Spring reactive boot app (2.0.0.RC1) as servlet in WebLogic 12c starts but NPE thrown on access - spring

Question

Running Spring boot reactive application based off of 2.0.0.RC1. It works by itself with a netty embedded container just fine.
Switching it to a servlet, sorting out the dependencies - exclusions, provisions, weblogic.xml instructions etc, then deploying to WebLogic 12c (12.1.3) container will start the application successfully. However when trying to access the rest url, handled by a single controller, WebLogic throws NPE. It never reaches Spring controller.
Error 500--Internal Server Error
java.lang.NullPointerException
at weblogic.servlet.internal.ServletResponseImpl.sendContentError(ServletResponseImpl.java:713)
at weblogic.servlet.internal.ServletResponseImpl.sendError(ServletResponseImpl.java:761)
at weblogic.servlet.internal.ServletResponseImpl.sendError(ServletResponseImpl.java:693)
at org.springframework.boot.web.servlet.support.ErrorPageFilter.handleErrorStatus(ErrorPageFilter.java:144)
at org.springframework.boot.web.servlet.support.ErrorPageFilter.doFilter(ErrorPageFilter.java:117)
at org.springframework.boot.web.servlet.support.ErrorPageFilter.access$000(ErrorPageFilter.java:59)
at org.springframework.boot.web.servlet.support.ErrorPageFilter$1.doFilterInternal(ErrorPageFilter.java:90)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.boot.web.servlet.support.ErrorPageFilter.doFilter(ErrorPageFilter.java:108)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:79)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.wrapRun(WebAppServletContext.java:3451)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.__run(WebAppServletContext.java:3417)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:120)
at weblogic.servlet.provider.WlsSubjectHandle.run(WlsSubjectHandle.java:57)
at weblogic.servlet.internal.WebAppServletContext.doSecuredExecute(WebAppServletContext.java:2280)
at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2196)
at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2174)
at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1632)
at weblogic.servlet.provider.ContainerSupportProviderImpl$WlsRequestExecutor.run(ContainerSupportProviderImpl.java:256)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:311)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:263)
I will paste the excerpts of all relevant sources below. First boot app:
#SpringBootApplication
#Configuration
//#EnableAutoConfiguration
//#ComponentScan(basePackages = {"ca.corp.uservice", "ca.corp.uservice.filecache"})
//#ImportResource({"/WEB-INF/ws-dispatcher-servlet.xml"})
//#EnableWebSecurity
public class FileCacheBootApp extends SpringBootServletInitializer implements WebApplicationInitializer {
public static void main(String[] args) {
SpringApplication.run(FileCacheBootApp.class, args);
}
#Override
protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
return application.sources(FileCacheBootApp.class);
}
...
}
Next the controller:
#RestController
#RequestMapping("/filecache")
public class FileCacheController implements FileCacheApi {
#Autowired
private FileCacheRepository repo;
// -------------- GET ---------------
#GetMapping(value = "{token}")
#Override public Mono<FileCacheable> get(#PathVariable("token") String token) {
return repo.findByToken(token).map(f -> load(f));
}
#GetMapping(value = "app")
#Override public Mono<FileCacheable> get(#RequestParam Long appid, #RequestParam String type, #RequestParam Integer langcode) {
return repo.findByUnique(appid, type, langcode).map(f -> load(f));
}
#GetMapping(value = "zip")
#Override public Mono<FileCacheable> get(#RequestParam String name, #RequestParam Integer langcode) {
return repo.findByNameAndLang(name, langcode);
}
...
}
And finally pom, spring fmw and servlet. Needed to do some jumps here to get it to run w/o conflicts in WebLogic container.
<!-- SPRING FRAMEWORK -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
<version>${spring-boot-version}</version>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
<exclusion>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
</exclusion>
<exclusion>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-to-slf4j</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
<version>2.0.2</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-to-slf4j</artifactId>
<version>2.0.2</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<version>${spring-boot-version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-mongodb-reactive</artifactId>
<version>${spring-boot-version}</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-webflux</artifactId>
<version>${spring-boot-version}</version>
<exclusions>
<exclusion>
<groupId>org.hibernate.validator</groupId>
<artifactId>hibernate-validator</artifactId>
</exclusion>
</exclusions>
</dependency>
<!-- SERVLET, VALIDATION and EL -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.0.1</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.el</groupId>
<artifactId>javax.el-api</artifactId>
<version>3.0.1-b04</version>
</dependency>
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.el</artifactId>
<version>3.0.1-b09</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>5.1.1.Final</version>
</dependency>
Weblogic.xml
<weblogic-version>12.1.3</weblogic-version>
<context-root>file-cache-uservice</context-root>
<container-descriptor>
<prefer-application-packages>
<package-name>org.springframework.*</package-name>
<package-name>org.hibernate.*</package-name>
<package-name>javax.validation.*</package-name>
<package-name>javax.validation.spi.*</package-name>
<package-name>org.apache.logging.log4j.*</package-name>
<package-name>org.slf4j.*</package-name>
</prefer-application-packages>
</container-descriptor>
I am trying to be as specific as possible w/o being an info overkill. If you'd like to know more details though... be glad to provide.
Any info or a pointer on the source of the NPE is appreciated.

Answer 1

Solved it. This bit was confusing... I added a dependency for the boot-web back in:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<version>${spring-boot-version}</version>
<exclusions>
<exclusion>
<groupId>org.hibernate.validator</groupId>
<artifactId>hibernate-validator</artifactId>
</exclusion>
</exclusions>
</dependency>
and then everything started responding. Which kind of makes sense except for the fact that you can't have that dependency if you run WebFlux boot stand alone.
It's a bit unclear as to why standalone (embedded container) cannot have web dependency, and external container must have it. But it works now.