Java Servlet Programming

HTML Forms

Managing HTML forms requires a little extra work and a few special tricks when you’re dealing with localized content. To understand the problem, imagine this situation. An HTML form is sent as part of a Japanese page. It asks the user for his name, which he enters as a string of Japanese characters. How is that name submitted to the servlet? And, more importantly, how can the servlet read it?

The answer to the first question is that all HTML form data is sent as a sequence of bytes. Those bytes are an encoded representation of the original characters. With Western European languages, the encoding is the default, ISO-8859-1, with one byte per character. For other languages, there can be other encodings. Browsers tend to encode form data using the same encoding that was applied to the page containing the form. Thus, if the Japanese page mentioned was encoded using Shift_JIS, the submitted form data would also be encoded using Shift_JIS. Note, however, that if the page did not specify a charset and the user had to manually choose Shift_JIS encoding for viewing, many browsers stubbornly submit the form data using ISO-8859-1.^[50] Generally, the encoded byte string contains a large number of special bytes that have to be URL-encoded. For example, if we assume the Japanese form sends the user’s name using a GET request, the resulting URL might look like this:

http://server:port/servlet/NameHandler?name=%8CK%8C%B4%90%B3%8E%9F

The answer to the second question, how can a servlet ...