J2ME configuration layer depth

Abstract: J2ME configuration layer depth

Java 2 Micro Edition (J2ME), is built on a profiles, configuration, the operating system and virtual machine, such as part of the structure above the standard. These elements form a complete J2ME real-time operating environment. Figure A shows how some of these combined. J2ME offers two configurations: Connected Limited Device Configuration (CLDC) and the Connected Device Configuration (CDC). This two configurations of equipment based on the memory footprint for different types of equipment.

Configuration designated smallest functional group and related Java Virtual Machine (JVM) should support the Java class libraries. Conceptually speaking, the configuration of the virtual machine (VM) running the top, such as when you use a CLDC and CDC configuration, you will relate to the VM relevant, because the two are closely linked.

However, it should be noted that in J2ME, is not affiliated with the allocation of a specific VM, he can work with other VM and support of the libraries. For example, the CLDC and applications can be designated basic function of the VM work together. On the details, see CLDC HotSpot Virtual Machine Application white pages.

To help you understand J2ME configuration layer role, I will CLDC and CDC were to elaborate.

CLDC
CLDC is for less than 512 KB memory footprint of the equipment configuration. CLDC is based KVM, it is highly optimized JVM, he addressed the 16-bit or 32-bit microprocessor, 160 to 512 KB of memory-based low-end, network connectivity, battery-powered equipment. Typical memory requirement is 128 KB make it to store KVM and related libraries. More information on the KVM from the Sun's KVM white pages to be.

On the network, CLDC targeted at the limited and intermittent wireless connectivity equipment, all J2ME CLDC software applications running on should be able at any other high-end running on the Java VM. Of course, this requires the support of the CLDC. CLDC configurations focus on I / O, networking, and security issues, international issues and the core Java libraries, and other related areas.

And event handling, user and application interaction, applications, content management, and other survival-related fields is to be dealt by the Profile. Use interface definition (for specific equipment, such as pagers, mobile phones and PDA) Profile is also within the scope of the layer, it built on the top, and use J2ME configuration. Mobile Information Device Profile (MIDP) is a J2ME profile, which defines the use of CLDC equipment of the user interface related norms.

CLDC J2SE access from the vast majority of the class, but some equipment aimed at the small memory footprint of the new category is not obtained from the J2SE APIs. J2SE done on the category of inheritance and CLDC new category-specific information, refer to a 1.0 CLDC 6.2 and 6.3 versions of the content. Java language specification in a number of floating-point support is no exception, no examples of the type of complete support and limited error handling capabilities.

Mentioned here CLDC HotSpot applications are also relevant, and it CLDC equivalent to the use of the equipment configuration in the Java VM KVM replacement. According to Sun, CLDC HotSpot VM is a high-performance implementation of the JVM (32 using CLDC v1.0 norms). He in the same memory footprint on the KVM operation than an order of magnitude higher than the better performance.

CDC: complete Java platform
CDC is applied to a larger memory, 2 MB or more particularly the equipment, CDC against limited and intermittent wireless connectivity equipment, CDC Foundation profile with the CVM and common definition of a complete J2ME environment.

CVM for users and embedded devices designed fully functional JVM, it supports all the Java 2 v1.3 VM security, JNI, JVMDI, RMI, cited weak functions and libraries. Essentially, CVM has a presence in all desktop systems with the function of the JVM.

CDC from the smallest of J2SE Java component data packets. Foundation profile from the user equipment needed to maintain the composition of the class library and APIs. So, if you work in a CDC J2ME-based environment, you need to update your code to make APIs replacement.

CDC is an extension of the CLDC therefore exists between the two configurations upward compatibility. CDC, and Foundation profile also provides real-time PersonalJava norms on the use of the application development process is fully compatible with.

Aggregate
J2ME model system so that different types of equipment "Special Edition" the creation of Java. As more and more equipment manufacturers have begun to accept the J2ME technology and the use of equipment J2ME increase, the updated J2ME profiles will be applied. Adopted for the development of Java-based device to provide a public platform for the smallest, J2ME configuration of the structure used to the way that these particular version of Java.

Source: www.jspcn.net

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