Part II Software When developing software there are several particularities to be aware of: Java is widespread used because of the platform independence of the compiled code. Pervasive devices usually process executables and data directly from the location in RAM or ROM where they are stored persistently (“Execute in place”). Since processing power and memory is limited, applications must be programmed efficiently. Often operating system and applications are not upgradable within the device’s lifetime. Applications on pervasive devices are usually not rebooted, and can therefore run nearly forever. It requires a very stable operating system and applications with very careful memory management to meet these requirements. On top of these operating systems, middleware components provide an abstraction of operating system specific dependencies.

Software Layers on a Device Application User Interface GUI TTS Speech Recognition Basic Components Database Access Security Communication Components Messaging Protocol Support Service Discovery Industry Specific Components TV API Phone API Smart Card Access Operating System Hardware Device Platform

6. Java The Java programming language is intended for the development of platform independent software. “Write once, run anywhere”. How Java works

6.1 Language Characteristics An important achievement of Java is that the language is kept very simple and the code is well readable. Java has been designed as a secure language. The byte-code is verified by the virtual machine ensuring that no illegal code is included. The code could be signed, which means that cryptographic algorithms are applied to ensure that the code originates from someone the user trusts. The Java program runs in a memory area of the system which is controlled by the virtual machine (“sandbox”). The program is allowed to perform any operation within the sandbox, but has only limited access to any system resource outside. For example unauthorized code cannot read or write any data on the system. Java programs can be distinguished as follows: Applications are stand-alone programs. Applets are mini-program running within a browser. Servlets are also related to web sites. While applets run on the client side, servlets are executed by the Web server.

6.2 Java Class Libraries Java Core Packages JavaBeans are Java components which developers can integrate into their applications, applets or servelets. 6.2 Java Class Libraries Java Core Packages Package Contents java.applet Classes for creating applets running within web browsers. java.awt Classes for creating graphical user interfaces. java.beans Classes for JavaBeans development. java.io Classes for system input and output, accessing a file system, and using persistent object (serialization). java.lang Fundamental Java classes and classes for obtaining reflective information about classes and objects. java.math Classes used within mathematical algorithms.

Optional Java Packages java.net High level support for networking. java.rmi Classes supporting Remote Method Invocation (RMI). java.security Classes for the Java security framework, including certificate management, RSA, and DSA interface. java.text Classes for handling text, dates, and numbers (e.g. String) java.util Manifold miscellaneous classes, such as collections framework, event model, internationalization, string tokenizing, data compression, and many more. Optional Java Packages package Contents javax.naming Classes for accessing naming and directory services. javax.sound Classes for the processing of audio data. javax.swing Classes for a more powerful and platform independent user interface than java.awt. org.omg.CORBA Provides the Corba API, including an Object Request Broker and IDL support.

6.3 Java Editions Standard Edition (J2SE) Java 2 Software Development Kit (SDK) is a product from Sun, which implement that specification. Java 2 Enterprise Edition (J2EE) offers additional features on top of the Standard Edition, such as servlets, JavaServer Pages, JDBC, Java Message Service, Java Naming, and Directory Interface, Java Transaction, Java Mail, XML, CORBA, and Enterprise Java Beans. Micro Edition The Java 2 Micro Edition (J2ME) has been introduced to meet the limitations and peculiarities of Pervasive Computing devices. J2ME introduces profiles, which specify language subsets for different group of devices. Java Card The Java Card is the smallest and most limited version of the Java family. Third party Java Independent from Sun, several companies offer manifold Java APIs, for example JavaBeans libraries.

The Flavors of Java within the Java 2 Family

6.5 PersonalJava and EmbeddedJava 6.4 Micro Edition Choosing subsets of the Java language particular for a specific device class is the basic concept of J2ME. Each subset is called a profile. Mobile Information Device Profile (MIDP) defines the Java functionality and APIs, which fit the screen size and memory constraints of PDAs. Each profile is based on one of two Configurations: Connected Device Configuration (CDC) is intended for devices which have at least 512 kilobytes of memory available to run Java and have a high bandwidth network connection. Connected Limited Device Configuration (CLDC) is intended for devices with only 128 kilobytes of memory for running Java and with limitations in the user interface, network bandwidth, and power supply. 6.5 PersonalJava and EmbeddedJava The PersonalJava Application Environment focuses on smart phones, set-top boxes, game consoles, PDAs, and other resource constrained network-connectable consumer devices.

6.6 Development Tools for Java PersonalJava is scalable, modular, and configurable. It is also possible to compile the Java byte code of a PersonalJava application into executable code, which can be placed directly into the ROM of a device. The EmbeddedJava Application Environment targets very small devices with very strict memory limitations, such as industrial controllers, pagers, telecommunication switches, or low-end phones. 6.6 Development Tools for Java Visual Café from Symantec, Jbuilder from Borland, Microsoft’s Visual Studio J++, and IBM’s Visual Age. Visual Age for Java supports the visual programming method: Software components like JavaBeans can be assembled in a visual composition editor almost intuitively to complex applications.