【SSM】spring核心思想——IOC和DI

文章目录

• 1. Spring 是什么？
• 2. IOC 是什么
• 3. DI 概念说明
• 4. Spring 的工作模式可以理解成一个买卖对象的市场
• 5. 以一个小程序来理解 IOC 和 DI
• 6. 以 XML 文件的方式将对象注入到我们自己创建的库中

1. Spring 是什么？

2. IOC 是什么

2.1 正向控制

2.2 反向控制

3. DI 概念说明

4. Spring 的工作模式可以理解成一个买卖对象的市场

5. 以一个小程序来理解 IOC 和 DI

@Component
public class Car {
    @Autowired
    private Framework framework;

    @Override
    public String toString() {
        return "Car{" +
                "framework=" + framework +
                '}';
    }
}

@Component
public class Framework {
    @Autowired
    private Bottom bottom;

    @Override
    public String toString() {
        return "Framework{" +
                "bottom=" + bottom +
                '}';
    }
}

@Component
public class Bottom {
    @Autowired
    private Tire t1;
    @Autowired
    private Tire t2;
    @Autowired
    private Tire t3;
    @Autowired
    private Tire t4;

    @Override
    public String toString() {
        return "Bottom{" +
                "t1=" + t1 +
                ", t2=" + t2 +
                ", t3=" + t3 +
                ", t4=" + t4 +
                '}';
    }
}

@Component
public class Tire {
    @Override
    public String toString() {
        return "轮子";
    }
}

@SpringBootApplication
public class IocApplication {

   public static void main(String[] args) {
      ConfigurableApplicationContext context = SpringApplication.run(IocApplication.class, args);

      Car car = context.getBean(Car.class);

      // 得到库中所有的 bean(对象)
      String[] beanDefinitionNames = context.getBeanDefinitionNames();
      for (String beanDefinitionName : beanDefinitionNames) {
         System.out.println(beanDefinitionName);
      }
       
      System.out.println(car);
   }

}

6. 以 XML 文件的方式将对象注入到我们自己创建的库中

6.1 新建一个 XML 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
        https://www.springframework.org/schema/beans/spring-beans.xsd">
</beans>

6.2 在 Main 中操作这个库

public class Main {
    public static void main(String[] args) {
        //1. 以 XML 配置文件手动创建 Spring 容器
        FileSystemXmlApplicationContext context = new FileSystemXmlApplicationContext("spring-config.xml");

        // 2. 打印容器中所有对象的 bean-id
        String[] names = context.getBeanDefinitionNames();
        System.out.println("所有对象陈列：");
        for (String name : names) {
            Object bean = context.getBean(name);

            // 得到此类的全名，即包含包名的名称
            String canonicalName = bean.getClass().getCanonicalName();

            System.out.println(name + "      " + canonicalName);
        }
        int count = context.getBeanDefinitionCount();
        System.out.println("一共有" + count + "个");
    }
}

6.2 XML 文件的方式注入 bean(对象)

<?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
        https://www.springframework.org/schema/beans/spring-beans.xsd">

<!--    xml的方式注入类，new 的过程也交给 Spring-->
    <bean id="empty-class" class="com.hsq.ioc2.EmptyClass"/>

<!--    构造方法注入类-->
    <bean id="second-class" class="com.hsq.ioc2.SecondClass">
<!--        依赖 EmptyClass 注入 SecondClass-->
        <constructor-arg ref="empty-class"/>
    </bean>

<!--    set 方法注入类-->
    <bean id="third-class" class="com.hsq.ioc2.ThirdClass">
        <property name="EmptyClass" ref="empty-class"/>
        <property name="SecondClass" ref="second-class"/>
    </bean>
</beans>

public class EmptyClass {
    public EmptyClass() {
        System.out.println("被调用");
    }
}

public class SecondClass {
    public SecondClass(EmptyClass emptyClass) {
        System.out.println("second 被调用");
    }
}

public class ThirdClass {
    public EmptyClass emptyClass;
    public SecondClass secondClass;

    public void setEmptyClass(EmptyClass emptyClass) {
        System.out.println("setEmptyClass() " + emptyClass);
        this.emptyClass = emptyClass;
    }

    public void setSecondClass(SecondClass secondClass) {
        System.out.println("setSecondClass() " + secondClass);
        this.secondClass = secondClass;
    }

    public ThirdClass() {
        System.out.println("third 被调用");
    }
}