sample.Iterator<Foo> it =
dr.take();
Foo data2 = it.next().
getData();
it.returnLoan();
dr.close();
 OMG package
 Typical naming
convention
 Overloaded
methods
 Generics for type
safety
 Close like JMS,
I/O stream
 Standard
collections

Since Initial Submission: DDS-XTypes
Dynamic Language Binding
TypeObject for type propagation
Built-in data types:
 Types: String, KeyedString, Bytes, KeyedBytes
 Added overloads to Publisher, Subscriber to create
statically type-safe readers and writers of these types
New QoS policies
Standard annotations

Since Initial Submission: Java Type Rep’n
Publish and subscribe to POJOs without
code generation
Based on Java reflection
More on this later

Since Initial Submission: Misc. Details
Improved static type safety of topic creation
Improved static type safety of topic, reader,
and writer listeners
Improved portability of TypeSupport creation
Improved Context loading
Miscellaneous alignments with C++ PSM
“Hello World” code example
Automated generation of binary jar and
source zip files

Java Type Representation: Intro
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);

Java Type Representation: Intro
Does not replace, modify existing
standard Language Bindings
Interoperable at wire level
 …with generated or dynamic types
 …in Java or any other language
Convenience feature for non-real-time
Java systems
 “Representation” is run-time, reflection-based:
no Java source code parsing or code generation
 Implication: Reflection slower than compiled
generated code
 Implication: If other languages are used, type
definitions must be “duplicated”

Java Type Representation: Approach
Leverage the knowledge of Java developers
Leverage 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

Java Type Representation: Approach
What this Representation has to do:
1. Define mappings between JRE concepts and DDS
concepts
 int  Int32 (IDL long)
 double  Float64 (IDL double)
 java.util.List  Sequence
 Serializable class  Structure
2. Allow customizability to support non-Java DDS concepts
 e.g. unsigned primitives, narrow vs. wide strings, unions
 Mechanism: @SerializeAs annotation

Java Type Representation: Example
Java
package com.acme;
class Foo
implements Serializable {
@Key int theInt;
transient float theFlt;
String theStr;
@SerializeAs(UINT_64)
BigInteger theUInt;
String[] theArr;
}
IDL
module com { module acme {
@Extensibility(MUTABLE)str
uct Foo {
@Key long theInt;
string theStr;
unsigned long theUInt;
sequence<string> theArr;
};
}}

Still TO DO
We will ask for a vote at the December meeting
Review the PSM with your stakeholders
 API
 Implementation: Context.createInstance
(only non-trivial implementation in the PSM)
 Specification document
Review the code license, copyrights
 (Will want AB, SMC guidance too)
 OMG and submitters (RTI, PrismTech) have joint copyright
 OMG-standard Java source files have BSD-style license
 Does not constrain licenses or biz models of impl’s
 Vendors redistributing these files must:
 Document license terms
 Acknowledge copyright holders
Will be further alignment within submission team,
including consideration of C++ PSM

Still TO DO
Copy specification into JavaDoc?
 Friendly for IDE users
 myWriter.setQos|
More examples? (non-normative)
 e.g. Application code examples
 e.g. No-op reference implementation
You tell us!
void setQos(DataWriterQos q)
Set the QoS of this DataWriter. The result
of subsequent calls to getQos will be
equal to the value set by this method.

Summary
DDS will have a first-class
Java API.
 That looks and behaves like a
typical Java API.
 That performs well.
 Soon.

Q & A

Java 5 PSM for DDS: Revised Submission Overview

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