@WebServlet在 Netbeans 11.0 中使用 java.lang.RuntimeException： com.example.NewServlet 失败。<init>(Ne

Question

某种噩梦 - 无法使用 Servlet 注释在 Apache Tomcat 9.0.22(或 Glassfish 5.0.1(和 Apache NetBeans IDE 11.0(Build incubator-netbeans-release-404-on-20190319(上启动原始 servlet。使用 JDK 1.8u221。这是代码：

@WebServlet(name = "NewServlet", urlPatterns = {"/meow"})
public class NewServlet extends HttpServlet {
    protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.getWriter().println("test");
    }
}

和web.xml文件：

<?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"
    version="3.1">
</web-app>

根本原因(注意行号，它总是1！

java.lang.RuntimeException: 
    com.example.NewServlet.<init>(NewServlet.java:1)
    java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490)
    java.base/java.lang.Class.newInstance(Class.java:584)
    org.apache.openejb.core.WebContext.newWeakableInstance(WebContext.java:147)
    org.apache.openejb.core.WebContext.newInstance(WebContext.java:181)
    org.apache.tomee.catalina.JavaeeInstanceManager.newInstance(JavaeeInstanceManager.java:78)
    org.apache.tomee.catalina.JavaeeInstanceManager.newInstance(JavaeeInstanceManager.java:124)
    org.apache.tomee.catalina.JavaeeInstanceManager.newInstance(JavaeeInstanceManager.java:119)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.tomee.catalina.OpenEJBValve.invoke(OpenEJBValve.java:45)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    org.apache.tomee.catalina.OpenEJBSecurityListener$RequestCapturer.invoke(OpenEJBSecurityListener.java:97)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:678)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:836)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1839)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.base/java.lang.Thread.run(Thread.java:834)

目标是仅通过注释声明 servlet，如 @WebServlet(name = "NewServlet", urlPatterns = {"/meow"}) 。

在 NetBeans 8.2 上使用 JDK1.8u221 进行了测试 - 一切按预期工作。我怀疑问题出在Apache NetBeans 11中，即使项目JDK设置为8(也是源代码/二进制格式(。

Answer 1

我今天在 Netbeans 12.0 中使用 OpenJDK 14 时遇到了这个问题。 事实证明，通过安装 nb-javac 插件解决了这个问题。

Answer 2

错误出在 Apache NetBeans 11 中。在更高版本(仍然是非官方的(11.1 中，即使没有 web.xml 文件，Servlet 注释也能正常工作。在 Apache NetBeans IDE 11.1 上使用 Apache Tomcat 9.0.22 和 Glassfish 5.0.1 进行测试(可从此网页下载(。