Spring bean注册

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包扫描方式

通常在Spring中我们需要将一些需要用到的类以bean的方式注册到容器中,而在Spring框架中,通常使用

  • @Controller
  • @Service
  • @Component
  • @Repository
    要是这些注解生效,我们需要给项目加上包扫描策略,如果是配置文件的方式,我们需要加上如下的xml配置
<context:component-scan base-package="com.spring.spel" use-default-filters="false">
       <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
       <!--两个属性,两者选择其中一个,否则会报错-->
       <!--<context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>-->
</context:component-scan>
  • base-backage:Spring会默认扫描该包以及下面的子包中被@Controller,@Service,@Component,@Repository修饰的类,同时将这些类加入到容器中。
  • use-default-filters:是否使用默认的包扫描方式,默认是扫描@Controller,@Service,@Component,@Repository修饰的类
  • exclude-filter:扫描不包括哪些
    • type:类型,类型一般分为annotation,custom,assignable,aspect,regex
  • include-filter:扫描包括哪些
    如果是采用java注解的方式进行包扫描,则需要做如下配置
@Configuration
@ComponentScan(value = "com.spring",excludeFilters = {
        @ComponentScan.Filter(type = FilterType.ANNOTATION,classes = Controller.class)
})
public class MainConfiguration {    
}

@Bean

被@Bean修饰的方法,返回回来的类会以方法名为bean名称注册到容器中。或者我们可以直接在@Bean的属性中指定bean的名称。

package com.spring.config;

import com.spring.bean.Person;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.stereotype.Controller;

@Configuration
public class MainConfiguration {

    /**
     * 如果@Bean的value没有参数,
     * 则以@Bean修饰的方法返回的bean名称以方法名为准,否则以value为准。
     * @return
     */
    @Bean
    public Person person(){
        return new Person("conjane",23);
    }

    @Bean
    public Person person3(){
        return new Person("conjane",23);
    }

    @Bean(value = "conjane")
    public Person person4(){
        return new Person("conjane",23);
    }
}

测试类

@Test
    public void testBeansInApplicationContext(){
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConfiguration.class);
        String[] beans = applicationContext.getBeanDefinitionNames();
        for (String bean:beans){
            System.out.println("=====>" + bean);
        }
    }

执行结果
=====>org.springframework.context.annotation.internalConfigurationAnnotationProcessor
=====>org.springframework.context.annotation.internalAutowiredAnnotationProcessor
=====>org.springframework.context.annotation.internalRequiredAnnotationProcessor
=====>org.springframework.context.annotation.internalCommonAnnotationProcessor
=====>org.springframework.context.event.internalEventListenerProcessor
=====>org.springframework.context.event.internalEventListenerFactory
=====>mainConfiguration
=====>person
=====>person3
=====>conjane

@Import

采用@Import方式,是将全类名作为bean名称注册到容器中。

package com.spring.config;

import com.spring.bean.Person;
import com.spring.spel.User;
import org.springframework.context.annotation.*;
import org.springframework.stereotype.Controller;

@Configuration
@Import(value = {Person.class, User.class})
public class MainConfiguration {

    /**
     * 如果@Bean的value没有参数,
     * 则以@Bean修饰的方法返回的bean名称以方法名为准,否则以value为准。
     * @return
     */
    @Bean
    public Person person(){
        return new Person("conjane",23);
    }

    @Bean
    public Person person3(){
        return new Person("conjane",23);
    }

    @Bean(value = "conjane")
    public Person person4(){
        return new Person("conjane",23);
    }
}

测试结果
=====>org.springframework.context.annotation.internalConfigurationAnnotationProcessor
=====>org.springframework.context.annotation.internalAutowiredAnnotationProcessor
=====>org.springframework.context.annotation.internalRequiredAnnotationProcessor
=====>org.springframework.context.annotation.internalCommonAnnotationProcessor
=====>org.springframework.context.event.internalEventListenerProcessor
=====>org.springframework.context.event.internalEventListenerFactory
=====>mainConfiguration
=====>com.spring.bean.Person
=====>com.spring.spel.User
=====>person
=====>person3
=====>conjane

ImportSelector

该方式需要实现ImportSelector接口,重写selectImports方法,该方法的参数类型是AnnotationMetadata,通过该参数可以获得有关修饰类的其他一些属性。

package com.spring.config;

import com.spring.bean.Person;
import com.spring.dao.MyImportSelector;
import com.spring.spel.User;
import org.springframework.context.annotation.*;
import org.springframework.stereotype.Controller;

@Configuration
@Import(value = {MyImportSelector.class})
@ComponentScan(value = "com.spring")
public class MainConfiguration {

    /**
     * 如果@Bean的value没有参数,
     * 则以@Bean修饰的方法返回的bean名称以方法名为准,否则以value为准。
     * @return
     */
    @Bean
    public Person person(){
        return new Person("conjane",23);
    }

    @Bean
    public Person person3(){
        return new Person("conjane",23);
    }

    @Bean(value = "conjane")
    public Person person4(){
        return new Person("conjane",23);
    }
}
package com.spring.dao;

import com.spring.bean.Person;
import com.spring.spel.User;
import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;

import java.util.Set;


public class MyImportSelector implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata annotationMetadata) {
        return new String[]{Person.class.getName(), User.class.getName()};
    }
}

测试结果
=====>org.springframework.context.annotation.internalConfigurationAnnotationProcessor
=====>org.springframework.context.annotation.internalAutowiredAnnotationProcessor
=====>org.springframework.context.annotation.internalRequiredAnnotationProcessor
=====>org.springframework.context.annotation.internalCommonAnnotationProcessor
=====>org.springframework.context.event.internalEventListenerProcessor
=====>org.springframework.context.event.internalEventListenerFactory
=====>mainConfiguration
=====>personController
=====>personDao
=====>personService
=====>com.spring.bean.Person
=====>com.spring.spel.User
=====>person
=====>person3
=====>conjane

ImportBeanDefinitionRegistrar

这样的需要实现ImportBeanDefinitionRegistrar接口,重写registerBeanDefinitions该方法。

package com.spring.dao;

import com.spring.bean.Person;
import org.springframework.beans.factory.config.BeanDefinition;
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;

public class MyBeanDefinitionRegistar implements ImportBeanDefinitionRegistrar {
    @Override
    public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry beanDefinitionRegistry) {
        BeanDefinition beanDefinition = new RootBeanDefinition(Person.class);
        beanDefinitionRegistry.registerBeanDefinition("personconjane",beanDefinition);
    }
}

配置类

package com.spring.config;

import com.spring.bean.Person;
import com.spring.dao.MyBeanDefinitionRegistar;
import com.spring.dao.MyImportSelector;
import com.spring.spel.User;
import org.springframework.context.annotation.*;
import org.springframework.stereotype.Controller;

@Configuration
@Import(value = {MyBeanDefinitionRegistar.class})
@ComponentScan(value = "com.spring")
public class MainConfiguration {

    /**
     * 如果@Bean的value没有参数,
     * 则以@Bean修饰的方法返回的bean名称以方法名为准,否则以value为准。
     * @return
     */
    @Bean
    public Person person(){
        return new Person("conjane",23);
    }

    @Bean
    public Person person3(){
        return new Person("conjane",23);
    }

    @Bean(value = "conjane")
    public Person person4(){
        return new Person("conjane",23);
    }
}

测试结果
=====>org.springframework.context.annotation.internalConfigurationAnnotationProcessor
=====>org.springframework.context.annotation.internalAutowiredAnnotationProcessor
=====>org.springframework.context.annotation.internalRequiredAnnotationProcessor
=====>org.springframework.context.annotation.internalCommonAnnotationProcessor
=====>org.springframework.context.event.internalEventListenerProcessor
=====>org.springframework.context.event.internalEventListenerFactory
=====>mainConfiguration
=====>personController
=====>personDao
=====>personService
=====>person
=====>person3
=====>conjane
=====>personconjane

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转载自blog.csdn.net/u010871004/article/details/86497610
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