在spring-boot-maven-plugin中设置mainClass导致我需要显式设置'defaultServletName'属性

Question

I had a springboot jar working well, until I added newrelic-agent jar to the classpath, now I need to specify a main-class. This makes sense because I now have several classes with a static main args method in the classpath. The recommended way to do this is to add it to the'spring-boot-maven-plugin'. So I did the following:

<plugin>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-maven-plugin</artifactId>
  <configuration>
    <mainClass>com.ebates.rclon.Application</mainClass>
  </configuration>
  <executions>
    <execution>
     <goals>
        <goal>repackage</goal>
     </goals>
    </execution>
  </executions>
</plugin>

After doing that I get:

java.lang.IllegalStateException: Unable to locate the default servlet for serving static content. Please set the 'defaultServletName' property explicitly.

• Why would specifying a main-class break spring boots autoconfiguration?
• How was the defaultServletName configured earlier?

Answer 1

I think I have a better understanding of this after some research and playing around.

• It wasn't that adding a mainClass was the issue. The Spring autoconfiguration had nothing to do with it, the issue is that since there are two jars in the classpath, a second main method was introduced and spring boot doesn't know which one to use when launching. By fixing that issue also revealed that there are multiple application contexts.

• In Spring MVC there is a default servlet context that is used when no other context if found for serving static content. When you enable this usually you do not specify a name, but if there are multiple candidate contexts in your classpath you need to name it. Here is an example on how to do that:

@Configuration public class MVCConfig extends WebMvcConfigurerAdapter
{

    @Override public void configureDefaultServletHandling(final 
                       DefaultServletHandlerConfigurer configurer)
    {
        configurer.enable("nameOfDefaultContextGoesHere");
    }

}