JSP Examples - JSTL

Defines several API classes defined by SUN.

Contains implementation classes provided by vendor.

Note:

It is recommended to place these jar files at server level.(D:\Tomcat 7.0\lib) instead of application

level.

To make core library available to JSP, we have to declare taglib directive as follows...

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<c:out>

where c is prefix and out is name of tag.

This tag can be used for writing Template text data and expressions to the JSP.

form-1:

<c:out value="durga" />

It prints durga to JSP

<c:out value="${param.user}" />

It prints the value of request parameter user to the JSP.

form-2:

If the main value is not available or it evaluates to null, then we can provide default value by using

default attribute.

<c:out value="${param.user}" default="Guest" />

test.jsp:

o/p: Hello Guest

Note:

<c:out> can accept the following 3 attributes

1.value

2.default

3.escapeXml

2.<c:set>

We can use <c:set> to set attributes in any scope and to set map and bean properties also.

Form-1:

We can use <c:set> to set attributes in any scope

<c:set var="name of the attribute" value="attributevalue" scope="request" />

scope attribute is optional and default scope is page scope.

test.jsp:

We can set map or bean properties by using <c:set>

We can specify bean or map object by using target attribute and property name by using property

attribute.

<c:set target="customer" property="name" value="pavan" />

The attributes for the <c:set> are:

1.var 2. value 3. scope 4. target 5. property

To remove attributes in the specified scope we can use this tag.

This tag can take the following 2 attributes

1.var Name of the Attribute

2.scope The Scope in which Attribute Present

Eg: <c:remove var="x" scope="session" />

If the scope is not specified then the container will search in the page scope for the required

attribute. If the attribute is not available then it will search in the request scope followed by

session and application scopes.

test.jsp:

This tag can be used to catch an exception within the JSP instead of forwarding to the error page.

The risky code we have to place as the body of <c:catch>

<c:catch >

Risky Code

</c:catch>

If an exception raised in the risky code, then this tag suppresses that exception and rest of the JSP

will be executed normally.

If an exception is raised we can hold that by using var attribute, which is the page scoped

attribute.

test.jsp:

http://localhost:7777/jsp1/catch1.jsp?uname=pavan&uage=47&uheight=5.11

User Name: pavan

Age:47

User Height: 5.11

http://localhost:7777/jsp1/catch1.jsp?uname=pavan&uage=ten&uheight=5.11

User Name: pavan

Oops ...Exception raised : java.lang.NumberFormatException: For input string: "ten"

User Height: 5.11

Summary of General Purpose Tags

target, property

For removing Attributes

For supporting an Expression

and to continue rest of Jsp

normally

Conditional Tags

1.<c:if>

We can use to implement core java if statement.

There are 2 forms are available for <c:if>

without body:

<c:if test="test_condition" var="x" scope="session"/>

In this case test_condition will be evaluated & store its results into variable x. In the rest of the

page where ever this test condition is required, we can use directly its value without evaluating

once again.

In this case both test and var attributes are mandatory. scope attribute is optional and default

scope is page.

test.jsp:

If test_condition is true then body will be executed otherwise without executing body rest of the

jsp will be continued.

In this case also we can store test result inside var attribute.

Both var and scope attributes are optional but test attribute is mandatory.

test.jsp:

<c:choose>,<c:when> and <c:otherwise>:

We can use these tags for implementing if-else and switch statements.

• Implementing if-else:

JSTL does not contain any tag for else. We can implement if-else statement by using above tags.

If test condition is true,Action-1 will be executed otherwise Action-2 will be executed.

Implementing switch statement:

1.<c:choose> should compulsory contains at least one <c:when> tag. But <c:otherwise> is optional.

• Every <c:when> tag implicitly contains break statement. Hence there is no chance of fall through

inside switch.

• We should take <c:otherwise> as last case only.

4.<c:choose> and <c:otherwise> won't take any attributes but <c:when> can take one mandatory

attribute test.

switch.jsp:

Summary of Conditional Tags

Java if - Statement

1.<c:forEach>:

form-1:

o/p: 10 times

<c:forEach begin="1" end="10" step="2" > 5 times

<c:forEach begin="4" end="0" step="-1" > Invalid b'z step value should not be -ve.

The begin attribute specifies the index where the loop has to start.

end index specifies the index where the loop has to terminate.

This loop internally maintains counter variable which is incremented by step attribute value.

The default value of step attribute is "1" and it is optional attribute.

form-2: <c:forEach> with var attribute:

<c:forEach> internally maintains a counter variable which can be accessed by using var attribute.

This variable is local variable. Hence from outside of for loop we cannot access.

test.jsp:

Form-3: <c:forEach> for iterating through Arrays and Collections:

Items attribute should be either Collection object or array object. This action will iterate over each

item in the collection until all elements completion.

We can represent current collection object by using var attribute.

Q. Write a JSP to print all elements of array:

test.jsp:

Q. Write a JSP to print all request headers information:

test.jsp:

Q. Write a JSP to print all request parameters information:

test.jsp:

http://localhost:7777/jsp1/forEach2A.jsp?user=durga&age=48&course=java&mail=durgaocjp@g

mail.com

Form-4: <c:forEach> with varStatus attribute:

varStatus attribute describes the status of iteration like current iteration number, is it first

iteration or not etc..

This attribute is of type javax.servlet.jsp.core.TagLoopStatus.

This class contains several methods which are useful during iteration.

returns the current item

returns the current index(counter value)

returns the number of iterations that have already performed.

Returns true if the current Iteration is the First iteration

Returns true if the current iteration is the last iteration

returns start index

returns end index

returns the incremented value

test.jsp:

It is a specialized version of forEach to perform StringTokenization based on some delimiter. It acts

as StringTokizer. We can store current token by using var attribute.

test.jsp:

<c:forTokens> can accept the following extra attributes also.

begin: specifies the index at which iteration should start. The index of first token is zero.

end: specifies the index where iteration should be terminated.

step: counter increment value between iterations

varStatus: to specify the status of iteration

test.jsp:

Note:

In the case of <c:forTokens>, items attribute should be String only. But in the case of <c:forEach>

the items attribute can be Collection, Array, Map OR String. Hence <c:forTokens> is considered as

specialized version of <c:forEach>

Summary of Iteration Tags

VarStatus

URL Related Tags

We can use this tag for importing the response of other pages in the current page response at

request processing time.(i.e. Dynamic Include)

Form-1:

<c:import url="second.jsp" />

Eg:

first.jsp:

<h1>The FREE videos are available in www.durgasoftvideos.com</h1>

Form-2:

We can import response from outside of current application also.(i.e cross context communication

is possible)

<c:import url="/second.jsp" context="/webapp2" />

url and context should be specified with absolute Path only i.e should starts with "/"

Form-3:

We can store the result of imported page into a variable specified by var attribute. In the rest of

the JSP, where ever that result is required we can use directly that variable without importing

once again.

test.jsp:

Another way to store the result of <c:import> is to use Reader object. It is alternative to var

attribute.

<c:import url="second.jsp" varReader="r" scope="page" />

Form-5:

While performing import we can send form parameters also to the Target JSP. For this we have to

use <c:param> tag. These parameters are available as form parameters in the target JSP.

first.jsp:

<h1> The offered courses are : ${param.c1} and ${param.c2}

2.<c:redirect>:

This action can be used to redirect the request to another page. This is exactly similar to

sendRedirect() method of ServletResponse.

Form-1:

<c:redirect url="second.jsp" />

url can be specified either with Relative path or absolute path

first.jsp:

<h1>Hello this is Second JSP</h1>

If we send the request to first.jsp then second.jsp will provide response through redirection.

Form-2:

We can redirect request to some other web application's resources also.

<c:redirect url="/second.jsp" context="/webapp2" />

url and context should be specified with Absolute Path only i.e. should starts with "/"

Form-3:

While performing redirection we can pass form parameters also to target resource.

first.jsp:

The offered courses are : ${param.c1} and ${param.c2}

3.<c:url>

We can use this standard action to rewrite urls to append session information and form

parameters.

Form-1:

<c:url value="second.jsp" var="x" scope="request"/>

The encoded url with sessionid will be stored inside x.

test.jsp:

<c:url value="/second.jsp" context="/webapp2" var="x" scope="request"/>

Form-3:

<h1>Offered courses are : ${param.c1} and ${param.c2}</h1>

Summary of URL related Tags

For importing the Response of

Web Components.

To rewrite URL for appending

Session Information &

Parameters (Form)

To send Parameters while

importing & redirecting.

Summary of All Core Library Tags:

JSTL SQL Library

It defines several tags for communicating with database.

To make sql library available to JSP, we have to write the following taglib directive.

<%@ taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql" %>

The following are important sql library tags

To create DataSource

To execute select query

To execute non-select query(insert|delete|update)

To provide parameter values in the case of PreparedStatement

To provide date values in the case of PreparedStatement

To implement transactions

Note: Transaction is a group of sql queries which will be executed on the policy "Either ALL or

None".

Note: It is not recommended to use JSTL SQL Library in our JSP, b'z JSP meant for presentation

logic but not for business logic and database logic.

test.jsp:

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JSTL Functional Library

It defines several tags for general String manipulation operations.

To use Functional Library,we have to write the following taglib directive in JSP.

<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>

The following are important tags in this library:

1.<fn:contains()>

Eg2:

split() method will split the given string according to the specified separator (delimiter)

join() method will join the given tokens into a single string based on separator.

Eg1:

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Eg2: