Swagger-core: java.lang.NoClassDefFoundError: javax/servlet/ServletConfig with Jersey 2 without Servlet

[Tpt]

When following the tutorial described here to setup Swagger with Jersey 2.23.2 with the "Using a custom Application subclass" approach. The following error is thrown:

Exception in thread "main" java.lang.NoClassDefFoundError: javax/servlet/ServletConfig
    at java.lang.Class.getDeclaredMethods0(Native Method)
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
    at java.lang.Class.getDeclaredMethods(Class.java:1975)
    at org.glassfish.jersey.server.model.IntrospectionModeller$2.run(IntrospectionModeller.java:253)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.glassfish.jersey.server.model.IntrospectionModeller.getAllDeclaredMethods(IntrospectionModeller.java:247)
    at org.glassfish.jersey.server.model.IntrospectionModeller.checkForNonPublicMethodIssues(IntrospectionModeller.java:172)
    at org.glassfish.jersey.server.model.IntrospectionModeller.doCreateResourceBuilder(IntrospectionModeller.java:119)
    at org.glassfish.jersey.server.model.IntrospectionModeller.access$000(IntrospectionModeller.java:80)
    at org.glassfish.jersey.server.model.IntrospectionModeller$1.call(IntrospectionModeller.java:112)
    at org.glassfish.jersey.server.model.IntrospectionModeller$1.call(IntrospectionModeller.java:109)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.processWithException(Errors.java:255)
    at org.glassfish.jersey.server.model.IntrospectionModeller.createResourceBuilder(IntrospectionModeller.java:109)
    at org.glassfish.jersey.server.model.Resource.from(Resource.java:797)
    at org.glassfish.jersey.server.ApplicationHandler.initialize(ApplicationHandler.java:465)
    at org.glassfish.jersey.server.ApplicationHandler.access$500(ApplicationHandler.java:184)
    at org.glassfish.jersey.server.ApplicationHandler$3.call(ApplicationHandler.java:350)
    at org.glassfish.jersey.server.ApplicationHandler$3.call(ApplicationHandler.java:347)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.processWithException(Errors.java:255)
    at org.glassfish.jersey.server.ApplicationHandler.<init>(ApplicationHandler.java:347)
    at org.glassfish.jersey.server.ApplicationHandler.<init>(ApplicationHandler.java:299)
    at org.glassfish.jersey.jdkhttp.JdkHttpHandlerContainer.<init>(JdkHttpHandlerContainer.java:98)
    at org.glassfish.jersey.jdkhttp.JdkHttpServerFactory.createHttpServer(JdkHttpServerFactory.java:111)
    at org.glassfish.jersey.jdkhttp.JdkHttpServerFactory.createHttpServer(JdkHttpServerFactory.java:93)
    at example.MyApp.main(MyApp.java:21)
Caused by: java.lang.ClassNotFoundException: javax.servlet.ServletConfig
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 29 more

Se also this StackOverflow discussion: http://stackoverflow.com/questions/38891661/swagger-with-jersey-2-throws-java-lang-noclassdeffounderror-javax-servlet-servl

[fehguy]

This was answered on stackoverflow. Just add the servlet dependency

[ajayyadava]

Hi @fehguy

I ran into the same problem. I am using GrizzlyServer. I would like to avoid switching the server. Is it possible to use swagger without switching away from Grizzly? If yes, then what dependency should I add to my pom.xml?

[ajayyadava]

Adding the following dependency worked for me.

    <dependency>
        <groupId>org.glassfish.jersey.containers</groupId>
        <artifactId>jersey-container-grizzly2-servlet</artifactId>
    </dependency>

[NunuM]

Hi,

After 3 years we have the same bug, why do I need to change to a servlet-based project while I have an already running Java HTTP server like a grizzly HTTP server, without all servlet weird configurations?

This occurs because in the dependency swagger-jersey2-jaxrs the class ApiListingResource wants the servlet instance to be injected. Why not provide a different implementation (this is one that runs on a non-servlet server, is not already parameterized, is just an example that works):

package me.nunum.whereami.facade;

import io.swagger.annotations.ApiOperation;
import io.swagger.config.FilterFactory;
import io.swagger.config.Scanner;
import io.swagger.config.SwaggerConfig;
import io.swagger.core.filter.SpecFilter;
import io.swagger.core.filter.SwaggerSpecFilter;
import io.swagger.jaxrs.Reader;
import io.swagger.jaxrs.config.JaxrsScanner;
import io.swagger.jaxrs.config.ReaderConfig;
import io.swagger.jaxrs.listing.SwaggerSerializers;
import io.swagger.models.Swagger;
import io.swagger.util.Yaml;

import java.util.*;
import javax.inject.Singleton;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Application;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.Cookie;
import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.UriInfo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Path("/api/doc")
@Singleton
public class ApiListingResource {
    static boolean initialized = false;
    Logger LOGGER = LoggerFactory.getLogger(io.swagger.jaxrs.listing.ApiListingResource.class);


    public Swagger mSwaggerConfig;

    public ApiListingResource() {
        mSwaggerConfig = new Swagger();
        mSwaggerConfig.setBasePath("/");
    }

    public ApiListingResource(Swagger swagger){
        this.mSwaggerConfig = swagger;
    }

    protected synchronized Swagger scan(Application app) {
        Swagger swagger = null;
        Scanner scanner = new Scanner() {
            @Override
            public Set<Class<?>> classes() {
                return app.getClasses();
            }

            @Override
            public boolean getPrettyPrint() {
                return false;
            }

            @Override
            public void setPrettyPrint(boolean b) {

            }
        };
        this.LOGGER.debug("using scanner " + scanner);
        SwaggerSerializers.setPrettyPrint(scanner.getPrettyPrint());
        swagger = this.mSwaggerConfig;
        new HashSet();
        Set classes;

        if (scanner instanceof JaxrsScanner) {
            classes = null;
        } else {
            classes = scanner.classes();
        }

        if (classes != null) {
            Reader reader = new Reader(swagger, new ReaderConfig() {
                @Override
                public boolean isScanAllResources() {
                    return false;
                }

                @Override
                public Collection<String> getIgnoredRoutes() {
                    return new ArrayList<>();
                }
            });
            swagger = reader.read(classes);
            if (scanner instanceof SwaggerConfig) {
                swagger = ((SwaggerConfig)scanner).configure(swagger);
            } else {
                SwaggerConfig configurator = new SwaggerConfig() {
                    @Override
                    public Swagger configure(Swagger swagger) {
                        return swagger;
                    }

                    @Override
                    public String getFilterClass() {
                        return "";
                    }
                };
                this.LOGGER.debug("configuring swagger with " + configurator);
                configurator.configure(swagger);
            }

        }

        initialized = true;
        return swagger;
    }

    @GET
    @Produces({"application/json"})
    @Path("/swagger.json")
    @ApiOperation(
            value = "The swagger definition in JSON",
            hidden = true
    )
    public Response getListingJson(@Context Application app, @Context HttpHeaders headers, @Context UriInfo uriInfo) {
        Swagger swagger = this.mSwaggerConfig;
        if (!initialized) {
            this.mSwaggerConfig = this.scan(app);
        }

        if (swagger != null) {
            SwaggerSpecFilter filterImpl = FilterFactory.getFilter();
            if (filterImpl != null) {
                SpecFilter f = new SpecFilter();
                swagger = f.filter(swagger, filterImpl, this.getQueryParams(uriInfo.getQueryParameters()), this.getCookies(headers), this.getHeaders(headers));
            }

            return Response.ok().entity(swagger).build();
        } else {
            return Response.status(404).build();
        }
    }

    @GET
    @Produces({"application/yaml"})
    @Path("/swagger.yaml")
    @ApiOperation(
            value = "The swagger definition in YAML",
            hidden = true
    )
    public Response getListingYaml(@Context Application app, @Context HttpHeaders headers, @Context UriInfo uriInfo) {
        Swagger swagger = this.mSwaggerConfig;
        if (!initialized) {
            this.mSwaggerConfig = this.scan(app);
        }

        try {
            if (swagger != null) {
                SwaggerSpecFilter filterImpl = FilterFactory.getFilter();
                this.LOGGER.debug("using filter " + filterImpl);
                if (filterImpl != null) {
                    SpecFilter f = new SpecFilter();
                    swagger = f.filter(swagger, filterImpl, this.getQueryParams(uriInfo.getQueryParameters()), this.getCookies(headers), this.getHeaders(headers));
                }

                String yaml = Yaml.mapper().writeValueAsString(swagger);
                String[] parts = yaml.split("\n");
                StringBuilder b = new StringBuilder();
                String[] arr$ = parts;
                int len$ = parts.length;

                for(int i$ = 0; i$ < len$; ++i$) {
                    String part = arr$[i$];
                    int pos = part.indexOf("!<");
                    int endPos = part.indexOf(">");
                    b.append(part);
                    b.append("\n");
                }

                return Response.ok().entity(b.toString()).type("application/yaml").build();
            }
        } catch (Exception var16) {
            var16.printStackTrace();
        }

        return Response.status(404).build();
    }

    protected Map<String, List<String>> getQueryParams(MultivaluedMap<String, String> params) {
        Map<String, List<String>> output = new HashMap();
        if (params != null) {
            Iterator i$ = params.keySet().iterator();

            while(i$.hasNext()) {
                String key = (String)i$.next();
                List<String> values = (List)params.get(key);
                output.put(key, values);
            }
        }

        return output;
    }

    protected Map<String, String> getCookies(HttpHeaders headers) {
        Map<String, String> output = new HashMap();
        if (headers != null) {
            Iterator i$ = headers.getCookies().keySet().iterator();

            while(i$.hasNext()) {
                String key = (String)i$.next();
                Cookie cookie = (Cookie)headers.getCookies().get(key);
                output.put(key, cookie.getValue());
            }
        }

        return output;
    }

    protected Map<String, List<String>> getHeaders(HttpHeaders headers) {
        Map<String, List<String>> output = new HashMap();
        if (headers != null) {
            Iterator i$ = headers.getRequestHeaders().keySet().iterator();

            while(i$.hasNext()) {
                String key = (String)i$.next();
                List<String> values = (List)headers.getRequestHeaders().get(key);
                output.put(key, values);
            }
        }

        return output;
    }
}

I am saying this because if you pick Jersey startup project from Maven archive, you end with "jersey-container-grizzly2-http" dependency, newer people will not have in mind the confusion around containers/servlets and will not conclude swagger set up.

[salah3x]

This is my solution to this issue:

package com.example;

import com.fasterxml.jackson.core.JsonProcessingException;
import io.swagger.annotations.ApiOperation;
import io.swagger.jaxrs.config.BeanConfig;
import io.swagger.models.Swagger;
import io.swagger.util.Yaml;

import javax.enterprise.context.ApplicationScoped;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Response;

@Path("/docs")
@ApplicationScoped
public class ApiListingResource {

    private final Swagger swagger;

    public ApiListingResource() {
        BeanConfig beanConfig = new BeanConfig();
        beanConfig.setTitle("MY REST API");
        beanConfig.setVersion("v1");
        beanConfig.setBasePath("/api");
        beanConfig.setResourcePackage("com.example.resource");
        beanConfig.setScan(true);
        this.swagger = beanConfig.getSwagger();
    }

    @GET
    @Produces({"application/json"})
    @Path("/swagger.json")
    public Response getListingJson() {
        return Response.ok(this.swagger).build();
    }

    @GET
    @Produces({"application/yaml"})
    @Path("/swagger.yaml")
    public Response getListingYaml() throws JsonProcessingException {
        String yaml = Yaml.mapper().writeValueAsString(this.swagger);
        return Response.ok(yaml).build();
    }
}

I registred this resource instead of the one provided by io.swagger.jaxrs.listing
The rest of the configuration is the same as described in the docs