Java Notions Dictionary

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JavaServer Pages Compilation
Page Compilation allows server code to be embedded in an HTML file. As a result, web developers can make changes to the server without have to recompile the code thus giving them the option of allowing customization of web content from the client side. This means that developers save time deploying the application and can focus on other things.
Page Compilation also makes using and writing Java servlets easier so users don't have to be Java language experts to use them!
Java Web Server
Cross Platform
Java Web Server's ability to be cross platform is due to the fact that it is written in Java. Since Java is a widely support and accepted language, most of the platforms support any application written in Java. As a result, Java Web Server can be used on more platforms than any other web server can.
Java Web Server Key Features
Cross Platform
Servlet API
Page Compilation
Session Tracking
Administration Applet
Presentation Templates
Secure Socket Layer (SSL)
Secure Area Sandboxes
Digital Signature
Access Control List
Proxy Support
System Requirements
Although JAR can be used as a general archiving tool, the primary motivation for its development was so that Java applets and their requisite components (.class files, images and sounds) can be downloaded to a browser in a single HTTP transaction, rather than opening a new connection for each piece.This greatly improves the speed with which an applet can be loaded onto a web page and begin functioning. The JAR format also supports compression, which reduces the size of the file and improves download time still further. Additionally, individual entries in a JAR file may be digitally signed by the applet author to authenticate their origin.
Java Compatible Certfication(JCC)
100% Pure Java certification is an award bestowed upon programs that meet the criteria set forth in this guide. Certified programs have the right to display the 100% Pure Java logo on their software package. The logo assures customers that the program relies only on the documented and specified Java platform, so that it will run on any computer hosting a Java Compatible application environment. The end result is that your program delivers on the promise of "Write Once, Run Anywhere".
Certification is the process by which you inspect your program for compliance to the standards defined in the 100% Pure Java Cookbook, using the procedures and test tools provided by Sun. Once your program meets the specified criteria, you submit your program along with the required documentation to an independent certification center for inspection and approval.
Java Compatibility test process requires a senior contributor able to both develop new tests and review and track test development by others in the security area. This is a key position for delivering the Java Compatibility Kit (JCK), a high visibility project within Java Software and the industry.
Java Development Kit (JDK)
The Java Development Kit contains the software and tools that you need to compile, debug, and run applets and applications that you've written using the Java programming language. The JDK software and documentation is free.
JDK 1.1.6
This is the latest maintenance release of the JDK Version 1.1. JDK 1.1 includes improvements over JDK 1.0. Current plans call for new maintenance releases of JDK 1.1 at semi-regular intervals. These releases represent ongoing support of the JDK 1.1 feature set.
JDK 1.0.2
This is the final release of JDK Version 1.0. It was released in May 1996.
JDK 1.2 Beta 4 This is a beta release of the JDK Version 1.2. JDK 1.2, which is still under development, includes improvements over JDK 1.1.
JavaSoft has developed a standard SQL database access interface, the JDBC API. This API provides Java programmers with a uniform interface to a wide range of relational databases, and provides a common base on which higher level tools and interfaces can be built. JDBC is now a standard part of Java and is included in the JDK.
The JDBC API defines Java classes to represent database connections, SQL statements, result sets, database metadata, etc. It allows a Java programmer to issue SQL statements and process the results. JDBC is the primary API for database access in Java.
The JDBC API is implemented via a driver manager that can support multiple drivers connecting to different databases. JDBC drivers can either be entirely written in Java so that they can be downloaded as part of an applet, or they can be implemented using native methods to bridge to existing database access libraries.

  JDBC drivers fit into one of four categories:
1.The JDBC-ODBC bridge provides JDBC access via most ODBC drivers. Note that some ODBC binary code and in many cases database client code must be loaded on each client machine that uses this driver, so this kind of driver is most appropriate on a corporate network, or for application server code written in Java in a 3-tier architecture.
2.A native-API partly-Java driver converts JDBC calls into calls on the client API for Oracle, Sybase, Informix, DB2, or other DBMS. Note that, like the bridge driver, this style of driver requires that some binary code be loaded on each client machine.
3.A net-protocol all-Java driver translates JDBC calls into a DBMS-independent net protocol which is then translated to a DBMS protocol by a server. This net server middleware is able to connect its all Java clients to many different databases. The specific protocol used depends on the vendor. In general, this is the most flexible JDBC alternative. It is likely that all vendors of this solution will provide products suitable for Intranet use. In order for these products to also support Internet access they must handle the additional requirements for security, access through firewalls, etc., that the Web imposes. Several vendors are adding JDBC drivers to their existing database middleware products.
4.A native-protocol all-Java driver converts JDBC calls into the network protcol used by DBMSs directly. This allows a direct call from the client machine to the DBMS server and is a practical solution for Intranet access. Since many of these protocols are proprietary the database vendors themselves will be the primary source for this style of driver. Several database vendors have these in progress.
Java Virtual Machine (JVM)
The Java Virtual Machine is the cornerstone of Sun's Java programming language. It is the component of the Java technology responsible for Java's cross-platform delivery, the small size of its compiled code, and Java's ability to protect users from malicious programs.
The Java Virtual Machine is an abstract computing machine. Like a real computing machine, it has an instruction set and uses various memory areas. It is reasonably common to implement a programming language using a virtual machine; the best-known virtual machine may be the P-Code machine of UCSD Pascal.
The first prototype implementation of the Java Virtual Machine, done at Sun Microsystems, Inc., emulated its instruction set in software on a handheld device that resembled a contemporary Personal Digital Assistant (PDA). Sun's current Java release, the Java Developer's Kit (JDK) version 1.0.2, emulates the Java Virtual Machine on Win32, MacOS, and Solaris platforms. However, the Java Virtual machine does not assume any particular implementation technology or host platform. It is not inherently interpreted, and it may just as well be implemented by compiling its instruction set to that of a real CPU, as for a conventional programming language. It may also be implemented in microcode, or directly in silicon.
The Java Virtual Machine knows nothing of the Java programming language, only of a particular file format, the class file format. A class file contains Java Virtual Machine instructions (or bytecodes) and a symbol table, as well as other ancillary information.
For the sake of security, the Java Virtual Machine imposes strong format and structural constraints on the code in a class file. However, any language with functionality that can be expressed in terms of a valid class file can be hosted by the Java Virtual Machine. Attracted by a generally available, machine-independent platform, implementors of other languages are turning to the Java Virtual Machine as a delivery vehicle for their languages. In the future, we will consider bounded extensions to the Java Virtual Machine to provide better support for other languages.
Jini Technology
The Jini project was the 1994 inspiration of Sun cofounder and vice president Bill Joy at his Sun Aspen Smallworks R&D lab in Aspen, Colorado. With the creation of Sun's JavaTM technology, Joy saw the potential to leverage its power to create a ubiquitous network. The Java application environment provides a good computing platform for distributed computing, because both code and data can move from machine to machine.
"The trend is very clear," says Joy. "We are moving toward a world in which it will be possible to move software codes that act as our personal agents between many different computers in a global network."
One of the goals of Jini technology is to make adding an electronic device to a network as easy as plugging in the base unit of a new cordless phone. In fact, like a cordless phone unit, devices using Jini technology have just two cables: a power cord and a phone plug. When new wireless networks become common, the devices won't even need the phone plug -- they'll become services on the network simply by turning on.
Another goal is to make distributed computing -- capabilities shared among many diverse machines across a common network -- a near-term reality.
JIT compiler ( Just-In-Time )
In the Java programming language and environment, a just-in-time (JIT) compiler is a program that turns Java bytecode (a program that contains instructions that must be interpreted) into instructions that can be sent directly to the processor. After you've written a Java program, the source language statements are compiled by the Java compiler into bytecode rather than into code that contains instructions that match a particular hardware platform's processor (for example, an Intel Pentium microprocessor or an IBM System/390 processor). The bytecode is platform-independent code that can be sent to any platform and run on that platform.
In the past, most programs written in any language have had to be recompiled, and sometimes, rewritten for each computer platform. One of the biggest advantages of Java is that you only have to write and compile a program once. The Java virtual machine on any platform will "translate" the compiled bytecode into instructions understandable by the particular processor. However, the virtual machine handles one bytecode instruction at a time. Using the optional Java just-in-time compiler (really a second compiler) at the particular system platform compiles the bytecode into the particular system code (as though the program had been compiled initially on that platform). Once the code has been (re-)compiled by the JIT compiler, it will usually run more quickly in the computer.
Compiler is actually a traditional compiler that runs on-the-fly. JITs do not have time to perform much optimization Low-level (C-like) code and method invocations run much faster All the other problems remain
Java Naming abd Directory Interface(JNDI)
JNDI is a Java Standard Extension, providing Java applications with a unified interface to multiple naming and directory services in the enterprise. As part of the Java Enterprise API set, JNDI enables seamless connectivity to heterogeneous enterprise naming and directory services. Developers can now build powerful and portable directory-enabled applications using this industry standard.
The Java Naming and Directory Interface (JNDI) is an API specified in the Java programming language. It provides naming and directory functionality to applications written in the Java programming language. The JNDI is defined to be independent of any specific directory service implementation. Thus, a variety of directories--new, emerging, and already deployed ones--can be accessed in a common way.
The JNDI architecture consists of an API (Application Programming Interface) and an SPI (Service Provider Interface). Java applications use the JNDI API to access a variety of naming and directory services. The JNDI SPI enables a variety of naming and directory services to be plugged in transparently, allowing the Java application using the JNDI API to access their services.
Java Native Interface is a standard programming interface for writing Java native methods and embedding the Java virtual machine into native applications. The primary goal is binary compatibility of native method libraries across all Java virtual machine implementations on a given platform.
JDK 1.2 extends the Java Native Interface (JNI) to incorporate new features in the Java platform. The changes are driven by licensee and user comments.
You must declare all methods, whether Java programming language methods or native methods, within a Java programming language class. When you write a method implementation in a programming language other than the Java programming language, you must include the keyword native as part of the method's definition within the Java programming language class. The native keyword signals to the Java compiler that the function is a native language function.
The Java Management API (JMAPI) is a collection of Java language classes and interfaces that allow developers to more easily build system, network, and service management applications that solve management problems. The Managed Object Server is the mechanism that provides active instantiated management objects to applications. It includes the agent object interfaces, SNMP agent interfaces, managed data interfaces, Java database connectivity (JDBC) interfaces, a database, and an HTTP server.

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