如何确保使用Spring @Configuration注释初始化相关配置？

Question

我正在尝试使用@Configuration注释来连接我的应用程序,但我在其中一个初始化程序中不断获得NullPointerException,因为它引用的bean尚未初始化(我认为).我已经尝试在web.xml中指定'root'配置类,并尝试进行包扫描,似乎都不起作用.

抱歉,大代码转储. 我试图生成一组更简单的类来重现这个问题,但当然,当我这样做时,一切都运行良好. 这是我的课程(导入省略):

DataSourceConfig.java:

@Configuration
public class DataSourceConfig {

    public DataSourceConfig() {
        System.err.println("DataSourceConfig constructed...");
    }

    @Bean
    public DataSource dataSource() {
        BasicDataSource bean = new BasicDataSource();
        bean.setDriverClassName("com.mysql.jdbc.Driver");
        bean.setUrl("jdbc:mysql://localhost:3306/observation");
        bean.setUsername("observation");
        bean.setPassword("*******");
        bean.setInitialSize(1);
        bean.setMaxActive(5);
        bean.setTestOnBorrow(true);
        System.err.println("dataSource bean initialized: " + bean.toString());
        return bean;
    }
}

HibernateConfig.java

@Configuration
@Import(DataSourceConfig.class)
public class HibernateConfig {

    public HibernateConfig() {
        System.err.println("HibernateConfig constructing...");
    }

    @Autowired
    private DataSourceConfig dataSourceConfig;

    @Bean
    protected NamingStrategy namingStrategy() {
        return new ImprovedNamingStrategy();
    }

    private AnnotationSessionFactoryBean sessionFactoryBean = null;

    @Bean
    @DependsOn("dataSourceConfig")
    public AnnotationSessionFactoryBean sessionFactory() {
        if (sessionFactoryBean == null) {
            sessionFactoryBean = new AnnotationSessionFactoryBean();
NPE Here--> sessionFactoryBean.setDataSource(dataSourceConfig.dataSource()); 
            sessionFactoryBean.setSchemaUpdate(true);
            sessionFactoryBean.setNamingStrategy(namingStrategy());
            sessionFactoryBean.setPackagesToScan(new String[] {
                    "com.newco.observations.domain",
                    "com.newco.observations.domain.*" });
            Properties props = new Properties();
            props.setProperty("hibernate.default_schema", "observation");
            props.setProperty("hibernate.dialect",
                    "org.hibernate.dialect.MySQLDialect");
            props.setProperty("hibernate.show_sql", "true");
            sessionFactoryBean.setHibernateProperties(props);
            System.err.println("sessionFactory initialized");
        }
        return sessionFactoryBean;
    }

    @Bean
    @DependsOn("dataSourceConfig")
    public JdbcTemplate jdbcTemplate() {
        return new JdbcTemplate(dataSourceConfig.dataSource());
    }

    @Bean
    @DependsOn("sessionFactory")
    public ResourceTransactionManager txManager() {
        HibernateTransactionManager bean = new HibernateTransactionManager();
        bean.setSessionFactory((SessionFactory) sessionFactory().getObject());
        return bean;
    }

    @Bean
    @DependsOn("sessionFactory")
    public HibernateTemplate hibernateTemplate() {
        return new HibernateTemplate((SessionFactory) sessionFactory()
                .getObject());
    }
}

DaoConfig.java:

@Configuration
@Import(HibernateConfig.class)
public class DaoConfig {

    public DaoConfig()
    {
        System.err.println("DaoConfig constructing...");
    }

    private @Autowired HibernateConfig hibernateConfig;

    @Bean
    @DependsOn("hibernateTemplate")
    public PhenomenonGroupDao phenomenonGroupDao()
    {
        PhenomenonGroupDaoImpl bean = new PhenomenonGroupDaoImpl();
        bean.setHibernateTemplate(hibernateConfig.hibernateTemplate());
        return bean;
    }

    @Bean
    @DependsOn("hibernateTemplate")
    public PhenomenonDao phenomenonDao()
    {
        PhenomenonDaoImpl bean = new PhenomenonDaoImpl();
        bean.setHibernateTemplate(hibernateConfig.hibernateTemplate());
        return bean;
    }

    @Bean
    @DependsOn("hibernateTemplate")
    public DiscretePhenomenonDao discretePhenomenonDao()
    {
        DiscretePhenomenonDaoImpl bean = new DiscretePhenomenonDaoImpl();
        bean.setHibernateTemplate(hibernateConfig.hibernateTemplate());
        return bean;
    }


}

您可以从System.err.println和@DependsOn注释中看到一种关于我正在做的事情.

我可以提供完整的日志,如果它有用,但这里是我认为相关的行(有一点格式化,使其更具可读性(可能)):

• 208 [Thread-0] INFO org.springframework.context.annotation.ConfigurationClassEnhancer
• 成功增强了com.bjk.observation.server.config.DaoConfig; 增强的类名是:com.bjk.observation.server.config.DaoConfig $$ EnhancerByCGLIB $$ 96e1956
• 229 [Thread-0] INFO org.springframework.beans.factory.support.DefaultListableBeanFactory
• 在org.springframework.beans.factory.support.DefaultListableBeanFactory@185572a中预先实例化单例:定义bean [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation. internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.annotation.internalPersistenceAnnotationProcessor,daoConfig,com.bjk.observation.server.config.DataSourceConfig#0,dataSource,com.bjk.observation.server.config. HibernateConfig#0,namingStrategy,sessionFactory,jdbcTemplate,txManager,hibernateTemplate,phenomenonGroupDao,phenomenonDao,discretePhenomenonDao]; 工厂层级DaoConfig构建的根...
• 252 [Thread-0] INFO org.springframework.beans.factory.support.DefaultListableBeanFactory
• 在org.springframework.beans.factory.support.DefaultListableBeanFactory@185572a中销毁单身人士:定义bean [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor, org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.annotation.internalPersistenceAnnotationProcessor,daoConfig,com.bjk.observation.server.config.DataSourceConfig#0,数据源,com.bjk.observation.server.config.HibernateConfig# 0,namingStrategy,的sessionFactory,JdbcTemplate的,txManager,的HibernateTemplate,phenomenonGroupDao,phenomenonDao,discretePhenomenonDao]; 工厂层级的根
• 253 [Thread-0] ERROR org.springframework.web.context.ContextLoader
• 上下文初始化失败org.springframework.beans.factory.BeanCreationException:创建名为'daoConfig'的bean时出错:注入自动连接的依赖项失败; 嵌套的例外是org.springframework.beans.factory.BeanCreationException:无法自动装配领域:私人com.bjk.observation.server.config.HibernateConfig com.bjk.observation.server.config.DaoConfig.hibernateConfig; 嵌套的例外是org.springframework.beans.factory.BeanCreationException:错误创建名为"com.bjk.observation.server.config.HibernateConfig#0"豆芽:黄的实例化失败; 嵌套异常是org.springframework.beans.BeanInstantiationException:无法实例bean类[com.bjk.observation.server.config.HibernateConfig]:构造抛出异常; 嵌套异常是java.lang.NullPointerException

Answer 1

我相信问题就在这里：

@Autowired
private DataSourceConfig dataSourceConfig;

您不应该显式地将自己与其他@Configuration带注释的类连接起来，而应该与它们生成的bean 连接起来。春天会为你解决管道问题。

因此，将上面的字段替换为更简单的字段：

@Autowired
private DataSource dataSource;

DataSourceSpring将从中获取DataSourceConfig并透明地将其注入到字段中。

同样，替换

@Autowired 
private HibernateConfig hibernateConfig;

和

@Autowired 
private HibernateTemplate hibernateTemplate;

您会注意到，@Configuration在使用像 之类的工厂 bean 时，这种风格感觉不太好AnnotationSessionFactoryBean，因为您经常必须getObject()自己调用它。有时，使用 XML 配置并将其与 java 配置风格混合起来更自然。