批量删除区别

delete() 和 deleteInBatch()
deleteAll() 和 deleteAllInBatch()

普通删除方法会根据唯一标识字段，生成多条 SQL 语句，而有 InBatch 的方法只会生成一条 SQL 语句

写入大量数据

@Transactional
public void save100WEntities() {
    for (int i = 0; i < 1000; i++) {
        respsitory.save(1000Entities);

         entityManager.flush();
        entityManager.clear();
    }
}

读取大量数据

需要满足3个条件：

1. ResultSetType 是 ResultSet.TYPE_FORWARD_ONLY
2. ResultSetConcurrency 是 ResultSet.CONCUR_READ_ONLY
3. FetchSize 是 Integer.MIN_VALUE

Statement statement = connection.createStatement(
        ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);
statement.setFetchSize(Integer.MIN_VALUE);

@Repository
public interface UserRepository extends JpaRepository<User, Integer> {
    @QueryHints(value = @QueryHint(name = FETCH_SIZE, value = "" + Integer.MIN_VALUE))
    Stream<User> findByIdIsNotNull();
}

@Transactional
public void run() {
    try (Stream<User> stream = userRepository.findByIdIsNotNull()) {
        stream.forEach(user -> {
            System.out.println(user);
            entityManager.detach(user);
        });
    }
}

Spring-AMQP 特性

• Listener container 使用 POJO 异步处理消息
• 提供一个高度抽象的 template（RabbitTemplate）发送和接收消息
• 使用 RabbitAdmin 来自动声明队列、Exchange 和 Binding

队列、Exchange 和 Binding 的设置

• Spring way
  使用 spring-boot-starter-amqp 会自动配置 ConnectionFactory、RabbitTemplate 和 AmqpAdmin 三个 Bean。

  @Configuration
  public class RabbitConfiguration {
  
    @Bean
  
    public DirectExchange exchange() {
  
        return new DirectExchange("infrastructure.direct");
  
    }
  
    @Bean
  
    public Queue queue(){
  
        return new Queue("queueName");
  
    }
  
    @Bean
  
    public Binding binding(){
  
        return BindingBuilder.bind(queue()).to(exchange()).with("routeKey");
  
    }
  
  }
  

• Just java

  ConnectionFactory connectionFactory = new CachingConnectionFactory();
  RabbitAdmin amqpAdmin = new RabbitAdmin(connectionFactory);
  
  Queue queue = new Queue("quueuName");
  
  DirectExchange exchange = new DirectExchange("exchangeName");
  
  amqpAdmin.declareQueue(queue);
  
  amqpAdmin.declareExchange(exchange);
  
  amqpAdmin.declareBinding(BindingBuilder.bind(queue).to(exchange).with("routeKey"));
  

1. 新建一个测试配置类 TestApplication

   @Configuration
   @EnableAutoConfiguration
   
   @ComponentScan(
   
         excludeFilters = @ComponentScan.Filter(value = {
   
                 Application.class,
   
                 ApplicationChecker.class
   
         }, type = FilterType.ASSIGNABLE_TYPE))
   
   public class TestApplication {
   
     // 配置测试使用内存数据库
   
     @Bean
   
     public DataSource dataSource() {
   
         return new EmbeddedDatabaseBuilder().setType(EmbeddedDatabaseType.H2).build();
   
     }
   
   }
   

开始向导

添加 dependency spring-boot-starter-redis，它默认使用 jedis（还支持 JRedis，SRP 和 Lettuce）
一个简单的 Hash 示例：

@SpringBootApplication
public class RedisDemo implements CommandLineRunner {

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    public static void main(String[] args) {
        SpringApplication.run(RedisDemo.class).close();
    }

    public void run(String... args) throws Exception {
        BoundHashOperations<String, String, String> ops = stringRedisTemplate.boundHashOps("com.foo");
        ops.put("name", "bar");
        ops.put("sex", "man");
        System.out.println(ops.entries()); // 打印结果：{name=bar, sex=man}
    }
}

使用注意

User user = new User();
user.setUsername("foo");
Email email = new Email();
email.setUser(user);  // 必须显示设置 user，否则关联字段值会为空
email.setEmail("foo@bar.com");
user.setEmail(email); 
userRepository.save(user);