Spring定义Bean的方式

今天药忘吃喽~ 2022-10-06 08:53 153阅读 0赞

# 声明式 #

## **`1. <bean/> 使用xml的方式定义bean`** ##

**`1）先引入spring的依赖`**

<dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-context</artifactId>
                <version>5.2.10.RELEASE</version>
            </dependency>

**`2）定义对象User`**

package com.frank.oneBean;
    
    /**
     * @author 小石潭记
     * @date 2021/6/11 21:54
     * @Description: ${todo}
     */
    public class User {
    
        private String name;
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    }

**`3）spring.xml`**

<?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="user" class="com.frank.oneBean.User" scope="singleton">
            <property name="name" value="spring bean"/>
        </bean>
    </beans>

**`4）使用`**ClassPathXmlApplicationContext读取xml的方式获取bean

package com.frank.oneBean;
    
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    /**
     * @author 小石潭记
     * @date 2021/6/11 21:55
     * @Description: ${todo} 该package主要介绍javaBean springBean
     */
    public class Main {
        public static void main(String[] args) {
            User user = new User(); // 对象
            user.setName("java bean");
            String name = user.getName();// 满足规范 private get set javaBean
            System.out.println(name);
    
            ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring.xml");
            User user1 = applicationContext.getBean("user", User.class); // springBean
            System.out.println(user1.getName());
        }
    }

**`2. @Bean`**

package com.frank.twoBeanMehtod;
    
    import org.springframework.context.annotation.Bean;
    
    /**
     * @author 小石潭记
     * @date 2021/6/11 22:06
     * @Description: ${todo}
     */
    public class Config {
    
        /**
         * 通过@Bean注册bean
         * @return
         */
        @Bean
        public User user() {
            return new User();
        }
    }

package com.frank.twoBeanMehtod;
    
    import org.springframework.beans.factory.support.AbstractBeanDefinition;
    import org.springframework.beans.factory.support.BeanDefinitionBuilder;
    import org.springframework.context.annotation.AnnotationConfigApplicationContext;
    
    /**
     * @author 小石潭记
     * @date 2021/6/11 21:55
     * @Description: ${todo} 该package主要介绍 通过config配置bean
     */
    public class Main {
        public static void main(String[] args) {
            // 注解的方式
            AnnotationConfigApplicationContext configApplicationContext = new AnnotationConfigApplicationContext(Config.class);
            User user = configApplicationContext.getBean("user", User.class);
            System.out.println(user);
        }
    }

**`3.@Component 扫描指定的包下的@Component的注解类`**

package com.frank.twoBeanMehtod;
    
    import org.springframework.context.annotation.ComponentScan;
    
    /**
     * @author 小石潭记
     * @date 2021/6/11 22:06
     * @Description: ${todo}
     */
    @ComponentScan("com.frank")  // 注释下面的@Bean 在user对象上添加@Component
    public class Config {
        
    }

在User上面添加注解**`@Component`**

package com.frank.twoBeanMehtod;
    
    import org.springframework.stereotype.Component;
    
    /**
     * @author 小石潭记
     * @date 2021/6/11 21:54
     * @Description: ${todo}
     */
    @Component
    public class User {
    
        private String name;
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    }

package com.frank.twoBeanMehtod;
    
    import org.springframework.context.annotation.AnnotationConfigApplicationContext;
    
    /**
     * @author 小石潭记
     * @date 2021/6/11 21:55
     * @Description: ${todo} 该package主要介绍 通过config配置bean
     */
    public class Main {
        public static void main(String[] args) {
            AnnotationConfigApplicationContext configApplicationContext = new AnnotationConfigApplicationContext(Config.class);
            User user = configApplicationContext.getBean("user", User.class);
            System.out.println(user);
        }
    }

# 编程式 #

4. BeanDefinition，删除user上面的**`@Component和config上面的@ComponentScan("com.frank") 然后通过`**BeanDefinition注册bean

package com.frank.twoBeanMehtod;
    
    import org.springframework.beans.factory.support.AbstractBeanDefinition;
    import org.springframework.beans.factory.support.BeanDefinitionBuilder;
    import org.springframework.context.annotation.AnnotationConfigApplicationContext;
    
    /**
     * @author 小石潭记
     * @date 2021/6/11 21:55
     * @Description: ${todo} 该package主要介绍 通过beanDefinition配置bean
     */
    public class Main {
        public static void main(String[] args) {
            AnnotationConfigApplicationContext configApplicationContext = new AnnotationConfigApplicationContext();
            // 使用beanDefinition定义bean
            AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition().getBeanDefinition();
            beanDefinition.setBeanClass(User.class);
            configApplicationContext.registerBeanDefinition("user", beanDefinition);
            configApplicationContext.refresh();
            User user = configApplicationContext.getBean("user", User.class);
            System.out.println(user);
        }
    }

5.使用BeanFctory定义bean

package com.frank.twoBeanMehtod;
    
    /**
     * @author 小石潭记
     * @date 2021/6/12 11:32
     * @Description: ${todo}
     */
    public class Person {
    }

package com.frank.twoBeanMehtod;
    
    import org.springframework.beans.factory.FactoryBean;
    import org.springframework.stereotype.Component;
    
    /**
     * @author 小石潭记
     * @date 2021/6/12 11:31
     * @Description: ${todo}
     */
    @Component("person")
    public class FrankFactoryBean implements FactoryBean {
        public Object getObject() throws Exception {
            Person person = new Person();
            return person;
        }
    
        public Class<?> getObjectType() {
            return Person.class;
        }
    }

AnnotationConfigApplicationContext configApplicationContext = new AnnotationConfigApplicationContext(Config.class);
            Person person = configApplicationContext.getBean("person", Person.class);
            System.out.println(person);

6.使用Supplier创建bean

AnnotationConfigApplicationContext configApplicationContext = new AnnotationConfigApplicationContext();
            /*configApplicationContext.registerBean(User.class, new Supplier<User>() {
                public User get() {
                    User user = new User();
                    user.setName("supplier-user");
                    return user;
                }
            });*/
    
            configApplicationContext.registerBean(User.class, () -> {
                User user = new User();
                user.setName("supplier-user");
                return user;
            });
            // 注册之后需要刷新 才会获取到bean
            configApplicationContext.refresh();
    
            User user = configApplicationContext.getBean("user", User.class);
            System.out.println(user.getName());

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMzMzcxNzY2_size_16_color_FFFFFF_t_70][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMzMzcxNzY2_size_16_color_FFFFFF_t_70 1][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMzMzcxNzY2_size_16_color_FFFFFF_t_70]: /images/20221005/285e95a984654167ba88d30f0270f62a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMzMzcxNzY2_size_16_color_FFFFFF_t_70 1]: /images/20221005/9ef05f2ad3d54c57a245faaa45d26bd3.png