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Copyright © 2013, Oracle and/or its affiliates. All rights reserved.
CLDC 8: New Features and
Opportunities for the Small
Java Core Libraries
Michael Lagally
Principal Member of Technical Staff
Roger Riggs,
Consulting Member of Technical Staff
The following is intended to outline our general product direction. It is
intended for information purposes only, and may not be incorporated into
any contract. It is not a commitment to deliver any material, code, or
functionality, and should not be relied upon in making purchasing
decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole
discretion of Oracle.
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Copyright © 2013, Oracle and/or its affiliates. All rights reserved.
CLDC 8
New Features and Opportunities for the Small Java Core
Abstract:
 CLDC has been the Java platform for connected devices such as feature
phones since 2000. It is a platform for devices with very limited memory
and CPU power.
 Oracle is leading an effort to update the CLDC platform with support for
Java 8 language features and new library APIs. The platform defines a
state-of-the-art runtime environment for small embedded devices and
provides a set of carefully defined libraries that are most useful on
resource-constrained devices.
 CLDC 8 targets embedded devices such as wireless modules, smart
meters, and healthcare monitoring and other M2M devices. The CLDC 8
configuration is standardized in the Java community process as JSR 360,
with experts from the embedded and mobile industry in the expert group.
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Program Agenda
 Java ME Evolution
 Connected Limited Device Configuration (CLDC)
 Generic Connection Framework (GCF)
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The Next Generation: Java ME 8 Platform
Themes
Key
Features
• First step in Java ME
Java SE alignment
• Dedicated embedded application platform
• Address increased range of use cases and markets
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•
•
•
Java ME CLDC 8: Updated VM + alignment with Java SE 8
Java ME Embedded Profile 8: Embedded application platform
Value-add new and enhanced APIs and features for embedded
Improved configurability and optimized footprint for deployment
• Target requirements starting at 128 KB RAM, 1 MB Flash/ROM
Target
Markets
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• Small to mid-embedded covering wide range of use cases/markets
• Intelligent edge devices, communication nodes, healthcare
devices, smart sensors, smart meters, general IoT and M2M
Copyright © 2013, Oracle and/or its affiliates. All rights reserved.
Java ME 8 Focus
Platform
Footprint
Java SE
Java ME
10MB-100MB
1MB-10MB
Java
Card
50KB-1MB
ARM 7 Cortex M ARM9/11
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MIPS32 - ARM Cortex A – PPC - Intel Atom
Device
CPU/
GPU/I-O
Towards a Common Java
Ensure close alignment between ME/SE
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Key
Principles
•
•
•
•
CLDC is a strict subset of Java SE
CLDC code works on Java SE
Java ME vs. Java SE is a footprint/functionality tradeoff
Java ME & Java SE release cycles are in sync
Benefits
•
•
•
•
Modern and flexible platform for delivering embedded software
Unified development experience & community across Java
Aligned Java language, core APIs, development, and tools
Enable 9+ Million Java developers to develop for Java Embedded
Copyright © 2013, Oracle and/or its affiliates. All rights reserved.
Java ME 8 Platform Overview
Additional
APIs
(Examples)
Messaging
Wireless
Communication
Protocols and
Data Conversion
Security and
Management
Additional
Optional APIs
Location
Web Services
Sensors
Additional
Optional JSRs
Vertical Specific
APIs
On-Device I/O
Access
Device I/O
API
Generic Connection
Framework
Java VM
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GCF
Application Platform
Java ME Embedded Profile
(MEEP 8, JSR 361)
Security and Trust
Services
Java ME CLDC 8 (JSR 360, aligned with Java SE 8)
SATSA
Constraints of small embedded devices
An embedded device is not a PC
•
•
•
•
•
•
•
•
•
•
•
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Low cost
Small Memory footprint (512k - several MB)
Limited CPU horsepower
Many devices have no display, no mouse, no keyboard
No PC user interface
UI often based on task-oriented direct manipulation sensors
Very few external interfaces
Small or no persistent storage (disk, flash memory)
Typically very limited OS
Typically dedicated use case, not a general purpose device
Low power
Copyright © 2013, Oracle and/or its affiliates. All rights reserved.
Sample prototyping board
Small Embedded
STM32F4 Discovery Board (Very Low Cost, ca. 15 USD)
 STM32F407VGT6 microcontroller
– 32-bit ARM Cortex-M4F core
– 1 MB Flash
– 192 KB RAM
 3-axis accelerometer
 Omni-directional digital microphone
 Audio DAC with integrated class D speaker driver
 Eight LEDs, two push buttons (user and reset)
 USB OTG FS with micro-AB connector
Source: http://www.st.com/st-web-ui/static/active/en/resource/technical/document/data_brief/DM00037955.pdf
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Sample prototyping board
Small Embedded
Raspberry Pi (Low Cost, ca. 25 USD)
 Broadcom BCM2835
– 700 MHz ARM1176JZF-S core
– 512 MB RAM
 2 USB ports
 SD card slot
 Onboard Network
 Audio / Video output
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Program Agenda
 Java ME Evolution
 Connected Limited Device Configuration (CLDC)
 Generic Connection Framework (GCF)
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CLDC 8: an Evolutionary update for CLDC
• Key Features
• Synchronize with Java SE 8 Language Features into Java ME
• Add developer friendly APIs to Java ME from Java SE
• Virtual Machine Update to align with developer tools
• Remain small and enable footprint optimizations
• Specification Characteristics
• CLDC 8 is an extended strict subset of Java SE 8
• Consolidated Generic Connection Framework
• Backward binary compatibility
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Java SE 8
CLDC 8
CLDC 8 architecture
GCF 8
Multicast
Secure
Datagram
Modem
Connection
HTTP
HTTPS
Socket
Server
Socket
Datagram
CLDC 8
NIO files
Compact Configuration
NIO channels
NIO buffers
java.lang
java.io
Logging
Java VM
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java.security
java.util
Configurations
CLDC is scalable to small and very small devices
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The “CLDC
Configuration” is the
complete set of
CLDC APIs
Provides
maximum
functionality for
applications
Typical CLDC
platform footprint
is 1-2 MB ROM
The CLDC Compact
Configuration
defines a subset for
very small target
platforms
Omits Logging,
NIO Files, and
NIO Channels
Tailored for very
constrained
devices (512 K
ROM)
Copyright © 2013, Oracle and/or its affiliates. All rights reserved.
CLDC 8 Footprint Considerations
Optimizing Footprint Even Further
 Stripping On Deployment
– For fixed-function, minimal footprint deployments
– Allows bundling application with the runtime and then stripping away
unnecessary components
– Result: Minimal, non-modifiable binary containing application and
runtime
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New Java Language Features
Assertions
• private void setInterval(int interval) {
assert interval > 0 && interval <= 1000 :
"Invalid value?”;
}
Generics
• Added support for AbstractCollection, AbstractList, AbstractSet,
Collection, Collections, Enumeration, Iterator, List, ListIterator
Enhanced for
Loop
Autoboxing
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• void processList(Vector<String> list) {
for (String item : list) {
...
}
•Hashtable<Integer, String> data = new Hashtable<>();
void add(int id, String value) {
data.put(id, value);
}
New Java Language Features
Enumerations
Varargs
Static imports
Annotations
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•enum Season {WINTER, SPRING, SUMMER, FALL};
private Season season;
void setSeason(Season newSeason) {
season = newSeason;
•void warning(String format, String... parameters) {
for(String p : parameters) {
process(p);
}
}
• import static data.Constants.RATIO;
...
double r = Math.cos(RATIO * theta);
•SuppressWarnings, Deprecated, Override
@Deprecated
public void clear();
•(JLS 7 section 9.6.3.2 @Retention - SOURCE retentions policy only.)
New Java Language Features
Strings in switches
Binary integral literals and
underscores in numeric literals
Multi-catch and more precise
rethrow
Improved Type Inference for Gen.
Instance Creation (diamond)
Try-with-resources statement
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• switch (arg) {
case "-data": ...
case "-out": ...
• long mask = 0xfff0_ff08_4fff_0fffl;
byte flags = 0b01001111;
•catch (IOException | InterruptedException ex) {
logger.log(ex);
throw ex;
• Hashtable<String, String> map =
new Hashtable<>();
•try (DataInputStream is = new DataInputStream(...)){
return is.readDouble();
}
Library Updates
 CLDC Library
– Platform extensibility via Service Providers (ServiceLoader)
– EventObject and EventListener
– Subset of NIO Buffers
– NIO Files and NIO Channels
– Logging
– StringBuilder and String Formatter
– Comparable interface
– Try with resources – Closeable and AutoCloseable
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Library Updates
 New Collections
– List – ArrayList, LinkedList
– Map – HashMap, LinkedHashMap, WeakHashMap
– Set – HashSet, LinkedHashSet
– Queue – Deque, ArrayDeque
– Iterable and Iterator, ListIterator
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Focus on: Service Providers
An extension mechanism for the Java platform
 A service is a well-known set of interfaces and abstract classes
that is implemented by a (service) provider.
 Providers can be installed to extend the Java platform.
 Providers are located and instantiated on demand.
 Providers are identified via a provider-configuration file in the
META-INF/services resource directory.
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Service Providers - Example
An extension mechanism for the Java platform
import com.XYZ.ServiceA;
ServiceLoader<ServiceA> sl1=
ServiceLoader.load(ServiceA.class);
Resources:
META-INF/services/com.XYZ.ServiceA:
ServiceAProvider1
ServiceAProvider2
ServiceAProvider3
META-INF/services/ServiceB:
ServiceBProvider1
ServiceBProvider2
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com.XYZ.ServiceA
ServiceA
Provider1
ServiceB
ServiceA
Provider3
ServiceB
Provider1
ServiceA
Provider3
ServiceB
Provider2
Updates to CLDC Virtual Machine
CLDC 8 supports the Java VM Specification for SE 7 with some
limitations
• Target devices are not able to support InvokeDynamic
• No support for reflection or retention of runtime annotations
Verification by Type Checking
• For classfile versions 51 and 52
• without a preverifier
Legacy Verification (Preverifier)
• For classfile versions 48 and older
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Unsupported Java SE 8 Features
 No reflection
 No serialization
 No InvokeDynamic/Lambda expressions
 No JNI and application native code
 No User-defined class loaders
 No runtime annotations
 No thread groups and daemon threads
 No concurrency utilities
 Limited Math APIs (No BigDecimals)
 Limited security APIs
 Limited collection APIs (No sorted collection classes)
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CLDC Summary
Language Alignment with SE 8
VM Alignment with SE 8
Library Alignment with SE 8
Compact Configuration for very small devices
GCF 8 to provides flexible networking
Developer leverage to tools, apis and knowledge
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Program Agenda
 Java ME Evolution
 Connected Limited Device Configuration (CLDC)
 Generic Connection Framework (GCF)
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Generic Connection Framework (GCF)
Consolidates GCF specification from CLDC, MIDP, CDC, and JSR
197
• Consistent IPv6 support
• Generic ConnectionOption mechanism to parameterize connections
• Permissions apply per protocol
• Extended failure information via exceptions from java.net
New and enhanced protocols
• File support via StreamConnection
• IP Multicast
• Latest version of security protocols via TLS 1.2
• Secure datagram connection via DTLS 1.2
• Modem connection enhances CommConnection with control of hardware handshake
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Generic Connection Framework (GCF)
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CLDC
CLDC 8
DatagramConnection
ContentConnection
InputConnection
OutputConnection
StreamConnection
SecureServerConnection
SecureDatagramConnection
ModemConnection
UDPMulticastConnection
CommConnection
HttpConnection
HttpsConnection
SecureConnection
ServerSocketConnection
SocketConnection
UDPDatagramConnection
Copyright © 2013, Oracle and/or its affiliates. All rights reserved.
New GCF Features
IPv6
• GCF consistently supports IPv6 addresses
• The value of the host field on Connector.open must be
a symbolic hostname, an IPv4 address or an IPv6
address surrounded by square brackets ('[', ']’).
• datagram://[2001:db8::7]:4567
• multicast://[FF0X::101]:4444
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New GCF Features
UDP Multicast
• GCF includes support for UDP Multicast
• 1 to n communication of UDP datagrams
• Multicast is important for distributed services:
Used for service announcement and discovery, media streaming
• Dynamic Discovery for configuration and rendezvous (mDNS,
Bonjour)
• The new protocol class UDPMulticastConnection enables
• Client and server scenarios
• Joining multicast groups
• Creating a multicast server socket
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New GCF Features
TLS protocol enhancements
• SecureConnection and SecureServerConnection
support TLS 1.2
• SecureServerConnection provides the server-side of a TLS
connection
• Both can be parameterized to:
• Select a set of cipher suites
• Select a minimum protocol version
• Request client authentication
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New GCF Features
DTLS protocol support for TLS over UDP
• SecureDatagramConnection provides client-side support
for DTLS
• It can be parameterized to:
• Select a set of cipher suites
• Select a minimum protocol version
• Request client authentication
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New GCF Features
NetworkUtilities
• Utility functions for name lookup, reverse name lookup
and for testing the reachability of a host (ping):
• getCanonicalHostName(String host)
• isReachable(String host, int ttl, int timeout)
• getByName(String host)
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New GCF Features
Modem Connection
• Purpose: monitor and control the signal lines of a serial
interface
• Getter and setter for the line mode (input/output)
• Getter and setter for the line state
• Listener for changes to the state of an input line
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New GCF Features
Additional protocol parameters
ConnectionOptions
• Type-safe mechanism for protocol-specific additional parameters
• Useful for selecting access points, proxy settings, proprietary protocol
extensions
• Multiple connection options can be used with varargs
Example
•ConnectionOption <String> keep = new ConnectionOption<>
("KeepAlive", "KEEP_ALIVE");
ConnectionOption <Integer> port = new
ConnectionOption<>("ProxyPort", 80);
Connection c = Connector.open(“my.server.com”, keep, port)
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New GCF Features: Access Point
Selecting a Network Access Point
 The AccessPoint API enables:
– Obtaining a list of available network access points
– Querying the access technology (e.g. 3GPP, CDMA, Wi-Fi, Wired)
– Getting Access-point technology-specific properties (e.g. 3GPP country
code, network code)
– Selection of an access point for a connection
– Detection of connect/disconnect situations
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New GCF Features: Access Point
Example
AccessPoint aps[] = AccessPoint.getAccessPoints(true);
AccessPoint ap = aps[0];
// attach an event listener to the first access point
ap.addListener(new AccessPointListener() {
public void notifyEvent(AccessPoint accessPoint, int eventType) {
if ((eventType == AccessPointListener.EVENT_TYPE_AVAILABLE))
System.out.println(“signalstrength = ”+ ap.getProperty(“signalstrength"));
}
});
// select the first access point for communication
ConnectionOption<String> id = new ConnectionOption<>("AccessPoint”, ap.getId());
Connection c = Connector.open("http://www.oracle.com/index.html", id);
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Development Tools for CLDC 8
 Standard JDK 7 or 8 tools can be used for application development
 Embedded-specific hints & warning messages
– Provides developer with additional information to optimize code
 Debug structures are optional
– Debug features can be ignored/filtered out to save footprint
 Future tools under consideration may include
– Optimizing converter/compiler plugin for optimizing CLDC 8 applications
 Integrated with Java ME SDK and IDEs
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Java ME 8 - JCP
Activities and Schedule
 JSR 360: CLDC 8
– EG Kick-off: February 2013
– Early Draft: May 2013
– Public Review: September 2013
– Final Draft: December 2013
 JSR 361: Java ME Embedded Profile
– On Parallel Schedule
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Copyright © 2013, Oracle and/or its affiliates. All rights reserved.
Summary
CLDC 8 New and Improved
 Long anticipated updates to CLDC to align with SE 8 features
 Created for resource constrained devices
 Library updates
– Collection API updates
– NIO Buffers, NIO Files, NIO Channels, Logging
– Service Loader
 Consolidated GCF Connections
– Plus Multicast connection, Connection options, IPV6
– Secure Server Socket and Secure Datagrams
 Tools and support for embedded platforms
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References and Related Sessions
 CLDC8 – www.jcp.org/en/jsr/detail?id=360
 Java.net project – java.net/projects/jsr360
 Related sessions:
– MEEP: A New Java Profile for the Embedded World [CON5330]
– Oracle Java ME Embedded: Small Embedded with Big Opportunities [CON2796]
– Java ME 8 Overview: A New Platform for Embedded Development for Small Devices
[CON2267]
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Copyright © 2013, Oracle and/or its affiliates. All rights reserved.
Safe Harbor Statement
The preceding is intended to outline our general product direction. It is
intended for information purposes only, and may not be incorporated
into any contract. It is not a commitment to deliver any material, code,
or functionality, and should not be relied upon in making purchasing
decisions.
The development, release, and timing of any features or functionality
described for Oracle’s products remains at the sole discretion of
Oracle.
44
Copyright © 2013, Oracle and/or its affiliates. All rights reserved.
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