spring-data JPA demo例子。jpa超简易例子。

最新推荐文章于 2023-03-22 02:41:49 发布

异世界指挥官

最新推荐文章于 2023-03-22 02:41:49 发布

阅读量259

点赞数

文章标签： jpa spring hibernate mysql

本文链接：https://blog.youkuaiyun.com/SacredOath/article/details/117471247

版权

本文通过一个简单的例子展示了Spring Data JPA相较于MyBatis的便利之处，如何实现几乎零代码的数据访问。包括了maven依赖、Spring配置、Repository接口的DSL查询方法、Lombok加持的实体类以及测试环节。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

jpa比mybatis简单太多了。加之spring-data，可以实现全自动的数据访问功能，几乎不用写代码。

1. maven依赖

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
			<version>4.2.9.RELEASE</version>
		</dependency>

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>4.2.9.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-orm</artifactId>
			<version>4.2.9.RELEASE</version>
			<type>jar</type>
			<scope>compile</scope>
		</dependency>
				<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
		<dependency>
		    <groupId>mysql</groupId>
		    <artifactId>mysql-connector-java</artifactId>
		    <version>5.1.38</version>
		</dependency>
				

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-test</artifactId>
			<version>4.2.9.RELEASE</version>
			<type>jar</type>
			<scope>test</scope>
		</dependency>
				<dependency>
	        <groupId>junit</groupId>
	        <artifactId>junit</artifactId>
	        <version>4.12</version>
	    </dependency>
		<!-- https://mvnrepository.com/artifact/com.mchange/c3p0 -->
		<dependency>
		    <groupId>com.mchange</groupId>
		    <artifactId>c3p0</artifactId>
		    <version>0.9.5.2</version>
		</dependency>
				<!-- https://mvnrepository.com/artifact/javax.persistence/javax.persistence-api -->
		<dependency>
		    <groupId>javax.persistence</groupId>
		    <artifactId>javax.persistence-api</artifactId>
		    <version>2.2</version>
		</dependency>
				<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
		<dependency>
		    <groupId>org.projectlombok</groupId>
		    <artifactId>lombok</artifactId>
		    <version>1.18.12</version>
		    <scope>provided</scope>
		</dependency>
		<!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core -->
		<dependency>
		    <groupId>org.hibernate</groupId>
		    <artifactId>hibernate-core</artifactId>
		    <version>4.3.8.Final</version>
		</dependency>
        
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>4.3.11.Final</version>
        </dependency>

		<!-- https://mvnrepository.com/artifact/org.hibernate.javax.persistence/hibernate-jpa-2.1-api -->
		<dependency>
		    <groupId>org.hibernate.javax.persistence</groupId>
		    <artifactId>hibernate-jpa-2.1-api</artifactId>
		    <version>1.0.0.Final</version>
		</dependency>
				
		<!-- https://mvnrepository.com/artifact/org.springframework.data/spring-data-jpa -->
		<dependency>
		    <groupId>org.springframework.data</groupId>
		    <artifactId>spring-data-jpa</artifactId>
		    <version>1.4.2.RELEASE</version>
		</dependency>

2. spring配置类

@Configuration
@ComponentScan(basePackages="hzz.mall")
@EnableJpaRepositories(basePackages="hzz.mall.repository")
public class RootConfiguration {

	//配置c3p0数据库连接池
    @Bean
    public DataSource dataSource() throws PropertyVetoException{
        ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource();
        comboPooledDataSource.setDriverClass("com.mysql.jdbc.Driver");
        comboPooledDataSource.setJdbcUrl("jdbc:mysql://127.0.0.1:3306/try1?useUnicode=true&characterEncoding=utf8&useSSL=false");
        comboPooledDataSource.setUser("root");
        comboPooledDataSource.setPassword("root");
        return comboPooledDataSource;
    }
    
    //使用hibernate的jpa适配器
	@Bean
	public JpaVendorAdapter jpaVendorAdapter() {
		HibernateJpaVendorAdapter adapter = new HibernateJpaVendorAdapter();
		adapter.setDatabase(Database.MYSQL);
		return adapter;
	}
	
	//该bean取代了persistence.xml文件。开启包扫描，扫描实体类。注入数据源。
	@Bean
	public LocalContainerEntityManagerFactoryBean entityManagerFactory(JpaVendorAdapter jpaVendorAdapter,DataSource dataSource) {
		LocalContainerEntityManagerFactoryBean emfb = new LocalContainerEntityManagerFactoryBean();
		emfb.setDataSource(dataSource);
		emfb.setPackagesToScan("hzz.mall.domain");
		emfb.setJpaVendorAdapter(jpaVendorAdapter);
		return emfb;
	}
	
	@Bean
	public PlatformTransactionManager transactionManager(){
		return new JpaTransactionManager();
	}
}

3. repository接口

public interface MyUserRepository extends JpaRepository<MyUser, Long> {

    MyUser findUserById(int id);
    
    MyUser getUserByUsername(String username);
    
}

定义方法的语言DSL格式：

find/get表示查询，remove/delete删除
详细规则见官方文档:
Defining Query Methods

4. 实体类

我使用了lombok所以没有写getter/setter等

@Data
@Entity(name="User")
public class MyUser{
	@Id
	private Long id;
	
	private String username;
}

5. 测试

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = RootConfiguration.class)
public class JpaTest {
	
	@Autowired
	private MyUserRepository myUserRepository;
	
	@Test
	public void findAllTest() {
		List<MyUser> findAll = myUserRepository.findAll();
		for (MyUser myUser : findAll) {
			System.out.println(myUser);
		}
	}
}