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1. What is the default character encoding of the request or response body?
2. How do I change how GET parameters are interpreted?
3. How do I change how POST parameters are interpreted?
4. How can I test if my configuration will work correctly?
5. How can I send higher characters in HTTP headers?
6. What can you recommend to just make everything work? – How to use UTF-8 everywhere.
7. Why does everything have to be this way?
8. I'm having a problem with character encoding in Tomcat 5
   

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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::

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5.x::

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

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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. References: HTTP Connector, AJP Connector.
2. Use a character encoding filter with the default encoding set to UTF-8
3. Change all your JSPs to set the correct Content-Type (include charset name in their contentType. For example, use <%@page contentType="mimetext/typehtml; charset=UTF-8" %> for the usual JSP pages and <jsp:directive.page contentType="text/html; charset=UTF-8" /> for the pages in XML syntax (aka JSP Documents).
4. Change all your servlets to set the content type for responses and to include charset name in the content type to be UTF-8. Use response.setContentType("text/html; charset=UTF-8") or response.setCharacterEncoding("UTF-8").
5. Change any content-generation libraries you use (Velocity, Freemarker, etc.) to use UTF-8 and to specify UTF-8 as in the content type of the responses that they generate.
6. Disable any valves or filters that may read request parameters before your character encoding filter or jsp page has a chance to set the encoding to UTF-8. For more information see http://www.mail-archive.com/users@tomcat.apache.org/msg21117.html.
   

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