Spring学习01-[Spring实现IOC的几种方式]

基于xml实现Spring的IOC

引入spring核心依赖

    <!--spring核心容器-->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>5.3.7</version>
    </dependency>

UserService依赖了UserDao

• userdao

public class UserDao {
    public void getUser(){
        System.out.println("获取了用户");
    }
}

• userService
  userDao需要被注入所以必须加set方法

public class UserService {

    private UserDao userDao;

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

    public void getUser(){
        userDao.getUser();
    }
}

• xml配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
                           http://www.springframework.org/schema/beans/spring-beans.xsd">

    <!--让spring帮我们去new对象 并且对象之间的依赖也让spring帮我们组织-->
    <bean name="userService" class="com.spring.service.UserService">
        <!--依赖注入-->
        <property name="userDao" ref="userDao"></property>
    </bean>

    <bean name="userDao" class="com.spring.dao.UserDao"></bean>

</beans>

• 测试

 @org.junit.Test
    public void test(){
        //要依赖spring注入，就需要从spring容器中获取UserService
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
        UserService userService = (UserService) context.getBean("userService");
        userService.getUser();
    }

基于注解实现Spring的IOC

@Component:被标注的类会交给spring进行管理，把这个类注册成一个bean

• 配置文件开启注解

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
                           http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">

    <!--告诉spring注解所在的包在哪儿-->
    <context:component-scan base-package="com.spring"/>
</beans>

• 在各个类上加上@Component注解

@Component
public class UserDao implements IUserDao{

    public void getUser() {
        System.out.println("获取了用户");
    }
}

@Component
public class UserService implements IUSerService{

   //此时可以用@Autowired 自动注入userDao
    @Autowired
    private UserDao userDao;

    public void getUser() {
        userDao.getUser();
    }
}

• 测试

    @org.junit.Test
    public void test(){
        //要依赖spring注入，就需要从spring容器中获取UserService
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
        UserService userService = (UserService) context.getBean("userService");
        userService.getUser();
    }

基于JavaConfig实现的Spring的IOC

还是需要在各个需要被注册成bean的类行加@Component注解
新建配置类

@Configuration  //=xml的配置类
@ComponentScan  //=<context:component-scan
public class SpringConfig {

}

• 测试类

  @org.junit.Test
    public void test(){
        //要依赖spring注入，就需要从spring容器中获取UserService
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
        UserService userService = (UserService) context.getBean("userService");
        userService.getUser();
    }

基于SpringBoot实现Spring的IOC

• 引入依赖

 <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.6.6</version>
  </parent>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

• 配置启动类

@SpringBootApplication
public class DemoApplication {

}

• 测试

 @org.junit.Test
    public void test(){
        //要依赖spring注入，就需要从spring容器中获取UserService
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(DemoApplication.class);
        UserService userService = (UserService) context.getBean("userService");
        userService.getUser();
    }