试图弄清楚为什么我在tomcat日志中出现以下错误：
Caused by: java.lang.LinkageError: loader constraint violation: when resolving method "org.slf4j.impl.StaticLoggerBinder.getLoggerFactory()Lorg/slf4j/ILoggerFactory;" the class loader (instance of org/apache/catalina/loader/WebappClassLoader) of the current class, org/slf4j/LoggerFactory, and the class loader (instance of sun/misc/Launcher$AppClassLoader) for the method's defining class, org/slf4j/impl/StaticLoggerBinder, have different Class objects for the type org/slf4j/ILoggerFactory used in the signature
在我的gradle文件中，我使用的是slf4j版本1.7.7，在Tomcat中，我有jul-to- slf4j-1.7.7.jar和slf4j-api-1.7.7.jar，所以我很困惑。
这是堆栈跟踪-感谢您的帮助！
Total time: 2.982 secs Using CATALINA_BASE: /usr/local/Cellar/tomcat/8.0.18/libexec Using CATALINA_HOME: /usr/local/Cellar/tomcat/8.0.18/libexec Using CATALINA_TMPDIR: /usr/local/Cellar/tomcat/8.0.18/libexec/temp Using JRE_HOME: /Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home Using CLASSPATH: /usr/local/Cellar/tomcat/8.0.18/libexec/bin/jul-to-slf4j-1.7.7.jar:/usr/local/Cellar/tomcat/8.0.18/libexec/bin/slf4j-api-1.7.7.jar:/usr/local/Cellar/tomcat/8.0.18/libexec/bin/logback-classic-1.1.2.jar:/usr/local/Cellar/tomcat/8.0.18/libexec/bin/logback-core-1.1.2.jar:/usr/local/Cellar/tomcat/8.0.18/libexec/bin/logback-config/:/usr/local/Cellar/tomcat/8.0.18/libexec/bin/bootstrap.jar:/usr/local/Cellar/tomcat/8.0.18/libexec/bin/tomcat-juli.jar 19:03:55.979 [main] INFO org.apache.catalina.startup.VersionLoggerListener - Server version: Apache Tomcat/8.0.18 19:03:55.981 [main] INFO org.apache.catalina.startup.VersionLoggerListener - Server built: Jan 23 2015 11:56:07 UTC 19:03:55.981 [main] INFO org.apache.catalina.startup.VersionLoggerListener - Server number: 8.0.18.0 19:03:55.982 [main] INFO org.apache.catalina.startup.VersionLoggerListener - OS Name: Mac OS X 19:03:55.982 [main] INFO org.apache.catalina.startup.VersionLoggerListener - OS Version: 10.10 19:03:55.982 [main] INFO org.apache.catalina.startup.VersionLoggerListener - Architecture: x86_64 19:03:55.982 [main] INFO org.apache.catalina.startup.VersionLoggerListener - Java Home: /Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home/jre 19:03:55.982 [main] INFO org.apache.catalina.startup.VersionLoggerListener - JVM Version: 1.8.0_25-b17 19:03:55.982 [main] INFO org.apache.catalina.startup.VersionLoggerListener - JVM Vendor: Oracle Corporation 19:03:55.982 [main] INFO org.apache.catalina.startup.VersionLoggerListener - CATALINA_BASE: /usr/local/Cellar/tomcat/8.0.18/libexec 19:03:55.983 [main] INFO org.apache.catalina.startup.VersionLoggerListener - CATALINA_HOME: /usr/local/Cellar/tomcat/8.0.18/libexec 19:03:55.983 [main] INFO org.apache.catalina.startup.VersionLoggerListener - Command line argument: -Djava.util.logging.config.file=/usr/local/Cellar/tomcat/8.0.18/libexec/conf/logging.properties 19:03:55.983 [main] INFO org.apache.catalina.startup.VersionLoggerListener - Command line argument: -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager 19:03:55.983 [main] INFO org.apache.catalina.startup.VersionLoggerListener - Command line argument: -Djava.endorsed.dirs=/usr/local/Cellar/tomcat/8.0.18/libexec/endorsed 19:03:55.983 [main] INFO org.apache.catalina.startup.VersionLoggerListener - Command line argument: -Dcatalina.base=/usr/local/Cellar/tomcat/8.0.18/libexec 19:03:55.984 [main] INFO org.apache.catalina.startup.VersionLoggerListener - Command line argument: -Dcatalina.home=/usr/local/Cellar/tomcat/8.0.18/libexec 19:03:55.984 [main] INFO org.apache.catalina.startup.VersionLoggerListener - Command line argument: -Djava.io.tmpdir=/usr/local/Cellar/tomcat/8.0.18/libexec/temp 19:03:55.984 [main] INFO org.apache.catalina.core.AprLifecycleListener - The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: /Users/jadekler/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:. 19:03:56.076 [main] INFO org.apache.coyote.http11.Http11NioProtocol - Initializing ProtocolHandler ["http-nio-8080"] 19:03:56.092 [main] INFO org.apache.tomcat.util.net.NioSelectorPool - Using a shared selector for servlet write/read 19:03:56.094 [main] INFO org.apache.coyote.ajp.AjpNioProtocol - Initializing ProtocolHandler ["ajp-nio-8009"] 19:03:56.096 [main] INFO org.apache.tomcat.util.net.NioSelectorPool - Using a shared selector for servlet write/read 19:03:56.096 [main] INFO org.apache.catalina.startup.Catalina - Initialization processed in 510 ms 19:03:56.115 [main] INFO org.apache.catalina.core.StandardService - Starting service Catalina 19:03:56.115 [main] INFO org.apache.catalina.core.StandardEngine - Starting Servlet Engine: Apache Tomcat/8.0.18 19:03:56.132 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deploying web application archive /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/websiteskeleton.war 19:03:56.812 [localhost-startStop-1] ERROR org.apache.catalina.core.StandardContext - Error during ServletContainerInitializer processing javax.servlet.ServletException: Failed to instantiate WebApplicationInitializer class at org.springframework.web.SpringServletContainerInitializer.onStartup(SpringServletContainerInitializer.java:160) ~[spring-web-4.1.0.RELEASE.jar:4.1.0.RELEASE] at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5143) ~[catalina.jar:8.0.18] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [catalina.jar:8.0.18] at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725) [catalina.jar:8.0.18] at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701) [catalina.jar:8.0.18] at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:714) [catalina.jar:8.0.18] at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:917) [catalina.jar:8.0.18] at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1701) [catalina.jar:8.0.18] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_25] at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_25] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_25] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_25] at java.lang.Thread.run(Thread.java:745) [na:1.8.0_25] Caused by: java.lang.LinkageError: loader constraint violation: when resolving method "org.slf4j.impl.StaticLoggerBinder.getLoggerFactory()Lorg/slf4j/ILoggerFactory;" the class loader (instance of org/apache/catalina/loader/WebappClassLoader) of the current class, org/slf4j/LoggerFactory, and the class loader (instance of sun/misc/Launcher$AppClassLoader) for the method's defining class, org/slf4j/impl/StaticLoggerBinder, have different Class objects for the type org/slf4j/ILoggerFactory used in the signature at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:306) ~[slf4j-api-1.7.7.jar:1.7.7] at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:276) ~[slf4j-api-1.7.7.jar:1.7.7] at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:288) ~[slf4j-api-1.7.7.jar:1.7.7] at com.websiteskeleton.core.HelloInitializer.<init>(HelloInitializer.java:13) ~[HelloInitializer.class:na] at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_25] at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_25] at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_25] at java.lang.reflect.Constructor.newInstance(Constructor.java:408) ~[na:1.8.0_25] at java.lang.Class.newInstance(Class.java:438) ~[na:1.8.0_25] at org.springframework.web.SpringServletContainerInitializer.onStartup(SpringServletContainerInitializer.java:157) ~[spring-web-4.1.0.RELEASE.jar:4.1.0.RELEASE] ... 12 common frames omitted 19:03:56.821 [localhost-startStop-1] ERROR org.apache.catalina.core.StandardContext - Context [/websiteskeleton] startup failed due to previous errors 19:03:56.825 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deployment of web application archive /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/websiteskeleton.war has finished in 693 ms 19:03:56.826 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deploying web application directory /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/docs 19:03:56.893 [localhost-startStop-1] INFO org.apache.jasper.servlet.TldScanner - At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time. 19:03:56.904 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deployment of web application directory /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/docs has finished in 78 ms 19:03:56.904 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deploying web application directory /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/examples 19:03:57.133 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deployment of web application directory /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/examples has finished in 228 ms 19:03:57.133 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deploying web application directory /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/host-manager 19:03:57.192 [localhost-startStop-1] INFO org.apache.jasper.servlet.TldScanner - At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time. 19:03:57.195 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deployment of web application directory /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/host-manager has finished in 62 ms 19:03:57.195 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deploying web application directory /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/manager 19:03:57.252 [localhost-startStop-1] INFO org.apache.jasper.servlet.TldScanner - At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time. 19:03:57.254 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deployment of web application directory /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/manager has finished in 59 ms 19:03:57.254 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deploying web application directory /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/ROOT 19:03:57.307 [localhost-startStop-1] INFO org.apache.jasper.servlet.TldScanner - At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time. 19:03:57.308 [localhost-startStop-1] INFO org.apache.catalina.startup.HostConfig - Deployment of web application directory /usr/local/Cellar/tomcat/8.0.18/libexec/webapps/ROOT has finished in 54 ms 19:03:57.310 [main] INFO org.apache.coyote.http11.Http11NioProtocol - Starting ProtocolHandler ["http-nio-8080"] 19:03:57.314 [main] INFO org.apache.coyote.ajp.AjpNioProtocol - Starting ProtocolHandler ["ajp-nio-8009"] 19:03:57.315 [main] INFO org.apache.catalina.startup.Catalina - Server startup in 1218 ms
Tomcat日志显示您在类路径上还有另一个slf4j-1.7.7.jar：
使用CLASSPATH：/usr/local/Cellar/tomcat/8.0.18/libexec/bin/jul-to- slf4j-1.7.7.jar： /usr/local/Cellar/tomcat/8.0.18/libexec/bin/slf4j -api-1.7.7.jar ：/usr/local/Cellar/tomcat/8.0.18/libexec/bin/logback- classic-1.1.2.jar：/usr/local/Cellar/tomcat/8.0.18/libexec /bin/logback- core-1.1.2.jar:/usr/local/Cellar/tomcat/8.0.18/libexec/bin/logback- config/:/usr/local/Cellar/tomcat/8.0.18/libexec/ bin / bootstrap.jar：/usr/local/Cellar/tomcat/8.0.18/libexec/bin/tomcat-juli.jar
初始化Tomcat后，它将初始化jul-to-slf4j和slf4j-api。这些jar由加载了Tomcat jar（sun / misc / Launcher $ AppClassLoader）的Classloader加载。
当您的应用程序尝试访问slf4j-api类时，它将使用WebApplication Classloader（org / apache / catalina / loader / WebappClassLoader），默认情况下，该应用程序在应用程序类路径中搜索系统类路径之前的类定义。请注意，这可以更改：https : //tomcat.apache.org/tomcat-8.0-doc/class-loader- howto.html
在Java中，类签名由类的完全限定名称和加载该类的类加载器组成。如果从两个不同的类加载器（相同的层次结构）两次加载一个类，则JVM将有两个不同的类。尝试将一个类的对象引用指向另一个类的变量将导致ClassCastException。请查看此博客文章（项目5）以获取有关此的更多信息：https : //techblug.wordpress.com/2012/03/17/classloader- tips/
因此，据我所知，您可以通过从Tomcat类路径中删除slf4j-*。jar来解决此问题，或者如果使用相同版本的slf4j拥有一个以上的webapp，则可以从webapp中删除jar。它将使用Tomcat类加载器加载的那些。
