java - Tomcat 找不到包含过滤器的自定义库

Question

在为 Tomcat 创建包含用于创建自定义日志的过滤器的库时，我做了以下操作:

• 编译(mvn package)一个包含单文件过滤器的 JAR 库，并将其放入 Tomcat 的全局 lib 文件夹
• 在 Tomcat 的全局 web.xml 文件中定义过滤器
• 重新启动 Tomcat 以确保更改生效

收到此错误:

10-Jul-2017 15:46:32.591 SEVERE [ContainerBackgroundProcessor[StandardEngine[Catalina]]] org.apache.catalina.core.StandardContext.filterStart Exception starting filter [ReqRespDumpFilter]
 java.lang.NoClassDefFoundError: Could not initialize class com.example.ReqRespDumpFilter
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:120)
    at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:262)
    at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:108)
    at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4481)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5121)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3690)
    at org.apache.catalina.startup.HostConfig.reload(HostConfig.java:1404)
    at org.apache.catalina.startup.HostConfig.checkResources(HostConfig.java:1377)
    at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1613)
    at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:304)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:123)
    at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1172)
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1394)
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1398)
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1366)
    at java.lang.Thread.run(Thread.java:748)
10-Jul-2017 16:58:11.581 SEVERE [ContainerBackgroundProcessor[StandardEngine[Catalina]]] org.apache.catalina.core.StandardContext.startInternal One or more Filters failed to start. Full details will be found in the appropriate container log file

未归档的 JAR:

Tomcat的全局配置tomcat/conf/web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                      http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
  version="4.0">
  ...
  <filter>
    <filter-name>ReqRespDumpFilter</filter-name>
    <filter-class>com.example.ReqRespDumpFilter</filter-class>
  </filter>

  <filter-mapping>
    <filter-name>ReqRespDumpFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
  ...
</web-app>

pom.xml 用于编译库:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>ReqRespDumpFilter</artifactId>
    <packaging>jar</packaging>
    <version>1.0-SNAPSHOT</version>
    <name>ReqRespDumpFilter Maven Webapp</name>
    <url>http://maven.apache.org</url>
    <dependencies>
        <!-- https://mvnrepository.com/artifact/javax.servlet/servlet-api -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
            <scope>provided</scope>
        </dependency>
        <!-- https://mvnrepository.com/artifact/log4j/log4j -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.4</version>
        </dependency>
    </dependencies>
    <build>
        <finalName>ReqRespDumpFilter</finalName>
        <sourceDirectory>src</sourceDirectory>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

ReqRespDumpFilter/src/com/example/ReqRespDumpFilter.java 过滤器源码:

package com.example;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.io.output.TeeOutputStream;
import org.apache.log4j.Logger;

public class ReqRespDumpFilter implements Filter {


    private static final Logger logger = Logger.getLogger(ReqRespDumpFilter.class);

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        try {
            HttpServletRequest httpServletRequest = (HttpServletRequest) request;
            HttpServletResponse httpServletResponse = (HttpServletResponse) response;

            Map<String, String> requestMap = this.getTypesafeRequestMap(httpServletRequest);
            BufferedRequestWrapper bufferedReqest = new BufferedRequestWrapper(httpServletRequest);
            BufferedResponseWrapper bufferedResponse = new BufferedResponseWrapper(httpServletResponse);

            final StringBuilder logMessage = new StringBuilder("REST Request - ")
                    .append("[HTTP METHOD:")
                    .append(httpServletRequest.getMethod())
                    .append("] [PATH INFO:")
                    .append(httpServletRequest.getPathInfo())
                    .append("] [REQUEST PARAMETERS:")
                    .append(requestMap)
                    .append("] [REQUEST BODY:")
                    .append(bufferedReqest.getRequestBody())
                    .append("] [REMOTE ADDRESS:")
                    .append(httpServletRequest.getRemoteAddr())
                    .append("]");

            chain.doFilter(bufferedReqest, bufferedResponse);
            logMessage.append(" [RESPONSE:").append(bufferedResponse.getContent()).append("]");
            logger.debug(logMessage);
        } catch (Throwable a) {
            logger.error(a);
        }
    }


    private Map<String, String> getTypesafeRequestMap(HttpServletRequest request) {
        Map<String, String> typesafeRequestMap = new HashMap<String, String>();
        Enumeration<?> requestParamNames = request.getParameterNames();
        while (requestParamNames.hasMoreElements()) {
            String requestParamName = (String) requestParamNames.nextElement();
            String requestParamValue = request.getParameter(requestParamName);
            typesafeRequestMap.put(requestParamName, requestParamValue);
        }
        return typesafeRequestMap;
    }


    @Override
    public void destroy() {
    }


    private static final class BufferedRequestWrapper extends HttpServletRequestWrapper {

        private ByteArrayInputStream bais = null;
        private ByteArrayOutputStream baos = null;
        private BufferedServletInputStream bsis = null;
        private byte[] buffer = null;


        public BufferedRequestWrapper(HttpServletRequest req) throws IOException {
            super(req);
            // Read InputStream and store its content in a buffer.
            InputStream is = req.getInputStream();
            this.baos = new ByteArrayOutputStream();
            byte buf[] = new byte[1024];
            int letti;
            while ((letti = is.read(buf)) > 0) {
                this.baos.write(buf, 0, letti);
            }
            this.buffer = this.baos.toByteArray();
        }


        @Override
        public ServletInputStream getInputStream() {
            this.bais = new ByteArrayInputStream(this.buffer);
            this.bsis = new BufferedServletInputStream(this.bais);
            return this.bsis;
        }


        String getRequestBody() throws IOException {
            BufferedReader reader = new BufferedReader(new InputStreamReader(this.getInputStream()));
            String line = null;
            StringBuilder inputBuffer = new StringBuilder();
            do {
                line = reader.readLine();
                if (null != line) {
                    inputBuffer.append(line.trim());
                }
            } while (line != null);
            reader.close();
            return inputBuffer.toString().trim();
        }

    }


    private static final class BufferedServletInputStream extends ServletInputStream {

        private ByteArrayInputStream bais;

        public BufferedServletInputStream(ByteArrayInputStream bais) {
            this.bais = bais;
        }

        @Override
        public int available() {
            return this.bais.available();
        }

        @Override
        public int read() {
            return this.bais.read();
        }

        @Override
        public int read(byte[] buf, int off, int len) {
            return this.bais.read(buf, off, len);
        }


    }

    public class TeeServletOutputStream extends ServletOutputStream {

        private final TeeOutputStream targetStream;

        public TeeServletOutputStream(OutputStream one, OutputStream two) {
            targetStream = new TeeOutputStream(one, two);
        }

        @Override
        public void write(int arg0) throws IOException {
            this.targetStream.write(arg0);
        }

        public void flush() throws IOException {
            super.flush();
            this.targetStream.flush();
        }

        public void close() throws IOException {
            super.close();
            this.targetStream.close();
        }
    }


    public class BufferedResponseWrapper implements HttpServletResponse {

        HttpServletResponse original;
        TeeServletOutputStream tee;
        ByteArrayOutputStream bos;

        public BufferedResponseWrapper(HttpServletResponse response) {
            original = response;
        }

        public String getContent() {
            return bos.toString();
        }

        public PrintWriter getWriter() throws IOException {
            return original.getWriter();
        }

        public ServletOutputStream getOutputStream() throws IOException {
            if (tee == null) {
                bos = new ByteArrayOutputStream();
                tee = new TeeServletOutputStream(original.getOutputStream(), bos);
            }
            return tee;

        }

        @Override
        public String getCharacterEncoding() {
            return original.getCharacterEncoding();
        }

        @Override
        public String getContentType() {
            return original.getContentType();
        }

        @Override
        public void setCharacterEncoding(String charset) {
            original.setCharacterEncoding(charset);
        }

        @Override
        public void setContentLength(int len) {
            original.setContentLength(len);
        }

        @Override
        public void setContentType(String type) {
            original.setContentType(type);
        }

        @Override
        public void setBufferSize(int size) {
            original.setBufferSize(size);
        }

        @Override
        public int getBufferSize() {
            return original.getBufferSize();
        }

        @Override
        public void flushBuffer() throws IOException {
            tee.flush();
        }

        @Override
        public void resetBuffer() {
            original.resetBuffer();
        }

        @Override
        public boolean isCommitted() {
            return original.isCommitted();
        }

        @Override
        public void reset() {
            original.reset();
        }

        @Override
        public void setLocale(Locale loc) {
            original.setLocale(loc);
        }

        @Override
        public Locale getLocale() {
            return original.getLocale();
        }

        @Override
        public void addCookie(Cookie cookie) {
            original.addCookie(cookie);
        }

        @Override
        public boolean containsHeader(String name) {
            return original.containsHeader(name);
        }

        @Override
        public String encodeURL(String url) {
            return original.encodeURL(url);
        }

        @Override
        public String encodeRedirectURL(String url) {
            return original.encodeRedirectURL(url);
        }

        @SuppressWarnings("deprecation")
        @Override
        public String encodeUrl(String url) {
            return original.encodeUrl(url);
        }

        @SuppressWarnings("deprecation")
        @Override
        public String encodeRedirectUrl(String url) {
            return original.encodeRedirectUrl(url);
        }

        @Override
        public void sendError(int sc, String msg) throws IOException {
            original.sendError(sc, msg);
        }

        @Override
        public void sendError(int sc) throws IOException {
            original.sendError(sc);
        }

        @Override
        public void sendRedirect(String location) throws IOException {
            original.sendRedirect(location);
        }

        @Override
        public void setDateHeader(String name, long date) {
            original.setDateHeader(name, date);
        }

        @Override
        public void addDateHeader(String name, long date) {
            original.addDateHeader(name, date);
        }

        @Override
        public void setHeader(String name, String value) {
            original.setHeader(name, value);
        }

        @Override
        public void addHeader(String name, String value) {
            original.addHeader(name, value);
        }

        @Override
        public void setIntHeader(String name, int value) {
            original.setIntHeader(name, value);
        }

        @Override
        public void addIntHeader(String name, int value) {
            original.addIntHeader(name, value);
        }

        @Override
        public void setStatus(int sc) {
            original.setStatus(sc);
        }

        @SuppressWarnings("deprecation")
        @Override
        public void setStatus(int sc, String sm) {
            original.setStatus(sc, sm);
        }

    }

}

Answer 1

您将获得:

 java.lang.NoClassDefFoundError: Could not initialize class com.example.ReqRespDumpFilter

因为此类包含 org.apache.log4j.Logger 实例的静态初始化程序.

都不是log4j或 commons-io存在于标准 Tomcat 发行版中，因此您需要确保它们也存在于您的 tomcat 中 lib目录。

此外，您需要复制/移动您的 log4j.properties/log4j.xml文件到 tomcat conf目录，以便可以访问以正确配置您的日志记录。您可能想要制作 log4j <scope>provided</scope>在您所有的应用程序中，以便集中配置。