CDI injection is not working in Servlets

Question

I really need your help. I'm working on this problem for weeks or months now. I apologize for the long post, but I want to explain the problem and my settings as precisely as possible.

My JAVA EE 6 web application mainly contains 3 Servlets: a javax.faces.webapp.FacesServlet, a StreamingServlet extending javax.servlet.http.HttpServlet and a ClientServlet extending org.eclipse.jetty.websocket.WebSocketServlet. I want to use CDI with these Servlets but it only works for the FacesServlet, to be more precisely, for the Beans the JSF actions are routed to. CDI injection doesn't work with the other 2 Servlets.

The setup for my project is as follows: Maven 3.0.4, Jetty 8.1.4 (jetty-maven-plugin), MyFaces 2.1.6, Weld 1.1.8.

The file pom.xml contains the dependencies for CDI:

...
<dependency>
    <groupId>javax.enterprise</groupId>
    <artifactId>cdi-api</artifactId>
    <version>1.1.EDR1.2</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>javax.annotation</groupId>
    <artifactId>jsr250-api</artifactId>
    <version>1.0</version>
</dependency>
<dependency>
    <groupId>org.jboss.weld.servlet</groupId>
    <artifactId>weld-servlet</artifactId>
    <version>${weld.version}</version>
    <scope>runtime</scope>
</dependency>
...

The file src/main/webapp/WEB-INF/beans.xml only contains an empty beans element for activating CDI:

<?xml version="1.0" encoding="UTF-8"?>
<beans 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/beans_1_0.xsd">
</beans>

The file scr/main/webapp/WEB-INF/jetty-env.xml contains the Jetty specific configuration for getting the bean manager via JNDI:

<!DOCTYPE Configure PUBLIC "-//Mort Bay Consulting//DTD Configure//EN" "http://www.eclipse.org/jetty/configure.dtd">

<Configure id="webAppCtx" class="org.eclipse.jetty.webapp.WebAppContext">
    <New id="BeanManager" class="org.eclipse.jetty.plus.jndi.Resource">
        <Arg>
            <Ref id="webAppCtx" />
        </Arg>
        <Arg>BeanManager</Arg>
        <Arg>
            <New class="javax.naming.Reference">
                <Arg>javax.enterprise.inject.spi.BeanManager</Arg>
                <Arg>org.jboss.weld.resources.ManagerObjectFactory</Arg>
                <Arg />
            </New>
        </Arg>
    </New>
</Configure>

The file src/main/webapp/WEB-INF/web.xml contains the servlet listener and the BeanManager reference for bootstrapping CDI:

...
<listener>
    <listener-class>org.jboss.weld.environment.servlet.Listener</listener-class>
</listener>

<resource-env-ref>
    <description>Object factory for the CDI Bean Manager</description>
    <resource-env-ref-name>BeanManager</resource-env-ref-name>
    <resource-env-ref-type>javax.enterprise.inject.spi.BeanManager</resource-env-ref-type>
</resource-env-ref>
...

With these settings I always got the following error when running the application using mvn jetty:run (first line is most important):

2012-07-31 11:09:33,546 [main] ERROR org.jboss.weld.environment.jetty.JettyPost72Container - Unable to create JettyWeldInjector. CDI injection will not be available in Servlets, Filters or Listeners
java.lang.IllegalArgumentException: Cannot load class for org.jboss.weld.environment.jetty.WeldDecorator
    at org.jboss.weld.environment.servlet.util.Reflections.classForName(Reflections.java:58)
    at org.jboss.weld.environment.jetty.JettyPost72Container.initialize(JettyPost72Container.java:66)
    at org.jboss.weld.environment.servlet.Listener.contextInitialized(Listener.java:162)
    at org.eclipse.jetty.server.handler.ContextHandler.callContextInitialized(ContextHandler.java:764)
    at org.eclipse.jetty.servlet.ServletContextHandler.callContextInitialized(ServletContextHandler.java:406)
    at org.eclipse.jetty.server.handler.ContextHandler.startContext(ContextHandler.java:756)
    at org.eclipse.jetty.servlet.ServletContextHandler.startContext(ServletContextHandler.java:242)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1234)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:699)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
    at org.mortbay.jetty.plugin.JettyWebAppContext.doStart(JettyWebAppContext.java:256)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.server.handler.HandlerCollection.doStart(HandlerCollection.java:224)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.doStart(ContextHandlerCollection.java:167)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.server.handler.HandlerCollection.doStart(HandlerCollection.java:224)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.server.handler.HandlerWrapper.doStart(HandlerWrapper.java:90)
    at org.eclipse.jetty.server.Server.doStart(Server.java:262)
    at org.mortbay.jetty.plugin.JettyServer.doStart(JettyServer.java:65)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.mortbay.jetty.plugin.AbstractJettyMojo.startJetty(AbstractJettyMojo.java:511)
    at org.mortbay.jetty.plugin.AbstractJettyMojo.execute(AbstractJettyMojo.java:364)
    at org.mortbay.jetty.plugin.JettyRunMojo.execute(JettyRunMojo.java:516)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:320)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)
Caused by: java.lang.NoClassDefFoundError: org/eclipse/jetty/servlet/ServletContextHandler$Decorator
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:415)
    at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:377)
    at org.jboss.weld.environment.servlet.util.Reflections.classForName(Reflections.java:51)
    ... 44 more
Caused by: java.lang.ClassNotFoundException: org.eclipse.jetty.servlet.ServletContextHandler$Decorator
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:415)
    at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:377)
    ... 56 more

The application was running but as the exception message states: CDI injection will not be available in Servlets.

A couple of days ago, I found the article Starting a CDI webapp from Maven with Weld-Servlet and Jetty Plugin and especially the section Last trick to allow injection in servlets. The author explains that Weld needs to decorate some Jetty internal classes in order to use the @Inject annotation in servlets and that we have to tell the Jetty classloader where to find this class in order to have the Weld servlet to decorate it.

I was waiting so long for this special information. So I added the file src/main/webapp/WEB-INF/jetty-context.xml:

<!DOCTYPE Configure PUBLIC "-//Jetty//Configure//EN" "http://www.eclipse.org/jetty/configure.dtd">

<Configure id="webAppCtx" class="org.eclipse.jetty.webapp.WebAppContext">
    <Set name="serverClasses">
        <Array type="java.lang.String">
            <Item>org.eclipse.jetty.servlet.ServletContextHandler.Decorator</Item>
        </Array>
    </Set>
</Configure> 

I also updated the pom.xml in order to incorporate the file jetty-context.xml (last line):

...
<plugin>
    <groupId>org.mortbay.jetty</groupId>
    <artifactId>jetty-maven-plugin</artifactId>
    <version>${jetty.version}</version>
    <configuration>
        <webApp>
            <contextPath>/${project.build.finalName}</contextPath>
        </webApp>
        <jettyEnvXml>src/main/webapp/WEB-INF/jetty-env.xml</jettyEnvXml>
        <contextXml>src/main/webapp/WEB-INF/jetty-context.xml</contextXml>
        ...

Now the above error disappeared. I was so happy for that short moment :)

In src/main/resources/log4j.properties I increased the log level for Weld:

...
log4j.logger.org.jboss.weld=DEBUG, stdout
log4j.additivity.org.jboss.weld=false
...

When starting the application I get the following Weld log messages:

...
2012-07-31 12:00:08,968 [main] INFO  org.jboss.weld.Bootstrap - WELD-000101 Transactional services not available. Injection of @Inject UserTransaction not available. Transactional observers will be invoked synchronously.
2012-07-31 12:00:09,109 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000103 Enabled alternatives for Manager
Enabled alternatives: [] []
Registered contexts: [interface javax.enterprise.context.SessionScoped, interface javax.enterprise.context.ApplicationScoped, interface javax.enterprise.context.Dependent, interface javax.enterprise.context.RequestScoped, interface javax.enterprise.context.ConversationScoped, interface javax.inject.Singleton]
Registered beans: 0
: [] []
2012-07-31 12:00:09,109 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000104 Enabled decorator types for Manager
Enabled alternatives: [] []
Registered contexts: [interface javax.enterprise.context.SessionScoped, interface javax.enterprise.context.ApplicationScoped, interface javax.enterprise.context.Dependent, interface javax.enterprise.context.RequestScoped, interface javax.enterprise.context.ConversationScoped, interface javax.inject.Singleton]
Registered beans: 0
: []
2012-07-31 12:00:09,109 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000105 Enabled interceptor types for Manager
Enabled alternatives: [] []
Registered contexts: [interface javax.enterprise.context.SessionScoped, interface javax.enterprise.context.ApplicationScoped, interface javax.enterprise.context.Dependent, interface javax.enterprise.context.RequestScoped, interface javax.enterprise.context.ConversationScoped, interface javax.inject.Singleton]
Registered beans: 0
: []
2012-07-31 12:00:09,171 [main] INFO  org.jboss.weld.environment.jetty.JettyPost72Container - Jetty7 detected, JSR-299 injection will be available in Listeners, Servlets and Filters.
2012-07-31 12:00:09,265 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Implicit Bean [javax.enterprise.inject.spi.InjectionPoint] with qualifiers [@Default]
2012-07-31 12:00:09,265 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: org.jboss.weld.bean-flat-Built-in-org.jboss.weld.context.DependentContext
2012-07-31 12:00:09,281 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.util.MediaType] with qualifiers [@Any @Default]
2012-07-31 12:00:09,281 [main] WARN  org.jboss.weld.interceptor.util.InterceptionTypeRegistry - Class 'javax.ejb.PostActivate' not found, interception based on it is not enabled
2012-07-31 12:00:09,281 [main] WARN  org.jboss.weld.interceptor.util.InterceptionTypeRegistry - Class 'javax.ejb.PrePassivate' not found, interception based on it is not enabled
2012-07-31 12:00:09,281 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.web.LoginBean] with qualifiers [@Any @Default]
2012-07-31 12:00:09,281 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: org.jboss.weld.bean-flat-Built-in-org.jboss.weld.context.http.HttpRequestContext
2012-07-31 12:00:09,281 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: org.jboss.weld.bean-flat-Built-in-org.jboss.weld.context.http.HttpSessionContext
2012-07-31 12:00:09,281 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.web.CustomerBean] with qualifiers [@Any @Default @Named]
2012-07-31 12:00:09,281 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: org.jboss.weld.bean-flat-Built-in-org.jboss.weld.context.bound.BoundConversationContext
2012-07-31 12:00:09,281 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: org.jboss.weld.bean-flat-Built-in-org.jboss.weld.context.ApplicationContext
2012-07-31 12:00:09,281 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.util.LocaleBean] with qualifiers [@Any @Default @Named]
2012-07-31 12:00:09,281 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: org.jboss.weld.bean-flat-Built-in-org.jboss.weld.context.bound.BoundRequestContext
2012-07-31 12:00:09,281 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: org.jboss.weld.bean-flat-Built-in-org.jboss.weld.context.SingletonContext
2012-07-31 12:00:09,281 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Implicit Bean [javax.enterprise.inject.Instance] with qualifiers [@Default]
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.DataReader] with qualifiers [@Any @Default @Named]
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.SessionBean] with qualifiers [@Any @Default @Named]
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.ConnectionTable] with qualifiers [@Any @Default @Named]
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: org.jboss.weld.bean-flat-Built-in-org.jboss.weld.context.http.HttpConversationContext
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.servlet.ClientServlet] with qualifiers [@Any @Default]
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: org.jboss.weld.bean-flat-Built-in-org.jboss.weld.context.RequestContext
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: org.jboss.weld.bean-flat-Built-in-javax.enterprise.context.Conversation
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Implicit Bean [javax.enterprise.event.Event] with qualifiers [@Default]
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.CustomerListBean] with qualifiers [@Any @Default]
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.Customer] with qualifiers [@Any @Default]
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.servlet.StreamingServlet] with qualifiers [@Any @Default]
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: org.jboss.weld.bean-flat-Built-in-org.jboss.weld.context.bound.BoundSessionContext
2012-07-31 12:00:09,296 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000106 Bean: Managed Bean [class de.telexiom.cardiom.SessionInfo] with qualifiers [@Any @Default]
2012-07-31 12:00:09,312 [main] DEBUG org.jboss.weld.Reflection - WELD-000601 interface javax.inject.Named is missing @Target. Weld will use this annotation, however this may make the application unportable.
2012-07-31 12:00:09,312 [main] DEBUG org.jboss.weld.Bootstrap - WELD-000100 Weld initialized. Validating beans
...

I use the Servlet 3.0 API, the StreamingServlet and the ClientServlet are configured via annotations. The problem is that the application scoped beans connectionTable and dataReader are not injected:

@WebServlet(value = "/stream", initParams = @WebInitParam(name = "maxIdleTime", value = "0"))
public class StreamingServlet extends HttpServlet
{
    @Inject
    private ConnectionTable connectionTable;
    ...

@WebServlet(value = "/push", loadOnStartup = 1, initParams = @WebInitParam(name = "maxIdleTime", value = "0"))
public class ClientServlet extends WebSocketServlet
{
    @Inject
    private ConnectionTable connectionTable;

    @Inject
    private DataReader dataReader;
    ...

Calling the (not) injected properties, I always get NullPointerExceptions. The problem also remains when configuring the Servlets via web.xml. I have no more ideas about what I am doing wrong. Reading all the articles about CDI in combination with Jetty and Maven, I wonder if I am the only one having these injection problems.

在我的JSF bean类UserBean.java注入工作中,我不必使用setter方法来初始化属性connectionTable和dataReader.

在DataReader构造函数中使用下面的输出语句(以及在ConnectionTable类中)

@ApplicationScoped
public class DataReader implements Serializable
{
    ...
    public DataReader()
    {
        System.out.println("DataReader.DataReader(): " + this);
    }
    ...

我想知道在stdout上显示的2个DataReader实例:

...
2012-07-31 14:03:04,843 [qtp5435124-17] DEBUG org.jboss.weld.JSF - WELD-000504 Resuming conversation with id null
31.07.2012 14:03:05 org.apache.myfaces.util.ExternalSpecifications isUnifiedELAvailable
INFO: MyFaces Unified EL support enabled
DataReader.DataReader(): DataReader$Proxy$_$$_WeldClientProxy@506e6d
ConnectionTable.ConnectionTable(): ConnectionTable$Proxy$_$$_WeldClientProxy@93b16c

2012-07-31 14:03:19,093 [qtp5435124-16] DEBUG org.jboss.weld.JSF - WELD-000504 Resuming conversation with id null
DataReader.DataReader(): DataReader@1cbd382

在基于表单的身份验证之后打印前5行,并且在使用注入的dataReader属性时第一次处理我的JSF操作时显示最后2行.由于bean是应用程序范围的,我真的很想知道2个构造函数的传递.但是根据应用程序的行为,我认为它没有任何问题.

My last assumption is that the servlets somehow live in seperated, independent contexts or containers or something like that. Because it is also not possible to get the FacesContext in the 2 other Servlets: FacesContext.getCurrentInstance() gives null. But I don't know if this is important in some way.

I hope anyone can help me to figure out the problem. Thank you in advance

Sebastian

Answer 1

错误很明显:

java.lang.NoClassDefFoundError: org/eclipse/jetty/servlet/ServletContextHandler$Decorator

Weld找不到上面的Jetty服务器类.它找不到这个类的原因是因为Jetty的类加载机制.Jetty的WebAppClassloader有一个默认的服务器类列表,它不会加载:参见http://wiki.eclipse.org/Jetty/Reference/Jetty_Classloading

Server Classes
-org.eclipse.jetty.continuation.             don't hide continuation classes
-org.eclipse.jetty.jndi.                     don't hide naming classes
-org.eclipse.jetty.plus.jaas.                don't hide jaas classes
-org.eclipse.jetty.websocket.                don't hide websocket extension
-org.eclipse.jetty.servlet.DefaultServlet    don't hide default servlet
org.eclipse.jetty.                           hide all other jetty classes

要允许Jetty加载此类,需要添加"-org.eclipse.jetty.servlet".到jetty-web.xml中的服务器类列表.

 <Configure class="org.eclipse.jetty.webapp.WebAppContext">
   <Call name="prependServerClass"><Arg>-org.eclipse.jetty.servlet.</Arg></Call>
 </Configure>

如果您使用嵌入式jetty,请调用以下方法:

 context.prependServerClass("-org.eclipse.jetty.servlet.");

Answer 2

嗯...你的配置与我的非常相似.我不知道的是这个'java-web-api'maven artefact.我在一个新项目中检查了这个并且瞧...它有效.然后我先后添加了对JSF和WebSocket的支持,但它没有再次运行.最后,我弄清楚错误是什么:我将'jetty-server'artefact添加为我的pom.xml的依赖项,但我没有设置范围.所以我使用了错误的服务器库或类似的东西.现在使用'提供'范围

<dependency>
    <groupId>org.eclipse.jetty</groupId>
    <artifactId>jetty-server</artifactId>
    <version>${jetty.version}</version>
    <scope>provided</scope>
</dependency>

一切似乎都工作,依赖注入也在servlet中工作.

关于你的pom我还有两个问题:

1. 你不必设置Jetty Maven插件的<jettyEnvXml>元素吗？

2. 再次在Jetty Maven插件中,您可以使用<webAppConfig>元素.我使用的是<webApp>元素,因为这是Eclipse代码完成所知的.其中一个元素是否被弃用而有利于另一个？