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Character Encoding Issues

Questions

  1. [#Q1 What is the default character encoding of the request or response body?]

  2. [#Q2 How do I change how GET parameters are interpreted?]

  3. [#Q3 How do I change how POST parameters are interpreted?]

  4. [#Q4 How can I test if my configuration will work correctly?]

  5. [#Q5 I'm having a problem with character encoding in Tomcat 5]

  6. [#Q6 What can you recommend to just make everything work?]

Answers

What is the default character encoding of the request or response body?

If a character encoding is not specified, the Servlet specification requires that an encoding of ISO-8859-1 is used. The character encoding for the body of an HTTP message (request or response) is specified in the Content-Type header field. An example of such a header is Content-Type: text/html; charset=ISO-8859-1 which explicitly states that the default (ISO-8859-1) is being used.

How do I change how GET parameters are interpreted?

There are two ways to specify how GET parameters are interpreted:

  1. Set the URIEncoding attribute on the <Connector> element in server.xml to something specific (e.g. URIEncoding="UTF-8").
  2. Set the useBodyEncodingForURI attribute on the <Connector> element in server.xml to true. This will cause the Connector to use the request body's encoding for GET parameters.

How do I change how POST parameters are interpreted?

POST requests should specify the encoding of the parameters and values they send. Since many clients fail to set an explicit encoding, the default is used (ISO-8859-1). In many cases this is not the preferred interpretation so one can employ a javax.servlet.Filter to set request encodings. Writing such a filter is trivial. Furthermore Tomcat already comes with such an example filter. Please take a look at:
4.x::

webapps/examples/WEB-INF/classes/filters/SetCharacterEncodingFilter.java

5.x::

webapps/servlets-examples/WEB-INF/classes/filters/SetCharacterEncodingFilter.java
webapps/jsp-examples/WEB-INF/classes/filters/SetCharacterEncodingFilter.java

6.x::

webapps/examples/WEB-INF/classes/filters/SetCharacterEncodingFilter.java

How can I test if my configuration will work correctly?

The following sample JSP should work on a clean Tomcat install for any input. If you set the URIEncoding="UTF-8" on the connector, it will also work with method="GET".

<%@ page contentType="text/html; charset=UTF-8" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
   <head>
     <title>Character encoding test page</title>
   </head>
   <body>
     <p>Data posted to this form was:
     <%
       request.setCharacterEncoding("UTF-8");
       out.print(request.getParameter("mydata"));
     %>

     </p>
     <form method="POST" action="index.jsp">
       <input type="text" name="mydata">
       <input type="submit" value="Submit" />
       <input type="reset" value="Reset" />
     </form>
   </body>
</html>

I'm having a problem with character encoding in Tomcat 5

In Tomcat 5 - there have been issues reported with respect to character encoding (usually of the the form "request.setCharacterEncoding(String) doesn't work"). Odds are, its not a bug. Before filing a bug report, see these bug reports as well as any bug reports linked to these bug reports:

  • [http://issues.apache.org/bugzilla/show_bug.cgi?id=23929 23929]

  • [http://issues.apache.org/bugzilla/show_bug.cgi?id=25360 25360]

  • [http://issues.apache.org/bugzilla/show_bug.cgi?id=25231 25231]

  • [http://issues.apache.org/bugzilla/show_bug.cgi?id=25235 25235]

  • [http://issues.apache.org/bugzilla/show_bug.cgi?id=22666 22666]

  • [http://issues.apache.org/bugzilla/show_bug.cgi?id=24557 24557]

  • [http://issues.apache.org/bugzilla/show_bug.cgi?id=24345 24345]

  • [http://issues.apache.org/bugzilla/show_bug.cgi?id=25848 25848]

What can you recommend to just make everything work?

Using UTF-8 as your character encoding for everything is a safe bet. This should work for pretty much every situation. In order to completely switch to using UTF-8, you need to make the following changes:

  1. Set URIEncoding="UTF-8" on your <Connector> in server.xml

  2. Use a [#Q3 character encoding filter] with the default encoding set to UTF-8

  3. Change all your JSPs to set the correct Content-Type (use <%@page cotnentType="mime/type; charset=UTF-8" %>)
  4. Change all your servlets to set the content type for responses to UTF-8
  5. Change any content-generation libraries you use (Velocity, Freemarker, etc.) to use UTF-8 as the content type
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