1 Overview of Tag Libraries and Utilities

Tag Syntax Symbology and Notes

For the syntax documentation in tag descriptions throughout this manual, note the following:

• Italic indicates that you must specify a value or string.

• Optional attributes are enclosed in square brackets: [...]

• Default values of optional attributes are indicated in bold.

• Choices in attribute values are separated by vertical bars: |

• Except where noted, you can use JSP runtime expressions to set tag attribute values: "<%= jspExpression %>"

• Tag descriptions in this manual use certain tag prefixes by convention; however, you can designate any desired prefix in your taglib directives.

Overview of Extended Type JavaBeans

JSP pages generally rely on core Java types in representing scalar values. However, neither of the following standard type categories is fully suitable for use in JSP pages:

• Primitive types such as int, float, and double

  Values of these types cannot have a specified scope. They cannot be stored in a JSP scope object (for page, request, session, or application scope), because only objects can be stored in a scope object.

• Wrapper classes in the standard java.lang package, such as Integer, Float, and Double

  Values of these types are objects, so they can theoretically be stored in a JSP scope object. However, they cannot be declared in a jsp:useBean action, because the wrapper classes do not follow the JavaBean model and do not provide zero-argument constructors.

  Additionally, instances of the wrapper classes are immutable. To change a value, you must create a new instance and assign it appropriately.

To work around these limitations in a JDK 1.4 or earlier environment, OC4J provides the JmlBoolean, JmlNumber, JmlFPNumber, and JmlString JavaBean classes in package oracle.jsp.jml to wrap the most common Java types.

For information, see Chapter 2, "JavaBeans for Extended Types".

Overview of JspScopeListener for Event-Handling

OC4J provides the JspScopeListener interface for lifecycle management of Java objects of various scopes within a JSP application.

Standard servlet and JSP event-handling is provided through the javax.servlet.http.HttpSessionBindingListener interface, but this is for session-based events only. The Oracle JspScopeListener can be integrated with HttpSessionBindingListener to manage session-based events, and can handle page-based, request-based, and application-based events as well.

For information, see "JSP Event-Handling with JspScopeListener".

Overview of Integration with XML and XSL

You can use JSP syntax to generate any text-based MIME type, not just HTML code. In particular, you can dynamically create XML output. When you use JSP pages to generate an XML document, however, you often want a stylesheet applied to the XML data before it is sent to the client. This is difficult in JavaServer Pages technology, because the standard output stream used for a JSP page is written directly back through the server.

OC4J provides special tags to specify that all or part of a JSP page should be transformed through an XSL stylesheet before it is output. Input can be from the tag body or from an XML DOM object, and output can be to an XML DOM object to the browser.

You can use these tags multiple times in a single JSP page if you want to specify different style sheets for different portions of the page.

There is additional XML support as well:

• A utility tag converts data from an input stream to an XML DOM object.

• Several tags, for such features as caching and SQL operations, now can take XML objects as input or send them as output.

XML utility tags are summarized in Table 1-1. Note that there is also XML functionality in the dbOpen SQL tag and the cacheXMLObj Web Object Cache tag. For more information, see Chapter 5, "XML and XSL Tag Support".

You can find information about standard JSP 1.2 XML support in the Oracle Application Server Containers for J2EE Support for JavaServer Pages Developer's Guide.

Summary of Data-Access JavaBeans and Tag Library

OC4J supplies a set of custom JavaBeans for use in accessing Oracle Database. The following beans are provided in the oracle.jsp.dbutil package:

• ConnBean opens a database connection. This bean also supports data sources and connection pooling.

• ConnCacheBean uses the Oracle connection caching implementation for database connections. (This requires JDBC 2.0.)

• DBBean executes a database query.

• CursorBean provides general DML support for queries; UPDATE, INSERT, and DELETE statements; and stored procedure calls.

For information, see "JavaBeans for Data Access".

For JSP programmers, OC4J also provides a custom tag library for SQL functionality, wrapping the functionality of the JavaBeans. These tags are summarized in Table 1-2. For further information, see "SQL Tags for Data Access".

Summary of JSP Markup Language (JML) Custom Tag Library

Although the JSP specification supports scripting languages other than Java, Java is the primary language used. Even though JavaServer Pages technology is designed to separate the dynamic/Java development effort from the static/HTML development effort, it is a hindrance if the Web developer does not know any Java, especially in small development groups where no Java experts are available.

OC4J provides custom tags as an alternative: the JSP Markup Language (JML). The Oracle JML tag library provides an additional set of JSP tags so that you can script your JSP pages without using Java statements. JML provides tags for variable declarations, control flow, conditional branches, iterative loops, parameter settings, and calls to objects. The JML tag library also supports XML functionality, as noted previously.

The following example shows use of the JML for tag, repeatedly printing "Hello World" in progressively smaller headings (H1, H2, H3, H4, H5):

<jml:for id="i" from="<%= 1 %>" to="<%= 5 %>" >
     <H<%=i%>>
            Hello World!
     </H<%=i%>>
</jml:for>

The JML tag library is summarized in Table 1-3. For more information, see Chapter 3, "JSP Markup Language Tags".

Summary of Oracle Application Server Personalization Tag Library

Web site personalization is a mechanism to tailor recommendations to users of a site, based on behavioral and demographic data. Recommendations are made in real-time, during a user's Web session. User behavior is saved to a database repository for use in building models for predictions of future user behavior.

OracleAS Personalization uses data mining algorithms in Oracle Database to choose the most relevant content available for a user. Recommendations are calculated by an OracleAS Personalization recommendation engine, using typically large amounts of data regarding past and current user behavior. This is superior to other approaches that rely on common-sense heuristics and require manual definition of rules in the system.

The OracleAS Personalization tag library brings this functionality to a wide audience of JSP developers for use in HTML, XML, or JavaScript pages. The tag interface is layered on top of the Java API of the recommendation engine.

Table 1-4 summarizes the OracleAS Personalization tag library. See Chapter 10, "Personalization Tags" for information.

Summary of Web Services Tag Library

The Web services tag library provided with OC4J enables developers to conveniently create JSP pages for Web service client applications. The implementation uses a SOAP-based mechanism, supporting RPC-style or document-style services. A client application would access a Web Services Description Language (WSDL) document, then use the WSDL information to access the operations of a Web service.

The tag library also uses the Oracle implementation of the dynamic invocation API, described in the Oracle Application Server Web Services Developer's Guide. When a client application acquires a WSDL document at runtime, the dynamic invocation API is the vehicle for invoking any SOAP operation described in the WSDL document.

The Web services tag library is summarized in Table 1-5. For more information, see Chapter 11, "Web Services Tags".

Summary of File Access and Mail Tags

OC4J provides tag libraries for file access (uploading and downloading) and for sending e-mail messages from an application.

For uploading files, you can use the httpUpload tag or the oracle.jsp.webutil.fileaccess.HttpUploadBean JavaBean. For downloading, there is the httpDownload tag or the HttpDownloadBean JavaBean. Table 1-6 summarizes the file access tags. For more information, see "File-Access JavaBeans and Tags".

For sending e-mail messages, optionally with server-side or client-side attachments, you can use the oracle.jsp.webutil.email.SendMailBean JavaBean or the sendMail tag. Table 1-7 summarizes the sendMail tag. See "Mail JavaBean and Tag" for more information.

Summary of EJB Tags

OC4J provides a custom tag library to simplify the use of Enterprise JavaBeans in JSP pages. The functionality of the OC4J EJB tags follows the J2EE specification. The tags allow you to instantiate EJBs by name, using configuration information in the web.xml file.

There are tags to create a home instance, create an EJB instance, and iterate through a collection of EJBs. Table 1-8 summarizes the EJB tag library. See "EJB Tags" for more information.

Summary of JSP Utility Tags

OC4J has utility tags for displaying a date, displaying an amount of money in the appropriate currency, displaying a number, iterating through a collection, evaluating and including the tag body (depending on whether the user belongs to a specified role), and displaying the last modification date of the current file. Table 1-9 summarizes these tags. See "General Utility Tags" for more information.

Oracle Application Server and JSP Caching Features

The Oracle Application Server and OC4J provide the following caching features:

• Oracle Application Server Web Cache

  This is an HTTP-level cache, maintained outside the application, providing very fast cache operations. It is a content-based cache, capable of caching static data (such as HTML, GIF, or JPEG files) or dynamic data (such as servlet or JSP results). Given that it exists as a content-based cache outside the application, it cannot cache objects (such as Java objects or XML DOM objects) in a Java object format. In addition, post-processing operations applicable to cached data cannot be coded in Java and are predefined by the cache itself.

  The OracleAS Web Cache provides an ESI processor to support Edge Side Includes, an XML-style markup language that allows dynamic content assembly away from the Web server. This technology enables you to separate cacheable pages into distinct cached objects, as desired. OC4J supports this technology through its JESI tag library.

  For an overview of Edge Side Includes and the OracleAS Web Cache, as well as detailed documentation of the JESI tag library, see Chapter 6, "JESI Tags for Edge Side Includes".

  For additional information about the OracleAS Web Cache, see the Oracle Application Server Web Cache Administrator's Guide.

• OC4J Web Object Cache

  This is an application-level cache that is embedded and maintained within a Java Web application. It is a hybrid cache, both Web-based and object-based. A custom tag library or API enables you to define page fragment boundaries and to capture, store, reuse, process, and manage the intermediate and partial execution results of JSP pages and servlets as cached objects. Each page fragment can produce a separate cache object. The produced objects can be HTML or XML text fragments, XML DOM objects, or Java serializable objects. These objects can be cached conveniently in association with HTTP request and session semantics. Alternatively, they can be reused outside HTTP, such as when an application outputs cached XML objects through Simple Mail Transfer Protocol (SMTP), Java Messaging Service (JMS), Advanced Queueing (AQ), or Simple Object Access Protocol (SOAP).

  For more information, see Chapter 7, "Web Object Cache Tags and API".

• Oracle Application Server Java Object Cache

  The Oracle Application Server Java Object Cache is a general-use Java cache to manage Java objects within a process, across processes, and on local disk. By managing local copies of objects that are difficult or expensive to retrieve or create, the Java Object Cache can significantly improve application performance. By default, the OC4J Web Object Cache uses the Oracle Application Server Java Object Cache as its underlying cache repository.

  For details about the Java Object Cache, see the Oracle Application Server Containers for J2EE Services Guide.

Role of the JSP Web Object Cache

It is important to understand the role of the OC4J Web Object Cache in the overall setup of a Web application. It works at the Java level and is closely integrated with the HTTP environment of servlet and JSP applications. By contrast, the Oracle Application Server Java Object Cache works at the Java object level, but is not integrated with HTTP. As for the OracleAS Web Cache, it is well integrated with HTTP and is orders of magnitude faster than the Web Object Cache, but it does not operate at the Java level and cannot be directly invoked by Web application code. For example, it cannot apply a style sheet to a cached DOM object within the J2EE container, reuse the cached result in other protocols, or allow direct DOM operations. OracleAS Web Cache can, however, apply a style sheet to text-based XML documents, as opposed to DOM objects, that were cached from the original Web server through HTTP.

The Web Object Cache is not intended for use as the main Web cache for an application. It is an auxiliary cache embedded within the same Java virtual machine that is running your servlets and JSP pages. Because the retrieval path for cached results in the Web Object Cache includes the JVM and the JSP and servlet engines, it generally takes much longer to serve a page from the Web Object Cache compared to the OracleAS Web Cache.

The Web Object Cache does not replace or eliminate the need for either the OracleAS Web Cache or the Oracle Application Server Java Object Cache. It is a complementary caching component in the overall framework of a Web application and should be used together with the other caching products, as appropriate. In fact, the Web Object Cache uses the Java Object Cache as its default repository. And through combined use of the OC4J JESI tags and Web Object Cache tags, you can use the Web Object Cache and OracleAS Web Cache together in the same page.

Summary of Tag Libraries for Caching

OC4J supplies two tag libraries for use with Oracle Application Server caching features:

• JESI tag library

• Web Object Cache tag library

This section summarizes those libraries.

Overview and Philosophy of JSTL

JSTL is intended as a convenience for JSP page authors who are not familiar or not comfortable with scripting languages such as Java. Historically, scriptlets have been used in JSP pages to process dynamic data. With JSTL, the intent is for JSTL tag usage to replace the need for scriptlets.

Readers who have used previous versions of the OC4J JSP product will recognize this as similar to the goals of the Oracle JavaServer Pages Markup Language (JML) tag library. While the JML tag library is still supported, use of the standard JSTL is encouraged. Also see "JSTL Usage Notes and Future Considerations".

Key JSTL features include the following:

• JSTL expression language (EL)

  The expression language further simplifies the code required to access and manipulate application data, making it possible to avoid request-time expressions as well as scriptlets. See the next section, "Summary of JSTL Expression Language".

• Core tags for expression language support, conditional logic and flow control, iterator actions, and access to URL-based resources

• Tags for XML processing, flow control, and XSLT transformations

• SQL tags for database access

• Tags for I18N-capable internationalization and formatting

  (The term "I18N" refers to an internationalization standard.)

Tag support is broken into four JSTL sublibraries according to the preceding functional areas. Table 1-12 shows the standard TLD URI and prefix for each sublibrary.

See "Overview of JSTL Tags and Additional Features" for more information.

Summary of JSTL Expression Language

The JSTL expression language makes use of the fact that JSP scoped attributes and request parameters are the preferred vehicles for passing information to and from JSP pages. By using the JSTL expression language, you can avoid having to use JSP scriptlets and request-time expressions.

In JSTL 1.0, the expression language can be used only in JSTL tag attribute values.

As an example, consider the following use of the JSTL c:if tag to pick out steel-making companies from a company list:

<c:if test="${company.industry == 'steel'}">
   ...
</c:if>

The rest of this section summarizes JSTL expression language syntax and documents how to enable JSTL expression language evaluation in your OC4J JSP applications.

<c:if test="${auto.price <= customer.priceLimit}">
   The <c:out value="${auto.makemodel}"/> is in your price range.
</c:if>

<%-- "productDir" is a Map object containing the description of
      products, "preferences" is a Map object containing the
      preferences of a user --%>
product:
<c:out value="${productDir[product.custId]}"/>
shipping preference:
<c:out value="${user.preferences['shipping']}"/>

Overview of JSTL Tags and Additional Features

The following sections provide a summary of JSTL tags and discuss some additional JSTL features:

• Scoped Variables

• Configuration Data and the Config Class

• JSTL Tag Summary

<c:forEach var="employee" items="${customers}">
   The current employee is <c:out value="${customer}"/>
</c:forEach>

http://www.w3.org/TR/xpath

JSTL Usage Notes and Future Considerations

Be aware off the following considerations:

• The Oracle Application Server 10g Release 2 (10.1.2) JSTL implementation is based on the Jakarta 1.0.3 JSTL version and is suitable for use with OC4J. See the following location for more information about Jakarta:

  http://jakarta.apache.org/taglibs/doc/standard-doc/intro.html
  
  

• The custom JML, XML, and data-access (SQL) tag libraries provided with OC4J pre-date JSTL and have areas of duplicate functionality. For standards compliance, it is now generally advisable to use JSTL instead of the custom libraries, and Oracle plans to desupport the JML library in future releases. For features in the custom libraries that are not yet available in JSTL, where there seems to be general usefulness, Oracle will try to have the features adopted into the JSTL standard as appropriate.

• For the filter functionality of JSTL XML tags to work in OC4J, you must set the SAX driver when starting OC4J. Otherwise, the JSTL demo Filter.jsp gives the following exception:

  javax.servlet.jsp.JspException: System property org.xml.sax.driver not specified
  
  

  When starting OC4J standalone, use the following option in the command line:

  -Dorg.xml.sax.driver=oracle.xml.parser.v2.SAXParser
  
  

  When starting Oracle Application Server, you can specify this setting through the system properties.

Oracle ADF Business Components Tag Library

Oracle Application Development Framework (Oracle ADF), offered as part of Oracle JDeveloper, includes the component technology Oracle ADF Business Components. This includes a library of custom Business Components data tags.

These data tags provide a simple tag-based approach for interaction with Business Components data sources, allowing complete access to business components with viewing, editing, and full DML control capabilities. The tag-based approach to building JSP applications with Business Components does not require extensive Java programming and is very much like coding an HTML page.

For more information, refer to the Oracle JDeveloper online help or to the following location on the Oracle Technology Network:

http://www.oracle.com/technology/products/jdev/content.html

Oracle JDeveloper User Interface Extension (UIX) Tag Library

Oracle JDeveloper provides a set of custom tags known as User Interface Extension (UIX) tags. The tags invoke UIX controls, generating the HTML to render tabs, buttons, tables, headers, and other layout and navigational components that implement the Oracle browser look and feel.

The tags are included on several palette pages: UIX JSP Border Layout, UIX JSP Form, UIX JSP Layout, UIX JSP Message Components, UIX JSP Page Layout, UIX JSP Simple Components, and UIX JSP Table.

For more information, refer to the Oracle JDeveloper online help or to the following location on the Oracle Technology Network:

http://www.oracle.com/technology/products/jdev/content.html

Oracle ADF Business Components UIX Tag Library

UIX JSP pages can include both Business Components data tags and Business Components UIX convenience tags that simplify the presentation of data.

The Business Components UIX convenience tags rely on an ApplicationModule data tag to get the data source from the Business Components application module. In addition to the Business Components UIX tags, you can use the (non-UIX) Business Components tags in UIX JSP pages.

For more information, refer to the Oracle JDeveloper online help or to the following location on the Oracle Technology Network:

http://www.oracle.com/technology/products/jdev/content.html

Oracle Reports Tag Library

Oracle Reports consists of Oracle Reports Developer (a component of the Oracle Developer Suite) and Oracle Reports Services (a component of the Oracle Application Server). The Oracle Reports Developer includes tags integrated with data model objects that are used to create JSP reports. The Oracle Reports custom tags allow you to quickly add report blocks and graphs to existing JSP files. These tags can be used as templates to enable you to build and insert your own data-driven Java component into an HTML page for a JSP-based Web report.

Key tags delimit and define the report block. Inside these tags, other tags define the content and the look and feel of the report data.

For more information, refer to the Oracle Reports Developer online help, available through the Help menu in Reports Builder. You can also find more information about Oracle Reports on the Oracle Technology Network:

http://www.oracle.com/technology/products/reports/index.html

Oracle Application Server Wireless Location Tag Library

Developers of location-based applications need specialized services for the following:

• Geocoding: associating geographical coordinates with addresses

• Mapping: providing a graphical map for a point, set of points, route, or driving maneuver

• Routing: providing driving directions

• Business directories ("yellow pages"): listing businesses by region and by either category or name

• Traffic: providing information about accidents, construction, and other incidents that affect traffic flow

The OracleAS Wireless location application components compose an API for performing geocoding, providing driving directions, and looking up business directories. Service proxies are included that map existing key providers to the API, and additional providers are expected to be accommodated in the future.

For JSP developers, a tag library is provided. For more information, refer to the Oracle Application Server Wireless Developer's Guide.

Oracle Application Server MapViewer Tag Library

The OracleAS MapViewer is a programmable tool for rendering maps using spatial data managed by Oracle Spatial or Oracle Locator (also referred to as Locator). OracleAS MapViewer provides tools that hide the complexity of spatial data queries and cartographic rendering, while providing customizable options for more advanced users. These tools can be deployed in a platform-independent manner and are designed to integrate with map-rendering applications.

For convenience, OracleAS MapViewer includes a JSP tag library that you can use to submit map requests.

For more information, see the Oracle Application Server MapViewer User's Guide.

Oracle Ultra Search Tag Library

Oracle Ultra Search provides a custom tag library for use by developers in incorporating content search functionality into JSP applications. The library includes the following functionality:

• The ability to retrieve search attributes, groups, languages, and lists of values (LOVs) for rendering the advance query form

• The ability to iterate through the resulting hit set and retrieve document attributes and properties for rendering the result page

• The ability to perform a search with "relevance boosting" and an estimation of the total hit count

For more information, see the Oracle Ultra Search Administrator's Guide. Alternatively, refer to the Oracle Ultra Search online documentation, under Oracle Ultra Search JSP Tag Library.

Oracle Application Server Portal Tag Library

With OracleAS Portal, developers can accomplish the following:

• Build and deploy Internet portals to deliver relevant information and applications to customers, employees, and partners.

• Develop portals rapidly, without code, using productive online tools.

• Increase user productivity with single sign-on and self-service publishing.

• Add value quickly with over 250 prebuilt portlets based on open standards.

The OracleAS Portal tag library provides further convenience for developers building customizable Internet portals. A developer can create internal JSP pages, which are stored inside the Portal database and downloaded when the portal is executed, or external JSP pages, which are stored in the file system, or some combination.

For more information, refer to Oracle Application Server Integrating JavaServer Pages with OracleAS Portal, available through the Oracle Technology Network:

http://www.oracle.com/technology/products/ias/portal/pdf/pd_jsps_10g.pdf

Oracle Business Intelligence Beans Tag Library

The Oracle Business Intelligence Beans (OracleBI Beans) product consists of Java components, utilities, and a JSP tag library that enable rapid development of analytical applications. OracleBI Beans applications leverage the capabilities of OLAP in Oracle Database. Using OracleBI Beans, you can develop both HTML-client and Java-client applications.

OracleBI Beans includes the following groups of Java components:

• Presentation beans: beans that let you view, manipulate, and print data

• OLAP beans: beans that interact with an Oracle OLAP data source

• Persistence service: a set of Java packages that support the storage and retrieval of object definitions in the OracleBI Beans Catalog

For further developer convenience, OracleBI Beans includes a JSP tag library. You can use JDeveloper to create OracleBI Beans JSP pages. A JDeveloper wizard prompts you for information related to the tag that you want to use and inserts the coded tag in the JSP page.

For more information, refer to the OracleBI Beans online help. Under "Building Web Modules", click "Using JSP Tags", then "List of BI Beans JSP Tags".

Oracle Application Server Multimedia Tag Library

Oracle Application Server provides the Multimedia Tag Library, a custom JSP tag library for use by developers and Web page authors when generating multimedia HTML tags in JSP pages and uploading multimedia data into interMedia objects.

Oracle interMedia enables Oracle Database to store, retrieve, manage, and manipulate images, audio, video, and other media data, while integrating it with other enterprise information. Specifically, Oracle interMedia supports media storage, media retrieval, media management, and manipulation of media data managed by Oracle and stored in binary large objects, file-based large objects, URLs that contain media data, and specialty servers. Oracle interMedia is accessible to applications through relational and object interfaces.

Oracle interMedia uses object types that are similar to Java classes to describe media data. These interMedia objects have a common media data storage model. Oracle interMedia also provides Java classes to enable users to write Java applications using interMedia objects. There are also Oracle interMedia Java classes for servlets and JavaServer Pages to facilitate retrieving and uploading media data from and to Oracle Database instances.

The Multimedia Tag Library includes a set of tags for retrieving media data and a set for uploading media data. The Multimedia JSP tags for media retrieval include a set of common attributes and tag-specific media-render-attributes. The common attributes are: custom-retrieval-attributes, database-connection-attributes, media-access-attributes, media-cache-control-attributes, and table-and-column-attributes. The media-render-attributes are described with each media retrieval tag.

See Oracle Application Server Multimedia Tag Library for JSP User's Guide and Reference for additional information about the Multimedia JSP tags.