在要submit的时候，页面右上角弹出通知:
Server Response Message
Internal server error
但是没有详细信息怎么办呢？
查看
$FLINK_HOME/log/flink-appleyuchi-standalonesession-5-Desktop.log
每次提交，都会在这个文件的末尾添加信息，所以我得到的是：
2020-09-29 13:14:03,845 WARN org.apache.flink.runtime.webmonitor.handlers.JarRunHandler [] - Configuring the job submission via query parameters is deprecated. Please migrate to submitting a JSON request instead.
2020-09-29 13:14:03,846 ERROR org.apache.flink.runtime.webmonitor.handlers.JarRunHandler [] - Unhandled exception.
java.util.concurrent.CompletionException: org.apache.flink.client.program.ProgramInvocationException: The program's entry point class 'TestSavepoints' was not found in the jar file.
at org.apache.flink.runtime.webmonitor.handlers.utils.JarHandlerUtils$JarHandlerContext.toPackagedProgram(JarHandlerUtils.java:158) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.webmonitor.handlers.utils.JarHandlerUtils$JarHandlerContext.applyToConfiguration(JarHandlerUtils.java:128) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.webmonitor.handlers.JarRunHandler.handleRequest(JarRunHandler.java:93) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.webmonitor.handlers.JarRunHandler.handleRequest(JarRunHandler.java:54) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.rest.handler.AbstractRestHandler.respondToRequest(AbstractRestHandler.java:73) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.rest.handler.AbstractHandler.respondAsLeader(AbstractHandler.java:172) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.rest.handler.LeaderRetrievalHandler.lambda$channelRead0$0(LeaderRetrievalHandler.java:81) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at java.util.Optional.ifPresent(Optional.java:159) [?:1.8.0_131]
at org.apache.flink.util.OptionalConsumer.ifPresent(OptionalConsumer.java:46) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.rest.handler.LeaderRetrievalHandler.channelRead0(LeaderRetrievalHandler.java:78) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.rest.handler.LeaderRetrievalHandler.channelRead0(LeaderRetrievalHandler.java:49) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.rest.handler.router.RouterHandler.routed(RouterHandler.java:110) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.rest.handler.router.RouterHandler.channelRead0(RouterHandler.java:89) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.rest.handler.router.RouterHandler.channelRead0(RouterHandler.java:54) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:102) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.rest.FileUploadHandler.channelRead0(FileUploadHandler.java:174) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.rest.FileUploadHandler.channelRead0(FileUploadHandler.java:68) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:438) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:328) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:302) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:253) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1421) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:930) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:697) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:632) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:549) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:511) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:918) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.shaded.netty4.io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) [flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_131]
Caused by: org.apache.flink.client.program.ProgramInvocationException: The program's entry point class 'TestSavepoints' was not found in the jar file.
at org.apache.flink.client.program.PackagedProgram.loadMainClass(PackagedProgram.java:389) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.client.program.PackagedProgram.<init>(PackagedProgram.java:139) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.client.program.PackagedProgram.<init>(PackagedProgram.java:61) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.client.program.PackagedProgram$Builder.build(PackagedProgram.java:557) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.webmonitor.handlers.utils.JarHandlerUtils$JarHandlerContext.toPackagedProgram(JarHandlerUtils.java:156) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
... 50 more
Caused by: java.lang.ClassNotFoundException: TestSavepoints
at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[?:1.8.0_131]
at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_131]
at org.apache.flink.util.FlinkUserCodeClassLoader.loadClassWithoutExceptionHandling(FlinkUserCodeClassLoader.java:61) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.util.ChildFirstClassLoader.loadClassWithoutExceptionHandling(ChildFirstClassLoader.java:74) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.util.FlinkUserCodeClassLoader.loadClass(FlinkUserCodeClassLoader.java:48) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_131]
at java.lang.Class.forName0(Native Method) ~[?:1.8.0_131]
at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_131]
at org.apache.flink.client.program.PackagedProgram.loadMainClass(PackagedProgram.java:387) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.client.program.PackagedProgram.<init>(PackagedProgram.java:139) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.client.program.PackagedProgram.<init>(PackagedProgram.java:61) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.client.program.PackagedProgram$Builder.build(PackagedProgram.java:557) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
at org.apache.flink.runtime.webmonitor.handlers.utils.JarHandlerUtils$JarHandlerContext.toPackagedProgram(JarHandlerUtils.java:156) ~[flink-dist_2.11-1.12-SNAPSHOT.jar:1.12-SNAPSHOT]
... 50 more
然后再根据上述log中的信息来设法寻求解决的思路．