1.
Java (software platform)
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Java is used in a wide variety of computing platforms from embedded devices and mobile phones to enterprise servers and supercomputers. While they are less common than standalone Java applications, Java applets run in secure, sandboxed environments to provide many features of native applications, in addition, several languages have been designed to run natively on the JVM, including Scala, Clojure and Apache Groovy. Java syntax borrows heavily from C and C++, but object-oriented features are modeled after Smalltalk, Java eschews certain low-level constructs such as pointers and has a very simple memory model where every object is allocated on the heap and all variables of object types are references. Memory management is handled through integrated automatic garbage collection performed by the JVM, on November 13,2006, Sun Microsystems made the bulk of its implementation of Java available under the GNU General Public License. The latest version is Java 8, the only supported version as of 2016, Oracle has announced that using older versions of their JVM implementation presents serious risks due to unresolved security issues. The Java platform is a suite of programs that facilitate developing and running programs written in the Java programming language. A Java platform will include an engine, a compiler. Java ME, Specifies several different sets of libraries for devices with limited storage, display and it is often used to develop applications for mobile devices, PDAs, TV set-top boxes, and printers. Java SE, For general-purpose use on desktop PCs, servers, Java EE, Java SE plus various APIs which are useful for multi-tier client–server enterprise applications. The Java platform consists of programs, each of which provides a portion of its overall capabilities. For example, the Java compiler, which converts Java source code into Java bytecode, is provided as part of the Java Development Kit, the Java Runtime Environment, complementing the JVM with a just-in-time compiler, converts intermediate bytecode into native machine code on the fly. The Java platform also includes a set of libraries. The heart of the Java platform is the concept of a machine that executes Java bytecode programs. This bytecode is the same no matter what hardware or operating system the program is running under, there is a JIT compiler within the Java Virtual Machine, or JVM. The JIT compiler translates the Java bytecode into native processor instructions at run-time, the use of bytecode as an intermediate language permits Java programs to run on any platform that has a virtual machine available. Since JRE version 1.2, Suns JVM implementation has included a just-in-time compiler instead of an interpreter, although Java programs are cross-platform or platform independent, the code of the Java Virtual Machines that execute these programs is not. Every supported operating platform has its own JVM, in most modern operating systems, a large body of reusable code is provided to simplify the programmers job. This code is provided as a set of dynamically loadable libraries that applications can call at runtime
2.
USB
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It is currently developed by the USB Implementers Forum. USB was designed to standardize the connection of peripherals to personal computers. It has become commonplace on other devices, such as smartphones, PDAs, USB has effectively replaced a variety of earlier interfaces, such as serial ports and parallel ports, as well as separate power chargers for portable devices. Also, there are 5 modes of USB data transfer, in order of increasing bandwidth, Low Speed, Full Speed, High Speed, SuperSpeed, USB devices have some choice of implemented modes, and USB version is not a reliable statement of implemented modes. Modes are identified by their names and icons, and the specifications suggests that plugs, unlike other data buses, USB connections are directed, with both upstream and downstream ports emanating from a single host. This applies to power, with only downstream facing ports providing power. Thus, USB cables have different ends, A and B, therefore, in general, each different format requires four different connectors, a plug and receptacle for each of the A and B ends. USB cables have the plugs, and the corresponding receptacles are on the computers or electronic devices, in common practice, the A end is usually the standard format, and the B side varies over standard, mini, and micro. The mini and micro formats also provide for USB On-The-Go with a hermaphroditic AB receptacle, the micro format is the most durable from the point of view of designed insertion lifetime. The standard and mini connectors have a lifetime of 1,500 insertion-removal cycles. Likewise, the component of the retention mechanism, parts that provide required gripping force, were also moved into plugs on the cable side. A group of seven companies began the development of USB in 1994, Compaq, DEC, IBM, Intel, Microsoft, NEC, a team including Ajay Bhatt worked on the standard at Intel, the first integrated circuits supporting USB were produced by Intel in 1995. The original USB1.0 specification, which was introduced in January 1996, Microsoft Windows 95, OSR2.1 provided OEM support for the devices. The first widely used version of USB was 1.1, the 12 Mbit/s data rate was intended for higher-speed devices such as disk drives, and the lower 1.5 Mbit/s rate for low data rate devices such as joysticks. Apple Inc. s iMac was the first mainstream product with USB, following Apples design decision to remove all legacy ports from the iMac, many PC manufacturers began building legacy-free PCs, which led to the broader PC market using USB as a standard. The USB2.0 specification was released in April 2000 and was ratified by the USB Implementers Forum at the end of 2001.1 specification, the USB3.0 specification was published on 12 November 2008. Its main goals were to increase the transfer rate, decrease power consumption, increase power output. USB3.0 includes a new, higher speed bus called SuperSpeed in parallel with the USB2.0 bus, for this reason, the new version is also called SuperSpeed
3.
Data logger
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A data logger is an electronic device that records data over time or in relation to location either with a built in instrument or sensor or via external instruments and sensors. Increasingly, but not entirely, they are based on a digital processor and they generally are small, battery powered, portable, and equipped with a microprocessor, internal memory for data storage, and sensors. Data loggers vary between general purpose types for a range of measurement applications to specific devices for measuring in one environment or application type only. It is common for general purpose types to be programmable, however, electronic data loggers have replaced chart recorders in many applications. One of the benefits of using data loggers is the ability to automatically collect data on a 24-hour basis. Upon activation, data loggers are typically deployed and left unattended to measure and this allows for a comprehensive, accurate picture of the environmental conditions being monitored, such as air temperature and relative humidity. The cost of data loggers has been declining over the years as technology improves, simple single channel data loggers cost as little as $25. More complicated loggers may costs hundreds or thousands of dollars, standardisation of protocols and data formats has been a problem but is now growing in the industry and XML, JSON, and YAML are increasingly being adopted for data exchange. The development of the Semantic Web and the Internet of Things is likely to accelerate this present trend, several protocols have been standardised including a smart protocol, SDI-12, that allows some instrumentation to be connected to a variety of data loggers. The use of this standard has not gained much acceptance outside the environmental industry, SDI-12 also supports multi drop instruments. Some datalogging companies are now supporting the MODBUS standard. This has been used traditionally in the control area. Another multi drop protocol which is now starting to become widely used is based upon CAN Bus. Some data loggers use a flexible scripting environment to adapt themselves to various non-standard protocols, the terms data logging and data acquisition are often used interchangeably. However, in a context they are quite different. A data logger is a data system, but a data acquisition system is not necessarily a data logger. Data loggers typically have slower sample rates, a maximum sample rate of 1 Hz may be considered to be very fast for a data logger, yet very slow for a typical data acquisition system. Data loggers are implicitly stand-alone devices, while typical data acquisition system must remain tethered to a computer to acquire data and this stand-alone aspect of data loggers implies on-board memory that is used to store acquired data
4.
OSGi
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Application life cycle management is implemented via APIs that allow for remote downloading of management policies. The service registry allows bundles to detect the addition of new services, or the removal of services, the OSGi specifications have evolved beyond the original focus of service gateways, and are now used in applications ranging from mobile phones to the open-source Eclipse IDE. Other application areas include automobiles, industrial automation, building automation, PDAs, grid computing, entertainment, fleet management, the OSGi specification is developed by the members in an open process and made available to the public free of charge under the OSGi Specification License. The OSGi Alliance has a program that is open to members only. As of November 2010, there are seven certified OSGi framework implementations, a separate page lists both certified and non-certified OSGi Specification Implementations, which include OSGi frameworks and other OSGi specifications. OSGi is a Java framework for developing and deploying modular software programs, each bundle is a tightly coupled, dynamically loadable collection of classes, jars, and configuration files that explicitly declare their external dependencies. The framework is conceptually divided into the areas, Bundles Bundles are normal jar components with extra manifest headers. Services The services layer connects bundles in a way by offering a publish-find-bind model for Plain Old Java Interfaces or Plain Old Java Objects. Services Registry The application programming interface for management services, life-Cycle The application programming interface for life cycle management for bundles. Modules The layer that defines encapsulation and declaration of dependencies, security The layer that handles the security aspects by limiting bundle functionality to pre-defined capabilities. Execution Environment Defines what methods and classes are available in a specific platform, there is no fixed list of execution environments, since it is subject to change as the Java Community Process creates new versions and editions of Java. Bundle-SymbolicName, The only required header, this entry specifies an identifier for a bundle. Bundle-Description, A description of the bundles functionality, bundle-ManifestVersion, Indicates the OSGi specification to use for reading this bundle. Bundle-Version, Designates a version number to the bundle, bundle-Activator, Indicates the class name to be invoked once a bundle is activated. Export-Package, Expresses which Java packages contained in a bundle will be available to the outside world. Import-Package, Indicates which Java packages will be required from the world to fulfill the dependencies needed in a bundle. A Life Cycle layer adds bundles that can be installed, started, stopped, updated and uninstalled. Bundles rely on the layer for class loading but add an API to manage the modules in run time
5.
Java Management Extensions
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Java Management Extensions is a Java technology that supplies tools for managing and monitoring applications, system objects, devices and service-oriented networks. Those resources are represented by objects called MBeans, in the API, classes can be dynamically loaded and instantiated. Managing and monitoring applications can be designed and developed using the Java Dynamic Management Kit, JSR003 of the Java Community Process defined JMX1.0,1.1 and 1.2. JMX2.0 was being developed under JSR255, the JMX Remote API1.0 for remote management and monitoring is specified by JSR160. An extension of the JMX Remote API for Web Services is being developed under JSR262, adopted early on by the J2EE community, JMX has been a part of J2SE since version 5.0. JMX is a trademark of Oracle Corporation, JMX uses a three-level architecture, The Probe level - also called the Instrumentation level - contains the probes instrumenting the resources The Agent level, or MBeanServer - the core of JMX. It acts as an intermediary between the MBean and the applications, the Remote Management level enables remote applications to access the MBeanServer through connectors and adaptors. A connector provides full access to the MBeanServer API using various communication. Applications can be generic consoles or domain-specific applications, external applications can interact with the MBeans through the use of JMX connectors and protocol adapters. Connectors serve to connect an agent with a remote JMX-enabled management application and this form of communication involves a connector in the JMX agent and a connector client in the management application. Protocol adapters provide a management view of the JMX agent through a given protocol, Management applications that connect to a protocol adapter are usually specific to the given protocol. A managed bean - sometimes simply referred to as an MBean - is a type of JavaBean, managed Beans are particularly used in the Java Management Extensions technology - but with Java EE6 the specification provides for a more detailed meaning of a managed bean. The MBean represents a resource running in the Java virtual machine, Java EE6 provides that a managed bean is a bean that is implemented by a Java class, which is called its bean class. It is a class, or is annotated @Decorator. It is not annotated with an EJB component-defining annotation or declared as an EJB bean class in ejb-jar. xml, no special declaration, such as an annotation, is required to define a managed bean. An MBean can notify the MBeanServer of its changes by implementing the javax. management. NotificationEmitter. The application interested in the MBeans changes registers a listener to the MBeanServer, note that JMX does not guarantee that the listeners will receive all notifications. There are two types of MBean, Standard MBeans implement a business interface containing setters and getters for the attributes
6.
Java servlet
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A Java servlet is a Java program that extends the capabilities of a server. Although servlets can respond to any types of requests, they most commonly implement applications hosted on Web servers, such Web servlets are the Java counterpart to other dynamic Web content technologies such as PHP and ASP. NET. Servlets are most often used to process or store a Java class in Java EE that conforms to the Java Servlet API, servlets could in principle communicate over any client–server protocol, but they are most often used with the HTTP protocol. Thus servlet is often used as shorthand for HTTP servlet, thus, a software developer may use a servlet to add dynamic content to a web server using the Java platform. The generated content is commonly HTML, but may be other such as XML. Servlets can maintain state in session variables across many server transactions by using HTTP cookies, to deploy and run a servlet, a web container must be used. A web container is essentially the component of a web server that interacts with the servlets, the web container is responsible for managing the lifecycle of servlets, mapping a URL to a particular servlet and ensuring that the URL requester has the correct access rights. The Servlet API, contained in the Java package hierarchy javax. servlet, defines the interactions of the web container. A Servlet is an object receives a request and generates a response based on that request. The basic Servlet package defines Java objects to represent servlet requests and responses, as well as objects to reflect the servlets configuration parameters, servlets may be packaged in a WAR file as a web application. Servlets can be generated automatically from JavaServer Pages by the JavaServer Pages compiler, the difference between servlets and JSP is that servlets typically embed HTML inside Java code, while JSPs embed Java code in HTML. A somewhat older usage is to use servlets in conjunction with JSPs in a pattern called Model 2, the current version of Servlet is 3.1. The Servlet1 specification was created by Pavni Diwanji while she worked at Sun Microsystems, starting with version 2.3, the specification was developed under the Java Community Process. JSR53 defined both the Servlet 2.3 and JavaServer Page 1.2 specifications, JSR154 specifies the Servlet 2.4 and 2.5 specifications. As of June 9,2015, the current version of the Servlet specification is 3.1, in his blog on java. net, Sun veteran and GlassFish lead Jim Driscoll details the history of servlet technology. James Gosling first thought of servlets in the days of Java. This was before what is now the Java Platform, Enterprise Edition was made into a specification, the advantages of using servlets are their fast performance and ease of use combined with more power over traditional CGI. Traditional CGI scripts written in Java have a number of disadvantages, When an HTTP request is made
7.
Java Web Start
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In computing, Java Web Start is a framework developed by Sun Microsystems that allows users to start application software for the Java Platform directly from the Internet using a web browser. Some key benefits of this technology include seamless version updating for globally distributed applications, unlike Java applets, Web Start applications do not run inside the browser. By default they run in the sandbox as applets, with several minor extensions like allowing to load. Only signed applications can be configured to have additional permissions, Web Start has an advantage over applets in that it overcomes many compatibility problems with browsers Java plugins and different JVM versions. Web Start programs are no longer a part of the web page. Web Start can also launch unmodified applets that are packaged inside. jar files and this file can also pass the applet parameters. Such applets also run in a separate frame, applet launcher may not support some specific cases like loading class as resource. Like applets, Java Web Start is cross-platform, the developer prepares a special XML file with JNLP extension. This file describes the requirements, code location, parameters. The browser downloads this file as any other and opens it with Web Start tool, Web Start tool downloads all necessary resources and launches the application. Java Web Start provides a series of classes in the javax. jnlp package which provide services to the application. Sun designed most of these services with the aim of allowing carefully controlled access to resources while restricting the application to authorized operations, Sun introduced version 1.0 of Web Start in March 2001, while 64-bit Windows support was added only in Java 6. Since J2SE1.4 Web Start comes as a part of Java Runtime Environment called javaws. Programmers often speak of the Java Network Launching Protocol interchangeably with the term Web Start, the JNLP protocol, defined with an XML schema, specifies how to launch Java Web Start applications. JNLP consists of a set of defining how exactly to implement the launching mechanism. JNLP files include information such as the location of the jar package file, a properly configured browser passes JNLP files to a Java Runtime Environment which in turn downloads the application onto the users machine and starts executing it. The development of JNLP took place under the Java Community Process as JSR56 and it includes the original 1.0 release, the subsequent 1.5 maintenance release, and as of 2006, the pending 6.0 maintenance release. The user does not have to remain connected to the Internet to execute the downloaded programs, updates of the software download from the Web and become available when the user has a connection to the Internet, thus easing the burden of deployment
8.
Source code
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In computing, source code is any collection of computer instructions, possibly with comments, written using a human-readable programming language, usually as ordinary text. The source code of a program is designed to facilitate the work of computer programmers. The source code is often transformed by an assembler or compiler into binary machine code understood by the computer, the machine code might then be stored for execution at a later time. Alternatively, source code may be interpreted and thus immediately executed, most application software is distributed in a form that includes only executable files. If the source code were included it would be useful to a user, programmer or a system administrator, the Linux Information Project defines source code as, Source code is the version of software as it is originally written by a human in plain text. The notion of source code may also be more broadly, to include machine code and notations in graphical languages. It is therefore so construed as to include code, very high level languages. Often there are several steps of program translation or minification between the source code typed by a human and an executable program. The earliest programs for stored-program computers were entered in binary through the front panel switches of the computer and this first-generation programming language had no distinction between source code and machine code. When IBM first offered software to work with its machine, the code was provided at no additional charge. At that time, the cost of developing and supporting software was included in the price of the hardware, for decades, IBM distributed source code with its software product licenses, until 1983. Most early computer magazines published source code as type-in programs, Source code can also be stored in a database or elsewhere. The source code for a piece of software may be contained in a single file or many files. Though the practice is uncommon, a source code can be written in different programming languages. For example, a program written primarily in the C programming language, in some languages, such as Java, this can be done at run time. The code base of a programming project is the larger collection of all the source code of all the computer programs which make up the project. It has become practice to maintain code bases in version control systems. Moderately complex software customarily requires the compilation or assembly of several, sometimes dozens or even hundreds, in these cases, instructions for compilations, such as a Makefile, are included with the source code
9.
JavaServer Pages
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JavaServer Pages is a technology that helps software developers create dynamically generated web pages based on HTML, XML, or other document types. Released in 1999 by Sun Microsystems, JSP is similar to PHP, ASP and Reacts JSX, to deploy and run JavaServer Pages, a compatible web server with a servlet container, such as Apache Tomcat or Jetty, is required. Architecturally, JSP may be viewed as an abstraction of Java servlets. JSPs are translated into servlets at runtime, therefore JSP is a Servlet, JSP can be used independently or as the view component of a server-side model–view–controller design, normally with JavaBeans as the model and Java servlets as the controller. This is a type of Model 2 architecture, the compiled pages, as well as any dependent Java libraries, contain Java bytecode rather than machine code. Like any other Java program, they must be executed within a Java virtual machine that interacts with the servers host operating system to provide an abstract, platform-neutral environment. JSPs are usually used to deliver HTML and XML documents, but through the use of OutputStream, the Web container creates JSP implicit objects like request, response, session, application, config, page, pageContext, out and exception. JSP Engine creates these objects during translation phase, JSP pages use several delimiters for scripting functions. %>, which encloses a JSP scriptlet, a scriptlet is a fragment of Java code that is run when the user requests the page. %> for expressions, where the scriptlet and delimiters are replaced with the result of evaluating the expression, Java code is not required to be complete or self-contained within a single scriptlet block. It can straddle markup content, provided that the page as a whole is syntactically correct, for example, any Java if/for/while blocks opened in one scriptlet must be correctly closed in a later scriptlet for the page to successfully compile. Content that falls inside a block of Java code is subject to that code. Content inside an if block will appear in the output when the if condition evaluates to true. Likewise, content inside a loop construct may appear multiple times in the output, the following would be a valid for loop in a JSP page, The output displayed in the users web browser would be, Counting to three, This number is 1. Version 2.0 of the JSP specification added support for the Expression Language, used to access data, in JSP2.1, it was folded into the Unified Expression Language, which is also used in JavaServer Faces. An example of EL Syntax, The value of variable in the object javabean is $, the JSP syntax add additional tags, called JSP actions, to invoke built-in functionality. Additionally, the technology allows for the creation of custom JSP tag libraries that act as extensions to the standard JSP syntax, some JSP containers support configuring how often the container checks JSP file timestamps to see whether the page has changed. Typically, this timestamp would be set to an interval during software development
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