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SetCharacterEncodingFilter.javaAPI DocExample5738Fri Sep 17 10:33:20 BST 2004filters

SetCharacterEncodingFilter

public class SetCharacterEncodingFilter extends Object implements Filter

Example filter that sets the character encoding to be used in parsing the incoming request, either unconditionally or only if the client did not specify a character encoding. Configuration of this filter is based on the following initialization parameters:

  • encoding - The character encoding to be configured for this request, either conditionally or unconditionally based on the ignore initialization parameter. This parameter is required, so there is no default.
  • ignore - If set to "true", any character encoding specified by the client is ignored, and the value returned by the selectEncoding() method is set. If set to "false, selectEncoding() is called only if the client has not already specified an encoding. By default, this parameter is set to "true".

Although this filter can be used unchanged, it is also easy to subclass it and make the selectEncoding() method more intelligent about what encoding to choose, based on characteristics of the incoming request (such as the values of the Accept-Language and User-Agent headers, or a value stashed in the current user's session.

author
Craig McClanahan
version
$Revision: 1.2 $ $Date: 2004/03/18 16:40:33 $

Fields Summary
protected String
encoding
The default character encoding to set for requests that pass through this filter.
protected FilterConfig
filterConfig
The filter configuration object we are associated with. If this value is null, this filter instance is not currently configured.
protected boolean
ignore
Should a character encoding specified by the client be ignored?
Constructors Summary
Methods Summary
public voiddestroy()
Take this filter out of service.



    // --------------------------------------------------------- Public Methods


               
       

        this.encoding = null;
        this.filterConfig = null;
public voiddoFilter(javax.servlet.ServletRequest request, javax.servlet.ServletResponse response, javax.servlet.FilterChain chain)
Select and set (if specified) the character encoding to be used to interpret request parameters for this request.

param
request The servlet request we are processing
param
result The servlet response we are creating
param
chain The filter chain we are processing
exception
IOException if an input/output error occurs
exception
ServletException if a servlet error occurs


        // Conditionally select and set the character encoding to be used
        if (ignore || (request.getCharacterEncoding() == null)) {
            String encoding = selectEncoding(request);
            if (encoding != null)
                request.setCharacterEncoding(encoding);
        }

	// Pass control on to the next filter
        chain.doFilter(request, response);
public voidinit(javax.servlet.FilterConfig filterConfig)
Place this filter into service.

param
filterConfig The filter configuration object


	this.filterConfig = filterConfig;
        this.encoding = filterConfig.getInitParameter("encoding");
        String value = filterConfig.getInitParameter("ignore");
        if (value == null)
            this.ignore = true;
        else if (value.equalsIgnoreCase("true"))
            this.ignore = true;
        else if (value.equalsIgnoreCase("yes"))
            this.ignore = true;
        else
            this.ignore = false;
protected java.lang.StringselectEncoding(javax.servlet.ServletRequest request)
Select an appropriate character encoding to be used, based on the characteristics of the current request and/or filter initialization parameters. If no character encoding should be set, return null.

The default implementation unconditionally returns the value configured by the encoding initialization parameter for this filter.

param
request The servlet request we are processing


        return (this.encoding);