Hibernate笔记7--JPA CRUD

Posted 2020-10-04 胡广勤

1.环境搭建,注意包结构的问题,src下建立名为META-INF的文件夹,放persistence.xml,位置放错,读不到会报错.

  1     <?xml version="1.0" encoding="UTF-8"?>
  2      <persistence xmlns="http://java.sun.com/xml/ns/persistence"
  3          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4          xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
  5         http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
  6          version="2.0">
  7 
  8          <!--配置持久化单元  -->
  9          <persistence-unit name="unit" transaction-type="RESOURCE_LOCAL">
 10              <!--配置jpa持久化类提供者  -->
 11              <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
 12              <!--配置数据库 Hibernate基本信息  -->
 13              <properties>
 14                  <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
 15                  <property name="hibernate.connection.url" value="jdbc:mysql:///day581"/>
 16                  <property name="hibernate.connection.username" value="root"/>
 17                  <property name="hibernate.connection.password" value="root"/>
 18                  <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
 19                  <property name="hibernate.hbm2ddl.auto" value="update"/>
 20                  <property name="hibernate.show_sql" value="true"/>
 21                  <property name="hibernate.format_sql" value="true"/>
 22                  <property name="hibernate.connection.isolation" value="4"/>
 23                      <!-- c3p0连接池 -->
 24                  <property name="hibernate.connection.provider_class" value="org.hibernate.connection.C3P0ConnectionProvider"/>
 25              </properties>
 26          </persistence-unit>
 27      </persistence>

2.实体类编写

  1 package huguangqin.com.cnblogs.entity;
  2  import java.io.Serializable;
  3  import javax.persistence.Column;
  4  import javax.persistence.Entity;
  5  import javax.persistence.GeneratedValue;
  6  import javax.persistence.GenerationType;
  7  import javax.persistence.Id;
  8  import javax.persistence.Table;
  9 
 10 @Entity
 11  @Table(name = "cst_customer")
 12  public class Customer implements Serializable {
 13      private static final long serialVersionUID = 1L;
 14 
 15     @Id
 16      @GeneratedValue(strategy = GenerationType.IDENTITY)
 17      @Column(name = "cust_id")
 18      private Long custId;
 19 
 20     @Column(name = "cust_name")
 21      private String custName;
 22 
 23     @Column(name = "cust_source")
 24      private String custSource;
 25 
 26     @Column(name = "cust_industry")
 27      private String custIndustry;
 28 
 29     @Column(name = "cust_level")
 30      private String custLevel;
 31 
 32     @Column(name = "cust_address")
 33      private String custAddress;
 34 
 35     @Column(name = "cust_phone")
 36      private String custPhone;
 37 
 38     public Long getCustId() {
 39          return custId;
 40      }
 41 
 42     public void setCustId(Long custId) {
 43          this.custId = custId;
 44      }
 45 
 46     public String getCustName() {
 47          return custName;
 48      }
 49 
 50     public void setCustName(String custName) {
 51          this.custName = custName;
 52      }
 53 
 54     public String getCustSource() {
 55          return custSource;
 56      }
 57 
 58     public void setCustSource(String custSource) {
 59          this.custSource = custSource;
 60      }
 61 
 62     public String getCustIndustry() {
 63          return custIndustry;
 64      }
 65 
 66     public void setCustIndustry(String custIndustry) {
 67          this.custIndustry = custIndustry;
 68      }
 69 
 70     public String getCustLevel() {
 71          return custLevel;
 72      }
 73 
 74     public void setCustLevel(String custLevel) {
 75          this.custLevel = custLevel;
 76      }
 77 
 78     public String getCustAddress() {
 79          return custAddress;
 80      }
 81 
 82     public void setCustAddress(String custAddress) {
 83          this.custAddress = custAddress;
 84      }
 85 
 86     public String getCustPhone() {
 87          return custPhone;
 88      }
 89 
 90     public void setCustPhone(String custPhone) {
 91          this.custPhone = custPhone;
 92      }
 93 
 94     // toString
 95      @Override
 96      public String toString() {
 97          return "Customer [custId=" + custId + ", custName=" + custName + ", custSource=" + custSource
 98                  + ", custIndustry=" + custIndustry + ", custLevel=" + custLevel + ", custAddress=" + custAddress
 99                  + ", custPhone=" + custPhone + "]";
100      }
101 
102 }
103 

3.工具类-JPAUtil,用于启动创建一次EntityManagerFactory,并获取EntityManager
   

  1  package huguangqin.com.cnblogs.util;
  2      import javax.persistence.EntityManager;
  3      import javax.persistence.EntityManagerFactory;
  4      import javax.persistence.Persistence;
  5 
  6     public class JPAUtil {
  7          private static EntityManagerFactory factory;
  8 
  9         static {
 10              factory = Persistence.createEntityManagerFactory("unit");
 11          }
 12 
 13         public static EntityManager getEntityManager() {
 14              return factory.createEntityManager();
 15          }
 16      }
 17 

4.测试代码

  1 package huguangqin.com.cnblogs.demo;
  2 
  3 import javax.persistence.EntityManager;
  4  import javax.persistence.EntityTransaction;
  5 
  6 import org.junit.Test;
  7 
  8 import huguangqin.com.cnblogs.entity.Customer;
  9  import huguangqin.com.cnblogs.util.JPAUtil;
 10 
 11 /**
 12   * 保存一个数据到客户表中:persist
 13   */
 14  public class JPATest1 {
 15      @Test
 16      public void addTest() {
 17          // 获取EntityManager
 18          EntityManager em = JPAUtil.getEntityManager();
 19          // 得到事务对象
 20         EntityTransaction et = em.getTransaction();
 21          // 开启事务
 22         et.begin();
 23          // CRUD
 24          Customer cust = new Customer();
 25          cust.setCustName("阿里");
 26          // 持久化
 27         em.persist(cust);
 28          // 提交事务
 29         et.commit();
 30          // 关闭资源
 31         em.close();
 32      }
 33 
 34     /**
 35       * 根据id查询:find
 36       */
 37      @Test
 38      public void findTest() {
 39          // 获取EntityManager
 40          EntityManager em = JPAUtil.getEntityManager();
 41          // 得到事务对象
 42         EntityTransaction et = em.getTransaction();
 43          // 开启事务
 44         et.begin();
 45          // 根据ID查询
 46         Customer customer = em.find(Customer.class, 1L);
 47          System.out.println(customer);
 48 
 49         // 提交事务
 50         et.commit();
 51          // 关闭资源
 52         em.close();
 53      }
 54 
 55     /**
 56       * 延迟加载测试(getReference),用到的时候才发送sql
 57       */
 58     @Test
 59      public void delayTest() {
 60          // 获取EntityManager
 61          EntityManager em = JPAUtil.getEntityManager();
 62          // 获取事务对象
 63         EntityTransaction et = em.getTransaction();
 64         // 开启事务
 65         et.begin();
 66          // 延迟加载
 67         Customer cust = em.getReference(Customer.class, 1L);
 68          System.out.println(cust);
 69          // 提交事务
 70         et.commit();
 71          // 关闭资源
 72         em.close();
 73      }
 74 
 75     /**
 76       * 修改:查询-修改(setter)
 77       */
 78      @Test
 79      public void updateTest() {
 80          // 获取EntityManager
 81          EntityManager em = JPAUtil.getEntityManager();
 82          // 获取事务对象
 83         EntityTransaction et = em.getTransaction();
 84          // 开启事务
 85         et.begin();
 86          // 修改
 87         Customer cust = em.find(Customer.class, 1L);
 88          cust.setCustName("Tecent");
 89 
 90         // 提交事务
 91         et.commit();
 92          // 关闭资源
 93         em.close();
 94      }
 95 
 96     /**
 97       *删除 remove
 98       */
 99      @Test
100      public void delTest() {
101          // 获取EntityManager
102          EntityManager em = JPAUtil.getEntityManager();
103          // 获取事务对象
104         EntityTransaction et = em.getTransaction();
105          // 开启事务
106         et.begin();
107          // 删除
108         Customer cust = em.find(Customer.class, 1L);
109          em.remove(cust);
110          // 提交事务
111         et.commit();
112          // 关闭资源
113         em.close();
114      }
115  }
116