'Unable to infer base url... springfox-swagger2 version 2.9.2

Version of springfox-swagger that I am using [ ![Download] 1]2

What kind of issue is this? Project structure: SwaggerConfig is in automate.api.config.swagger.SwaggerConfiguration Auth Config is in automate.api.web.auth.keycloak.FalconKeycloakConfigurerAdapter

image

dependencies

As for Spring Boot

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.3.RELEASE</version>
        <relativePath/>
    </parent>

As for swagger

<dependency>
  <groupId>io.springfox</groupId>
  <artifactId>springfox-swagger2</artifactId>
  <version>${spring.springfox-swagger2.version}</version>
</dependency>
<dependency>
  <groupId>io.springfox</groupId>
  <artifactId>springfox-swagger-ui</artifactId>
  <version>${spring.springfox-swagger2.version}</version>
</dependency>

Swagger 2 config

@Configuration
@EnableSwagger2
public class SwaggerConfiguration {
    @Bean
    public Docket api() {
        return new Docket(DocumentationType.SWAGGER_2)
                .select()
                .apis(RequestHandlerSelectors.any())
                .paths(PathSelectors.any())
                .build();
    }
}

Security config

@Override
  protected void configureAccessRules(final HttpSecurity http) throws Exception {
    http.csrf()
        .disable()
        .authorizeRequests()
        .antMatchers("/actuator/health")
        .permitAll()
       .antMatchers(HttpMethod.GET,
                    "/v2/api-docs",
                    "/swagger-resources/**",
                    "/swagger-ui.html**",
                    "/webjars/**",
                    "favicon.ico")
            .permitAll();
  }

Example for one of my controllers All of my controllers mapped like /api/...

@RestController
@RequestMapping(value = "/api", produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
public class ExampleResource {
    private ExampleFacade catalog;

    @Autowired
    public ExampleResource(ExampleFacade catalog) {
        this.catalog = catalog;
    }

    @RequestMapping(method = RequestMethod.GET, value = "/examples")
    public List<ExampleDTO> index() {
        return catalog.listExamples();
    }
}

ISSUE

/v2/api-docs works perfectly, I get back all of my endpoints with their details /swagger-ui.html gives me back a pop up that shows "Unable to infer base url......"

Then I turned on the TRACE log level on my spring-boot app, like

logging:
  level:
    org:
      springframework:
        web: TRACE

My logs looks like:

[2019-05-22 21:12:06] TRACE [nio-8080-exec-1] o.s.w.s.DispatcherServlet GET "/v2/api-docs", parameters={}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:06] TRACE [nio-8080-exec-1] o.s.w.s.m.m.a.ServletInvocableHandlerMethod Arguments: [null, SecurityContextHolderAwareRequestWrapper[ org.springframework.security.web.header.HeaderWriterFilter$HeaderWriterRequest@b9ed904]]
[2019-05-22 21:12:06] DEBUG [nio-8080-exec-1] o.s.w.s.m.m.a.HttpEntityMethodProcessor Using 'application/json;q=0.8', given [text/html, application/xhtml+xml, image/webp, image/apng, application/signed-exchange;v=b3, application/xml;q=0.9, */*;q=0.8] and supported [application/json, application/*+json, application/json, application/*+json]
[2019-05-22 21:12:06] TRACE [nio-8080-exec-1] o.s.w.s.m.m.a.HttpEntityMethodProcessor Writing [BaseView(data=springfox.documentation.spring.web.json.Json@65455d18)]
[2019-05-22 21:12:06] TRACE [nio-8080-exec-1] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:06] DEBUG [nio-8080-exec-1] o.s.w.s.DispatcherServlet Completed 200 OK, headers={masked}
[2019-05-22 21:12:10] TRACE [nio-8080-exec-2] o.s.w.s.DispatcherServlet GET "/swagger-ui.html", parameters={}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:10] TRACE [nio-8080-exec-2] o.s.w.s.h.SimpleUrlHandlerMapping Mapped to HandlerExecutionChain with [ResourceHttpRequestHandler ["classpath:/META-INF/resources/", "classpath:/resources/", "classpath:/static/", "classpath:/public/", "/"]] and 5 interceptors
[2019-05-22 21:12:10] TRACE [nio-8080-exec-2] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:10] DEBUG [nio-8080-exec-2] o.s.w.s.DispatcherServlet Completed 200 OK, headers={masked}
[2019-05-22 21:12:10] TRACE [nio-8080-exec-3] o.s.w.s.DispatcherServlet GET "/webjars/springfox-swagger-ui/springfox.css?v=2.9.2", parameters={masked}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:10] TRACE [nio-8080-exec-4] o.s.w.s.DispatcherServlet GET "/webjars/springfox-swagger-ui/swagger-ui.css?v=2.9.2", parameters={masked}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:10] TRACE [nio-8080-exec-3] o.s.w.s.h.SimpleUrlHandlerMapping Matching patterns [/webjars/**, /**]
[2019-05-22 21:12:10] TRACE [nio-8080-exec-3] o.s.w.s.h.SimpleUrlHandlerMapping Mapped to HandlerExecutionChain with [ResourceHttpRequestHandler ["classpath:/META-INF/resources/webjars/"]] and 5 interceptors
[2019-05-22 21:12:10] TRACE [nio-8080-exec-4] o.s.w.s.h.SimpleUrlHandlerMapping Matching patterns [/webjars/**, /**]
[2019-05-22 21:12:10] TRACE [nio-8080-exec-4] o.s.w.s.h.SimpleUrlHandlerMapping Mapped to HandlerExecutionChain with [ResourceHttpRequestHandler ["classpath:/META-INF/resources/webjars/"]] and 5 interceptors
[2019-05-22 21:12:10] TRACE [nio-8080-exec-6] o.s.w.s.DispatcherServlet GET "/webjars/springfox-swagger-ui/swagger-ui-bundle.js?v=2.9.2", parameters={masked}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:10] TRACE [nio-8080-exec-3] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:10] DEBUG [nio-8080-exec-3] o.s.w.s.DispatcherServlet Completed 200 OK, headers={masked}
[2019-05-22 21:12:10] TRACE [nio-8080-exec-5] o.s.w.s.DispatcherServlet GET "/webjars/springfox-swagger-ui/swagger-ui-standalone-preset.js?v=2.9.2", parameters={masked}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:10] TRACE [nio-8080-exec-7] o.s.w.s.DispatcherServlet GET "/webjars/springfox-swagger-ui/springfox.js?v=2.9.2", parameters={masked}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:10] TRACE [nio-8080-exec-6] o.s.w.s.h.SimpleUrlHandlerMapping Matching patterns [/webjars/**, /**]
[2019-05-22 21:12:10] TRACE [nio-8080-exec-6] o.s.w.s.h.SimpleUrlHandlerMapping Mapped to HandlerExecutionChain with [ResourceHttpRequestHandler ["classpath:/META-INF/resources/webjars/"]] and 5 interceptors
[2019-05-22 21:12:10] TRACE [nio-8080-exec-5] o.s.w.s.h.SimpleUrlHandlerMapping Matching patterns [/webjars/**, /**]
[2019-05-22 21:12:10] TRACE [nio-8080-exec-5] o.s.w.s.h.SimpleUrlHandlerMapping Mapped to HandlerExecutionChain with [ResourceHttpRequestHandler ["classpath:/META-INF/resources/webjars/"]] and 5 interceptors
[2019-05-22 21:12:10] TRACE [nio-8080-exec-7] o.s.w.s.h.SimpleUrlHandlerMapping Matching patterns [/webjars/**, /**]
[2019-05-22 21:12:10] TRACE [nio-8080-exec-7] o.s.w.s.h.SimpleUrlHandlerMapping Mapped to HandlerExecutionChain with [ResourceHttpRequestHandler ["classpath:/META-INF/resources/webjars/"]] and 5 interceptors
[2019-05-22 21:12:10] TRACE [nio-8080-exec-4] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:10] DEBUG [nio-8080-exec-4] o.s.w.s.DispatcherServlet Completed 200 OK, headers={masked}
[2019-05-22 21:12:10] TRACE [nio-8080-exec-7] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:10] DEBUG [nio-8080-exec-7] o.s.w.s.DispatcherServlet Completed 200 OK, headers={masked}
[2019-05-22 21:12:10] TRACE [nio-8080-exec-5] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:10] DEBUG [nio-8080-exec-5] o.s.w.s.DispatcherServlet Completed 200 OK, headers={masked}
[2019-05-22 21:12:10] TRACE [nio-8080-exec-6] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:10] DEBUG [nio-8080-exec-6] o.s.w.s.DispatcherServlet Completed 200 OK, headers={masked}
[2019-05-22 21:12:10] TRACE [nio-8080-exec-8] o.s.w.s.DispatcherServlet GET "/swagger-resources/configuration/ui", parameters={}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:10] TRACE [nio-8080-exec-8] o.s.w.s.m.m.a.RequestMappingHandlerMapping Mapped to public org.springframework.http.ResponseEntity<springfox.documentation.swagger.web.UiConfiguration> springfox.documentation.swagger.web.ApiResourceController.uiConfiguration()
[2019-05-22 21:12:10] TRACE [nio-8080-exec-8] o.s.w.s.m.m.a.ServletInvocableHandlerMethod Arguments: []
[2019-05-22 21:12:10] DEBUG [nio-8080-exec-8] o.s.w.s.m.m.a.HttpEntityMethodProcessor Using 'application/json', given [application/json] and supported [application/json, application/*+json, application/json, application/*+json]
[2019-05-22 21:12:10] TRACE [nio-8080-exec-8] o.s.w.s.m.m.a.HttpEntityMethodProcessor Writing [BaseView(data=springfox.documentation.swagger.web.UiConfiguration@7594a0c7)]
[2019-05-22 21:12:10] TRACE [nio-8080-exec-8] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:10] DEBUG [nio-8080-exec-8] o.s.w.s.DispatcherServlet Completed 200 OK, headers={masked}
[2019-05-22 21:12:10] TRACE [nio-8080-exec-9] o.s.w.s.DispatcherServlet GET "/swagger-resources/configuration/security", parameters={}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:10] TRACE [nio-8080-exec-9] o.s.w.s.m.m.a.RequestMappingHandlerMapping Mapped to public org.springframework.http.ResponseEntity<springfox.documentation.swagger.web.SecurityConfiguration> springfox.documentation.swagger.web.ApiResourceController.securityConfiguration()
[2019-05-22 21:12:10] TRACE [nio-8080-exec-9] o.s.w.s.m.m.a.ServletInvocableHandlerMethod Arguments: []
[2019-05-22 21:12:10] DEBUG [nio-8080-exec-9] o.s.w.s.m.m.a.HttpEntityMethodProcessor Using 'application/json', given [application/json] and supported [application/json, application/*+json, application/json, application/*+json]
[2019-05-22 21:12:10] TRACE [nio-8080-exec-9] o.s.w.s.m.m.a.HttpEntityMethodProcessor Writing [BaseView(data=springfox.documentation.swagger.web.SecurityConfiguration@4605258b)]
[2019-05-22 21:12:10] TRACE [nio-8080-exec-9] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:10] DEBUG [nio-8080-exec-9] o.s.w.s.DispatcherServlet Completed 200 OK, headers={masked}
[2019-05-22 21:12:10] TRACE [io-8080-exec-10] o.s.w.s.DispatcherServlet GET "/swagger-resources", parameters={}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:10] TRACE [io-8080-exec-10] o.s.w.s.m.m.a.RequestMappingHandlerMapping Mapped to public org.springframework.http.ResponseEntity<java.util.List<springfox.documentation.swagger.web.SwaggerResource>> springfox.documentation.swagger.web.ApiResourceController.swaggerResources()
[2019-05-22 21:12:10] TRACE [io-8080-exec-10] o.s.w.s.m.m.a.ServletInvocableHandlerMethod Arguments: []
[2019-05-22 21:12:10] DEBUG [io-8080-exec-10] o.s.w.s.m.m.a.HttpEntityMethodProcessor Using 'application/json', given [application/json] and supported [application/json, application/*+json, application/json, application/*+json]
[2019-05-22 21:12:10] TRACE [io-8080-exec-10] o.s.w.s.m.m.a.HttpEntityMethodProcessor Writing [BaseView(data=[springfox.documentation.swagger.web.SwaggerResource@b35c0d2])]
[2019-05-22 21:12:10] TRACE [io-8080-exec-10] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:10] DEBUG [io-8080-exec-10] o.s.w.s.DispatcherServlet Completed 200 OK, headers={masked}
[2019-05-22 21:12:11] TRACE [nio-8080-exec-1] o.s.w.s.DispatcherServlet GET "/null/swagger-resources/configuration/ui", parameters={}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:11] TRACE [nio-8080-exec-1] o.s.w.s.h.SimpleUrlHandlerMapping Mapped to HandlerExecutionChain with [ResourceHttpRequestHandler ["classpath:/META-INF/resources/", "classpath:/resources/", "classpath:/static/", "classpath:/public/", "/"]] and 5 interceptors
[2019-05-22 21:12:11] DEBUG [nio-8080-exec-1] o.s.w.s.r.ResourceHttpRequestHandler Resource not found
[2019-05-22 21:12:11] TRACE [nio-8080-exec-1] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:11] DEBUG [nio-8080-exec-1] o.s.w.s.DispatcherServlet Completed 404 NOT_FOUND, headers={masked}
[2019-05-22 21:12:11] TRACE [nio-8080-exec-1] o.s.w.s.DispatcherServlet "ERROR" dispatch for GET "/error", parameters={}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:11] TRACE [nio-8080-exec-1] o.s.w.s.m.m.a.RequestMappingHandlerMapping Mapped to public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
[2019-05-22 21:12:11] TRACE [nio-8080-exec-1] o.s.w.s.m.m.a.ServletInvocableHandlerMethod Arguments: [SecurityContextHolderAwareRequestWrapper[ FirewalledRequest[ org.apache.catalina.core.ApplicationHttpRequest@dc7df80]]]
[2019-05-22 21:12:11] DEBUG [nio-8080-exec-1] o.s.w.s.m.m.a.HttpEntityMethodProcessor Using 'application/json', given [application/json] and supported [application/json, application/*+json, application/json, application/*+json]
[2019-05-22 21:12:11] TRACE [nio-8080-exec-1] o.s.w.s.m.m.a.HttpEntityMethodProcessor Writing [BaseView(data={timestamp=Wed May 22 21:12:11 CEST 2019, status=404, error=Not Found, message=No message available, path=/null/swagger-resources/configuration/ui})]
[2019-05-22 21:12:11] TRACE [nio-8080-exec-1] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:11] DEBUG [nio-8080-exec-1] o.s.w.s.DispatcherServlet Exiting from "ERROR" dispatch, status 404, headers={masked}
[2019-05-22 21:12:12] TRACE [nio-8080-exec-2] o.s.w.s.DispatcherServlet GET "/null/swagger-resources/configuration/security", parameters={}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:12] TRACE [nio-8080-exec-2] o.s.w.s.h.SimpleUrlHandlerMapping Mapped to HandlerExecutionChain with [ResourceHttpRequestHandler ["classpath:/META-INF/resources/", "classpath:/resources/", "classpath:/static/", "classpath:/public/", "/"]] and 5 interceptors
[2019-05-22 21:12:12] DEBUG [nio-8080-exec-2] o.s.w.s.r.ResourceHttpRequestHandler Resource not found
[2019-05-22 21:12:12] TRACE [nio-8080-exec-2] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:12] DEBUG [nio-8080-exec-2] o.s.w.s.DispatcherServlet Completed 404 NOT_FOUND, headers={masked}
[2019-05-22 21:12:12] TRACE [nio-8080-exec-2] o.s.w.s.DispatcherServlet "ERROR" dispatch for GET "/error", parameters={}, headers={masked} in DispatcherServlet 'dispatcherServlet'
[2019-05-22 21:12:12] TRACE [nio-8080-exec-2] o.s.w.s.m.m.a.RequestMappingHandlerMapping Mapped to public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
[2019-05-22 21:12:12] TRACE [nio-8080-exec-2] o.s.w.s.m.m.a.ServletInvocableHandlerMethod Arguments: [SecurityContextHolderAwareRequestWrapper[ FirewalledRequest[ org.apache.catalina.core.ApplicationHttpRequest@723fa0fe]]]
[2019-05-22 21:12:12] DEBUG [nio-8080-exec-2] o.s.w.s.m.m.a.HttpEntityMethodProcessor Using 'application/json', given [application/json] and supported [application/json, application/*+json, application/json, application/*+json]
[2019-05-22 21:12:12] TRACE [nio-8080-exec-2] o.s.w.s.m.m.a.HttpEntityMethodProcessor Writing [BaseView(data={timestamp=Wed May 22 21:12:12 CEST 2019, status=404, error=Not Found, message=No message available, path=/null/swagger-resources/configuration/security})]
[2019-05-22 21:12:12] TRACE [nio-8080-exec-2] o.s.w.s.DispatcherServlet No view rendering, null ModelAndView returned.
[2019-05-22 21:12:12] DEBUG [nio-8080-exec-2] o.s.w.s.DispatcherServlet Exiting from "ERROR" dispatch, status 404, headers={masked}

Unfortunately, I see there is something weird with the path mapping at the and of the logs: GET "/null/swagger-resources/configuration/ui" GET "/null/swagger-resources/configuration/security" etc...

Please, help me ! :)

I gooogled for this problem and read these ones:

Why does springfox-swagger2 UI tell me "Unable to infer base url."

https://github.com/springfox/springfox/issues/2191

https://github.com/springfox/springfox/issues/2907

swagger-ui.html 400 bad request

https://github.com/springfox/springfox/issues/2501 https://github.com/springfox/springfox/issues/2396



Solution 1:[1]

Now, I managed to solve my issue. One of the issues was the pathMApping.

I needed to change my configuration to explicitly to "/", like here

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import springfox.documentation.builders.PathSelectors;
import springfox.documentation.builders.RequestHandlerSelectors;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spring.web.plugins.Docket;
import springfox.documentation.swagger2.annotations.EnableSwagger2;

@Configuration
@EnableSwagger2
public class SwaggerConfiguration {
  @Bean
  public Docket api() {
    return new Docket(DocumentationType.SWAGGER_2)
        .select()
        .apis(RequestHandlerSelectors.any())
        .paths(PathSelectors.any())
        .build()
        .pathMapping("/");
  }
}

Other issue was I used ResponseBodyAdvice

import io.falcon.automate.api.web.views.BaseView;
import io.falcon.automate.api.web.views.ErrorView;
import org.springframework.core.MethodParameter;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;


@ControllerAdvice
public class ResponseAdvice implements ResponseBodyAdvice<Object> {

    @Override
    public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {
        return true;
    }

    /**
     * Wraps all responses in base view class
     * @param body
     * @param returnType
     * @param selectedContentType
     * @param selectedConverterType
     * @param request
     * @param response
     * @return
     */
    @Override
    public Object beforeBodyWrite(
            Object body,
            MethodParameter returnType,
            MediaType selectedContentType,
            Class<? extends HttpMessageConverter<?>> selectedConverterType,
            ServerHttpRequest request,
            ServerHttpResponse response
    ) {
        if (body instanceof ErrorView) {
            return body;
        }
        return new BaseView(body);
    }
}

If I commented out my response wrapper class, everything works like a charm.....

The only issue, that I need my response wrapper. :/

Solution 2:[2]

To solve the issue you just need to add the following to the ResponseBodyAdvice implemented class, at @ControllerAdvice annotation you just need to define the base package of your application directory, so this won't return a null when calling the swagger-ui url.

For example, have a look at first line @ControllerAdvice annotation input parameter

@ControllerAdvice("com.main.abc.package")
public class AdapterAdvice implements ResponseBodyAdvice<Object> {
    
    @Override
    public boolean supports(MethodParameter methodParameter, Class<? extends HttpMessageConverter<?>> aClass) {
        return true;
    }

    @Override
    public Object beforeBodyWrite(
            Object body,
            MethodParameter methodParameter,
            MediaType mediaType,
            Class<? extends HttpMessageConverter<?>> aClass,
            ServerHttpRequest serverHttpRequest,
            ServerHttpResponse serverHttpResponse) {
        // just some wrapper logic, you can just omit the below and return the body Object you got as a param
        Map<String, Object> data = new HashMap<>();
        data.put("serverTime", new Date(System.currentTimeMillis()));
        if(body instanceof Map && ((Map)body).get("error") != null ){
            data.put("isSuccess", false);
            if(((Map)body).get("trace") != null){
                ((Map)body).remove("trace");
            }
        } else if (body instanceof ApiError && ((ApiError)body).getResponseStatusCode().equalsIgnoreCase("0")){
            data.put("isSuccess", false);
        } else {
            data.put("isSuccess", true);
        }
        data.put("mainResponse",body);

        return data;
    }
}

Solution 3:[3]

In my case with Swagger 3.0.0 - especially io.springfox:springfox-boot-starter - specifying the spring-boot URL context-path solved this loop with "/null/swagger-resources/":

In application.properties: server.servlet.context-path=/

Or if you have an application.yml file:

server:
  servlet:
    context-path: /

Warning: It will change the base path of all web services, not only Swagger

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 lombocska
Solution 2
Solution 3 electrobabe