JPA 增、删、改、查入门实例

package me.cjx.pojo;import java.io.Serializable;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name = "user")public class User implements Serializable {/**     *      */private static final long serialVersionUID = 1L;@Id@GeneratedValue@Column(name = "id")private int id;@Column(name = "name")private String name;@Column(name = "passwd")private String passwd;public User() {}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getPasswd() {return passwd;}public void setPasswd(String passwd) {this.passwd = passwd;}}

package me.cjx.pojo;import java.util.List;import javax.persistence.EntityManager;import javax.persistence.EntityManagerFactory;import javax.persistence.EntityTransaction;import javax.persistence.Persistence;import javax.persistence.Query;public class TestJPA {private static EntityManagerFactory factory = null;private static EntityManager entity = null;public EntityManager getEntityManager() {factory = Persistence.createEntityManagerFactory("JPA");entity = factory.createEntityManager();return entity;}public static void main(String[] args) {User user = new User();TestJPA test = new TestJPA();user.setId(1);user.setName("Robin");user.setPasswd("123456");test.insert(user);user = new User();test.update(user);user = test.findUser(13);test.delete(2);}public void insert(User user) {EntityManager entity = getEntityManager();EntityTransaction tran = entity.getTransaction();tran.begin();entity.persist(user);tran.commit();}public void update(User user) {EntityManager entity = getEntityManager();EntityTransaction tran = entity.getTransaction();tran.begin();entity.merge(user);tran.commit();}public void delete(int id) {EntityManager entity = getEntityManager();EntityTransaction tran = entity.getTransaction();tran.begin();User user = entity.find(User.class, id);entity.remove(user);tran.commit();}public User findUser(int id) {User user = new User();EntityManager entity = getEntityManager();EntityTransaction tran = entity.getTransaction();tran.begin();user = entity.find(User.class, id);tran.commit();return user;}public List<?> findAllUser() {User user = new User();EntityManager entity = getEntityManager();EntityTransaction tran = entity.getTransaction();tran.begin();Query query = entity.createQuery("select o from User o");List<?> list = query.getResultList();for (int i = 0; i < list.size(); i++) {user = (User) list.get(i);System.out.println(user.getId() + "/t" + user.getName() + "/t" + user.getPasswd());}tran.commit();return list;}}