我是开发网络应用程序的新手，所以一开始我选择使用 Jetty Maven 插件来编写我的第一个简单的网络应用程序。生成简单的 Hello world servlet 和少量测试 jsps 非常容易，但现在我被困在与我的 MySQL 数据库建立连接。我从码头文档（eclipse.org 上的旧文档和新文档）中阅读了几页，在 Stack Overflow 的帮助下，我设法创建了一些码头配置文件。这是我的 jetty-env.xml 文件：
<?xml version="1.0"?>
<!DOCTYPE Configure PUBLIC "-//Mort Bay Consulting//DTD Configure//EN" "http://www.eclipse.org/jetty/configure_9_0.dtd">
<Configure id="lp3" class="org.eclipse.jetty.maven.plugin.JettyWebAppContext">
<New id="lp3" class="org.eclipse.jetty.plus.jndi.Resource">
<Arg></Arg>
<Arg>jdbc/lp3</Arg>
<Arg>
<New class="com.mysql.jdbc.jdbc2.optional.MysqlConnectionPoolDataSource">
<Set name="Url">jdbc:mysql://localhost:3306/databasename</Set>
<Set name="User">user</Set>
<Set name="Password">pass</Set>
</New>
</Arg>
</New>
</Configure>
但是在 mvn: jetty:run 我收到这样的错误：
2013-06-28 21:43:24.397:INFO:oejs.Server:main: jetty-9.0.3.v20130506
2013-06-28 21:43:24.932:WARN:oejx.XmlConfiguration:main: Config error at <New id="lp3" class="org.eclipse.jetty.plus.jndi.Resource"><Arg/><Arg>jdbc/lp3</Arg><Arg>| <New class="com.mysql.jdbc.jdbc2.optional.MysqlConnectionPoolDataSource"><Set name="Url">jdbc:mysql://localhost:3306/databasename</Set><Set name="User">user</Set><Set name="Password">pass</Set></New>| </Arg></New> java.lang.reflect.InvocationTargetException in file:/C:/Blazej/Java/LP3Voter/LP3Voter/src/main/webapp/WEB-INF/jetty-env.xml
2013-06-28 21:43:24.932:WARN:oejw.WebAppContext:main: Failed startup of context o.e.j.m.p.JettyWebAppContext@a2d6c5{/,file:/C:/Blazej/Java/LP3Voter/LP3Voter/src/main/webapp/,STARTING}{file:/C:/Blazej/Java/LP3Voter/LP3Voter/src/main/webapp/}
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
at org.eclipse.jetty.util.TypeUtil.construct(TypeUtil.java:549)
at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.newObj(XmlConfiguration.java:794)
at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.configure(XmlConfiguration.java:413)
at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.configure(XmlConfiguration.java:289)
at org.eclipse.jetty.xml.XmlConfiguration.configure(XmlConfiguration.java:248)
at org.eclipse.jetty.plus.webapp.EnvConfiguration.configure(EnvConfiguration.java:124)
at org.eclipse.jetty.webapp.WebAppContext.configure(WebAppContext.java:464)
at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1316)
at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:724)
at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:490)
at org.eclipse.jetty.maven.plugin.JettyWebAppContext.doStart(JettyWebAppContext.java:275)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:69)
at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:108)
at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:90)
at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:58)
at org.eclipse.jetty.server.handler.ContextHandlerCollection.doStart(ContextHandlerCollection.java:175)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:69)
at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:108)
at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:90)
at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:58)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:69)
at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:108)
at org.eclipse.jetty.server.Server.start(Server.java:342)
at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:90)
at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:58)
at org.eclipse.jetty.server.Server.doStart(Server.java:290)
at org.eclipse.jetty.maven.plugin.JettyServer.doStart(JettyServer.java:68)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:69)
at org.eclipse.jetty.maven.plugin.AbstractJettyMojo.startJetty(AbstractJettyMojo.java:540)
at org.eclipse.jetty.maven.plugin.AbstractJettyMojo.execute(AbstractJettyMojo.java:352)
at org.eclipse.jetty.maven.plugin.JettyRunMojo.execute(JettyRunMojo.java:167)
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:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
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.LinkageError: loader constraint violation: loader (instance of org/eclipse/jetty/webapp/WebAppClassLoader) previously initiated loading for a different type with name "org/eclipse/jetty/util/log/Logger"
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:791)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:420)
at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:382)
at org.eclipse.jetty.plus.jndi.NamingEntry.save(NamingEntry.java:183)
at org.eclipse.jetty.plus.jndi.Resource.<init>(Resource.java:38)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
at org.eclipse.jetty.util.TypeUtil.construct(TypeUtil.java:549)
at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.newObj(XmlConfiguration.java:794)
at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.configure(XmlConfiguration.java:413)
at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.configure(XmlConfiguration.java:289)
at org.eclipse.jetty.xml.XmlConfiguration.configure(XmlConfiguration.java:248)
at org.eclipse.jetty.plus.webapp.EnvConfiguration.configure(EnvConfiguration.java:124)
at org.eclipse.jetty.webapp.WebAppContext.configure(WebAppContext.java:464)
at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1316)
at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:724)
at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:490)
at org.eclipse.jetty.maven.plugin.JettyWebAppContext.doStart(JettyWebAppContext.java:275)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:69)
at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:108)
at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:90)
at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:58)
at org.eclipse.jetty.server.handler.ContextHandlerCollection.doStart(ContextHandlerCollection.java:175)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:69)
at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:108)
at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:90)
at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:58)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:69)
at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:108)
at org.eclipse.jetty.server.Server.start(Server.java:342)
at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:90)
at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:58)
at org.eclipse.jetty.server.Server.doStart(Server.java:290)
at org.eclipse.jetty.maven.plugin.JettyServer.doStart(JettyServer.java:68)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:69)
at org.eclipse.jetty.maven.plugin.AbstractJettyMojo.startJetty(AbstractJettyMojo.java:540)
at org.eclipse.jetty.maven.plugin.AbstractJettyMojo.execute(AbstractJettyMojo.java:352)
at org.eclipse.jetty.maven.plugin.JettyRunMojo.execute(JettyRunMojo.java:167)
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:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
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)
2013-06-28 21:43:24.962:INFO:oejs.ServerConnector:main: Started ServerConnector@1d5ecb6{HTTP/1.1}{0.0.0.0:8080}
我不知道为什么它不起作用。我试图为此找到解决方案。在某处我读到我还必须创建另一个配置文件 - jetty.xml，它以某种方式设置 webapp。所以我做了一个jetty.xml，看起来像这样：
<?xml version="1.0"?>
<!DOCTYPE Configure PUBLIC "-//Mort Bay Consulting//DTD Configure//EN" "http://www.eclipse.org/jetty/configure_9_0.dtd">
<Call name="setAttribute">
<Arg>org.eclipse.jetty.webapp.configuration</Arg>
<Arg>
<Array type="java.lang.String">
<Item>org.eclipse.jetty.webapp.WebInfConfiguration</Item>
<Item>org.eclipse.jetty.webapp.WebXmlConfiguration</Item>
<Item>org.eclipse.jetty.webapp.MetaInfConfiguration</Item>
<Item>org.eclipse.jetty.webapp.FragmentConfiguration</Item>
<Item>org.eclipse.jetty.plus.webapp.EnvConfiguration</Item>
<Item>org.eclipse.jetty.plus.webapp.PlusConfiguration</Item>
<Item>org.eclipse.jetty.webapp.JettyWebXmlConfiguration</Item>
<Item>org.eclipse.jetty.webapp.TagLibConfiguration</Item>
</Array>
</Arg>
</Call>
将其添加到 pom.xml 后，我得到另一个错误：
Failed to execute goal org.eclipse.jetty:jetty-maven-plugin:9.0.3.v20130506:run (start-jetty) on project LP3Voter: Failure: Unknown configuration type: Call in org.eclipse.jetty.xml.XmlConfiguration@19bb90f
我还在 WEB-INF/web.xml 文件中添加了有关 jndi/lp3 的信息。还有我的 pom.xml：
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.fomfel</groupId>
<artifactId>LP3Voter</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>LP3Voter Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-plus</artifactId>
<version>9.0.3.v20130506</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.2</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-jndi</artifactId>
<version>9.0.3.v20130506</version>
</dependency>
<!-- <dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-util</artifactId>
<version>9.0.3.v20130506</version>
</dependency>-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.25</version>
<type>jar</type>
<scope>compile</scope>
</dependency>
</dependencies>
<build>
<finalName>LP3Voter</finalName>
<plugins>
<plugin>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-maven-plugin</artifactId>
<version>9.0.3.v20130506</version>
<configuration>
<scanIntervalSeconds>10</scanIntervalSeconds>
<jettyEnvXml>src/main/webapp/WEB-INF/jetty-env.xml</jettyEnvXml>
<jettyConfig>src/main/webapp/WEB-INF/jetty.xml</jettyConfig>
<stopKey>foo</stopKey>
<stopPort>9999</stopPort>
</configuration>
<executions>
<execution>
<id>start-jetty</id>
<phase>pre-integration-test</phase>
<goals>
<goal>run</goal>
</goals>
<configuration>
<scanIntervalSeconds>5</scanIntervalSeconds>
<daemon>true</daemon>
</configuration>
</execution>
<execution>
<id>stop-jetty</id>
<phase>post-integration-test</phase>
<goals>
<goal>stop</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
我很困惑为什么它不起作用，经过几个小时的尝试我放弃了。谁能帮我找到解决方案？任何想法将不胜感激。
更新 我不确定是什么问题，但我的解决方案是从 pom.xml中删除jetty-jndi和jetty-util 。在那之后，我遇到了一些异常，缺少来自 jetty.jndi 的类，所以我把它放回了我的 pom.xml。接下来，由于缺少一些日志实用程序，我添加了 jetty-util 并且它开始工作。Maven对我来说仍然是一个谜......