Spring Boot - 环境@Autowired抛出NullPointerException [英] Spring Boot - Environment @Autowired throws NullPointerException

问题描述

我使用 Spring Boot 0.5.0.M5 进行项目设置。

在其中一个配置文件中我试图 @Autowire Environment 但是失败的是 NullPointerException 。

In one of the configuration files I am trying to @Autowire Environment but that fails with a NullPointerException.

以下是我目前的情况：

Application.java

@EnableAutoConfiguration
@Configuration
@ComponentScan
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

JpaConfig.java 其中我正在尝试 @Autowire Environment

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(basePackages = "com.ui.persistence.repository")
public class JpaConfig {
    private static final String DATABASE_DRIVER = "db.driver";
    private static final String DATABASE_PASSWORD = "db.password";
    private static final String DATABASE_URL = "db.url";
    private static final String DATABASE_USERNAME = "db.username";
    private static final String HIBERNATE_DIALECT = "hibernate.dialect";
    private static final String HIBERNATE_SHOW_SQL = "hibernate.show_sql";
    private static final String ENTITYMANAGER_PACKAGES_TO_SCAN 
        = "entitymanager.packages.to.scan";

    @Autowired
    private Environment env;

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName(env.getProperty(DATABASE_DRIVER));
        dataSource.setUrl(env.getProperty(DATABASE_URL));
        dataSource.setUsername(env.getProperty(DATABASE_USERNAME));
        dataSource.setPassword(env.getProperty(DATABASE_PASSWORD));
        return dataSource;
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean entityManagerFactoryBean 
                = new LocalContainerEntityManagerFactoryBean();
        entityManagerFactoryBean.setDataSource(dataSource());
        entityManagerFactoryBean.setPersistenceProviderClass(
                HibernatePersistence.class);
        entityManagerFactoryBean.setPackagesToScan(
                env.getProperty(ENTITYMANAGER_PACKAGES_TO_SCAN));
        entityManagerFactoryBean.setJpaProperties(hibernateProperties());
        return entityManagerFactoryBean;
    }
}

我正在尝试加载在a中配置的数据库属性属性文件。但是， Environment 未注入，代码因 NullPointerException 而失败。我没有XML文件中的任何配置。

I am trying to load the database properties configured in a properties file. However, the Environment is not injected and the code fails with NullPointerException. I do not have any configuration in XML files.

对于属性文件，我已经配置 PropertySourcesPlaceholderConfigurer 这样：

For the properties file I have configured PropertySourcesPlaceholderConfigurer this way:

@Configuration
@PropertySource("classpath:database.properties")
public class PropertyConfig {
    @Bean
    public static PropertySourcesPlaceholderConfigurer propertyPlaceHolderConfigurer() {
        return new PropertySourcesPlaceholderConfigurer();
    }
}

我尝试过交换 @自动装配， @Resource 和 @Inject 但到目前为止还没有任何工作。非常感谢任何帮助。谢谢。

I have tried swapping @Autowired, @Resource and @Inject but nothing has worked so far. Would appreciate any help. Thanks.

推荐答案

我相信Spring和 EntityManagerFactory ，你可能已经违反了那些（在4.0.0.RC1中修复） - 如果你的 @Configuration 类被超级实例化，它可能没有资格自动装配。您可以从日志输出中判断是否是这种情况。

I believe there were some lifecycle issues with Spring and the EntityManagerFactory, and you might have fallen foul of those (fixed in 4.0.0.RC1) - if your @Configuration class gets instantiated super early, it might not be eligible for autowiring. You can probably tell from the log output if that is the case.

您是否感兴趣，是否知道 JpaConfig提供的功能如果您使用 @EnableAutoConfiguration ，那么和 PropertyConfig 已预先打开当您 @ComponentScan 您的存储库定义的包时？请参阅 JPA以Spring Boot中的示例为例。

Just out of interest, did you know that the functionality provided by your JpaConfig and PropertyConfig is already presetn out of the box if you use @EnableAutoConfiguration (as long as you @ComponentScan that package where your repositories are defined)? See the JPA sample in Spring Boot for an example.

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