Won't run: Unable to determine mode of operation. To use npm mode, ensure 'flow-build-info.json' exists on the classpath

[fschon]

I tried to compile and run the project and get the following exception:

HTTP ERROR 500 Problem accessing /. Reason:

Server Error

Caused by: javax.servlet.ServletException: javax.servlet.ServletException: com.vaadin.flow.server.startup.ServletDeployer@a1f5568f==com.vaadin.flow.server.VaadinServlet,jsp=null,order=-1,inst=false,async=true at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:146) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132) at org.eclipse.jetty.server.Server.handle(Server.java:502) at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:370) at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:267) at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305) at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103) at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:117) at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:765) at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:683) at java.base/java.lang.Thread.run(Thread.java:834) Caused by: javax.servlet.ServletException: com.vaadin.flow.server.startup.ServletDeployer@a1f5568f==com.vaadin.flow.server.VaadinServlet,jsp=null,order=-1,inst=false,async=true at org.eclipse.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:692) at org.eclipse.jetty.servlet.ServletHolder.getServlet(ServletHolder.java:520) at org.eclipse.jetty.servlet.ServletHolder.prepare(ServletHolder.java:811) at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:537) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:146) at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132) at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:257) at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1701) at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255) at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1345) at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203) at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:480) at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1668) at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201) at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1247) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144) at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:220) at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:126) ... 10 more Caused by: java.lang.IllegalStateException: Unable to determine mode of operation. To use npm mode, ensure 'flow-build-info.json' exists on the classpath. With Maven, this is handled by the 'prepare-frontend' goal. To use compatibility mode, add the 'flow-server-compatibility-mode' dependency. If using Vaadin with Spring Boot, instead set the property 'vaadin.compatibilityMode' to 'true' in 'application.properties'. at com.vaadin.flow.server.DefaultDeploymentConfiguration.checkCompatibilityMode(DefaultDeploymentConfiguration.java:270) at com.vaadin.flow.server.DefaultDeploymentConfiguration.(DefaultDeploymentConfiguration.java:125) at com.vaadin.flow.server.VaadinServlet.createDeploymentConfiguration(VaadinServlet.java:166) at com.vaadin.flow.server.VaadinServlet.createDeploymentConfiguration(VaadinServlet.java:151) at com.vaadin.flow.server.VaadinServlet.createServletService(VaadinServlet.java:185) at com.vaadin.flow.server.VaadinServlet.init(VaadinServlet.java:72) at org.eclipse.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:671) ... 28 more Caused by: javax.servlet.ServletException: com.vaadin.flow.server.startup.ServletDeployer@a1f5568f==com.vaadin.flow.server.VaadinServlet,jsp=null,order=-1,inst=false,async=true at org.eclipse.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:692) at org.eclipse.jetty.servlet.ServletHolder.getServlet(ServletHolder.java:520) at org.eclipse.jetty.servlet.ServletHolder.prepare(ServletHolder.java:811) at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:537) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:146) at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132) at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:257) at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1701) at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255) at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1345) at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203) at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:480) at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1668) at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201) at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1247) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144) at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:220) at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:126) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132) at org.eclipse.jetty.server.Server.handle(Server.java:502) at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:370) at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:267) at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305) at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103) at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:117) at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:765) at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:683) at java.base/java.lang.Thread.run(Thread.java:834) Caused by: java.lang.IllegalStateException: Unable to determine mode of operation. To use npm mode, ensure 'flow-build-info.json' exists on the classpath. With Maven, this is handled by the 'prepare-frontend' goal. To use compatibility mode, add the 'flow-server-compatibility-mode' dependency. If using Vaadin with Spring Boot, instead set the property 'vaadin.compatibilityMode' to 'true' in 'application.properties'. at com.vaadin.flow.server.DefaultDeploymentConfiguration.checkCompatibilityMode(DefaultDeploymentConfiguration.java:270) at com.vaadin.flow.server.DefaultDeploymentConfiguration.(DefaultDeploymentConfiguration.java:125) at com.vaadin.flow.server.VaadinServlet.createDeploymentConfiguration(VaadinServlet.java:166) at com.vaadin.flow.server.VaadinServlet.createDeploymentConfiguration(VaadinServlet.java:151) at com.vaadin.flow.server.VaadinServlet.createServletService(VaadinServlet.java:185) at com.vaadin.flow.server.VaadinServlet.init(VaadinServlet.java:72) at org.eclipse.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:671) ... 28 more Caused by: java.lang.IllegalStateException: Unable to determine mode of operation. To use npm mode, ensure 'flow-build-info.json' exists on the classpath. With Maven, this is handled by the 'prepare-frontend' goal. To use compatibility mode, add the 'flow-server-compatibility-mode' dependency. If using Vaadin with Spring Boot, instead set the property 'vaadin.compatibilityMode' to 'true' in 'application.properties'. at com.vaadin.flow.server.DefaultDeploymentConfiguration.checkCompatibilityMode(DefaultDeploymentConfiguration.java:270) at com.vaadin.flow.server.DefaultDeploymentConfiguration.(DefaultDeploymentConfiguration.java:125) at com.vaadin.flow.server.VaadinServlet.createDeploymentConfiguration(VaadinServlet.java:166) at com.vaadin.flow.server.VaadinServlet.createDeploymentConfiguration(VaadinServlet.java:151) at com.vaadin.flow.server.VaadinServlet.createServletService(VaadinServlet.java:185) at com.vaadin.flow.server.VaadinServlet.init(VaadinServlet.java:72) at org.eclipse.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:671) at org.eclipse.jetty.servlet.ServletHolder.getServlet(ServletHolder.java:520) at org.eclipse.jetty.servlet.ServletHolder.prepare(ServletHolder.java:811) at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:537) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:146) at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132) at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:257) at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1701) at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255) at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1345) at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203) at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:480) at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1668) at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201) at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1247) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144) at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:220) at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:126) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132) at org.eclipse.jetty.server.Server.handle(Server.java:502) at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:370) at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:267) at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305) at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103) at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:117) at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:765) at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:683) at java.base/java.lang.Thread.run(Thread.java:834) Powered by Jetty:// 9.4.15.v20190215