Response Encoding

The response encoding is the character encoding of the textual response generated by a web component. The response encoding must be set appropriately so that the characters are rendered correctly for a given locale. A web container sets an initial response encoding for a JSP page from the following sources:

• The CHARSET value of the contentType attribute of the page directive

• The encoding specified by the pageEncoding attribute of the page directive

• The page encoding value of a JSP property group whose URL pattern matches the page

If none of these is provided, ISO-8859-1 is used as the default response encoding.

The setCharacterEncoding, setContentType, and setLocale methods can be called repeatedly to change the character encoding. Calls made after the servlet response’s getWriter method has been called or after the response is committed have no effect on the character encoding. Data is sent to the response stream on buffer flushes (for buffered pages) or on encountering the first content on unbuffered pages.

Calls to setContentType set the character encoding only if the given content type string provides a value for the charset attribute. Calls to setLocale set the character encoding only if neither setCharacterEncoding nor setContentType has set the character encoding before. To control the response encoding from JSP pages, you can use the JSTL fmt.setLocale tag.

To obtain the character encoding for a locale, the setLocale method checks the locale encoding mapping for the web application. For example, to map Japanese to the Japanese-specific encoding Shift_JIS, follow these steps:

1. Select the WAR.

2. Click the Advanced Settings button.

3. In the Locale Character Encoding table, Click the Add button.

4. Enter ja in the Extension column.

5. Enter Shift_JIS in the Character Encoding column.

If a mapping is not set for the web application, setLocale uses a Application Server mapping.

The first application in Chapter 5, JavaServer Pages Technology allows a user to choose an English string representation of a locale from all the locales available to the Java 2 platform and then outputs a date localized for that locale. To ensure that the characters in the date can be rendered correctly for a wide variety of character sets, the JSP page that generates the date sets the response encoding to UTF-8 by using the following directive:

<%@ page contentType="text/html; charset=UTF-8" %>