如果在一个Tomcat Server上会部署多个Web应用，又希望这多个Web应用共用一套错误页面，而不是使用默认的错误页面。就需要自定义错误页面了。
在每个web应用中都可以通过error-page来配置错误页面。但是多个Web应用时，要在每个应用的web.xml中都配置一个错误页面，就显得有些麻烦了。然而希望通过在tomcat/conf/web.xml中来配置错误页面，是不能实现的。因为Tomcat部署应用时会将公共的web.xml与每个web应用的web.xml进行合并，查找页面时，其实还是在每个web应用的目录下查找的。
为了达到共用的目录，只能自己来重写Tomcat的默认实现了。所幸，Tomcat也是支持我们这样去做的。
package com.fjn.frame.catalina.valves; import java.io.IOException; import java.io.InputStream; import java.io.Writer; import java.util.Scanner; import org.apache.catalina.connector.Request; import org.apache.catalina.connector.Response; import org.apache.catalina.util.RequestUtil; import org.apache.catalina.util.ServerInfo; import org.apache.catalina.valves.ErrorReportValve; /** * * 要使用这个类来自定义错误页面，需要调整 server.xml中Host的errorReportValveClass属性值为这个类。 * 另外需要将这个类打成jar包放在tomcat/lib目录下。 * @since tomcat 6.0 * @author fs1194361820@163.com 2015年6月4日 * */ public class ErrorPageValve extends ErrorReportValve { private static final String ERROR_PAGE_NAME = "errorPage.html"; @Override protected void report(Request request, Response response, Throwable throwable) { // Do nothing on non-HTTP responses int statusCode = response.getStatus(); // Do nothing on a 1xx, 2xx and 3xx status // Do nothing if anything has been written already if (statusCode < 400 || response.getContentCount() > 0 || !response.isError()) { return; } String message = RequestUtil.filter(response.getMessage()); if (message == null) { if (throwable != null) { String exceptionMessage = throwable.getMessage(); if (exceptionMessage != null && exceptionMessage.length() > 0) { message = RequestUtil .filter((new Scanner(exceptionMessage)).nextLine()); } } if (message == null) { message = ""; } } // Do nothing if there is no report for the specified status code String report = null; try { report = sm.getString("http." + statusCode); } catch (Throwable t) { ; } if (report == null) return; StringBuffer sb = new StringBuffer(); try { buildHTMLFromErrorPage(sb); } catch (Exception ex) { } if (sb.length() < 1) { defaultBuildHTML(sb, statusCode, message, report, throwable); } try { try { response.setContentType("text/html"); response.setCharacterEncoding("utf-8"); } catch (Throwable t) { if (container.getLogger().isDebugEnabled()) container.getLogger().debug("status.setContentType", t); } Writer writer = response.getReporter(); if (writer != null) { // If writer is null, it's an indication that the response has // been hard committed already, which should never happen writer.write(sb.toString()); } } catch (IOException e) { ; } catch (IllegalStateException e) { ; } } private void defaultBuildHTML(StringBuffer sb, int statusCode, String message, String report, Throwable throwable) { sb.append("<html><head><title>"); sb.append(ServerInfo.getServerInfo()).append(" - "); sb.append(sm.getString("errorReportValve.errorReport")); sb.append("</title>"); sb.append("<style><!--"); sb.append(org.apache.catalina.util.TomcatCSS.TOMCAT_CSS); sb.append("--></style> "); sb.append("</head><body>"); sb.append("<h1>"); sb.append( sm.getString("errorReportValve.statusHeader", "" + statusCode, message)).append("</h1>"); sb.append("<HR size="1" noshade="noshade">"); sb.append("<p><b>type</b> "); if (throwable != null) { sb.append(sm.getString("errorReportValve.exceptionReport")); } else { sb.append(sm.getString("errorReportValve.statusReport")); } sb.append("</p>"); sb.append("<p><b>"); sb.append(sm.getString("errorReportValve.message")); sb.append("</b> <u>"); sb.append(message).append("</u></p>"); sb.append("<p><b>"); sb.append(sm.getString("errorReportValve.description")); sb.append("</b> <u>"); sb.append(report); sb.append("</u></p>"); if (throwable != null) { String stackTrace = getPartialServletStackTrace(throwable); sb.append("<p><b>"); sb.append(sm.getString("errorReportValve.exception")); sb.append("</b> <pre>"); sb.append(RequestUtil.filter(stackTrace)); sb.append("</pre></p>"); int loops = 0; Throwable rootCause = throwable.getCause(); while (rootCause != null && (loops < 10)) { stackTrace = getPartialServletStackTrace(rootCause); sb.append("<p><b>"); sb.append(sm.getString("errorReportValve.rootCause")); sb.append("</b> <pre>"); sb.append(RequestUtil.filter(stackTrace)); sb.append("</pre></p>"); // In case root cause is somehow heavily nested rootCause = rootCause.getCause(); loops++; } sb.append("<p><b>"); sb.append(sm.getString("errorReportValve.note")); sb.append("</b> <u>"); sb.append(sm.getString("errorReportValve.rootCauseInLogs", ServerInfo.getServerInfo())); sb.append("</u></p>"); } sb.append("<HR size="1" noshade="noshade">"); sb.append("<h3>").append(ServerInfo.getServerInfo()).append("</h3>"); sb.append("</body></html>"); } private void buildHTMLFromErrorPage(StringBuffer buffer) throws IOException { InputStream in=null; Scanner scanner = null; try { // 优先从当前路径下查找文件 in=this.getClass().getResourceAsStream(ERROR_PAGE_NAME); if(in==null){ // 从当前jar包内的根目录 或者tomcat/lib目录下 in=Thread.currentThread().getContextClassLoader().getResourceAsStream(ERROR_PAGE_NAME); } if(in==null){ in=ClassLoader.getSystemResourceAsStream(ERROR_PAGE_NAME); } scanner = new Scanner(in); while (scanner.hasNextLine()) { String line = scanner.nextLine(); // line=RequestUtil.filter(line); buffer.append(line); } } catch (Exception ex) { } finally { if (scanner != null) { scanner.close(); } if(in!=null){ in.close(); } } } }