错误实例化servlet类[*]如何解决此错误

Question

HTTP状态500 –内部服务器错误类型异常报告

实例化servlet类[WelcomeServlet]时发生消息错误

描述服务器遇到意外状况，阻止其满足请求。

例外

javax.servlet.ServletException：实例化servlet类[WelcomeServlet]时出错org.apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase.java:526）org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:92）org.apache.catalina.valves.AbstractAccessLogValve.invoke（AbstractAccessLogValve.java:678）org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:343）org.apache.coyote.http11.Http11Processor.service（Http11Processor.java:408）org.apache.coyote.AbstractProcessorLight.process（AbstractProcessorLight.java:66）org.apache.coyote.AbstractProtocol $ ConnectionHandler.process（AbstractProtocol.java:860）org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.doRun（NioEndpoint.java:1589）org.apache.tomcat.util.net.SocketProcessorBase.run（SocketProcessorBase.java:49）java.base / java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1128）java.base / java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:628）org.apache.tomcat.util.threads.TaskThread $ WrappingRunnable.run（TaskThread.java:61）java.base / java.lang.Thread.run（Thread.java:834）根本原因

java.lang.UnsupportedClassVersionError：WelcomeServlet已由Java Runtime的最新版本（类文件版本56.0）进行了编译，此版本的Java Runtime仅可识别55.0以下的类文件版本（无法加载类[WelcomeServlet] ）org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal（WebappClassLoaderBase.java:2424）org.apache.catalina.loader.WebappClassLoaderBase.findClass（WebappClassLoaderBase.java:865）org.apache.catalina.loader.WebappClassLoaderBase.loadClass（WebappClassLoaderBase.java:1334）org.apache.catalina.loader.WebappClassLoaderBase.loadClass（WebappClassLoaderBase.java:1188）org.apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase.java:526）org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:92）org.apache.catalina.valves.AbstractAccessLogValve.invoke（AbstractAccessLogValve.java:678）org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:343）org.apache.coyote.http11.Http11Processor.service（Http11Processor.java:408）org.apache.coyote.AbstractProcessorLight.process（AbstractProcessorLight.java:66）org.apache.coyote.AbstractProtocol $ ConnectionHandler.process（AbstractProtocol.java:860）org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.doRun（NioEndpoint.java:1589）org.apache.tomcat.util.net.SocketProcessorBase.run（SocketProcessorBase.java:49）java.base / java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1128）java.base / java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:628）org.apache.tomcat.util.threads.TaskThread $ WrappingRunnable.run（TaskThread.java:61）java.base / java.lang.Thread.run（Thread.java:834）注意服务器日志中提供了根本原因的完整堆栈跟踪。

Apache Tomcat / 9.0.26

Answer 1

这是您的问题：

java.lang.UnsupportedClassVersionError: WelcomeServlet has been compiled by a more recent version of the java Runtime (class file version 56.0),
this version of the Java Runtime only recognizes class file versions up to 55.0 (unable to load class [WelcomeServlet])