配置jpa

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">
        <!--
        配置使用什么 ORM 产品来作为 JPA 的实现
        . 实际上配置的是  javax.persistence.spi.PersistenceProvider 接口的实现类
        . 若 JPA 项目中只有一个 JPA 的实现产品, 则也可以不配置该节点.
        -->
        <provider>org.hibernate.ejb.HibernatePersistence</provider>

        <!-- 添加持久化类 -->
        <class>com.jpa.main.Customer</class>
        <class>com.jpa.main.Order</class>

        <class>com.jpa.main.Department</class>
        <class>com.jpa.main.Manager</class>

        <class>com.jpa.main.Item</class>
        <class>com.jpa.main.Category</class>

        <!--
        配置二级缓存的策略
        ALL：所有的实体类都被缓存
        NONE：所有的实体类都不被缓存.
        ENABLE_SELECTIVE：标识 @Cacheable(true) 注解的实体类将被缓存
        DISABLE_SELECTIVE：缓存除标识 @Cacheable(false) 以外的所有实体类
        UNSPECIFIED：默认值，JPA 产品默认值将被使用
        -->
        <shared-cache-mode>ENABLE_SELECTIVE</shared-cache-mode>

        <properties>
            <!-- 连接数据库的基本信息 -->
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql:///ssh01"/>
            <property name="javax.persistence.jdbc.user" value="root"/>
            <property name="javax.persistence.jdbc.password" value="wzy123"/>

            <!-- 配置 JPA 实现产品的基本属性. 配置 hibernate 的基本属性 -->
            <property name="hibernate.format_sql" value="true"/>
            <property name="hibernate.show_sql" value="true"/>
            <property name="hibernate.hbm2ddl.auto" value="update"/>

            <!-- 二级缓存相关 -->
            <property name="hibernate.cache.use_second_level_cache" value="true"/>
            <property name="hibernate.cache.region.factory_class" value="org.hibernate.cache.ehcache.EhCacheRegionFactory"/>
            <property name="hibernate.cache.use_query_cache" value="true"/>
        </properties>
    </persistence-unit>
</persistence>

测试类

package com.jpa.main;

import java.util.Date;
import java.util.HashMap;
import java.util.Map;

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) {

        //1. 创建 EntitymanagerFactory
        String persistenceUnitName = "jpa-1";

        Map<String, Object> properites = new HashMap<String, Object>();
        properites.put("hibernate.show_sql", true);

        EntityManagerFactory entityManagerFactory =
                Persistence.createEntityManagerFactory(persistenceUnitName);
                //Persistence.createEntityManagerFactory(persistenceUnitName, properites);
                //使用这个构造器可以添加一些属性
　　　　　　　　　 //但必须是这样的<property name="hibernate.show_sql" value="true"/>

        //2. 创建 EntityManager. 类似于 Hibernate 的 SessionFactory
        EntityManager entityManager = entityManagerFactory.createEntityManager();

        //3. 开启事务
        EntityTransaction transaction = entityManager.getTransaction();
        transaction.begin();

        //4. 进行持久化操作
        Customer customer = new Customer();
        customer.setAge();
        customer.setEmail("tom@atguigu.com");
        customer.setLastName("Tom");
        customer.setBirth(new Date());
        customer.setCreatedTime(new Date());

        entityManager.persist(customer);//保存操作

        //5. 提交事务
        transaction.commit();

        //6. 关闭 EntityManager
        entityManager.close();

        //7. 关闭 EntityManagerFactory
        entityManagerFactory.close();
    }

}

实体类映射

package com.jpa.main;
import java.util.Date;
import java.util.HashSet;
import java.util.Set;

import javax.persistence.Basic;
import javax.persistence.Cacheable;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Transient;

@Table(name="JPA_CUTOMERS")
@Entity
public class Customer {

    private Integer id;
    private String lastName;

    private String email;
    private int age;

    private Date createdTime;
    private Date birth;

    public Customer() {
        // TODO Auto-generated constructor stub
    }

    public Customer(String lastName, int age) {
        super();
        this.lastName = lastName;
        this.age = age;
    }//    @TableGenerator(name="ID_GENERATOR",  //Table主键生成策略，不常用
//            table="jpa_id_generators",
//            pkColumnName="PK_NAME",
//            pkColumnValue="CUSTOMER_ID",
//            valueColumnName="PK_VALUE",
//            allocationSize=100)//id每次增长100
//    @GeneratedValue(strategy=GenerationType.TABLE,generator="ID_GENERATOR")
    //注解一般标注在get方法上
    @GeneratedValue(strategy=GenerationType.AUTO)//生成主键的方式
    @Id
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    @Column(name="LAST_NAME",length=,nullable=false)
    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;
    }
    @Basic//不写默认是这个注解，字段名就是这个名
    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Temporal(TemporalType.TIMESTAMP)//日期格式化@Temporal
    public Date getCreatedTime() {
        return createdTime;
    }

    public void setCreatedTime(Date createdTime) {
        this.createdTime = createdTime;
    }

    @Temporal(TemporalType.DATE)
    public Date getBirth() {
        return birth;
    }

    public void setBirth(Date birth) {
        this.birth = birth;
    }

    //工具方法. 不需要映射为数据表的一列.表示这只是一个普通方法 ，和数据表字段无关
    @Transient
    public String getInfo(){
        return "lastName: " + lastName + ", email: " + email;
    }

    @Override
    public String toString() {
        return "Customer [id=" + id + ", lastName=" + lastName + ", email="
                + email + ", age=" + age + ", createdTime=" + createdTime
                + ", birth=" + birth + "]";
    }

}