Servlet UnavailableException：启动码头时持有人中没有类

Question

谁能告诉我是什么原因导致码头服务器启动时出现此异常。我正在使用码头 9.2.2

javax.servlet.UnavailableException：持有人中没有类

web.xml 包含

<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

<servlet>
    <servlet-name>com.test.api.TestApiApplication</servlet-name>
</servlet>
<servlet-mapping>
    <servlet-name>com.test.api.TestApiApplication</servlet-name>
    <url-pattern>/v1/*</url-pattern>
</servlet-mapping>
</web-app>

TestApiApplication.java 扩展了应用程序

public class TestApiApplication extends Application {

 public TestApiApplication() {
 }

@Override
 public Set<Class<?>> getClasses() {
    Set<Class<?>> s = new HashSet<Class<?>>();
    s.add(TestResource.class);
    return s;
 } 
}

我的 pom.xml 的深入版本是：

<properties>
    <jersey.version>2.11</jersey.version>
    <spring.framework.version>4.0.6.RELEASE</spring.framework.version>
    <jaxrs.version>2.0</jaxrs.version>
</properties>
<dependencies>

    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
    </dependency>
    <dependency>
        <groupId>javax.ws.rs</groupId>
        <artifactId>javax.ws.rs-api</artifactId>
        <version>2.0</version>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.containers</groupId>
        <artifactId>jersey-container-servlet-core</artifactId>
        <version>${jersey.version}</version>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.containers</groupId>
        <artifactId>jersey-container-servlet</artifactId>
        <version>${jersey.version}</version>
    </dependency>

    <dependency>
        <groupId>com.sun.jersey</groupId>
        <artifactId>jersey-json</artifactId>
        <version>1.18.1</version>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.containers</groupId>
        <artifactId>jersey-container-jetty-servlet</artifactId>
        <version>2.11</version>
    </dependency>
</dependencies>

完整的堆栈跟踪是：

javax.servlet.UnavailableException: No class in holder
    at org.eclipse.jetty.servlet.BaseHolder.doStart(BaseHolder.java:88)
    at org.eclipse.jetty.servlet.ServletHolder.doStart(ServletHolder.java:332)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.servlet.ServletHandler.initialize(ServletHandler.java:868)
    at org.eclipse.jetty.servlet.ServletContextHandler.startContext(ServletContextHandler.java:298)
    at org.eclipse.jetty.webapp.WebAppContext.startWebapp(WebAppContext.java:1341)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1334)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:741)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:497)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.deploy.bindings.StandardStarter.processBinding(StandardStarter.java:41)
    at org.eclipse.jetty.deploy.AppLifeCycle.runBindings(AppLifeCycle.java:186)
    at org.eclipse.jetty.deploy.DeploymentManager.requestAppGoal(DeploymentManager.java:498)
    at org.eclipse.jetty.deploy.DeploymentManager.addApp(DeploymentManager.java:146)
    at org.eclipse.jetty.deploy.providers.ScanningAppProvider.fileAdded(ScanningAppProvider.java:180)
    at org.eclipse.jetty.deploy.providers.ScanningAppProvider$1.fileAdded(ScanningAppProvider.java:64)
    at org.eclipse.jetty.util.Scanner.reportAddition(Scanner.java:609)
    at org.eclipse.jetty.util.Scanner.reportDifferences(Scanner.java:528)
    at org.eclipse.jetty.util.Scanner.scan(Scanner.java:391)
    at org.eclipse.jetty.util.Scanner.doStart(Scanner.java:313)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.deploy.providers.ScanningAppProvider.doStart(ScanningAppProvider.java:150)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.deploy.DeploymentManager.startAppProvider(DeploymentManager.java:560)
    at org.eclipse.jetty.deploy.DeploymentManager.doStart(DeploymentManager.java:235)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:132)
    at org.eclipse.jetty.server.Server.start(Server.java:380)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:114)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.Server.doStart(Server.java:347)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at yjava.servlet.container.jetty.JettyDaemon.start(JettyDaemon.java:40)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.apache.commons.daemon.support.DaemonLoader.start(DaemonLoader.java:177)

Answer 1

需要知道 Jetty 是如何启动的yjava.servlet.container.jetty.JettyDaemon才能更深入地回答。

如果您希望使用 Servlet 3.0 技术自动装配 Jersey org.glassfish.jersey.servlet.init.JerseyServletContainerInitializer，那么该类JettyDaemon必须为 Jetty 启用各种注释扫描配置。

对于初学者来说，您的 web.xml 声明很糟糕。

您的（重新格式化为可读）

<web-app version="3.0" 
         xmlns="http://java.sun.com/xml/ns/javaee" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

该 XML 无效，该web-app元素未关闭，并且您缺少一些必需的属性。

对于 Servlet 3.0 正确：

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

但是您的环境是 Servlet 3.1，根据您选择的 Jetty 9 以及在 pom.xml 中使用 servlet-api 3.1.0，因此声明将是：

<?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_3_1.xsd"
     metadata-complete="false"
     version="3.1">
</web-app>