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248

Chapter 11 The JSP page Directive: Structuring Generated Servlets

markup tags; it is discussed in Chapter 14 (Creating Custom JSP Tag Librar 

ies).

The 

page

 directive lets you define one or more of the following case sen 

sitive attributes: 

import

, 

contentType

, 

isThreadSafe

, 

session

, 

buffer

,

autoflush

, 

extends

, 

info

, 

errorPage

, 

isErrorPage

, and 

language

.

These attributes are explained in the following sections.

11.1 The import Attribute

The 

import

 attribute of the 

page

 directive lets you specify the packages that

should be imported by the servlet into which the JSP page gets translated. If

you don't explicitly specify any classes to import, the servlet imports

java.lang.*

, 

javax.servlet.*

, 

javax.servlet.jsp.*

, 

javax.serv 

let.http.*

, and possibly some number of server specific entries. Never

write JSP code that relies on any server specific classes being imported auto 

matically. Use of the 

import

 attribute takes one of the following two forms:

<%@ page import="package.class" %>

<%@ page import="package.class1,...,package.classN" %>

For example, the following directive signifies that all classes in the

java.util

 package should be available to use without explicit package iden 

tifiers.

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

The 

import

 attribute is the only 

page

 attribute that is allowed to appear

multiple times within the same document. Although 

page

 directives can

appear anywhere within the document, it is traditional to place 

import

 state 

ments either near the top of the document or just before the first place that

the referenced package is used.

Directories for Custom Classes

If you import classes that are not in any of the standard 

java

 or

javax.servlet

 packages, you need to be sure that those classes have been

properly installed on your server. In particular, most servers that support

automatic servlet reloading do not permit classes that are in the auto reload 

ing directories to be referenced by JSP pages. The particular locations used

for servlet classes vary from server to server, so you should consult your

server's documentation for definitive guidance. The locations used by Apache

Tomcat 3.0, the JSWDK 1.0.1, and the Java Web Server 2.0 are summarized

Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.

Servlet and JSP training courses by book's author: courses.coreservlets.com.