面对 java.lang.NoClassDefFoundError 的问题：org/apache/velocity/context/Context

Question

我是一个新的学习速度。我试图通过为此编写一个 servlet 以 HTML 格式显示模板。以下是我的servlet代码

        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            PrintWriter out = response.getWriter();
              VelocityEngine velocityEngine = new VelocityEngine();
              try {
                velocityEngine.init();
                Template template = velocityEngine.getTemplate("./src/Menu.txt");

              VelocityContext context = new VelocityContext();
              context.put( "special-1", "./src/special-1.txt" );
              context.put( "special-2", "./src/special-2.txt" );
              context.put( "special-3", "./src/special-3.txt" );
              StringWriter writer = new StringWriter();
              template.merge(context, writer);
              out.println(writer);
              } catch (Exception e) {
                    e.printStackTrace();
                }
        }

以下是我得到的堆栈跟踪...

    SEVERE: A child container failed during start
    java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
        at java.util.concurrent.FutureTask$Sync.innerGet(Unknown Source)
        at java.util.concurrent.FutureTask.get(Unknown Source)
        at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1123)
        at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:800)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
        at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
        at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
        at java.util.concurrent.FutureTask.run(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)
    Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
        ... 7 more
    Caused by: java.lang.NoClassDefFoundError: org/apache/velocity/context/Context
        at java.lang.Class.getDeclaredFields0(Native Method)
        at java.lang.Class.privateGetDeclaredFields(Unknown Source)
        at java.lang.Class.getDeclaredFields(Unknown Source)
        at org.apache.catalina.util.Introspection.getDeclaredFields(Introspection.java:106)
        at org.apache.catalina.startup.WebAnnotationSet.loadFieldsAnnotation(WebAnnotationSet.java:263)
        at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:142)
        at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:67)
        at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:405)
        at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:881)
        at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:376)
        at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
        at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5322)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        ... 7 more
    Caused by: java.lang.ClassNotFoundException: org.apache.velocity.context.Context
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1702)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1547)
        ... 21 more

有人可以帮我吗？

Answer 1

您需要将velocity-version.jar添加到您的服务器类路径中，您可以将其放在您的tomcat服务器的lib文件夹中，也可以将这个jar放在您的项目的WEB-INF/lib文件夹中。