JUnit Sample for Spring3 annotation using JPA with Hibernate－Jemmy Walker

　　剛學技術時，SQL學得最好，Log是最差，現在反而倒過來了，對ORM產品上手特別鈍感，這也許我很快先學會iBatis的緣故，慣用SQL操作，卻沒有物件對映到資料庫的概念。以下飯粒只是用JUnit很簡單的存取一個Accounts table裡名字欄位，因為併使Spring3的annotation context、JPA using Hibernate，試完後，真的會癱掉：

　　使用AnnotationConfigContext載入Config類別進行JUnit，其測試程式如下：

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(loader = AnnotationConfigContextLoader.class,
        value = "com.foo.dao.BaseDaoConfig")
public class TestBaseDaoImpl {
    @Autowired
    private IBaseDao<Accounts> baseDao;
    @Test
    public void testDao() {
        List<Accounts> accounts =
            baseDao.find("from Accounts a where a.id = ?", new Integer(1));
        assertNotNull(accounts);
        assertEquals(accounts.size(), 1);
        for (Accounts account : accounts) {
            System.out.println(account.getName_tw());
        }
    }
} (figure 1)

　　上例是很一般的DAO的使用，但在JPA寫法有幾點要特別注意，一個是Value Object，要宣告@Entity才能被JPA取得如下片段：

@Entity
@Table(name = "_Accounts")
public class Accounts {
    @Column(name = "id")
    private Integer id;
    @Column(name = "name_tw")
    private String name_tw;
    // get/set...
} (figure 2)

　　再來就是DAO的寫法：第一個要注意的是@PersistenceContext的注入；第二個是JPQL是不同於一般SQL，from後面是接Class Name(上述@Entity)而不是Table Name(@Table)，可以從from後開始寫，若要用Select，則是Select a from Accounts a where a.id=?，不能用Select *，要用別名不帶欄位。

public class BaseDaoImpl<T> implements IBaseDao<T> {
@PersistenceContext
protected EntityManager em;

    @SuppressWarnings("unchecked")
    public List<T> find(String jpql, Object param) {
        return em.createQuery(jpql).setParameter(1, param).getResultList();
    }
} (figure 3)

　　接著是怎麼用Config類別載入JPA設定。過程是TestBaseDaoImpl(figure 1)—>AnnotationConfigContextLoader—>BaseDaoConfig(figure 4)—>RootConfig(figure 5)—>load resources.xml。有關JPA設定就藏在resources.xml了.

BaseDaoConfig.java

@Configuration
@Import(RootConfig.class)
public class BaseDaoConfig {
    @Bean
    public IBaseDao iBaseDao() {
        return new BaseDaoImpl();
    }
}

(figure 4)

RootConfig.java

@Configuration
@ImportResource("classpath:resources.xml")
public class RootConfig {
    private @Value("#{jdbcProperties.driverClassName}") String driverClass;
    private @Value("#{jdbcProperties.url}") String jdbcUrl;
    private @Value("#{jdbcProperties.username}") String username;
    private @Value("#{jdbcProperties.password}") String password;

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName(this.driverClass);
        dataSource.setUrl(this.jdbcUrl);
        dataSource.setUsername(this.username);
        dataSource.setPassword(this.password);
        return dataSource;
    }
} (figure 5)

　　resources.xml設定內容：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:tx="http://www.springframework.org/schema/tx"
        xmlns:util="http://www.springframework.org/schema/util"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
http://www.springframework.org/schema/util
http://www.springframework.org/schema/util/spring-util-3.0.xsd">
    <util:properties id="jdbcProperties" location="classpath:jdbc.properties"/>
    <tx:annotation-driven/>

<bean
        class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />
    
    <bean id="emf"
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"
        destroy-method="destroy">
        <property name="dataSource" ref="dataSource" />
        <property name="jpaVendorAdapter"> 
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"/>
        </property>
        <property name="jpaProperties">     
            <props>
                <prop key="showSql">true</prop>
                <prop key="generateDdl">true</prop>
                <prop key="databasePlatform">org.hibernate.dialect.Oracle10gDialect</prop>
                <prop key="hibernate.query.factory_class"> 
                    org.hibernate.hql.classic.ClassicQueryTranslatorFactory
                </prop>
            </props>
        </property>
    </bean>
    <bean id="transactionManager"
        class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="dataSource" ref="dataSource"/>
        <property name="entityManagerFactory"
            ref="emf" />
    </bean>
</beans>