SpringBoot Bean 创建方式 XML + Annotation

最新推荐文章于 2025-04-05 20:45:28 发布

原创最新推荐文章于 2025-04-05 20:45:28 发布 · 367 阅读

0 ·

CC 4.0 BY-SA版权

Spring Boot 专栏收录该内容

15 篇文章

订阅专栏

本文详细介绍了Spring框架中创建Bean的多种方式，包括通过XML、注解和工厂方法等，并提供了具体的代码示例，深入解析了每种创建方式的实现原理。

Spring创建bean方式多种，直接上代码：

通过XML创建Bean有三种方式：默认无参构造，静态工厂，实例工厂
通过Annotation创建Bean有三种方式：注解配置方式，获取配置类中使用Bean注解方式，直接使用注解配置注册Bean，通过扫描指定包路径下通过注解声明的Bean实例。

package com.example.demo;

import com.example.demo.bean.UserService;
import com.example.demo.bean.annotation.BeanAnnotationUserService;
import com.example.demo.bean.annotation.BeanConfig;
import com.example.demo.bean.annotation.ServiceAnnotationUserService;
import com.example.demo.bean.xml.BeanFactoryUserService;
import com.example.demo.bean.xml.BeanInstanceFactoryUserService;
import com.example.demo.bean.xml.BeanXmlUserServcie;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import javax.annotation.Resource;

@SpringBootTest
class DemoApplicationTests {

	@Test
	void testClassPathXmlApplicationContext() {
		ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml");
		UserService userServcie = (UserService)context.getBean("beanXmlUserServcie");
		System.out.println(userServcie.toString());
	}

	@Test
	void testFactoryClassPathXmlApplicationContext() {
		ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml");
		UserService userServcie = (UserService)context.getBean("beanFactoryUserService");
		System.out.println(userServcie.toString());
	}

	@Test
	void testInsFactoryClassPathXmlApplicationContext() {
		ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml");
		UserService userServcie = (UserService)context.getBean("beanInstanceFactoryUserService");
		System.out.println(userServcie.toString());
	}

	@Test
	void testAnnotationConfigApplicationContext() {
		ApplicationContext context = new AnnotationConfigApplicationContext(BeanAnnotationUserService.class);
		UserService userServcie = (UserService)context.getBean("beanAnnotationUserService");
		System.out.println(userServcie.toString());
	}

	@Test
	void testBeanConfigAnnotationConfigApplicationContext() {
		ApplicationContext context = new AnnotationConfigApplicationContext(BeanConfig.class);
		UserService userServcie = (UserService)context.getBean("beanAnnotationUserServiceConfig");
		System.out.println(userServcie.toString());
	}

	@Test
	void testServiceAnnotationConfigApplicationContext() {
		ApplicationContext context = new AnnotationConfigApplicationContext("com.example.demo.bean.annotation");
		UserService userServcie = (UserService)context.getBean("serviceAnnotationUserService");
		System.out.println(userServcie.toString());
	}
}

创建一个UserService空接口，方便测试Bean对象获取。

package com.example.demo.bean;

public interface UserService {
}

通过XML获取Bean对象BeanXmlUserServcie

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

    <bean id="beanXmlUserServcie" class="com.example.demo.bean.xml.BeanXmlUserServcie"></bean>
</beans>

package com.example.demo.bean.xml;

import com.example.demo.bean.UserService;

/**
 * @author wangSong
 */
public class BeanXmlUserServcie implements UserService {
    @Override
    public String toString() {
        return "this bean is create by Spring bean Xml";
    }
}

通过静态工厂获取Bean实例对象 BeanFactoryUserService

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

    <bean id="beanFactoryUserService" class="com.example.demo.bean.xml.StaticFactory" factory-method="createUserService"></bean>
</beans>

package com.example.demo.bean.xml;

import com.example.demo.bean.UserService;

public class StaticFactory {

    public static UserService  createUserService(){
        return new BeanFactoryUserService();
    }
}

package com.example.demo.bean.xml;

import com.example.demo.bean.UserService;

public class BeanFactoryUserService implements UserService {
    @Override
    public String toString() {
        return "this bean is create by Spring Bean Static Factory Xml";
    }
}

通过实例工厂获取Bean对象BeanInstanceFactoryUserService

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

    <bean id="instanceFactory" class="com.example.demo.bean.xml.InstanceFactory"></bean>
    <bean id="beanInstanceFactoryUserService" factory-bean="instanceFactory" factory-method="createUserService"></bean>

</beans>

package com.example.demo.bean.xml;

import com.example.demo.bean.UserService;

public class InstanceFactory {

    public  UserService  createUserService(){
        return new BeanInstanceFactoryUserService();
    }
}

package com.example.demo.bean.xml;

import com.example.demo.bean.UserService;

public class BeanInstanceFactoryUserService implements UserService {
    @Override
    public String toString() {
        return "this bean is create by Spring Bean Instance Factory Xml";
    }
}

通过注解配置获取配置的Bean实例，也可以直接获取指定class对象Bean实例。

package com.example.demo.bean.annotation;

import com.example.demo.bean.UserService;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class BeanConfig {

    @Bean(name="beanAnnotationUserServiceConfig")
   public UserService getBeanUserService(){
       return new BeanAnnotationUserService();
   }
}

通过扫描包下注解类，获取Bean实例

package com.example.demo.bean.annotation;

import com.example.demo.bean.UserService;
import org.springframework.stereotype.Service;

@Service(value="serviceAnnotationUserService")
public class ServiceAnnotationUserService implements UserService {
    @Override
    public String toString() {
        return "this bean is create by Spring Service Annotation ";
    }
}