Java Webアプリ開発における文字化け対策 - 概要

package filters;

public class SetCharacterEncodingFilter
    implements Filter
{

    protected String encoding;
    protected FilterConfig filterConfig;
    protected boolean ignore;
    
    /**
     * Constructor
     * 
     */
    public SetCharacterEncodingFilter()
    {
        encoding = null;
        filterConfig = null;
        ignore = true;
    }

    /**
     * @see javax.servlet.Filter#destroy()
     */
    public void destroy()
    {
        encoding = null;
        filterConfig = null;
    }

    /**
     * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
        throws IOException, ServletException
    {
        if(ignore || request.getCharacterEncoding() == null)
        {
            String encoding = selectEncoding(request);
            if(encoding != null)
                request.setCharacterEncoding(encoding);
        }
        chain.doFilter(request, response);
    }

    /**
     * @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
     */
    public void init(FilterConfig filterConfig)
        throws ServletException
    {
        this.filterConfig = filterConfig;
        encoding = filterConfig.getInitParameter("encoding");
        String value = filterConfig.getInitParameter("ignore");
        if(value == null)
            ignore = true;
        else
        if(value.equalsIgnoreCase("true"))
            ignore = true;
        else
        if(value.equalsIgnoreCase("yes"))
            ignore = true;
        else
            ignore = false;
    }

    /**
     * @param request
     * @return
     */
    protected String selectEncoding(ServletRequest request)
    {
        return encoding;
    }
}

<!-- 抜粋 -->
  <filter>
    <filter-name>EncodeFilter</filter-name>
    <filter-class>filters.SetCharacterEncodingFilter</filter-class>
    <init-param>
      <param-name>encoding</param-name>
    <!-- UTF-8やShift_JISなどの文字コードを適当に記入してください -->
      <param-value>UTF-8</param-value>
    </init-param>
  </filter>

  <filter-mapping>
    <filter-name>EncodeFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

<%@ page contentType="text/html; charset=UTF-8" %>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>

public class MyServlet extends HttpServlet { 
  public void doGet(HttpServletRequest req, HttpServletResponse res) 
              throws ServletException, IOException {

    res.setContentType("text/html; charset=UTF-8");    //コンテンツ・タイプ
    req.setCharacterEncoding("UTF-8");    //パラメータの文字コード
    
...

<meta http-equiv="content-type" content="text/html; charset=UTF-8">

<native2ascii encoding="utf-8" src="リソースファイルのパス" dest="${classes.dir}"
                       includes="**/*.properties" />