persistence.xml
<?xml version="1.0" encoding="UTF-8"?> <persistence version="2.0" xmlns="http://java.sun.com/xml/ns/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"> <persistence-unit name="jpa-1" transaction-type="RESOURCE_LOCAL"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <!-- <class>helloworld.Customer</class> --> <properties> <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" /> <property name="javax.persistence.jdbc.url" value="jdbc:mysql://x.x.x.x:3306/jpa-test?useUnicode=true&characterEncoding=utf8" /> <property name="javax.persistence.jdbc.user" value="admin" /> <property name="javax.persistence.jdbc.password" value="123456" /> <property name="hibernate.format_sql" value="true" /> <property name="hibernate.show_sql" value="true" /> <property name="hibernate.hbm2ddl.auto" value="update" /> </properties> </persistence-unit> </persistence>
测试代码
package helloworld; import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.EntityTransaction; import javax.persistence.Persistence; public class Main { public static void main(String[] args) { // TODO Auto-generated method stub String persistenceUnitName = "jpa-1"; EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory(persistenceUnitName); EntityManager entityManager = entityManagerFactory.createEntityManager(); EntityTransaction transaction = entityManager.getTransaction(); transaction.begin(); // insert(entityManager); // find(entityManager); // getReference(entityManager); // remove(entityManager); // merge(entityManager); // flush(entityManager); // manyToOnePersist(entityManager); // manyToOneFind(entityManager); // manyToOneRemove(entityManager); manyToOneUpdate(entityManager); transaction.commit(); entityManager.close(); entityManagerFactory.close(); } // 1.插入 private static void insert(EntityManager entityManager) { Customer customer = new Customer(); customer.setEmail("[email protected]"); customer.setLastName("123"); customer.setAge(23); customer.setCla(33); customer.setFf("aa"); customer.setId(10); entityManager.persist(customer); } // 2.查询(注意,如果修改了对象属性,会被提交到数据库) private static void find(EntityManager entityManager) { Customer customer = entityManager.find(Customer.class, 1); System.out.println("----------------"); System.out.println(customer); } // 3.引用查询,在调用对象的时候才执行sql private static void getReference(EntityManager entityManager) { Customer customer = entityManager.getReference(Customer.class, 1); System.out.println("----------------"); System.out.println(customer); } // 4.删除 private static void remove(EntityManager entityManager) { Customer customer = entityManager.find(Customer.class, 2); entityManager.remove(customer); System.out.println("----------------"); } // 5.合并(根据ID判断,存在ID的记录并且数据有变化的则update,不存在则insert) private static void merge(EntityManager entityManager) { Customer customer = new Customer(); customer.setEmail("[email protected]"); customer.setLastName("4"); customer.setAge(2); customer.setCla(2); customer.setFf("3"); Customer customer2 = entityManager.merge(customer);// 没有id,插入数据 System.out.println("----------------" + customer.getId()); System.out.println("----------------" + customer2.getId()); System.out.println(customer.equals(customer2)); Customer customer_1 = new Customer(); customer_1.setEmail("[email protected]"); customer_1.setLastName("4"); customer_1.setAge(21); customer_1.setCla(2); customer_1.setFf("3"); customer_1.setId(5); Customer customer_2 = entityManager.merge(customer_1);// 有id的数据,如果数据有变化则修改 System.out.println("----------------" + customer_1.getId()); System.out.println("----------------" + customer_2.getId()); System.out.println(customer_1.equals(customer_2)); } // 6.将缓存数据刷新到数据库,不执行该方法,需要在执行commit的时候才提交到数据库 private static void flush(EntityManager entityManager) { Customer customer = entityManager.find(Customer.class, 1); System.out.println("----------------"); customer.setAge(1234); entityManager.flush(); System.out.println(customer); } // 7.保存多对一的数据时,建议先保存一的,再保存多的,这样不会多出update语句 private static void manyToOnePersist(EntityManager entityManager) { Order order = new Order(); order.setOrderName("order1"); Order order2 = new Order(); order2.setOrderName("order2"); Customer customer = new Customer(); customer.setEmail("[email protected]"); customer.setLastName("4"); customer.setAge(2); customer.setCla(2); customer.setFf("3"); order.setCustomer(customer); order2.setCustomer(customer); entityManager.persist(customer); entityManager.persist(order); entityManager.persist(order2); } // 8.查询多对一数据 private static void manyToOneFind(EntityManager entityManager) { Order order = entityManager.find(Order.class, 1); System.out.println(order.getOrderName()); System.out.println(order.getCustomer()); order.setOrderName("victor"); } // 9.不能直接删除一的一端,因为有外键关联 private static void manyToOneRemove(EntityManager entityManager) { Customer customer = entityManager.find(Customer.class, 12); entityManager.remove(customer); } // 10.修改多对一数据 private static void manyToOneUpdate(EntityManager entityManager) { Order order = entityManager.find(Order.class, 3); order.setOrderName("vv"); order.getCustomer().setAge(100); } }
Customer类:
package helloworld; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.Table; @Table(name = "JPA_CUSTOMERS") @Entity public class Customer { @Override public String toString() { return "Customer [id=" + id + ", lastName=" + lastName + ", email=" + email + ", age=" + age + ", cla=" + cla + ", ff=" + ff + "]"; } private Integer id; private String lastName; private String email; private int age; private int cla; private String ff; @GeneratedValue(strategy = GenerationType.AUTO) @Id public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public int getCla() { return cla; } public void setCla(int cla) { this.cla = cla; } public String getFf() { return ff; } public void setFf(String ff) { this.ff = ff; } }
Order类:
package helloworld; import javax.persistence.Column; import javax.persistence.ConstraintMode; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.ForeignKey; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.Table; @Table(name = "JPA_ORDER") @Entity public class Order { private Integer id; private String orderName; private Customer customer; @GeneratedValue(strategy = GenerationType.AUTO) @Id public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } @Column(name = "order_name") public String getOrderName() { return orderName; } public void setOrderName(String orderName) { this.orderName = orderName; } //映射单向n-1的关联关系 @JoinColumn(name = "customer_id")//, foreignKey = @ForeignKey(ConstraintMode.NO_CONSTRAINT)) @ManyToOne(fetch=FetchType.LAZY) public Customer getCustomer() { return customer; } public void setCustomer(Customer customer) { this.customer = customer; } @Override public String toString() { return "Order [id=" + id + ", orderName=" + orderName + ", customer=" + customer + "]"; } }