Home > Articles > Programming > Java

Using JSP Scripting Elements

  • Print
  • + Share This
JavaServer Pages (JSP) scripting elements are primary ways of performing server-side tricks in your JSP pages. Drew Falkman's beginner's guide teaches you how to get started using these elements.
This sample chapter is excerpted from Drew Falkman's JRun Web Application Construction Kit (Que, 2001).
This chapter is from the book

The JSP scripting elements (or scriptlets for short) are the way you can perform Java and JavaScript (in a few JSP engines, such as Macromedia JRun) scripting magic. They are always enclosed in <% %> brackets.

Scripting elements are processed by JRun (or another JSP engine) before any custom actions are processed. In the scripting element <% Date today = new Date(); %>, the Java keyword new signals JRun to create a new object. Date() tells Java it will be a Date object created from the java.util.Date class. The result is a new date object, whose value is the current date and time. This is where the variable today gets its value.

NOTE

A Java object is an instance of a class. Each class will define within itself what its objects will be made up of. For example, the Date object here will contain a date. The Date class defines how that information will be stored and how it can be accessed.

Classes also contain methods that are ways of accessing the object. To use a method, you specify the method name, following a dot (.) after the object name. Here, you could use the getTime() method of the Date class like this: today.getTime(), where today is the name of the Date object. Calling this method would return the number of milliseconds between midnight on January 1, 1970 and the time and date stored in the today Date object.

In every scripting element, the <% signals to the JRun processor that it should be processing the information that follows. Expressions are modified scripting elements, with an added = sign, and are used to output String information directly to the JSP page. Scripting elements always begin and end with <% %> tags. Expressions always begin and end with <%= and %> tags. Between the expression tags, there must be valid scripting information that will output a String result. If there is any additional information between the tags, you get an error. We are telling it to output the following:

new Date()

Most of the time, JSP templates consist of a mixture of scripting elements and expressions. You can use the scripting elements to process data and the expressions to output the results. Say you want to change the formatting of the date in the JSP template. To do this, you need to take a different approach than you used earlier. Listing 1 is a new version of the hello template; save it as hello3.jsp, and browse the file to see output similar to what is shown in Figure 1.

Listing 1—The hello3.jsp File

<%@ page import="java.util.*,java.text.*"%>
<html>
<head>
  <title>Hello 2</title>
</head>

<body>

Hello, and welcome to JRun!
<br>

<% Date today = new Date();
  DateFormat formatter; 
  formatter = DateFormat.getDateInstance(DateFormat.SHORT, Locale.US);%>

It is now <%= formatter.format(today) %>


</body>
</html>

Figure 1 JRun allows you to perform processes with scripting elements and then output the results in expressions.

What if you had not placed your expression within the script tags? Try removing the <% %> tags, saving the page, and executing the page. You should see output similar to that in Figure 2—obviously not what you want. Because content that is not within <% %> tags are sent to the client as-is, using the script outside a <% %> block causes the text of the script itself, rather than the data returned by the script, to be sent to the client. Why? Because if it's outside a <% %> block, JRun will never process it.

Figure 2 If scripting code is sent to the browser, it usually means you have omitted the <% %> tags.

If you are intending to output information using an expression, remember to include the equals sign. Omitting it can cause an error. To test this, remove the = from the line <%= formatter.DateFormat(today) %>. Add a semicolon at the end of your expression, after the close ) parenthesis. This seems minor, but Java syntax requires this after every expression outside a JSP Expression (like it was before we made this modification). This line should now look like this: <% formatter.DateFormat(today); %>. Now save the template, and reload it in your browser. Note that the date is missing, as shown in Figure 3. This happens because JSP expressions signal to JRun to output the element following the =, whereas normal scripting elements simply process the data.

Figure 3 If = is not included in an expression, the data will not be sent to the browser.

NOTE

When working with scripting elements, it doesn't matter how many spaces you have between the <% and %> tags. You can even bump scripts right up against them.

One of the main ways to use scripting is to format different types of data. Listing 1, for example, uses the DateFormat class to change the way a date (today) is formatted. Take a look at the first scripting element:

<%   Date today = new Date();
   DateFormat formatter; 
   formatter = DateFormat.getDateInstance(DateFormat.SHORT, Locale.US);%>

The first thing we did here is to create a new date object, but writing the script directly instead of using the jsp:param action. This is because in this example we want to do more with the date object. The next two lines create a DateFormat object, and modify that object using the getDateInstance() method. Then, we output information in the following expression:

<%= formatter.format(today) %>

The formatter object applies the format to the new date, today, by passing it to the called method format(). Take note of JRun's capability to process and then output the results of that processing.

NOTE

Many Java method calls can be passed arguments. These arguments specify information necessary to execute the method. For example, the DateFormat.format() method needs to be passed a Date object to format.

In JRun, JavaScript can also be used to perform scripting tasks. This is wonderful for those who are already familiar with JavaScript for performing client-side processing. However, because of the portability of Java and all the tools available, the examples throughout this book use Java.

Remember that JSP code is processed on the server, not on the client. The JSP code you write is never sent to the Web browser. What is sent to the browser? Most browsers feature a View Source option that displays code as received. If you view the source of the page generated when you call hello3.jsp in your browser, you see something like this:

<html>
<head>
  <title>Hello 2</title>
</head>

<body>

Hello, and welcome to JRun!
<br>



It is now 6/10/01

</body>
</html>

As you can see, there is no JSP code here at all. The <% %> tags, the expressions, the equal signs—all have been stripped out by the JRun Server, and what was sent to the client is the output that they generated.

TIP

Viewing the generated source is an invaluable debugging trick. If you ever find that output is not being generated as expected, viewing the source can help you understand exactly what was generated and why.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020