JPA环境搭建及基础映射
?1，先加入必要库：2，在类路径下建立一个src/META-INF/persistence.xml文件，如下图：3，persistence.xml文件中放入如下内容：

?注：数据库连接和密码需要修改成自己对应的3，写实体类：
package junit.test;import java.util.Date;import java.util.List;import javax.persistence.EntityManager;import javax.persistence.EntityManagerFactory;import javax.persistence.Persistence;import javax.persistence.Query;import org.junit.Test;import com.jerval.jpa.domain.Person;import com.jerval.jpa.domain.PersonGender;public class PersonTest {/* * 增，删，改都必须要有事务支持，否则不能执行 */@Testpublic void save() {EntityManagerFactory factory = Persistence.createEntityManagerFactory("jerval");EntityManager em = factory.createEntityManager();em.getTransaction().begin();Person person = new Person();// person.setId("aaa");person.setName("杰威");person.setPersonGender(PersonGender.WOMAN);person.setBirthday(new Date());person.setInfo("测试一下大文本方式来放文本信息");em.persist(person);em.getTransaction().commit();em.close();factory.close();}// 相当于Hibernate中的get方法@Testpublic void find() {EntityManagerFactory factory = Persistence.createEntityManagerFactory("jerval");EntityManager em = factory.createEntityManager();em.getTransaction().begin();Person person = em.find(Person.class, 1);System.out.println(person.getName());em.getTransaction().commit();em.close();factory.close();}// 相当于Hibernate中的load方法@Testpublic void reference() {EntityManagerFactory factory = Persistence.createEntityManagerFactory("jerval");EntityManager em = factory.createEntityManager();em.getTransaction().begin();Person person = em.getReference(Person.class, 1);System.out.println(person.getName());em.getTransaction().commit();em.close();factory.close();}@Testpublic void update() {EntityManagerFactory factory = Persistence.createEntityManagerFactory("jerval");EntityManager em = factory.createEntityManager();em.getTransaction().begin();Person person = em.find(Person.class, 1);person.setName("aaa");em.getTransaction().commit();em.close();factory.close();}@Testpublic void delete() {EntityManagerFactory factory = Persistence.createEntityManagerFactory("jerval");EntityManager em = factory.createEntityManager();em.getTransaction().begin();Person person = em.find(Person.class, 1);em.remove(person);em.getTransaction().commit();em.close();factory.close();}@SuppressWarnings("unchecked")@Testpublic void query() {EntityManagerFactory factory = Persistence.createEntityManagerFactory("jerval");EntityManager em = factory.createEntityManager();/* * 采用占位查询，问号后的数字可以指定参数的开始索引 Query query = * em.createQuery("select o from Person o where id = ?100"); * query.setParameter(100, 2); *//* 采用命名空间查询 */// Query query =// em.createQuery("select o from Person o where o.id = :id");Query query = em.createQuery("select o from Person o ");// query.setParameter("id", 1);// query.setParameter("name", 1);// Person person = (Person) query.getSingleResult();List<Person> persons = query.getResultList();for (Person person : persons) {System.out.println(person.getName());}// query = em.createQuery("select count(*) from Person");也可以// query = em.createQuery("select count(o) from Person o where 1=1");// System.out.println(query.getSingleResult());em.close();factory.close();}@Testpublic void deleteQuery() {EntityManagerFactory factory = Persistence.createEntityManagerFactory("jerval");EntityManager em = factory.createEntityManager();em.getTransaction().begin();Query query = em.createQuery("delete from Person o where o.id = :id");query.setParameter("id", 3);query.executeUpdate();em.getTransaction().commit();em.close();factory.close();}@Testpublic void updateQuery() {EntityManagerFactory factory = Persistence.createEntityManagerFactory("jerval");EntityManager em = factory.createEntityManager();em.getTransaction().begin();Query query = em.createQuery("update Person o set o.name=:name where o.id = :id");query.setParameter("name", "aaaa");query.setParameter("id", 2);query.executeUpdate();em.getTransaction().commit();em.close();factory.close();}}
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