What is Spring framework? Introduction to Spring Framework IOC Container

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1. Introduction to Spring open source framework

Spring is an open source framework and a lightweight Java development framework that emerged in 2003. Derived from some of the ideas and prototypes described by Rod Johnson in his book Expert One-On-One J2EE Development and Design. It was created to solve the complexities of enterprise application development.

Spring uses basic JavaBeans to accomplish things that were previously only possible with EJBs. However, Spring's uses are not limited to server-side development. Any Java application can benefit from Spring in terms of simplicity, testability, and loose coupling. Simply put, Spring is a lightweight Inversion of Control (IoC) and Aspect-Oriented (AOP) container framework.

The basic framework of spring mainly includes six modules: DAO, ORM, AOP, JEE, WEB, and CORE.

Spring ORM: Spring can be integrated with the ORM framework. For example, Spring integrates the Hibernate framework, and Spring also provides the HibernateDaoSupport tool class, which simplifies the operation of Hibernate.
Spring WEB: Spring provides support for Struts, Springmvc, and supports WEB development. At the same time, Spring itself also provides solutions based on MVC.
Spring AOP: Spring provides aspect-oriented programming, which can provide transaction management for a certain layer, such as adding transaction control to the Service layer.
Spring JEE: Support for J2EE development specifications, such as EJB.
Spring Core: Provides the creation of IOC container objects and processing of dependent object relationships.

2. IOC container and DI (Dependency injection) under Spring

Control layer code:

private OrderServiceImp orderService;
    
public void setOrderService(OrderServiceImp orderService) {
       this.orderService = orderService;
}

<bean>
        <property></property>
</bean>
<bean></bean>

private OrderServiceImp orderService;
    
public OrderAction(OrderServiceImp orderService) {
        this.orderService = orderService;
    }

XML file:

<bean>
      <constructor-arg></constructor-arg>
</bean>
<bean></bean>

@Autowired   //@Resource
private OrderServiceImp orderService;

@Service("orderService")
public class OrderServiceImp implements IOrderService {

    @Autowired
    private JavaOrderMDaoImp javaOrderMDao;

    @Autowired
    private JavaOrderDDaoImp javaOrderDDao;

    @Override
    public List<javaordermlist> findOrderM(OrderSearch search) {
        return javaOrderMDao.findJavaOrderM(search);
    }

    @Override
    public List<javaorderdlist> findOrderD(OrderSearch search) {
        return javaOrderDDao.findJavaOrderD(search);
    }

}</javaorderdlist></javaordermlist>

@Repository("javaOrderMDao")
public class JavaOrderMDaoImp extends BaseHibernateDAO<javaorderm> implements IJavaOrderMDao {...}</javaorderm>

@Repository("javaOrderDDao")
public class JavaOrderDDaoImp extendsBaseHibernateDAO<javaorderd> implements IJavaOrderDDao {...}</javaorderd>

Notes: ##  ⑴ The persistence layer DAO layer annotation Repository specifies the name, and the name declared in the Service layer must be consistent.

 ⑵ Service layer Service layer annotation The name is specified in Service, and the name declared in the control layer must be consistent.

⑶ Annotation method for injecting dependency annotations:

@Component         把对象加入ioc容器，对象引用名称是类名，第一个字母小写
@Component(“name”) 把指定名称的对象，加入ioc容器
@Repository        主要用于标识加入容器的对象是一个持久层的组件(类)
@Service           主要用于标识加入容器的对象是一个业务逻辑层的组件
@Controller        主要用于标识加入容器的对象是一个控制层的组件
@Resource          注入属性(DI), 会从容器中找对象注入到@Resource修饰的对象上
@Autowired         注入属性(DI), 会从容器中找对象注入到@Autowired修饰的对象上

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