JSP

}

If you want to use the characters

%> "Inside A Scriptlet, Enter"

% /> "INSTEAD. Finally, Note That The XML Equivalent of

<% Code%> IS

Code

4.3 JSP Declarativesa JSP

Declaration Lets You Define Methods or Fields That Get Insert Class (Outside of There W) The Request. IT HAS The Following Form:

<%! Java code%>

Since declarations do not generate any output, they are normally used in conjunction with JSP expressions or scriptlets. For example, here is a JSP fragment that prints out the number of times the current page has been requested since the server booted (or the servlet class WAS Changed and Reloaded:

<%! private int accesscount = 0;%>

Accesses to page Since Server reboot:

<% = accesscount%>

As with scriptlets, if you want to use the characters

%> ", Enter"

% /> "INSTEAD. Finally, Note That The XML Equivalent of

<%! Code%> IS

Code

5. JSP DirectiveSa JSP

Directure Affects The Overall Structure of The Servlet Class. It usually has the full Form:

<% @ Directive Attribute = "Value"%>

However, You Can Also Combine Multiple Attribute Settings for a Single Directive, As Follows:

<% @ Directive Attribute1 = "Value1"

Attribute2 = "Value2"

...

Attributen = "Valuen"%>

There Are Two Main Types of Directive:

Page, Which Lets You Do Things Like Import Classes, Customize The Servlet Superclass, and The Like;

Include, Which Lets you insert a file into the servlet class at the time the jsp file is translated into a servlet. The specification also exercions the

taglib directive, which is not supported in JSP version 1.0, but is intended to let JSP authors define their own tags. It is expected that this will be the main new contribution of JSP 1.1.5.1 The JSP page DirectiveThe

Page Directive Lets You Define One or more of the folload case-sensitive attributes:

Import = "package.class" or import = "package.class1, ..., package.classn". this lets you specify what package for example: <% @ Page Import = "java.util. *" %> The import attribute is the only one that is allowed to appear multiple times contentType = "MIME-Type" or contentType =.. "MIME-Type; charset = Character-Set" This specifies the MIME type of the output The default is . text / html For example, the directive <% @ page contentType = "text / plain"%> has the same effect as the scriptlet <% response.setContentType ( "text / plain");%> isThreadSafe = "true | false ". A value of true (the default) indicates normal servlet processing, where multiple requests can be processed simultaneously with a single servlet instance, under the assumption that the author synchronized access to instance variables. A value of false indicates that the servlet should implement SingleThreadModel, with requests Either Delivered Serially or with Simultaneous Requests Being Given Separate Servlet Instances. Session = "TR ue |. false "A value of true (the default) indicates that the predefined variable session (of type HttpSession) should be bound to the existing session if one exists, otherwise a new session should be created and bound to it A value of. false indicates that no sessions will be used, and attempts to access the variable session will result in errors at the time the JSP page is translated into a servlet buffer =. "sizekb | none" This specifies the buffer size for the JspWriter out.. The default is server-specific, but must be at least 8kb. Autoflush = "True | FALSE"

. A value of true, the default, indicates that the buffer should be flushed when it is full. A value of false, rarely used, indicates that an exception should be thrown when the buffer overflows. A value of false is illegal when also using buffer = "none". extends = "package.class". This indicates the superclass of servlet that will be generated. Use this with extreme caution, since the server may be using a custom superclass already. info = "message". This defines .. a string that can be retrieved via the getServletInfo method errorPage = "url" This specifies a JSP page that should process any Throwables thrown but not caught in the current page isErrorPage =. "true | false" This indicates whether or not the. current page can act as the error page for another JSP page. The default is false. language = "java". At some point, this is intended to specify the underlying language being used. for now, do not bother with this since java Is Both the default and the only legal choice. The Xml Syntax for Defin ING DIRECTIVES IS

For Example, The XML Equivalent of

<% @ page import = "java.util. *"%> IS

5.2 The JSP Include DirectiveTHIS Directive Lets You include Files at The Time The JSP Page IS Translated Into a servlet. The Directive Looks Like this:

<% @ include file = "relative URL"%>

The URL specified is normally interpreted relative to the JSP page that refers to it, but, as with relative URLs in general, you can tell the system to interpret the URL relative to the home directory of the Web server by starting the URL with a forward slash. The contents of the included file are parsed as regular JSP text, and thus can include static HTML, scripting elements, directives, and actions.For example, many sites include a small navigation bar on each page. Due to problems with HTML frames , this is usually implemented by way of a small table across the top of the page or down the left-hand side, with the HTML repeated for each page in the site. The include directive is a natural way of doing this, saving the developers From The Maintenance Nightmare of actually Copying The HTML INTO Each Separate File. Here's Some RepereSentative Code: