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spring 组件基于注解的注册方式

2019-06-13 09:02:28来源：博客园阅读 ()

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{

    @Override
    public 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{

    @Override
    public 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>{

    @Override
    public Color getObject() throws Exception {
        return new Color();
    }

    @Override
    public Class<?> getObjectType() {
        return Color.class;
    }

    @Override
    public boolean isSingleton() {
        return false;
    }

}


package com.annotation.factorybean;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration  
public class MainConfig {
    
    @Bean
    public 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();
        
        
        
    }
}