spring 组件基于注解的注册方式

spring 中常用的组件标签有：

@Controller：控制层

@Service：业务层

@Repository：数据层

@Component:普通的pojo注入到spring容器

组件注册方式：

@ComponentScan 扫描那些要注入到spring容器的组件的包路径

package com.annotation.component;
import org.springframework.stereotype.Controller;import org.springframework.context.annotation.Configuration;@Controller
public class PersonController {}package com.annotation.register;
import org.springframework.context.annotation.ComponentScan;//表明这是个注解配置类
@Configuration
@ComponentScan(value={"com.annotation.component"})
public class  Config {}package com.annotation.register;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import com.annotation.component.controller.PersonController;public class Test {public static void main(String[] args) {   AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(Config.class);PersonController personController = annotationConfigApplicationContext.getBean(PersonController.class);}
}

@bean :主要作用在方法上，name可以指定bean在容器中的名称，不指定的话默认是方法名；initMethod指定bean的初始化方法；destroyMethod指定bean的销毁方法

package com.annotation.component;public class Blue {}package com.annotation.register;import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.annotation.component.bean.Blue;@Configuration
public class MainConfig {@Bean(name="blue")public Blue getColor(){return new Blue();}}package com.annotation.register;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;import com.annotation.component.bean.Blue;public class Test {public static void main(String[] args) {AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MainConfig.class);Blue blue= annotationConfigApplicationContext.getBean(Blue.class);System.out.println(blue);}
}

@Import :

注入一个bean
导入ImportSelector的实现类，selectImports方法里面配置要注入的bean
导入ImportBeanDefinitionRegistrar的实现类，registerBeanDefinitions方法里面配置要注入的bean

package com.annotation.component.bean;public class Blue {}package com.annotation.component.bean;public class Yellow {}package com.annotation.component.bean;public class Green{}package com.annotation.importbean;import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import com.annotation.component.bean.White;@Configuration
@Import(value = { White.class,MyImportSelector.class,MyImportBeanDefinitionRegistrar.class })
public class MainConfig {}package com.annotation.importbean;import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;public class MyImportSelector implements ImportSelector{@Overridepublic String[] selectImports(AnnotationMetadata annotationmetadata) {return new String[]{"com.annotation.component.bean.Yellow"};}}package com.annotation.importbean;import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;import com.annotation.component.bean.Green;public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar{@Overridepublic void registerBeanDefinitions(AnnotationMetadata annotationmetadata,BeanDefinitionRegistry beandefinitionregistry) {RootBeanDefinition beanDefinition = new RootBeanDefinition(Green.class);beandefinitionregistry.registerBeanDefinition("com.annotation.component.bean.Green", beanDefinition);}}package com.annotation.importbean;import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class Test {public static void main(String[] args) {    AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MainConfig.class);String[] names = annotationConfigApplicationContext.getBeanDefinitionNames();for (String name : names) {System.out.println(name);}annotationConfigApplicationContext.close();}
}

implements FactoryBean

getObject 方法表示要注入的对象，getObjectType表示对象类型，isSingleton表示是否单例
annotationConfigApplicationContext.getBean("colorFactoryBean") 表示获取的是工程里面注入的对象，即Color
annotationConfigApplicationContext.getBean("&colorFactoryBean") 表示获取的是工程对象本身，即ColorFactoryBean

package com.annotation.component.bean;public class Color {}package com.annotation.factorybean;import org.springframework.beans.factory.FactoryBean;import com.annotation.component.bean.Color;public class ColorFactoryBean implements FactoryBean<Color>{@Overridepublic Color getObject() throws Exception {return new Color();}@Overridepublic Class<?> getObjectType() {return Color.class;}@Overridepublic boolean isSingleton() {return false;}}package com.annotation.factorybean;import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;@Configuration
public class MainConfig {@Beanpublic ColorFactoryBean colorFactoryBean(){return new ColorFactoryBean();}}package com.annotation.factorybean;import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class Test {public static void main(String[] args) {AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MainConfig.class);Object obj1 = annotationConfigApplicationContext.getBean("colorFactoryBean");Object obj2 = annotationConfigApplicationContext.getBean("colorFactoryBean");        System.out.println(obj1==obj2);//获取factorybean 本身Object obj3 = annotationConfigApplicationContext.getBean("&colorFactoryBean");System.out.println(obj3.getClass());annotationConfigApplicationContext.close();}
}

转载于:https://www.cnblogs.com/chenzhubing/p/11010745.html

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