bean注入到spring容器中的方式

目录

一.@Bean直接导入单个类

二.@ComponentScan组件扫描

三.@import导入

四.把需要注入的对象封装为FactoryBean

    //默认是方法名
    //指定value 则以value为准
    @Bean("stu")
    public Student stu() {
        return new Student("ws",100);
    }

test

@Test
    public void Test1() {
        ApplicationContext app = new AnnotationConfigApplicationContext(MyConfigura.class);

        Object bean = app.getBean("stu");
        System.out.println(bean);
    }

二.@ComponentScan组件扫描

@ComponentScan 默认扫描（@Controller.@Service、@Repostory、@Component)

@Component
@Data
public class Pig {
}

test：

    @Test
    public void Test2() {
        ApplicationContext app = new AnnotationConfigApplicationContext(MyConf.class);

        System.out.println(app.getBean("pig"));

    }

三.@import导入

1.import直接参数导入

@Configuration
@import({Cat.class})
public class MyConfigura {

}

test:

@Test
    public void Test1() {
        ApplicationContext app = new AnnotationConfigApplicationContext(MyConfigura.class);

        Object bean = app.getBean("com.ws.project.entity.Cat");
        //import直接导入加的bean是全类名
        System.out.println(bean);
    }

 2.importselector自定义规则实现

实现importSelector接口

public class MyimportSelector implements importSelector {
    @Override
    public String[] selectimports(Annotationmetadata annotationmetadata) {
        //直接在
        return new String[]{"com.ws.project.entity.Cat1",
                    "com.ws.project.entity.Cat2"};
    }
}

@Configuration
//@import({Cat.class})
@import({MyimportSelector.class})
public class MyConfigura {
}

test

@Test
    public void Test1() {
        ApplicationContext app = new AnnotationConfigApplicationContext(MyConfigura.class);

        Object bean1 = app.getBean("com.ws.project.entity.Cat1");
        Object bean = app.getBean("com.ws.project.entity.Cat2");
        System.out.println(bean1 + "n" +bean);
    }

3.实现importBeanDefinitionRegistrar

获得BeanDefinitionRegistry可以手动直接往Ioc容器中塞

public class MyimportBeanDefinitionRegistrar implements importBeanDefinitionRegistrar {
    @Override
    public void registerBeanDefinitions(Annotationmetadata importingClassmetadata, BeanDefinitionRegistry registry) {
        //可以加入一些逻辑
        //比如 当容器中存在Cat1 和 Cat2 我才可以创建 Cat3
        boolean cat1 = registry.containsBeanDefinition("com.ws.project.entity.Cat1");
        boolean cat2 = registry.containsBeanDefinition("com.ws.project.entity.Cat2");
        if (cat1 & cat2) {
            //创建beanDefinition
            BeanDefinition beanDefinition = new RootBeanDefinition(Cat3.class);
            //放到容器中
            registry.registerBeanDefinition("cat3",beanDefinition);
        }
    }
}

@Configuration
//@import({Cat.class})
@import({MyimportSelector.class,MyimportBeanDefinitionRegistrar.class})
public class MyConfigura {
}

Test

@Test
    public void Test1() {
        ApplicationContext app = new AnnotationConfigApplicationContext(MyConfigura.class);

        Object bean = app.getBean("cat3");
        System.out.println(bean);
    }

四.把需要注入的对象封装为FactoryBean

继承FactoryBean

public class MyFactoryBean implements FactoryBean {
    @Override
    public Dog getObject() throws Exception {
        return new Dog();
    }

    @Override
    public Class getObjectType() {
        return Dog.class;
    }

    @Override
    public boolean isSingleton() {
        //是否单例
        return true;
    }
}

把MyFactoryBean注册

@Configuration
public class MyConfigura {
 
    @Bean
    public MyFactoryBean factoryBean() {
        return new MyFactoryBean();
    }

}

Test: getBean(factoryBean) 会发现拿到的是Dog对象

@Test
    public void Test1() {
        ApplicationContext app = new AnnotationConfigApplicationContext(MyConfigura.class);
        Object bean = app.getBean("factoryBean");
        System.out.println(bean);
    }