Tomcat：Custom a common error page valve for all web application in tomcat

浏览数：31 / 时间：2015年06月11日

　　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 [email protected] 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();
            }
        }
    }
    
}