Spring Boot 1.5不支援Java 11造成ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader

原因：
Spring Boot 1.5不支援Java 11
改用JDK 8後就正常

如果要把專案改成Java 11，可以參考以下文章
Spring Boot 1.5.x to 2.0.x Migration – first step of migration to Java 11
https://altkomsoftware.pl/en/blog/spring-boot-migration-java/

Exception in thread "main" java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$AppClassLoader and java.net.URLClassLoader are in module java.base of loader 'bootstrap')
 at org.springframework.boot.devtools.restart.DefaultRestartInitializer.getUrls(DefaultRestartInitializer.java:93)
 at org.springframework.boot.devtools.restart.DefaultRestartInitializer.getInitialUrls(DefaultRestartInitializer.java:56)
 at org.springframework.boot.devtools.restart.Restarter.<init>(Restarter.java:140)
 at org.springframework.boot.devtools.restart.Restarter.initialize(Restarter.java:546)
 at org.springframework.boot.devtools.restart.RestartApplicationListener.onApplicationStartingEvent(RestartApplicationListener.java:67)
 at org.springframework.boot.devtools.restart.RestartApplicationListener.onApplicationEvent(RestartApplicationListener.java:45)
 at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
 at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
 at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
 at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:122)
 at org.springframework.boot.context.event.EventPublishingRunListener.starting(EventPublishingRunListener.java:69)
 at org.springframework.boot.SpringApplicationRunListeners.starting(SpringApplicationRunListeners.java:48)
 at org.springframework.boot.SpringApplication.run(SpringApplication.java:292)
 at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118)
 at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107)
 at com.example.demo.DemoJavaWebApplication.main(DemoJavaWebApplication.java:12)