Within an application that is marked as distributable, all requests that are part of a session 

can only be handled on a single Java Virtual Machine at any one time. In addition all objects 

placed into the session must implement the Serializable interface.  The servlet container may 

throw an IllegalArgumentException if a non serializable object is placed into the session 

(Section 7.7.2 in Servlet 2.2 spec).

2.7.3

Specifying Content Types

A JSP page can use the 

contentType

 attribute of the page directive to indicate the content 

type of the response it provides to requests. Since this value is part of a directive, a given 

page will always provide the same content type. If a page determines that the response 

should be of a different content type, it should do so  early , determine what other JSP page 

or Servlet will handle this request and it should forward the request to the other JSP page or 

Servlet.

A registry of content types names is kept by IANA. See:

ftp://venera.isi.edu/in notes/iana/assignments/media types/media types

2.7.4

Delivering Localized Content

The Java Platform support for localized content is based on a uniform representation of text 

internally as Unicode 2.0 (ISO010646) characters and the support for a number of character 

encodings to and from Unicode.

Any Java Virtual Machine (JVM) must support Unicode and Latin 1 encodings but most 

support many more. The character encodings supported by the JVM from Sun are described 

at:

http://java.sun.com/products/jdk/1.1/docs/guide/intl/encoding.doc.html

The JSP 1.1 specification assumes that JSP pages that will deliver content in a given 

character encoding will be written in that character encoding. In particular, the 

contentType

 attribute of the 

page

 directive describes both the character encoding of the 

JSP page and the character encoding of the resulting stream.

The valid names to describe the character encodings are those of IANA. They are described 

at:

ftp://venera.isi.edu/in notes/iana/assignments/character sets

The 

contentType

 attribute must only be used when the character encoding is organized 

such that ASCII characters stand for themselves, at least until the 

contentType

 attribute is 

found. The directive containing the 

contentType

 attribute should appear as early as 

possible in the JSP page.

49

JavaServer Pages 1.1 Specification  

November 30, 1999