Autowired property is null - Spring Boot Configuration

问题

I am stuck with null values in an autowired property. I am hoping I could get some help.

We are using for the project spring-boot version 0.5.0.M6.

The four configuration files with beans are in one package and are sorted by "area":

Data source configuration
Global method security configuration (as we use Spring-ACL)
MVC configuration
Spring Security configuration

The main method that bootstraps everything is in the following file:

@EnableAspectJAutoProxy
@EnableSpringConfigured
@EnableAutoConfiguration(exclude = {
    DataSourceTransactionManagerAutoConfiguration.class,
    HibernateJpaAutoConfiguration.class,
    JpaRepositoriesAutoConfiguration.class,
    SecurityAutoConfiguration.class,
    ThymeleafAutoConfiguration.class,
    ErrorMvcAutoConfiguration.class,
    MessageSourceAutoConfiguration.class,
    WebSocketAutoConfiguration.class
})
@Configuration
@ComponentScan
public class IntegrationsImcApplication {

    public static void main(String[] args) throws Exception {
        ApplicationContext ctx = SpringApplication.run(
                IntegrationsImcApplication.c lass, args);
    }
}

The first file that holds the data source configuration beans is as follows (I have omitted some method body parts to make it more readable):

@EnableTransactionManagement(mode = AdviceMode.ASPECTJ)
@Configuration
public class RootDataSourceConfig 
        extends TomcatDataSourceConfiguration 
        implements TransactionManagementConfigurer {

    @Override
    public DataSource dataSource() {
        return jpaDataSource();
    }

    public PlatformTransactionManager annotationDrivenTransactionManager() {
        return jpaTransactionManager();
    }

    @Bean
    public HibernateExceptionTranslator hibernateExceptionTranslator() {
        return new HibernateExceptionTranslator();
    }

    @Bean(name="jpaDataSource")
    public DataSource jpaDataSource() {......}

    @Bean(name = {"transactionManager","txMgr"})
    public JpaTransactionManager jpaTransactionManager() {......}

    @Bean(name = "entityManagerFactory")
    public EntityManagerFactory jpaEmf() {......}
}

And here is the next configuration file, that depends on the data source from above. It has about 20 beans related to ACL configuration, but it fails on the firsts bean that uses data source:

@EnableGlobalMethodSecurity(prePostEnabled = true)
@Configuration
public class RootGlobalMethodSecurityConfig 
        extends GlobalMethodSecurityConfiguration 
        implements Ordered {

    @Autowired
    public DataSource dataSource;

    @Override
    public int getOrder() {
        return IntegrationsImcApplication.ROOT_METHOD_SECURITY_CO NFIG_ORDER;
    }

    @Bean
    public MutableAclService aclService() 
            throws CacheException, IOException {

        MutableJdbcAclService aclService = new MutableJdbcAclService(
                dataSource, aclLookupStrategy(), aclCache());
        aclService.setClassIdentityQuery("SELECT @@IDENTITY");
        aclService.setSidIdentityQuery("SELECT @@IDENTITY");
        return aclService;
    }

    ...................................
}

Basically invoking aclService() throws an error as dataSource is null. We have tried ordering the configuration files by implementing the Ordered interface. We also tried using @AutoConfigureAfter(RootDataSourceConfig.class) but this did not help either. Instead of doing @Autowired on the DataSource we also tried injecting the RootDataSourceConfig class itself, but it was still null. We tried using @DependsOn and @Ordered on those beans but again no success. It seems like nothing can be injected into this configuration.

The console output at the startup is listing the beans in the order we want them, with data source being the first. We are pretty much blocked by this.

Is there anything weird or unique we are doing here that is not working? If this is as designed, then how could we inject data source differently?

Repo: github

回答1:

Eager initialization of a bean that depends on a DataSource is definitely the problem. The root cause is nothing to do with Spring Boot or autoconfiguration, but rather plain old-fashioned chicken and egg - method security is applied via an aspect which is wrapped around your business beans by a BeanPostProcessor. A bean can only be post processed by something that is initialized very early. In this case it is too early to have the DataSource injected (actually the @Configuration class that needs the DataSource is instantiated too early to be wrapped properly in the @Configuration processing machinery, so it cannot be autowired). My proposal (which only gets you to the same point with the missing AuthenticationManager) is to declare the GlobalMethodSecurityConfiguration as a nested class instead of the one that the DataSource is needed in:

@EnableGlobalMethodSecurity(prePostEnabled = true)
@Configuration
protected static class ActualMethodSecurityConfiguration extends GlobalMethodSecurityConfiguration {

    @Autowired
    @Qualifier("aclDaoAuthenticationProvider")
    private AuthenticationProvider aclDaoAuthenticationProvider;

    @Autowired
    @Qualifier("aclAnonymousAuthenticationProvider")
    private AnonymousAuthenticationProvider aclAnonymousAuthenticationProvider;

    @Autowired
    @Qualifier("aclExpressionHandler")
    private MethodSecurityExpressionHandler aclExpressionHandler;

    @Override
    protected void configure(AuthenticationManagerBuilder auth)
            throws Exception {
        auth.authenticationProvider(aclDaoAuthenticationProvider);
        auth.authenticationProvider(aclAnonymousAuthenticationProvider);
    }

    @Override
    public MethodSecurityExpressionHandler createExpressionHandler() {
        return aclExpressionHandler;
    }

}

i.e. stick that inside the RootMethodSecurityConfiguration and remove the @EnableGlobalMethodSecurity annotation from that class.

回答2:

I might have resolved the problem.

GlobalMethodSecurityConfiguration.class has the following setter that tries to autowire permission evaluators:

@Autowired(required = false)
public void setPermissionEvaluator(List<PermissionEvaluator> permissionEvaluators) {
    ....
}

And in my case the aclPermissionEvaluator() bean needs aclService() bean, which in turn depends on another autowired property: dataSource. Which seems not to be autowired yet.

To fix this I implemented BeanFactoryAware and get dataSource from beanFactory instead:

public class RootMethodSecurityConfiguration extends GlobalMethodSecurityConfiguration implements BeanFactoryAware {

    private DataSource dataSource;

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        this.dataSource = beanFactory.getBean("dataSource", DataSource.class);
    }
    ....
}

After this, other exception showed up, whereSecurityAutoConfiguration.class is complaining about missing AuthenticationManager, so I just excluded it from @EnableAutoConfiguration. I am not sure if its ideal, but I have custom security configuration, so this way everything works ok.

来源：https://stackoverflow.com/questions/20856825/autowired-property-is-null-spring-boot-configuration

标签

java

spring-boot

configuration

nullpointerexception

autowired