Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
A software developer is a person concerned with facets of the software development process. Their work includes researching, designing, developing, and testing software. A software developer may take part in design, computer programming, or software project management...
A dynamic web page is a kind of web page that has been prepared with fresh information , for each individual viewing. It is not static because it changes with the time , the user , the user interaction , the context A dynamic web page is a kind of web page that has been prepared with fresh...
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
, or other document types. Released in 1999 as Sun's answer to ASP
Active Server Pages
Active Server Pages , also known as Classic ASP or ASP Classic, was Microsoft's first server-side script engine for dynamically-generated Web pages. Initially released as an add-on to Internet Information Services via the Windows NT 4.0 Option Pack Active Server Pages (ASP), also known as Classic...
PHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document...
, JSP was designed to address the perception that the Java programming environment didn't provide developers with enough support for the Web.
To deploy and run, a compatible web server with servlet container is required. The Java Servlet and the JavaServer Pages (JSP) specifications from Sun Microsystems and the JCP
Java Community Process
The Java Community Process or JCP, established in 1998, is a formalized process that allows interested parties to get involved in the definition of future versions and features of the Java platform....
(Java Community Process) must both be supported by the container.
Overview
Architecturally, JSP may be viewed as a high-level abstraction of Java servlet
Java Servlet
A servlet is a Java programming language class used to extend the capabilities of servers that host applications accessed via a request-response programming model. Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by Web servers...
s. JSPs are loaded in the server and are operated from a structured special installed Java server packet called a Java EE Web Application, often packaged as a file archive.
JSP allows Java code and certain pre-defined actions to be interleaved with static web markup content, with the resulting page being compiled and executed on the server to deliver an HTML or XML document. The compiled pages and any dependent Java libraries use Java bytecode rather than a native software format, and must therefore be executed within a Java virtual machine
Java Virtual Machine
A Java virtual machine is a virtual machine capable of executing Java bytecode. It is the code execution component of the Java software platform. Sun Microsystems stated that there are over 4.5 billion JVM-enabled devices.-Overview:...
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
to provide an abstract platform-neutral environment.
JSP syntax is a fluid mix of two basic content forms: scriptlet elements and markup. Markup is typically standard HTML or XML, while scriptlet
Scriptlet
In JavaServer Pages technology, a scriptlet is a piece of Java-code embedded in the HTML-like JSP code.The scriptlet is everything inside the tags. Between these the user can add any valid Scriplet i.e. any valid Java Code....
elements are delimited blocks of Java code which may be intermixed with the markup. When the page is requested the Java code is executed and its output is added, in situ
In situ
In situ is a Latin phrase which translated literally as 'In position'. It is used in many different contexts.-Aerospace:In the aerospace industry, equipment on board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may...
, with the surrounding markup to create the final page. JSPs must be compiled to Java bytecode classes before they can be executed, but such compilation is needed only when a change to the source JSP file has occurred.
Java code is not required to be complete (self contained) within its scriptlet element block, but can straddle markup content providing the page as a whole is syntactically correct (for example, any Java if/for/while blocks opened in one scriptlet element must be correctly closed in a later element for the page to successfully compile). This system of split inline coding sections is called step over scripting because it can wrap around the static markup by stepping over it. Markup which falls inside a split block of code is subject to that code, so markup inside an if block will only appear in the output when the if condition evaluates to true; likewise markup inside a loop construct may appear multiple times in the output depending upon how many times the loop body runs.
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
-like tags, called JSP actions, to invoke built-in functionality. Additionally, the technology allows for the creation of JSP tag libraries that act as extensions to the standard HTML or XML tags. JVM operated tag libraries provide a platform independent way of extending the capabilities of a web server
Web server
Web server can refer to either the hardware or the software that helps to deliver content that can be accessed through the Internet....
. Note that not all commercial Java servers are Java EE specification compliant.
Starting with version 1.2 of the JSP specification, JavaServer Pages have been developed under the Java Community Process
Java Community Process
The Java Community Process or JCP, established in 1998, is a formalized process that allows interested parties to get involved in the definition of future versions and features of the Java platform....
. JSR 53 defines both the JSP 1.2 and Servlet 2.3 specifications and JSR 152 defines the JSP 2.0 specification. As of May 2006 the JSP 2.1 specification has been released under JSR 245 as part of Java EE 5. As of Dec 10, 2009 the JSP 2.2 specification has been released as a maintenance release of JSR 245.
A servlet is a Java programming language class used to extend the capabilities of servers that host applications accessed via a request-response programming model. Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by Web servers...
by a JSP compiler. The compiler either generates a servlet in Java code that is then compiled by the Java compiler, or it may compile the servlet to byte code which is directly executable. JSPs can also be interpreted
JSP Weaver
JSP Weaver is a JavaServer Pages interpreter. Unlike JSP compilers it evaluates the JSP files directly, without generating or compiling intermediate Java source files for the JSP Java servlet....
on-the-fly, reducing the time taken to reload changes.
Regardless of whether the JSP compiler generates Java source code for a servlet or emits the byte code directly, it is helpful to understand how the JSP compiler transforms the page into a Java servlet. For example, consider the following input JSP and its resulting generated Java Servlet.
import com.foo.bar; // Imported as a result of <%@ page import="com.foo.bar" %>
import …
class _myservlet implements javax.servlet.Servlet, javax.servlet.jsp.HttpJspPage {
// Inserted as a
// result of <%! int serverInstanceVariable = 1;%>
int serverInstanceVariable = 1;
…
public void _jspService( javax.servlet.http.HttpServletRequest request,
javax.servlet.http.HttpServletResponse response )
throws javax.servlet.ServletException,
java.io.IOException
{
javax.servlet.ServletConfig config = …; // Get the servlet config
Object page = this;
PageContext pageContext = …; // Get the page context for this request
javax.servlet.jsp.JspWriter out = pageContext.getOut;
HttpSession session = request.getSession( true );
try {
out.print( "\r\n" );
out.print( "\r\n" );
…
// From <% int localStackBasedVariable = 1; %>
int localStackBasedVariable = 1;
…
out.print( "
\r\n" );
out.print( "
" );
// From <%= toStringOrBlank( "expanded inline data " + 1 ) %>
out.print( toStringOrBlank( "expanded inline data " + 1 ) );
out.print( "
\r\n" );
…
} catch ( Exception _exception ) {
// Clean up and redirect to error page in <%@ page errorPage="myerror.jsp" %>
}
}
}
JSP 2.0
The new version of the JSP specification includes new features meant to improve programmer productivity. Namely:
Expression Language is a scripting language which allows access to Java components through JSP. Since JSP 2.0, it has been used inside JSP tags to separate Java code from JSP, and to allow easier access to Java components ....
Apache Velocity is an open source software project directed by the Apache Software Foundation. Velocity is a Java-based template engine that provides a simple yet powerful template language to reference objects defined in Java code...
Templates are a feature of the C++ programming language that allow functions and classes to operate with generic types. This allows a function or class to work on many different data types without being rewritten for each one....
(among other things).
A faster/easier way to display parameter values.
A clear way to navigate nested beans.
The Java EE 5 Platform has focused on easing development by making use of Java language annotations that were introduced by J2SE 5.0. JSP 2.1 supports this goal by defining annotations for dependency injection on JSP tag handlers and context listeners.
Another key concern of the Java EE 5 specification has been the alignment of its web tier technologies, namely JavaServer Pages (JSP), JavaServer Faces
JavaServer Faces
JavaServer Faces is a Java-based Web application framework intended to simplify development integration of web-based user interfaces....
The JavaServer Pages Standard Tag Library , is a component of the Java EE Web application development platform. It extends the JSP specification by adding a tag library of JSP tags for common tasks, such as XML data processing, conditional execution, loops and internationalization...
The Java Unified Expression Language is a special purpose programming language mostly used in Java web applications for embedding expressions into web pages....
(EL), which integrates the expression languages defined by JSP 2.0 and JSF 1.1.
The main key additions to the Unified EL that came out of the alignment work have been:
A pluggable API for resolving variable references into Java objects and for resolving the properties applied to these Java objects, support for deferred expressions, which may be evaluated by a tag handler when needed, unlike their regular expression counterparts, which get evaluated immediately when a page is executed and rendered, and
support for l-value expression, which appear on the left hand side of an assignment operation. When used as an l-value, an EL expression represents a reference to a data structure, for example: a JavaBeans property, that is assigned some user input.
The new Unified EL is defined in its own specification document, which is delivered along with the JSP 2.1 specification.
Thanks to the Unified EL, JSTL tags, such as the JSTL iteration tags, can now be used with JSF components in an intuitive way.
JSP 2.0 introduced a problem in the tag library section on how the JSP version information was represented. The specification itself is inconsistent, sometimes referring to a jsp-version element, and at other times a version attribute on the root element. JSF specifications have gone with the later interpretation; however some JSP implementations still expect the jsp-version element.
JSP 2.1 leverages the Servlet 2.5 specification for its web semantics.
ASP.NET is a Web application framework developed and marketed by Microsoft to allow programmers to build dynamic Web sites, Web applications and Web services. It was first released in January 2002 with version 1.0 of the .NET Framework, and is the successor to Microsoft's Active Server Pages ...
In computing, ColdFusion is the name of a commercial rapid application development platform invented by Jeremy and JJ Allaire in 1995. ColdFusion was originally designed to make it easier to connect simple HTML pages to a database, by version 2 it had...
EAR is a file format used by Java EE for packaging one or more modules into a single archive so that the deployment of the various modules onto an application server happens simultaneously and coherently...
FreeMarker is a Java-based template engine focusing on the MVC software architecture. Although it's mostly used for Servlet-based Web Application development, it can be used for any other kind of text output, such as generating CSS, Java source code, etc. Unlike JSP, it is not dependent on the...
In software, JAR is an archive file format typically used to aggregate many Java class files and associated metadata and resources into one file to distribute application software or libraries on the Java platform.JAR files are built on the ZIP file format and have the .jar file extension...
A servlet is a Java programming language class used to extend the capabilities of servers that host applications accessed via a request-response programming model. Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by Web servers...
JHTML stands for Java HTML. This is a page authoring system developed at Art Technology Group . Files with a ".jhtml" filename extension contain standard HTML tags in addition to proprietary tags that reference Java objects running on a special server setup to handle requests for pages of this...
PHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document...
Python Server Pages is a name used by several different implementations of server-side script engines for creating dynamically-generated web pages by embedding Python in HTML...
Thymeleaf is a Java XML/XHTML/HTML5 template engine that can work both in web and non-web environments. It is better suited for serving XHTML/HTML5 at the view layer of MVC-based web applications, but it can process any XML file even in offline environments.In web applications Thymeleaf aims to be...
