java - Tomcat 8.0.36 : WebappClassLoaderBase elusive nullpointerexception

Question

问题:

问题是我在 Tomcat 的 WebappClassLoaderBase 中得到了一个 NullPointerException，但没有过多解释为什么会发生这种情况。据我所知，它从 8.0.35 版开始发生......

异常跟踪:

java.lang.NullPointerException
    org.apache.catalina.loader.WebappClassLoaderBase.binaryNameToPath(WebappClassLoaderBase.java:2562)
    org.apache.catalina.loader.WebappClassLoaderBase.findLoadedClass0(WebappClassLoaderBase.java:2730)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1208)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1166)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1099)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:670)
    org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2508)
    org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2497)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.lang.Thread.run(Thread.java:745)

产生问题的web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">

<servlet>
    <servlet-name>FirstServlet</servlet-name>
    <async-supported>true</async-supported>
</servlet>

<servlet>
    <servlet-name>SecondServlet</servlet-name>
    <enabled>false</enabled>
</servlet>

<session-config>
    <session-timeout>7</session-timeout>
    <cookie-config>
        <http-only>true</http-only>
        <secure>true</secure>
    </cookie-config>
</session-config>

<security-constraint>
    <display-name>HTTPS</display-name>
    <web-resource-collection>
        <web-resource-name>HTTPS Constraint</web-resource-name>
        <url-pattern>/*</url-pattern>
    </web-resource-collection>
    <user-data-constraint>
        <transport-guarantee>CONFIDENTIAL</transport-guarantee>
    </user-data-constraint>
</security-constraint>
<!-- IMPORTED web.xml MODULES END -->

</web-app>

Answer 1

我通过添加 <servlet-class> 解决了这个问题web.xml 中的标签文件。

AFAICT 我不需要这样做，因为在我的代码中我有 @WebServlet应该已经在 Tomcat 中注册了类名的注解。