java - 如何使用 Eclipse 为 Jetty 编写一个简单的 Servlet？

标签 java eclipse servlets jetty war

我下载了适用于 Java EE 和 Jetty 8.1 的 Eclipse，并希望实现一个非常简单的 Servlet。

当我使用 java -jar start.jar 启动 Jetty 时，它工作正常。

为了开发 Servlet，我这样做了:

  1. 在 Eclipse 中，我选择了“新建动态 Web 项目”。

  2. 我在 Eclipse 的“构建路径”中添加了 jetty\lib\servlet-api-3.0.jar。

  3. 在那个项目“New Servlet”中，生成了一个 Servlet，我添加了一些代码:

    /**
 * Servlet implementation class MyServlet
 */
@WebServlet("/MyServlet")
public class MyServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, 
                HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, 
                HttpServletResponse response)
        throws ServletException, IOException {
        PrintWriter out = response.getWriter();
        out.println("<html><body><h1>My Servlet</h1></body></html>");
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, 
                HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, 
                HttpServletResponse response)
        throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

}

  4. 我在 WebContent\WEB-INF\web.xml 中创建了一个文件 web.xml，内容如下:

    <?xml version="1.0" encoding="utf-8" ?>
<web-app 
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
version="2.4">
<servlet>
    <servlet-name>My Servlet</servlet-name>
<servlet-class>MyServlet.class</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>My Servlet</servlet-name>
    <url-pattern>/Servlet</url-pattern>
</servlet-mapping>

  5. 我将 build\classes 中已编译的 .class 文件复制到 WebContent\WEB-INF\classes

  6. 现在我选择将项目作为 .war 文件导出到 jetty\webapps\MySite.war。

  7. 我使用 java -jar start.jar 启动 Jetty 并访问 localhost:8080/MySite/Servlet 但现在我收到此消息:

    Servlet Not Initialized

javax.servlet.UnavailableException: Servlet Not Initialized
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:546)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:485)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:483)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:233)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1065)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:412)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:192)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:999)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)
at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:250)
at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:149)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:111)
at org.eclipse.jetty.server.Server.handle(Server.java:351)
at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:451)
at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:916)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:647)
at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:233)
at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:76)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:615)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:45)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:599)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:534)
at java.lang.Thread.run(Thread.java:722)

如果我访问 localhost:8080/MySite/ 我会看到两个文件夹 WEB-INF\ 和 META-INF\ 都有大小0 字节。

所以它看起来不像我在 Eclipse 中的 .war-export 工作。

如何使用 Eclipse 为 Jetty 导出我的简单 Servlet？

我现在已经安装了 Jetty WTP plugin对于 Eclipse，但我无法使用它运行此 servlet:

2012-01-30 10:06:50.322:INFO:oejs.Server:jetty-8.1.0.RC4
2012-01-30 10:06:50.353:INFO:oejdp.ScanningAppProvider:Deployment monitor C:\Users\Jonas\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\webapps at interval 1
2012-01-30 10:06:50.353:INFO:oejdp.ScanningAppProvider:Deployment monitor C:\Users\Jonas\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\contexts at interval 1
2012-01-30 10:06:50.353:INFO:oejd.DeploymentManager:Deployable added: C:\Users\Jonas\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\contexts\MySite.xml
2012-01-30 10:06:50.650:WARN:oejuc.AbstractLifeCycle:FAILED o.e.j.w.WebAppContext{/MySite,file:/C:/Users/Jonas/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/MySite/},C:\Users\Jonas\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0/wtpwebapps/MySite: java.lang.NoClassDefFoundError: org/objectweb/asm/ClassVisitor
java.lang.NoClassDefFoundError: org/objectweb/asm/ClassVisitor
    at org.eclipse.jetty.annotations.AnnotationConfiguration.createAnnotationParser(AnnotationConfiguration.java:111)
    at org.eclipse.jetty.annotations.AnnotationConfiguration.configure(AnnotationConfiguration.java:73)
    at org.eclipse.jetty.webapp.WebAppContext.configure(WebAppContext.java:428)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1208)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:699)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:454)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.deploy.bindings.StandardStarter.processBinding(StandardStarter.java:36)
    at org.eclipse.jetty.deploy.AppLifeCycle.runBindings(AppLifeCycle.java:183)
    at org.eclipse.jetty.deploy.DeploymentManager.requestAppGoal(DeploymentManager.java:491)
    at org.eclipse.jetty.deploy.DeploymentManager.addApp(DeploymentManager.java:138)
    at org.eclipse.jetty.deploy.providers.ScanningAppProvider.fileAdded(ScanningAppProvider.java:142)
    at org.eclipse.jetty.deploy.providers.ScanningAppProvider$1.fileAdded(ScanningAppProvider.java:53)
    at org.eclipse.jetty.util.Scanner.reportAddition(Scanner.java:604)
    at org.eclipse.jetty.util.Scanner.reportDifferences(Scanner.java:535)
    at org.eclipse.jetty.util.Scanner.scan(Scanner.java:398)
    at org.eclipse.jetty.util.Scanner.doStart(Scanner.java:332)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.deploy.providers.ScanningAppProvider.doStart(ScanningAppProvider.java:118)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.deploy.DeploymentManager.startAppProvider(DeploymentManager.java:552)
    at org.eclipse.jetty.deploy.DeploymentManager.doStart(DeploymentManager.java:227)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.util.component.AggregateLifeCycle.doStart(AggregateLifeCycle.java:58)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:53)
    at org.eclipse.jetty.server.handler.HandlerWrapper.doStart(HandlerWrapper.java:91)
    at org.eclipse.jetty.server.Server.doStart(Server.java:263)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.xml.XmlConfiguration$1.run(XmlConfiguration.java:1214)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.eclipse.jetty.xml.XmlConfiguration.main(XmlConfiguration.java:1137)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.eclipse.jetty.start.Main.invokeMain(Main.java:457)
    at org.eclipse.jetty.start.Main.start(Main.java:600)
    at org.eclipse.jetty.start.Main.main(Main.java:82)
Caused by: 
java.lang.ClassNotFoundException: org.objectweb.asm.ClassVisitor
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at org.eclipse.jetty.annotations.AnnotationConfiguration.createAnnotationParser(AnnotationConfiguration.java:111)
    at org.eclipse.jetty.annotations.AnnotationConfiguration.configure(AnnotationConfiguration.java:73)
    at org.eclipse.jetty.webapp.WebAppContext.configure(WebAppContext.java:428)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1208)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:699)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:454)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.deploy.bindings.StandardStarter.processBinding(StandardStarter.java:36)
    at org.eclipse.jetty.deploy.AppLifeCycle.runBindings(AppLifeCycle.java:183)
    at org.eclipse.jetty.deploy.DeploymentManager.requestAppGoal(DeploymentManager.java:491)
    at org.eclipse.jetty.deploy.DeploymentManager.addApp(DeploymentManager.java:138)
    at org.eclipse.jetty.deploy.providers.ScanningAppProvider.fileAdded(ScanningAppProvider.java:142)
    at org.eclipse.jetty.deploy.providers.ScanningAppProvider$1.fileAdded(ScanningAppProvider.java:53)
    at org.eclipse.jetty.util.Scanner.reportAddition(Scanner.java:604)
    at org.eclipse.jetty.util.Scanner.reportDifferences(Scanner.java:535)
    at org.eclipse.jetty.util.Scanner.scan(Scanner.java:398)
    at org.eclipse.jetty.util.Scanner.doStart(Scanner.java:332)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.deploy.providers.ScanningAppProvider.doStart(ScanningAppProvider.java:118)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.deploy.DeploymentManager.startAppProvider(DeploymentManager.java:552)
    at org.eclipse.jetty.deploy.DeploymentManager.doStart(DeploymentManager.java:227)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.util.component.AggregateLifeCycle.doStart(AggregateLifeCycle.java:58)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:53)
    at org.eclipse.jetty.server.handler.HandlerWrapper.doStart(HandlerWrapper.java:91)
    at org.eclipse.jetty.server.Server.doStart(Server.java:263)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.xml.XmlConfiguration$1.run(XmlConfiguration.java:1214)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.eclipse.jetty.xml.XmlConfiguration.main(XmlConfiguration.java:1137)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.eclipse.jetty.start.Main.invokeMain(Main.java:457)
    at org.eclipse.jetty.start.Main.start(Main.java:600)
    at org.eclipse.jetty.start.Main.main(Main.java:82)

最佳答案

首先，你的 web.xml 是错误的。

The servlet-class element contains the fully qualified class name of the servlet.

来自您使用的 web.xml 架构 http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd在第 923 行。因此，第 9 行的 servlet-class 元素的内容应该是 MyServlet，而不是 MyServlet.class。

其次，只使用一种方式来注册一个servlet、filter或listener，说清楚。如果您更喜欢使用注释将它们注册到 servlet 容器。您最好删除 web.xml 中的 servlet 和 servlet-mapping 元素。否则，你最好删除 java 源代码中的注释。如果你想使用 web.xml，你应该将架构版本从 2.4 更新到 3.0

最后，您的第二个问题来自 Jetty WTP Eclipse 插件，可以通过尝试以下方法解决:jetty run error for websockets project

关于java - 如何使用 Eclipse 为 Jetty 编写一个简单的 Servlet？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/9058587/

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