1、JPA-HelloWorld

一、创建JPA工程

POM依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com</groupId>
    <artifactId>jpa</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.14</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.4.1.Final</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-jpamodelgen</artifactId>
            <version>5.4.1.Final</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.ehcache</groupId>
            <artifactId>ehcache</artifactId>
            <version>3.6.3</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <!-- 指定jdk -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

二、persistence.xml 配置

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd"
             version="2.2">
    <persistence-unit name="jpaname" transaction-type="RESOURCE_LOCAL">
        <!--
        配置使用什么 ORM 产品来作为 JPA 的实现
        1. 实际上配置的是  javax.persistence.spi.PersistenceProvider 接口的实现类
        2. 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.jpa.HibernatePersistenceProvider</provider>

        <!-- 添加持久化类 -->
        <class>com.jpa.entity.Customer</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.cj.jdbc.Driver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://xxx.xxx.xxx.xxx/jpa?useSSL=false"/>
            <property name="javax.persistence.jdbc.user" value="xxx"/>
            <property name="javax.persistence.jdbc.password" value="xxx"/>

            <!-- 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>

三、实体类

package com.jpa.entity;

import javax.persistence.*;

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

    private Integer id;
    private String lastName;
    private String email;
    private int age;

    public Customer() {}

    public Customer(String lastName, int age) {
        super();
        this.lastName = lastName;
        this.age = age;
    }

    @GeneratedValue(strategy = GenerationType.AUTO)
    @Id
    public Integer getId() {
        return id;
    }

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

    @Column(name = "LAST_NAME", length = 50, nullable = false)
    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    @Basic
    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;
    }

    @Override
    public String toString() {
        return "Customer{" +
                "id=" + id +
                ", lastName='" + lastName + '\'' +
                ", email='" + email + '\'' +
                ", age=" + age +
                '}';
    }
}

四、测试

package com.jpa;

import com.jpa.entity.Customer;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
import java.util.HashMap;
import java.util.Map;

public class Main {

    public static void main(String[] args) {

        //1. 创建 EntitymanagerFactory
        String persistenceUnitName = "jpaname";

        Map<String, Object> properites = new HashMap<String, Object>(10);
        properites.put("hibernate.show_sql", true);

        EntityManagerFactory entityManagerFactory =
                Persistence.createEntityManagerFactory(persistenceUnitName);
//                Persistence.createEntityManagerFactory(persistenceUnitName, properites);

        //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(12);
        customer.setEmail("[email protected]");
        customer.setLastName("Tom");

        entityManager.persist(customer);

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

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

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

项目结构

结果