基础

基础

Spring data 提供一个核心接口 CrudRepository 用来提供访问数据库的基本方法，T是访问数据库的实体类，ID是数据库主键数据类型

public interface CrudRepository extends Repository {
 
   S save(S entity);      ①
 
  Optional findById(ID primaryKey); ②
 
  Iterable findAll();               ③
 
  long count();                        ④
 
  void delete(T entity);               ⑤
 
  boolean existsById(ID primaryKey);   ⑥
 
  // … more functionality omitted.
}

① 保存数据
② 根据ID值查找数据
③ 返回所有数据
④ 返回数据的数量
⑤ 删除提供的数据
⑥ 提供的数据是否存在

Spring Data 已经实现了接口的方法，在使用中，只需要提供继承CrudRepository的接口，不需要自己实现相同的方法

下面进行测试

1. 创建数据表

   CREATE DATABASE jpa_demo;
   USE jpa_demo;
   CREATE TABLE t_user(
       id BIGINT PRIMARY KEY AUTO_INCREMENT,
       firstName VARCHAR(20) NOT NULL,
       lastName VARCHAR(20) NOT NULL
   ) ENGINE = INNODB;
   

2. 配置Spring Data，这里采用JavaConfig配置

   @Configuration                                   // 这里声明这个文件是配置文件
   @EnableJpaRepositories({"com.lee.repository"})   // 这里制定repository所在的包(package)
   public class DataSourceConfig {
    
     @Bean
     public DataSource dataSource() {
         Properties prop = new Properties();
         DriverManagerDataSource ds = new DriverManagerDataSource();
         
         try {
             String path = getClass().getClassLoader().getResource("db.properties").getPath();
    
             FileInputStream in = new FileInputStream(path);
             prop.load(in);
    
             String driver = prop.getProperty("driver");
             String url = prop.getProperty("url");
             String username = prop.getProperty("uname");
             String password = prop.getProperty("pass");
    
             ds.setDriverClassName(driver);
             ds.setUrl(url);
             ds.setUsername(username);
             ds.setPassword(password);
             in.close();
         } catch (FileNotFoundException e) {
    
         } catch (IOException e) {
    
         }
         
         return ds;
     }
    
     // JPA Hibernate
     @Bean
     public JpaVendorAdapter jpaVendorAdapter() {
        HibernateJpaVendorAdapter adapter = new HibernateJpaVendorAdapter();
        adapter.setDatabase(Database.MYSQL);
        adapter.setDatabasePlatform("org.hibernate.dialect.MySQL5InnoDBDialect");
        adapter.setShowSql(true);
        adapter.setGenerateDdl(false);
      
        return adapter;
     }
         
     @Bean
     public LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource, JpaVendorAdapter jpaVendorAdapter) {
        LocalContainerEntityManagerFactoryBean emfb = new LocalContainerEntityManagerFactoryBean();
        emfb.setDataSource(dataSource);
        emfb.setJpaVendorAdapter(jpaVendorAdapter);
        emfb.setPackagesToScan("com.lee.entity");
      
        return emfb;
     }
      
     @Bean
     pblic PlatformTransactionManager transactionManager(EntityManagerFactory entityManagerFactory) {
        return new JpaTransactionManager(entityManagerFactory);
     }
         
   }   
   

3. 创建Entity，Entity需要提供getter, setter方法，用于关联数据表中的对应字段

@Entity                    // 声明这个类是实体类(Entity)
@Table(name = "t_user")    // 指定关联的数据表的名称
public class User {
    private Long id;
    private String firstName;
    private String lastName;
 
    public User() {
        this("testFirstName", "testLastName");
    }
 
    public User(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }
 
    @Id                   // 声明这个属性是数据库中的ID字段
    @GeneratedValue       // 声明这个ID值是自增长(数据库中 AUTO_INCREMENT)
    public Long getId() {
        return id;
    }
 
    public void setId(Long id) {
        this.id = id;
    }
 
    @Column(name = "firstName")    // 在getter方法声明这个属性关联数据库中firstName字段
    public String getFirstName() {
        return firstName;
    }
 
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
 
    @Column(name = "lastName")    // 在getter方法声明这个属性关联数据库中lastName字段
    public String getLastName() {
        return lastName;
    }
 
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
 
    /*
    用于打印信息
     */
    @Override
    public String toString() {
        return new StringBuilder()
                .append("id:").append(id)
                .append(", firstName:").append(firstName)
                .append(", lastName:").append(lastName)
                .toString();
    }
}

4. 创建repository

   public interface UserRepository extends CrudRepository {
   }
   

5. JUnit测试

   @RunWith(SpringJUnit4ClassRunner.class)
   @ContextConfiguration(classes = {DataSourceConfig.class})
   @FixMethodOrder(MethodSorters.NAME_ASCENDING)
   public class UserRepositoryTest {
    
       @Autowired
       private UserRepository userRepository;
       private static User user;
    
       @Test
       public void test_00_init() {
           user = new User("Lee", "Fly");
           System.out.println(user);
       }
    
       @Test
       public void test_01_save() {
           user = userRepository.save(user);
           System.out.println(user);
           assertNotNull(user.getId());
       }
    
       @Test
       public void test_02_update() {
           String rename = "ModifyName";
           user.setFirstName(rename);
           user = userRepository.save(user);
           System.out.println(user);
           assertEquals(rename, user.getFirstName());
       }
    
       @Test
       public void test_10_delete() {
           userRepository.delete(user);
           assertNull(userRepository.findOne(user.getId()));
       }
   }
   

注意：在配置文件中使用了数据库配置信息文件, db.properties, 没有给出, 可以更改成自己的配置方式, 或使用下面的源码
源码地址: https://github.com/LeeSpringFly/learnSpringData
如果运行正常，每一个测试都会显示绿条，表示成功