JSP - Syntax

This chapter will give basic idea on simple syntax (ie. elements) involved with JSP development:

The Scriptlet:

A scriptlet can contain any number of JAVA language statements, variable or method declarations, or expressions that are valid in the page scripting language.

Following is the syntax of Scriptlet:


You can write XML equivalent of the above syntax as follows:


Any text, HTML tags, or JSP elements you write must be outside the scriptlet. Following is the simple and first example for JSP:


NOTE: Assuming that Apache Tomcat is installed in C:\apache-tomcat-7.0.2 and your environment is setup as per environment setup tutorial.

Let us keep above code in JSP file hello.jsp and put this file in C:\apache-tomcat-7.0.2\webapps\ROOTdirectory and try to browse it by giving URL http://localhost:8080/hello.jsp. This would generate following result:

JSP Declarations:

A declaration declares one or more variables or methods that you can use in Java code later in the JSP file. You must declare the variable or method before you use it in the JSP file.

Following is the syntax of JSP Declarations:


You can write XML equivalent of the above syntax as follows:


Following is the simple example for JSP Declarations:


JSP Expression:

A JSP expression element contains a scripting language expression that is evaluated, converted to a String, and inserted where the expression appears in the JSP file.

Because the value of an expression is converted to a String, you can use an expression within a line of text, whether or not it is tagged with HTML, in a JSP file.

The expression element can contain any expression that is valid according to the Java Language Specification but you cannot use a semicolon to end an expression.

Following is the syntax of JSP Expression:


You can write XML equivalent of the above syntax as follows:


Following is the simple example for JSP Expression:


This would generate following result:


JSP Comments:

JSP comment marks text or statements that the JSP container should ignore. A JSP comment is useful when you want to hide or "comment out" part of your JSP page.

Following is the syntax of JSP comments:


Following is the simple example for JSP Comments:


This would generate following result:


There are a small number of special constructs you can use in various cases to insert comments or characters that would otherwise be treated specially. Here's a summary:

Syntax	Purpose
<%-- comment --%>	A JSP comment. Ignored by the JSP engine.
%lt;!-- comment -->	An HTML comment. Ignored by the browser.
<\%	Represents static <% literal.
%\>	Represents static %> literal.
\'	A single quote in an attribute that uses single quotes.
\"	A double quote in an attribute that uses double quotes.

JSP Directives:

A JSP directive affects the overall structure of the servlet class. It usually has the following form:


There are three types of directive tag:

Directive	Description
<%@ page ... %>	Defines page-dependent attributes, such as scripting language, error page, and buffering requirements.
<%@ include ... %>	Includes a file during the translation phase.
<%@ taglib ... %>	Declares a tag library, containing custom actions, used in the page

We would explain JSP directive in separate chapter JSP - Directives

JSP Actions:

JSP actions use constructs in XML syntax to control the behavior of the servlet engine. You can dynamically insert a file, reuse JavaBeans components, forward the user to another page, or generate HTML for the Java plugin.

There is only one syntax for the Action element, as it conforms to the XML standard:


Action elements are basically predefined functions and there are following JSP actions available:

Syntax	Purpose
jsp:include	Includes a file at the time the page is requested
jsp:include	Includes a file at the time the page is requested
jsp:useBean	Finds or instantiates a JavaBean
jsp:setProperty	Sets the property of a JavaBean
jsp:getProperty	Inserts the property of a JavaBean into the output
jsp:forward	Forwards the requester to a new page
jsp:plugin	Generates browser-specific code that makes an OBJECT or EMBED tag for the Java plugin
jsp:element	Defines XML elements dynamically.
jsp:attribute	Defines dynamically defined XML element's attribute.
jsp:body	Defines dynamically defined XML element's body.
jsp:text	Use to write template text in JSP pages and documents.

We would explain JSP actions in separate chapter JSP - Actions
JSP Implicit Objects:

JSP supports nine automatically defined variables, which are also called implicit objects. These variables are:

Objects	Descriptionobject associated with the request.
request	This is the HttpServletRequest?
response	This is theHttpServletResponseobject associated with the response to the client.
out	This is thePrintWriterobject used to send output to the client.
session	This is theHttpSessionobject associated with the request.
application	This is theServletContextobject associated with application context.
config	This is theServletConfigobject associated with the page.
pageContext	This encapsulates use of server-specific features like higher performanceJspWriters.
page	This is simply a synonym forthis, and is used to call the methods defined by the translated servlet class.
Exception	TheExceptionobject allows the exception data to be accessed by designated JSP.

We would explain JSP Implicit Objects in separate chapter JSP - Implicit Objects.

Control-Flow Statements:

JSP provides full power of Java to be embedded in your web application. You can use all the APIs and building blocks of Java in your JSP programming including decision making statements, loops etc.

Decision-Making Statements:

The if...else block starts out like an ordinary Scriptlet, but the Scriptlet is closed at each line with HTML text included between Scriptlet tags.


This would produce following result:


Now look at the following switch...caseblock which has been written a bit differentlty using out.println()and inside Scriptletas:


This would produce following result:


Loop Statements:

You can also use three basic types of looping blocks in Java: for, while,and do…while blocks in your JSP programming.

Let us look at the following for loop example:


This would produce following result:


Above example can be written using while loop as follows:


This would also produce following result:
JSP Operators:

JSP supports all the logical and arithmetic operators supported by Java. Following table give a list of all the operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom.

Within an expression, higher precedence operators will be evaluated first.

Category	Operator	Associativity
Postfix	() [] . (dot operator)	Left to right
Unary	++ - - ! ~	Right to left
Multiplicative	* / %	Left to right
Additive	+ -	Left to right
Shift	>> >>> <<	Left to right
Relational	> >= < <=	Left to right
Equality	== !=	Left to right
Bitwise AND	&	Left to right
Bitwise XOR	^	Left to right
Bitwise OR	|	Left to right
Logical AND	&&	Left to right
Logical OR	||	Left to right
Conditional	?:	Right to left
Assignment	= += -= *= /= %= >>= <<= &= ^= |=	Right to left
Comma	,	Left to right

JSP Literals:

The JSP expression language defines the following literals:

• Boolean: true and false
• Integer: as in Java
• Floating point: as in Java
• String: with single and double quotes; " is escaped as \", ' is escaped as \', and \ is escaped as \\.
• Null: null

I will consider XML formatted file hibernate.cfg.xml to specify required Hibernate properties in my examples. Most of the properties take their default values and it is not required to specify them in the property file unless it is really required. This file is kept in the root directory of your application's classpath.

---