IllegalStateException - @ComponentScanning a springframework package

Question

I've been working through the following tutorial:

http://spring.io/guides/gs/rest-service/

I was initially able to get the code to work correctly (Run the finished tutorial, send an HTTP message and get the correct response) and successfully expand upon it.

After expanding further, I ran into the following exception:

java.lang.IllegalStateException: Could not evaluate condition on org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfiguration#propertySourcesPlaceholderConfigurer due to internal class not found. This can happen if you are @ComponentScanning a springframework package (e.g. if you put a @ComponentScan in the default package by mistake)
    at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:51)
    at org.springframework.context.annotation.ConditionEvaluator.shouldSkip(ConditionEvaluator.java:92)
    at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsForBeanMethod(ConfigurationClassBeanDefinitionReader.java:174)
    at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsForConfigurationClass(ConfigurationClassBeanDefinitionReader.java:136)
    at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitions(ConfigurationClassBeanDefinitionReader.java:116)
    at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:330)
    at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:243)
    at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:254)
    at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:94)
    at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:611)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:464)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:109)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:691)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:321)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:961)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:950)
    at com.aharrison.hello.Application.main(Application.java:15)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)

I've since stripped the code back down to only what is shown in the example, but I am still experiencing the exception.

I think it could possibly be related to the following issue, although it is marked as closed:

https://github.com/spring-projects/spring-boot/issues/2050

I'm not very experienced with Spring, so I can't fully comprehend what is being discussed.

Here are my current classes:

Greeting.java:

package com.aharrison.hello;

public class Greeting {
    private final long id;
    private final String content;

    public Greeting(long id, String content) {
        this.id = id;
        this.content = content;
    }

    public long getId() {
        return id;
    }

    public String getContent() {
        return content;
    }
}

GreetingController:

package com.aharrison.hello;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.concurrent.atomic.AtomicLong;

@RestController
public class GreetingController {
    private static final String template = "Hello, %s!";
    private final AtomicLong counter = new AtomicLong();

    @RequestMapping("/greeting")
    public Greeting greeting(@RequestParam(value="name", defaultValue="World") String name) {
        return new Greeting(counter.incrementAndGet(), String.format(template, name));
    }
}

Application.java :

package com.aharrison.hello;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;

/**
 * Created by Adam on 12/26/2014.
 */
@ComponentScan
@EnableAutoConfiguration
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>com.aharrison</groupId>
<artifactId>SpringRestAPI</artifactId>
<version>1.0-SNAPSHOT</version>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <version>1.2.0.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.1.3.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.data</groupId>
        <artifactId>spring-data-mongodb</artifactId>
        <version>1.6.1.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.mongodb</groupId>
        <artifactId>mongo-java-driver</artifactId>
        <version>2.12.2</version>
    </dependency>
</dependencies>

Questions:

1. What is causing the exception in this situation? Is there something wrong with my code above, or is the problem environment related?
2. When the exception says "..if you put a @ComponentScan in the default package by mistake", which is the default package it is referring to? Is this applicable to the current situation?

Thanks in advance.

Answer 1

When I run the code that you have provided everything works fine. The only change I had to make was in the pom.xml where I added the following:

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.2.0.RELEASE</version>
</parent>

This enables the whole Spring Boot mechanism and is required in order for you to be able to start the application.

See below for the successful output from my test run:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.2.0.RELEASE)

2014-12-27 17:41:12.472  INFO 4065 --- [           main] com.aharrison.hello.Application          : Starting Application on My-MacBook-Pro.local with PID 4065 (/Users/wassgren/test/target/test-classes started by wassgren in /Users/wassgren/test/test-di)
2014-12-27 17:41:12.506  INFO 4065 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@4a668b6e: startup date [Sat Dec 27 17:41:12 CET 2014]; root of context hierarchy
2014-12-27 17:41:13.407  INFO 4065 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Overriding bean definition for bean 'beanNameViewResolver': replacing [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration.class]] with [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter.class]]
2014-12-27 17:41:14.186  INFO 4065 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration' of type [class org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2014-12-27 17:41:14.703  INFO 4065 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080/http
2014-12-27 17:41:15.047  INFO 4065 --- [           main] o.apache.catalina.core.StandardService   : Starting service Tomcat
2014-12-27 17:41:15.048  INFO 4065 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.0.15
2014-12-27 17:41:15.154  INFO 4065 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2014-12-27 17:41:15.154  INFO 4065 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 2651 ms
2014-12-27 17:41:16.399  INFO 4065 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean        : Mapping servlet: 'dispatcherServlet' to [/]
2014-12-27 17:41:16.404  INFO 4065 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2014-12-27 17:41:16.404  INFO 4065 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'characterEncodingFilter' to: [/*]
2014-12-27 17:41:16.907  INFO 4065 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@4a668b6e: startup date [Sat Dec 27 17:41:12 CET 2014]; root of context hierarchy
2014-12-27 17:41:16.979  INFO 4065 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/greeting],methods=[],params=[],headers=[],consumes=[],produces=[],custom=[]}" onto public com.aharrison.hello.Greeting com.aharrison.hello.GreetingController.greeting(java.lang.String)
2014-12-27 17:41:16.981  INFO 4065 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],methods=[],params=[],headers=[],consumes=[],produces=[],custom=[]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2014-12-27 17:41:16.981  INFO 4065 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],methods=[],params=[],headers=[],consumes=[],produces=[text/html],custom=[]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest)
2014-12-27 17:41:17.013  INFO 4065 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2014-12-27 17:41:17.014  INFO 4065 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2014-12-27 17:41:17.059  INFO 4065 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2014-12-27 17:41:17.206  INFO 4065 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2014-12-27 17:41:17.292  INFO 4065 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080/http
2014-12-27 17:41:17.294  INFO 4065 --- [           main] com.aharrison.hello.Application          : Started Application in 5.245 seconds (JVM running for 6.088)

Answer 2

Remove the @ComponentScan which is placed above the Application class. @SpringBootApplication adds it by default, if the classes you need to be scanned are within the same package as the Application class.