title: How to load a custom DaoAuthenticationProvider into the Spring Context?
body: <p>I have this issue with Spring Security.</p>
  
  <p>I have a java-config implementation with a SecurityConfig class, that extends WebSecurityConfigurerAdapter.</p>
  
  <p>In this class I want to override the method "configure()"</p>
  
  <pre><code>@Configuration
  @EnableWebSecurity
  @EnableGlobalMethodSecurity(prePostEnabled = true, securedEnabled = true, proxyTargetClass = true)
  public class SecurityConfig extends WebSecurityConfigurerAdapter{
  
      @Override
      protected void configure(AuthenticationManagerBuilder auth) throws Exception {
          MyDaoAuthenticationProvider provider = new MyDaoAuthenticationProvider();
          provider.setPasswordEncoder(passwordEncoder());
          provider.setUserDetailsService(securityService);
          auth.authenticationProvider(provider);
      }
  
      //...
  
  }   
  </code></pre>
  
  <p>All is OK and it works.</p>
  
  <p>The problem is that "MyDaoAuthenticationProvider" component is not loaded on the Spring Context.
  So I can't inject or Autowired any components in this class:</p>
  
  <pre><code>public class MyDaoAuthenticationProvider extends DaoAuthenticationProvider {
  
      @Autowired
      AuthenticationHandler authenticationHandler;    // &lt;- authenticationHandler is null, is not resolved
  
      @Override
      public Authentication authenticate(Authentication authentication) throws AuthenticationException {
          authenticationHandler.authenticate(authentication);    // &lt;- NullPointerException in this point
      }
  
  }
  </code></pre>
  
  <p>This is the AuthenticationHandler class:</p>
  
  <pre><code>@Component
  public class AuthenticationHandler {
  
      public void authenticate (Authentication authentication) {
          // do stuff
      }
  
  }
  </code></pre>
  
  <p>If I put the @Component on the MyDaoAuthenticationProvider class and I add the @Autowired annotation in the SecurityConfig class:</p>
  
  <pre><code>@Autowired
  MyDaoAuthenticationProvider provider;
  </code></pre>
  
  <p>the application crash on the start with this error:</p>
  
  <pre><code>org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'myDaoAuthenticationProvider' defined in file [...\MyDaoAuthenticationProvider.class]: Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: A UserDetailsService must be set
      at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1578)
      at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:545)
      at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
      at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
      at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
      at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
      at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
      at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772)
      at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839)
      at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538)
      at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:446)
      at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:328)
      at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107)
      at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4812)
      at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5255)
      at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
      at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1408)
      at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1398)
      at java.util.concurrent.FutureTask.run(FutureTask.java:266)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
      at java.lang.Thread.run(Thread.java:745)
  Caused by: java.lang.IllegalArgumentException: A UserDetailsService must be set
      at org.springframework.util.Assert.notNull(Assert.java:115)
      at org.springframework.security.authentication.dao.DaoAuthenticationProvider.doAfterPropertiesSet(DaoAuthenticationProvider.java:105)
      at org.springframework.security.authentication.dao.AbstractUserDetailsAuthenticationProvider.afterPropertiesSet(AbstractUserDetailsAuthenticationProvider.java:122)
      at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1637)
      at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1574)
      ... 21 more
  </code></pre>
  
  <p>What I have to do to resolve this issue?
  Thanks.</p>
  
  <p>EDIT</p>
  
  <p><strong>SOLUTION</strong></p>
  
  <p>Thanks to OrangeDog, I fixed the problem with this implementation:</p>
  
  <pre><code>@Bean
  public MyDaoAuthenticationProvider myAuthProvider() throws Exception {
      MyDaoAuthenticationProvider provider = new MyDaoAuthenticationProvider();
      provider.setPasswordEncoder(passwordEncoder());
      provider.setUserDetailsService(securityService);
      return provider;
  }
  
  @Override
  protected void configure(AuthenticationManagerBuilder auth) throws Exception {
      auth.authenticationProvider(myAuthProvider());
  }
  </code></pre>
  
  <p>With this configuration, the bean is correctly initialized and there's no more the error "java.lang.IllegalArgumentException: A UserDetailsService must be set".</p>
  
  <p>Furthermore, the bean is loaded into the Spring Context, so all the injected components in the DaoAuthenticationProvider are correctly resolved.</p>