It is possible to specify certain properties for a group of JSP pages:
A JSP property group is defined by naming the group and specifying one or more URL patterns; all the properties in the group apply to the resources that match any of the URL patterns. If a resource matches URL patterns in more than one group, the pattern that is most specific applies. To define a property group in a deployment descriptor using NetBeans 5.5, follow these steps:
Instead of performing the preceding steps, you can define a JSP property group by editing the XML by hand using NetBeans 5.5 by doing the following:
The following sections discuss the properties and explain how they are interpreted for various combinations of group properties, individual page directives, and web application deployment descriptor versions.
Deactivating EL Expression Evaluation
Each JSP page has a default mode for EL expression evaluation. The default value varies depending on the version of the web application deployment descriptor. The default mode for JSP pages delivered using a Servlet 2.3 or earlier descriptor is to ignore EL expressions; this provides backward compatibility. The default mode for JSP pages delivered with a Servlet 2.4 descriptor is to evaluate EL expressions; this automatically provides the default that most applications want. For tag files (see Encapsulating Reusable Content Using Tag Files, page 212), the default is to always evaluate expressions.
You can override the default mode through the isELIgnored attribute of the page directive in JSP pages and through the isELIgnored attribute of the tag directive in tag files. You can also explicitly change the default mode by doing one of the following:
Table 48 summarizes the EL evaluation settings for JSP pages.
Table 49 summarizes the EL evaluation settings for tag files.
Declaring Page Encodings
You set the page encoding of a group of JSP pages using the JSP property group configuration in the deployment descriptor by doing one of the following:
A translation-time error results if you define the page encoding of a JSP page with one value in the JSP configuration element and then give it a different value in a pageEncoding directive.
Defining Implicit Includes
You can implicitly include preludes and codas for a group of JSP pages by adding items to the Include Preludes and Codas lists. Their values are context-relative paths that must correspond to elements in the web application. When the elements are present, the given paths are automatically included (as in an include directive) at the beginning and end, respectively, of each JSP page in the property group. When there is more than one include or coda element in a group, they are included in the order they appear. When more than one JSP property group applies to a JSP page, the corresponding elements will be processed in the same order as they appear in the JSP configuration section.
For example, the Duke's Bookstore application uses the files /template/prelude.jspf and /template/coda.jspf to include the banner and other boilerplate in each screen. To add these files to the Duke's Bookstore property group using the deployment descriptor, follow these steps:
Instead of performing the preceding steps, you can add preludes and codas by editing the XML by hand using NetBeans 5.5 by doing the following:
Preludes and codas can put the included code only at the beginning and end of each file. For a more flexible approach to building pages out of content chunks, see A Template Tag Library (page 253).
Eliminating Extra White Space
White space included in the template text of JSP pages is preserved by default. This can have undesirable effects. For example, a carriage return added after a taglib directive would be added to the response output as an extra line.
If you want to eliminate the extra white space from the page, you can add a trim-directive-whitespaces element to a jsp-property-group element in the deployment descriptor and set it to true.
Alternatively, a page author can set the value of the TRimDirectiveWhitespaces attribute of the page directive to true or false. This will override the value specified in the deployment descriptor.
Custom tag authors can eliminate white space from the output generated by a tag file by setting the trimDirectiveWhiteSpace attribute of the tag directive to true.