SpringDocWebFluxConfiguration throws NoClassDefFoundError: javax/servlet/ServletException

Describe the bug

We’re trying to migrate JHipster to use Springdoc instead of Springfox.

https://github.com/jhipster/jhipster-bom/pull/556

In a Spring WebFlux application, I have the following dependencies:

<dependency>
    <groupId>org.springdoc</groupId>
    <artifactId>springdoc-openapi-webflux-core</artifactId>
</dependency>
<dependency>
    <groupId>org.springdoc</groupId>
    <artifactId>springdoc-openapi-data-rest</artifactId>
</dependency>

When the app starts, I get the following error:

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 
'openApiResource' defined in class path resource 
[org/springdoc/webflux/core/SpringDocWebFluxConfiguration.class]: Unsatisfied dependency expressed through 
method 'openApiResource' parameter 2; nested exception is 
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'responseBuilder' 
defined in class path resource [org/springdoc/webflux/core/SpringDocWebFluxConfiguration.class]: Bean 
instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: 
Failed to instantiate [org.springdoc.core.GenericResponseService]: Factory method 'responseBuilder' threw 
exception; nested exception is java.lang.NoClassDefFoundError: javax/servlet/ServletException

Another strange thing that happens with these two dependencies. A new webflux + MongoDB app fails with the following when running mvn verify:

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate 
[org.springdoc.core.GenericResponseService]: Factory method 'responseBuilder' threw exception; nested 
exception is java.lang.NoClassDefFoundError: Could not initialize class 
org.springdoc.core.GenericResponseService

However, if I change replace both dependencies with springdoc-openapi-webflux-ui, all tests pass.

To Reproduce

Steps to reproduce the behavior:

• What version of spring-boot you are using? 2.5.7
• What modules and versions of springdoc-openapi are you using? 1.5.13
• What is the actual and the expected result using OpenAPI Description (yml or json)?
• Provide with a sample code (HelloController) or Test that reproduces the problem

I can provide steps to reproduce, but it’s kinda complicated. Here’s an attempt:

git clone -b springdocs [e-mail]:mshima/jhipster-bom.git
cd jhipster-bom
./mvnw install -Dgpg.skip=true
cd ..
git clone -b skip_ci-doc [e-mail]:mshima/generator-jhipster.git
cd generator-jhipster
npm link

Then, create a new JHipster project (for example, in your ~/Downloads directory):

mkdir webflux-mongodb
cd webflux-mongodb

Create a .yo-rc.json file in this directory with the following contents:

{
  "generator-jhipster": {
    "applicationType": "monolith",
    "reactive": true,
    "baseName": "sampleWebfluxMongodb",
    "packageName": "tech.jhipster.sample",
    "packageFolder": "tech/jhipster/sample",
    "authenticationType": "jwt",
    "cacheProvider": "no",
    "enableHibernateCache": false,
    "websocket": false,
    "databaseType": "mongodb",
    "devDatabaseType": "mongodb",
    "prodDatabaseType": "mongodb",
    "searchEngine": false,
    "buildTool": "maven",
    "enableTranslation": true,
    "nativeLanguage": "en",
    "languages": ["en", "fr"],
    "testFrameworks": ["gatling", "cypress"],
    "serverPort": "8080",
    "jhiPrefix": "jhi",
    "clientPackageManager": "npm",
    "clientFramework": "angularX",
    "creationTimestamp": 1596513172471,
    "jwtSecretKey": "ZjY4MTM4YjI5YzMwZjhjYjI2OTNkNTRjMWQ5Y2Q0Y2YwOWNmZTE2NzRmYzU3NTMwM2NjOTE3MTllOTM3MWRkMzcyYTljMjVmNmQ0Y2MxOTUzODc0MDhhMTlkMDIxMzI2YzQzZDM2ZDE3MmQ3NjVkODk3OTVmYzljYTQyZDNmMTQ=",
    "jhipsterVersion": "7.4.0",
    "skipClient": false,
    "skipServer": false,
    "skipUserManagement": false,
    "skipCheckLengthOfIdentifier": false,
    "skipFakeData": false,
    "entitySuffix": "",
    "dtoSuffix": "DTO",
    "blueprints": [],
    "otherModules": [],
    "pages": [],
    "devServerPort": 4200,
    "clientTheme": "none",
    "clientThemeVariant": "",
    "withAdminUi": true,
    "serviceDiscoveryType": false,
    "enableGradleEnterprise": false
  }
}

Then, run jhipster.

Once the app is finished, run ./mvnw verify to see the test failures.

To start the app:

docker-compose -f src/main/docker/mongodb.yml up -d
./mvnw

[mshima]

@bnasslahsen just an update. Your solution worked, fixed the problem. Is there is a way to detect this conflict?

• Maybe the pageable config could be moved to a config in common package, so we can import it: https://github.com/springdoc/springdoc-openapi/blob/6c86b61cd666e7de1cee926ac34c47243f6ff741/springdoc-openapi-data-rest/src/main/java/org/springdoc/data/rest/SpringDocDataRestConfiguration.java#L88-L104

• There is a conditional at hateos package: https://github.com/springdoc/springdoc-openapi/blob/6c86b61cd666e7de1cee926ac34c47243f6ff741/springdoc-openapi-hateoas/src/main/java/org/springdoc/hateoas/SpringDocHateoasConfiguration.java#L55 but not at data-rest package: https://github.com/springdoc/springdoc-openapi/blob/6c86b61cd666e7de1cee926ac34c47243f6ff741/springdoc-openapi-data-rest/src/main/java/org/springdoc/data/rest/SpringDocDataRestConfiguration.java#L127-L131

I really appreciate your help. I think this bug can be closed now.

[bnasslahsen]

@mshima,

Exactly, you are right! When using groups, the OpenAPIService scope should be PROTOTYPE. This a sample code how it’s implemented in springdoc-openapi:

https://github.com/springdoc/springdoc-openapi/blob/cfe86b6554bd46e2e4b74f686d1e9837fee65f29/springdoc-openapi-common/src/main/java/org/springdoc/core/SpringdocBeanFactoryConfigurer.java#L86-L92

This is not working in your case, as you have declared in JHipsterSpringDocAutoConfiguration a conflicting condition:

• @AutoConfigureBefore(SpringDocConfiguration.class) vs @Import(SpringDocConfiguration.class) . This causes the CacheOrGroupedOpenApiCondition not to be verified.

I believe the straight forward solution will be as follow (The less of springdoc-openapi Beans overriding/duplication):

package tech.jhipster.config.apidoc;

import io.swagger.v3.oas.models.OpenAPI;
import org.springdoc.core.SpringDocConfiguration;
import tech.jhipster.config.JHipsterProperties;

import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.AutoConfigureBefore;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.Profile;

import static tech.jhipster.config.JHipsterConstants.SPRING_PROFILE_API_DOCS;

/**
 * OpenApi OpenAPI configuration.
 * <p>
 * Warning! When having a lot of REST endpoints, OpenApi can become a performance issue.
 * In that case, you can use the "no-api-docs" Spring profile, so that this bean is ignored.
 */
@Configuration
@ConditionalOnWebApplication
@ConditionalOnClass(OpenAPI.class)
@Profile(SPRING_PROFILE_API_DOCS)
@AutoConfigureBefore(SpringDocConfiguration.class)
@AutoConfigureAfter(JHipsterProperties.class)
@Import(JHipsterSpringDocGroupsConfiguration.class)
public class JHipsterSpringDocAutoConfiguration {}

As you can see, i have also not loaded JHipsterSpringDocWebFluxConfiguration or JHipsterSpringDocMvcConfiguration as the loading of MultipleOpenApiWebMvcResource and MultipleOpenApiWebFluxResource is already done by the sprindoc-openapi starter.

Of course, you can also remove springdoc.cache.disabled = true, from the generated application.yml.

Don’t hesitate to let me know, if these instructions help you solve the cache issue.