characterencodingfilter.java

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/*
* ====================================================================
*
* JavaWebStudio 开源项目
*
* Struts_db v0.1
*
* ====================================================================
*/

package bookshop.util;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
* 中文过滤器
*/
public class CharacterEncodingFilter implements Filter 
{
    
    // ----------------------------------------------------- Instance Variables
    
    /**
    * The default character encoding to set for requests that pass through
    * this filter.
    */
    protected String encoding = null;
    
    /**
    * The filter configuration object we are associated with. If this value
    * is null, this filter instance is not currently configured.
    */
    protected FilterConfig filterConfig = null;
    
    /**
    * Should a character encoding specified by the client be ignored?
    */
    protected boolean ignore = true;
    
    // --------------------------------------------------------- Public Methods
    
    /**
    * Take this filter out of service.
    */
    public void destroy() 
    {
        
        this.encoding = null;
        this.filterConfig = null;
        
    }
    
    /**
    * 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
    */
    public void doFilter(ServletRequest request, ServletResponse response,
        FilterChain chain)
        throws IOException, ServletException 
    {
        
        // 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);
        
    }
    
    /**
    * Place this filter into service.
    *
    * @param filterConfig The filter configuration object
    */
    public void init(FilterConfig filterConfig) throws ServletException 
    {
        
        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 Methods
    
    /**
    * 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
    * <code>null</code>.
    * <p>
    * The default implementation unconditionally returns the value configured
    * by the <strong>encoding</strong> initialization parameter for this
    * filter.
    *
    * @param request The servlet request we are processing
    */
    protected String selectEncoding(ServletRequest request) 
    {
        
        return (this.encoding);
        
    }
    
}//EOC