Spring 数据 JPA Repository @autowired 给出 null

Question

我一直在试用 spring-data-jpa。在Reference Documentation的帮助下和我之前的 spring 知识，我已经设置了 spring-data-jpa 配置，但是我 @Autowired 的 Repository 总是返回 null。我在这里提到了其他问题，但我还没有找到解决方案。

我的ApplicationContext配置是

@Configuration
@EnableJpaRepositories("devopsdistilled.operp.server.data")
@EnableTransactionManagement
@PropertySource("server/jdbc.properties")
@ComponentScan("devopsdistilled.operp.server.data")
public class JpaContext {

    @Inject
    private Environment env;

    @Value("devopsdistilled.operp.server.data.entity")
    private String packagesToScan;

    @Bean
    public static PropertySourcesPlaceholderConfigurer getPropertySourcesPlaceholderConfigurer() {
        return new PropertySourcesPlaceholderConfigurer();
    }

    @Bean
    public DataSource dataSource() {
        BasicDataSource dataSource = new BasicDataSource();
        dataSource.setDriverClassName(env.getProperty("jdbc.driverClassName"));
        dataSource.setUrl(env.getProperty("jdbc.url"));
        dataSource.setUsername(env.getProperty("jdbc.username"));
        dataSource.setPassword(env.getProperty("jdbc.password"));
        dataSource.setInitialSize(2);
        dataSource.setMaxActive(10);
        return dataSource;
    }

    @Bean
    public JpaVendorAdapter jpaVendorAdapter() {
        HibernateJpaVendorAdapter jpaVendorAdapter = new HibernateJpaVendorAdapter();
        jpaVendorAdapter.setDatabase(Database.MYSQL);
        jpaVendorAdapter.setGenerateDdl(true);
        jpaVendorAdapter.setShowSql(true);
        jpaVendorAdapter
                .setDatabasePlatform("org.hibernate.dialect.MySQL5Dialect");
        return jpaVendorAdapter;
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean emf = new LocalContainerEntityManagerFactoryBean();
        emf.setDataSource(this.dataSource());
        emf.setJpaVendorAdapter(this.jpaVendorAdapter());
        emf.setPackagesToScan(packagesToScan);
        emf.setJpaProperties(this.hibernateProperties());
        return emf;
    }

    @Bean
    public JpaDialect jpaDialect() {
        return new HibernateJpaDialect();
    }

    @Bean
    public JpaTransactionManager transactionManager() {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(entityManagerFactory()
                .getObject());
        transactionManager.setJpaDialect(jpaDialect());
        return transactionManager;
    }

    @Bean
    public Properties hibernateProperties() {
        Properties hibernateProps = new Properties();
        hibernateProps.setProperty("hibernate.hbm2ddl.auto", "create");
        return hibernateProps;
    }

    @Bean
    public PersistenceExceptionTranslationPostProcessor exceptionTranslationPostProcessor() {
        return new PersistenceExceptionTranslationPostProcessor();
    }
}

我的实体定义如下

@Entity
public class Item implements Serializable {<p></p>

<pre><code>private static final long serialVersionUID = 7751126479626962944L;
private Long id;
private String name;

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

@Override
public String toString() {
    return new String("Id: " + getId() + "\nName: " + getName());
}
</code></pre>

<p>}
</p>

我的Repository定义如下

@Repository
public interface ItemRepository extends JpaRepository {
}

虽然我尝试按如下方式运行示例应用程序

<p></p>

<p>public class ServerApp {</p>

<pre><code>@Inject
ItemRepository itemRepository;

public static void main(String[] args) {
    ApplicationContext context = new AnnotationConfigApplicationContext(
            JpaContext.class);
    new ServerApp().sampleMethod();
    System.out.println(context);
}

public void sampleMethod() {
    Item item = new Item();
    item.setName("Test Item");
    item = itemRepository.save(item);
    System.out.println(itemRepository.findOne(item.getId()));
    System.out.println("From sampleMethod");
}
</code></pre>

<p>}
</p>

我在控制台中得到以下输出。

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See <a href="http://www.slf4j.org/codes.html#StaticLoggerBinder" rel="noreferrer noopener nofollow">http://www.slf4j.org/codes.html#StaticLoggerBinder</a> for further details.
Apr 29, 2013 5:31:24 PM org.hibernate.annotations.common.Version 
INFO: HCANN000001: Hibernate Commons Annotations {4.0.1.Final}
Apr 29, 2013 5:31:24 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {4.1.9.Final}
Apr 29, 2013 5:31:24 PM org.hibernate.cfg.Environment 
INFO: HHH000206: hibernate.properties not found
Apr 29, 2013 5:31:24 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
Apr 29, 2013 5:31:24 PM org.hibernate.ejb.Ejb3Configuration configure
INFO: HHH000204: Processing PersistenceUnitInfo [
    name: default
    ...]
Apr 29, 2013 5:31:24 PM org.hibernate.service.jdbc.connections.internal.ConnectionProviderInitiator instantiateExplicitConnectionProvider
INFO: HHH000130: Instantiating explicit connection provider: org.hibernate.ejb.connection.InjectedDataSourceConnectionProvider
Apr 29, 2013 5:31:25 PM org.hibernate.dialect.Dialect 
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQL5Dialect
Apr 29, 2013 5:31:25 PM org.hibernate.engine.transaction.internal.TransactionFactoryInitiator initiateService
INFO: HHH000268: Transaction strategy: org.hibernate.engine.transaction.internal.jdbc.JdbcTransactionFactory
Apr 29, 2013 5:31:25 PM org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory 
INFO: HHH000397: Using ASTQueryTranslatorFactory
Apr 29, 2013 5:31:25 PM org.hibernate.validator.internal.util.Version 
INFO: HV000001: Hibernate Validator 4.3.1.Final
Apr 29, 2013 5:31:25 PM org.hibernate.tool.hbm2ddl.SchemaExport execute
INFO: HHH000227: Running hbm2ddl schema export
Hibernate: drop table if exists Item
Hibernate: create table Item (id bigint not null auto_increment, name varchar(255), primary key (id))
Apr 29, 2013 5:31:25 PM org.hibernate.tool.hbm2ddl.SchemaExport execute
INFO: HHH000230: Schema export complete
Exception in thread "main" java.lang.NullPointerException
    at devopsdistilled.operp.server.ServerApp.sampleMethod(ServerApp.java:27)
    at devopsdistilled.operp.server.ServerApp.main(ServerApp.java:20)

从输出中可以看出，存在 NullPointerException，因此 ItemRepository 不是 Autowired。

我已经为存储库编写了一个测试，如下所示。

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = JpaContext.class)
@Transactional
public class ItemRepositoryTest {<p></p>

<pre><code>@Inject
private ItemRepository itemRepository;
private Item item;

@Before
public void setUp() throws Exception {
    item = new Item();
    item.setName("Test Item");
}

@Test
public void testSave() {
    item = itemRepository.save(item);
    Assert.assertEquals(item, itemRepository.findOne(item.getId()));
}
</code></pre>

<p>}</p>

<p></p>

我的配置中缺少什么？

我该如何解决这个问题？

谢谢

Answer 1

我认为问题出在这一行:

new ServerApp().sampleMethod();

当您从 main 调用时，您仍然可以依赖 Autowiring ，但您需要使用 ApplicationContext 来检索 bean。

像这样:

ServerApp app = context.getBean("ServerApp");  

注意 重要的是要注意这个函数是重载的，所以你可能更幸运地重载

当您使用 new 关键字时，您将绕过 Spring 并使用纯 Java 实例化。