Question

是什么原因引起的？这似乎是一个非常混乱的原因。

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error that prevented it from fulfilling this request.

exception

java.lang.NullPointerException
    java.util.concurrent.ConcurrentHashMap.putVal(Unknown Source)
    java.util.concurrent.ConcurrentHashMap.putIfAbsent(Unknown Source)
    java.lang.ClassLoader.getClassLoadingLock(Unknown Source)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1149)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1116)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:510)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:1110)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:785)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1425)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
    java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.lang.Thread.run(Unknown Source)
note The full stack trace of the root cause is available in the Apache Tomcat/8.5.3 logs.

以下是包含：

import java.util.Set;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Application;

添加web.xml 请注意：我已经为url-pattern尝试了多个值，它似乎只是更改了我得到错误的URI。 'Hello'是java源代码中的类名。

<?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>HelloWorldTomcatService</servlet-name>
        <init-param>
            <param-name>com.package.from.java.file</param-name>
            <param-value>Hello</param-value>
        </init-param>
        </servlet>
    <servlet-mapping>
        <servlet-name>HelloWorldTomcatService</servlet-name>
        <url-pattern></url-pattern>
    </servlet-mapping>
    <session-config>
        <session-timeout>30</session-timeout>
    </session-config>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

Answer 1

java.lang.NullPointerException
    java.util.concurrent.ConcurrentHashMap.putVal(Unknown Source)
    java.util.concurrent.ConcurrentHashMap.putIfAbsent(Unknown Source)
    java.lang.ClassLoader.getClassLoadingLock(Unknown Source)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1149)

此特定条目可能是由web.xml条目引起的，该条目需要<xxx-class>，例如<servlet-class>，<filter-class>或<listener-class>，但它实际上不存在或空。

事实上，您的<servlet>条目缺少<servlet-class>。它应该引用servlet类的FQN，你想在<servlet-name>指定的名称下注册，如下所示。

<servlet>
    <servlet-name>someServlet</servlet-name>
    <servlet-class>com.example.SomeServlet</servlet-class>
</servlet>

也就是说，如果它实际上是您尝试注册的JAX-RS servlet，那么<init-param><param-name>也看起来不太好。您确定您正在阅读正确的教程/资源，以学习JAX-RS并将其集成到Tomcat中吗？众所周知的是由Lars Vogel提供的。

来自org.apache.catalina.loader.WebappClassLoaderBase.loadClass

1 个答案: