实现我的目标的复杂方法确实是编写我自己的
javax.servlet.Filter并将其嵌入过滤器链中。该解决方案符合Tomcat Wiki-
字符编码问题中提供的Apache
Tomcat建议。
更新（2010-07-31）：
此过滤器的第一个版本解释了查询字符串本身，这是一个坏主意。
POST与其他servlet过滤器（如URL重写）结合使用时，它不能正确处理请求，并且出现问题。该版本将包装最初提供的参数并重新编码。为了使其正常工作，
URIEncoding（例如在Tomcat中）必须将其配置为
ISO-8859-1。
package de.roland_illig.webapps.webapp1;import java.io.IOException;import java.nio.ByteBuffer;import java.nio.CharBuffer;import java.nio.charset.Charset;import java.nio.charset.CharsetDeprer;import java.nio.charset.CodingErrorAction;import java.nio.charset.IllegalCharsetNameException;import java.nio.charset.UnsupportedCharsetException;import java.util.ArrayList;import java.util.Arrays;import java.util.Collections;import java.util.Enumeration;import java.util.linkedHashMap;import java.util.List;import java.util.Map;import java.util.regex.Pattern;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletRequestWrapper;import javax.servlet.http.HttpServletResponse;public class EncodingFilter implements Filter { private static final Pattern PAT_COMMA = Pattern.compile(",\s*"); private String inputEncodingParameterName = null; private final List<Charset> encodings = new ArrayList<Charset>(); @Override @SuppressWarnings("unchecked") public void init(FilterConfig config) throws ServletException { String encodingsStr = "UTF-8"; Enumeration<String> en = config.getInitParameterNames(); while (en.hasMoreElements()) { final String name = en.nextElement(); final String value = config.getInitParameter(name); if (name.equals("encodings")) { encodingsStr = value; } else if (name.equals("inputEncodingParameterName")) { inputEncodingParameterName = value; } else { throw new IllegalArgumentException("Unknown parameter: " + name); } } for (String encoding : PAT_COMMA.split(encodingsStr)) { Charset charset = Charset.forName(encoding); encodings.add(charset); } } @SuppressWarnings("unchecked") @Override public void doFilter(ServletRequest sreq, ServletResponse sres, FilterChain fc) throws IOException, ServletException { final HttpServletRequest req = (HttpServletRequest) sreq; final HttpServletResponse res = (HttpServletResponse) sres; final Map<String, String[]> params; try { params = Util.depreParameters(req.getParameterMap(), encodings, inputEncodingParameterName); } catch (IOException e) { res.sendError(400, e.getMessage()); return; } HttpServletRequest wrapper = new ParametersWrapper(req, params); fc.doFilter(wrapper, res); } @Override public void destroy() { // nothing to do } static abstract class Util { static CharsetDeprer strictDeprer(Charset cs) { CharsetDeprer dec = cs.newDeprer(); dec.onMalformedInput(CodingErrorAction.REPORT); dec.onUnmappableCharacter(CodingErrorAction.REPORT); return dec; } static int[] toCodePoints(String str) { final int len = str.length(); int[] prePoints = new int[len]; int i = 0, j = 0; while (i < len) { int cp = Character.prePointAt(str, i); prePoints[j++] = cp; i += Character.charCount(cp); } return j == len ? prePoints : Arrays.copyOf(prePoints, len); } public static String repre(String enpred, CharsetDeprer deprer) throws IOException { byte[] bytes = new byte[enpred.length()]; int bytescount = 0; for (int i = 0; i < enpred.length(); i++) { char c = enpred.charAt(i); if (!(c <= 'u00FF')) throw new IOException("Invalid character: #" + (int) c); bytes[bytescount++] = (byte) c; } CharBuffer cbuf = deprer.depre(ByteBuffer.wrap(bytes, 0, bytescount)); String result = cbuf.toString(); return result; } static String ensureDefinedUnipre(String s) throws IOException { for (int cp : toCodePoints(s)) { if (!Character.isDefined(cp)) throw new IOException("Undefined unipre pre point: " + cp); } return s; } static Map<String, String[]> depreParameters(Map<String, String[]> originalParams, List<Charset> charsets, String ieName) throws IOException { Map<String, String[]> params = new linkedHashMap<String, String[]>(); Charset ie = null; { String[] values = originalParams.get(ieName); if (values != null) { for (String value : values) { if (!value.isEmpty() && value.indexOf('%') == -1) { try { if (ie != null) throw new IOException("Duplicate value for input encoding parameter: " + ie + " and " + value + "."); ie = Charset.forName(value); } catch (IllegalCharsetNameException e) { throw new IOException("Illegal input encoding name: " + value); } catch (UnsupportedCharsetException e) { throw new IOException("Unsupported input encoding: " + value); } } } } } Charset[] css = (ie != null) ? new Charset[] { ie } : charsets.toArray(new Charset[charsets.size()]); for (Charset charset : css) { try { params.clear(); CharsetDeprer deprer = strictDeprer(charset); for (Map.Entry<String, String[]> entry : originalParams.entrySet()) { final String enpredName = entry.getKey(); final String name = ensureDefinedUnipre(Util.repre(enpredName, deprer)); for (final String enpredValue : entry.getValue()) { final String value = ensureDefinedUnipre(Util.repre(enpredValue, deprer)); String[] oldValues = params.get(name); String[] newValues = (oldValues == null) ? new String[1] : Arrays.copyOf(oldValues, oldValues.length + 1); newValues[newValues.length - 1] = value; params.put(name, newValues); } } return params; } catch (IOException e) { continue; } } List<String> kvs = new ArrayList<String>(); for (Map.Entry<String, String[]> entry : originalParams.entrySet()) { final String key = entry.getKey(); for (final String value : entry.getValue()) { kvs.add(key + "=" + value); } } throw new IOException("Could not depre the parameters: " + kvs.toString()); } } @SuppressWarnings("unchecked") static class ParametersWrapper extends HttpServletRequestWrapper { private final Map<String, String[]> params; public ParametersWrapper(HttpServletRequest request, Map<String, String[]> params) { super(request); this.params = params; } @Override public String getParameter(String name) { String[] values = params.get(name); return (values != null && values.length != 0) ? values[0] : null; } @Override public Map getParameterMap() { return Collections.unmodifiableMap(params); } @Override public Enumeration getParameterNames() { return Collections.enumeration(params.keySet()); } @Override public String[] getParameterValues(String name) { return params.get(name); } }}尽管代码的大小相当小，但是有些实现细节可能会出错，因此我希望Tomcat已经提供了类似的过滤器。
要激活此过滤器，我将以下内容添加到了我的
web.xml：
<filter> <filter-name>EncodingFilter</filter-name> <filter-class>de.roland_illig.webapps.webapp1.EncodingFilter</filter-class> <init-param> <param-name>encodings</param-name> <param-value>US-ASCII, UTF-8, EUC-KR, ISO-8859-15, ISO-8859-1</param-value> </init-param> <init-param> <param-name>inputEncodingParameterName</param-name> <param-value>ie</param-value> </init-param></filter><filter-mapping> <filter-name>EncodingFilter</filter-name> <url-pattern>/*</url-pattern></filter-mapping>
