我正準備進行Oracle JPAD認證,所以我在Java SE環境中使用實體玩弄了一點點(至少,這是我的想法...)。我注意到了一些我希望有人能夠闡明的東西。Java SE環境中的JPA:在persistence.xml中加載的實體類沒有defenition
Pro JPA2是我正在閱讀的書。在第2章結尾的某處,有一個示例persistence.xml文件,其中定義了一個類。好吧,所以這是在Java SE環境中的方法,因爲你並不是真的在容器中放置整個shebang。但是這裏有一件奇怪的事情:我有兩個使用@Entity註解的Entity類,並沒有將這些添加到persistence.xml中。但仍然是被加載!我gobsmacked。我現在能想到的唯一的事情是,我不是在SE環境或者它是一個新的休眠功能...
的persistence.xml:
<?xml version="1.0" encoding="UTF-8" ?>
<persistence xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0" xmlns="http://java.sun.com/xml/ns/persistence">
<persistence-unit name="employees" transaction-type="RESOURCE_LOCAL">
<properties>
<property name="javax.persistence.jdbc.driver" value="org.hsqldb.jdbcDriver" />
<property name="javax.persistence.jdbc.url" value="jdbc:hsqldb:mem:." />
<property name="javax.persistence.jdbc.user" value="SA" />
<property name="javax.persistence.jdbc.password" value="" />
<property name="hibernate.show_sql" value="false" />
<property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect" />
<property name="hibernate.connection.shutdown" value="true" />
<property name="hibernate.hbm2ddl.auto" value="create-drop" />
</properties>
</persistence-unit>
</persistence>
實體:
@Entity
@Access(AccessType.FIELD)
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private Date startDate;
private Long salary;
public Employee() {
}
public Employee(String name) {
this.name = name;
}
public Employee(String name, Long salary) {
this.name = name;
this.salary = salary;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Date getStartDate() {
return startDate;
}
public void setStartDate(Date startDate) {
this.startDate = startDate;
}
public Long getSalary() {
return salary;
}
public void setSalary(Long salary) {
this.salary = salary;
}
@Override
public String toString() {
return "Employee [name=" + name + ", salary=" + salary + ", startDate=" + startDate + "]";
}
}
測試:
public class TestConnection {
private static EntityManagerFactory entityManagerFactory;
private static EntityManager entityManager;
private static final String PERSISTENCE_UNIT_NAME = "employees";
@BeforeClass
public static void initEntityManager() throws Exception {
entityManagerFactory = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
entityManager = entityManagerFactory.createEntityManager();
TableStructurePrinter.outputTableStructure(entityManager);
}
@AfterClass
public static void closeEntityManager() {
entityManager.close();
entityManagerFactory.close();
}
@BeforeMethod
public void setupDB() throws Exception {
entityManager.getTransaction().begin();
LoadEmployees.load(entityManager, 4);
}
@AfterMethod
public void cleanDB() throws Exception {
entityManager.getTransaction().rollback();
}
@Test
public void testCountEmployees() {
Query q = entityManager.createQuery("select e from Employee e");
assertEquals(q.getResultList().size(), 4);
}
}
從我TableStructurePrinter輸出(這是從INFORMA一個簡單的SELECT語句TION_SCHEMA.SYSTEM_TABLES和INFORMATION_SCHEMA.SYSTEM_COLUMNS):
T.TABLE_TYPE T.TABLE_NAME C.ORDINAL_POSITION C.COLUMN_NAME C.TYPE_NAME C.COLUMN_SIZE
=================== =================== =================== =================== =================== ===================
TABLE EMPLOYEE 1 ID BIGINT 64
TABLE EMPLOYEE 2 NAME VARCHAR 255
TABLE EMPLOYEE 3 SALARY BIGINT 64
TABLE EMPLOYEE 4 STARTDATE TIMESTAMP 26
我認爲你是對的,我甚至沒有意識到一個jar文件是在所有創建...但檢查jar,我看到實體不是直接在根,他們在自己的各自的包。所以現在我實際上有兩個問題:-) - 爲什麼創建了jar? - 爲什麼類加載,即使它們不直接在根中? (對不起,但我無法得到格式在這個答覆中工作...我正在研究它:-)) – Cesar
@Cesar「根」不是根包,但jar文件本身(從上面引述:「持久化單元的根目錄是JAR文件...」),因此即使它們位於該jar中的它們各自的包中也會被發現。爲什麼創建jar取決於你的構建過程,所以你必須查看。 – Thomas