setcharacterencodingfilter.java

来自「网络编程技术与实例源码」· Java 代码 · 共 100 行

/*
 * Created on 2005-5-9 
 */
package test;

import javax.servlet.*;
import java.io.IOException;

public class SetCharacterEncodingFilter implements Filter {
    /*
     * 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;

    /**
     * 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;
    }

    /**
     * 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);
    }
}