Java Applet Advantages and Disadvantages

Java applet

A Java applet is an applet delivered in the form of Java bytecode. Java applets can run in a Web browser using a Java Virtual Machine (JVM), or in Sun's AppletViewer, a stand-alone tool for testing applets. Java applets were introduced in the first version of the Java language in 1995. Java applets are usually written in the Java programming language but they can also be written in other languages that compile to Java bytecode such as Jython.

Applets are used to provide interactive features to web applications that cannot be provided by HTML. Since Java's bytecode is platform independent, Java applets can be executed by browsers for many platforms, including Windows, Unix, Mac OS and Linux.There are open source tools like applet2app which can be used to convert an applet to a stand alone Java application/windows executable/linux executable. This has the advantage of running a Java applet in offline mode without the need for internet browser software.

A Java Servlet is sometimes informally compared to be "like" a server-side applet, but it is different in its language, functions, and in each of the characteristics described here about applets.

Technical information

Java applets are executed in a sandbox by most web browsers, preventing them from accessing local data. The code of the applet is downloaded from a web server and the browser either embeds the applet into a web page or opens a new window showing the applet's user interface. The applet can be displayed on the web page by making use of the deprecated applet HTML element [1], or the recommended object element [2]. This specifies the applet's source and the applet's location statistics.

A Java applet extends the class java.applet.Applet, or in the case of a Swing applet, javax.swing.JApplet. The class must override methods from the applet class to set up a user interface inside itself (Applet is a descendant of Panel which is a descendant of Container).

Advantages

A Java applet can have any or all of the following advantages:

* it is simple to make it work on Linux, Windows and Mac OS i.e. to make it cross platform
* the same applet can work on "all" installed versions of Java at the same time, rather than just the latest plug-in version only. However, if an applet requires a later version of the JRE the client will be forced to wait during the large download.
* it is supported by most web browsers
* it will cache in most web browsers, so will be quick to load when returning to a web page but may get stuck in the cache and have issues when new versions come out.
* it can have full access to the machine it is running on if the user agrees
* it can improve with use: after a first applet is run, the JVM is already running and starts quickly, benefitting regular users of Java but the JVM will need to restart each time the browser starts fresh.
* it can run at a comparable (but generally slower) speed to other compiled languages such as C++, but many times faster than JavaScript
* it can move the work from the server to the client, making a web solution more scalable with the number of users/clients

Disadvantages

A Java applet is open to any of the following disadvantages:

* it requires the Java plug-in, which isn't available by default on all web browsers.
* an implementation of the Sun Java plug-in does not exist for AMD64/Intel64 processors.1
* it cannot start until the Java Virtual Machine is running, and this may have significant startup time the first time it is used.
* if untrusted, it has severely limited access to the user's system - in particular having no direct access to the client's disk or clipboard.
* some organizations only allow software installed by the administrators. As a result, many users cannot view applets by default.
* applets may require a specific JRE.

1. However, open source and freeware implementations are available, such as the GCJ plugin, and Blackdown Java plugin.

Compatibility issues

Sun has made a considerable effort to ensure compatibility is maintained between Java versions as they evolve. For example, Microsoft's Internet Explorer, the most popular web browser since the late 1990s, used to ship with the Microsoft Java Virtual Machine as the default. The MSJVM had some extra non-Java features added which, if used, would prevent MSJVM applets from running on Sun's Java (but not the other way round).[citation needed] Sun sued for breach of trademark, as the point of Java was that there should be no proprietary extensions and that code should work everywhere. Development of MSJVM was frozen by a legal settlement, leaving many users with an extremely outdated Java virtual machine. Later, in October 2001, MS stopped including Java with Windows, and for some years it has been left to the computer manufacturers to ship Java independently of the OS.

Some browsers (notably Netscape) do not do a good job of handling height=100% on applets which makes it difficult to make an applet fill most of the browser window (JavaScript can, with difficulty, be used for this). Having the applet create its own main window is not a good solution either, as this leaves the browser window as a largely useless extra window and leads to a large chance of the applet being terminated unintentionally by the user closing the parent browser window.

Alternatives

Alternative technologies exist (for example, DHTML, Flash, and Microsoft Silverlight) that satisfy some of the scope of what is possible with an applet.

Another alternative to applets for client side Java is Java Web Start, which runs outside the browser. In addition to the features available to applets, a simple permissions box can give Java Web Start programs read and/or write access to specified files stored on the client, and to the client's clipboard.

HIBERNATE - Features of Hibernate

HIBERNATE - Features of Hibernate

Transparent persistence without byte code processing Transparent persistence JavaBeans style properties are persisted No build-time source or byte code generation / processing Support for extensive subset of Java collections API Collection instance management Extensible type system Constraint transparency Automatic Dirty Checking Detached object support Object-oriented query language Powerful object-oriented query language Full support for polymorphic queries New Criteria queries Native SQL queries Object / Relational mappings Three different O/R mapping strategies Multiple-objects to single-row mapping Polymorphic associations Bidirectional associations Association filtering Collections of basic types Indexed collections Composite Collection Elements Lifecycle objects Automatic primary key generation Multiple synthetic key generation strategies Support for application assigned identifiers Support for composite keys Object/Relational mapping definition XML mapping documents Human-readable format XDoclet support HDLCA (Hibernate Dual-Layer Cache Architecture) Thread safeness Non-blocking data access Session level cache Optional second-level cache Optional query cache Works well with others High performance Lazy initialization Outer join fetching Batch fetching Support for optimistic locking with versioning/timestamping Highly scalable architecture High performance No "special" database tables SQL generated at system initialization time (Optional) Internal connection pooling and PreparedStatement caching J2EE integration JMX support Integration with J2EE architecture (optional) New JCA support

Hibernate (Java)

Hibernate (Java)

Written in Java
OS Cross-platform (JVM)
Platform Java Virtual Machine
Genre Object-relational mapping

Website http://www.thiyagaraajblog.tk

Hibernate is an object-relational mapping (ORM) library for the Java language, providing a framework for mapping an object-oriented domain model to a traditional relational database. Hibernate solves Object-Relational impedance mismatch problems by replacing direct persistence-related database accesses with high-level object handling functions. The Hibernate 2.1 framework won a Jolt Award in 2005 [1]

Hibernate is free as open source software that is distributed under the GNU Lesser General Public License.

Feature summary

Hibernate's primary feature is mapping from Java classes to database tables (and from Java data types to SQL data types). Hibernate also provides data query and retrieval facilities. Hibernate generates the SQL calls and relieves the developer from manual result set handling and object conversion, keeping the application portable to all SQL databases, with database portability delivered at very little performance overhead.

Hibernate provides transparent persistence for Plain Old Java Objects (POJOs). The only strict requirement for a persistent class is a no-argument constructor, not compulsorily public. (Proper behavior in some applications also requires special attention to the equals() and hashCode() methods.[1])

Hibernate provides a dirty checking feature that avoids unnecessary database write actions by performing SQL updates only on the modified fields of persistent objects.

Hibernate can be used both in standalone Java applications and in Java EE applications using servlets or EJB session beans.

History

Hibernate was developed by a team of Java software developers around the world led by Gavin King. JBoss, Inc. (now part of Red Hat) later hired the lead Hibernate developers and worked with them in supporting Hibernate.

The current version of Hibernate is Version 3.x . This version has new features like a new Interceptor/Callback architecture, user defined filters, and JDK 5.0 Annotations (Java's metadata feature). Hibernate 3 is also very close to the EJB 3.0 specification (although it was finished before the EJB 3.0 specification was released by the Hibernate wrapper for the Core module which provides conformity with the JSR 220 JPA Entity Manager standard).

Application programming interface

The Hibernate API is provided in the Java package org.hibernate.

org.hibernate.SessionFactory interface

References immutable and threadsafe object creating new Hibernate sessions. Hibernate-based applications are usually designed to make use only of a single instance of the class implementing this interface (often exposed using a singleton design pattern).

org.hibernate.Session interface

Represents a Hibernate session i.e. the main point of the manipulation performed on the database entities. The latter activities include (among the other things) managing the persistence state (transient, persisted, detached) of the objects, fetching the persisted ones from the database and the management of the transaction demarcation.

Session is intended to last as long as the logical transaction on the database. Due to the latter feature Session implementations are not expected to be threadsafe nor to be used by multiple clients