首先，我们创建一个包含 spring-context 依赖的 maven 项目，然后定义一个 User.class
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public class User { private long id; private String name; public long getId() { return id; } public void setId(long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "User{" + "id=" + id + ", name='" + name + '\'' + '}'; } } |
在 resources 目录下，创建 dependency-look-up.xml 配置文件
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<?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 https://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id = "user" class="org.example.overview.dependency.domain.User"> <property name="id" value="1"/> <property name="name" value="彭于晏"/> </bean> <bean id="superUser" class="org.example.overview.dependency.domain.SuperUser" parent="user" primary="true"> <property name="address" value="杭州"/> </bean> <bean id="objectFactory" class="org.springframework.beans.factory.config.ObjectFactoryCreatingFactoryBean"> <property name="targetBeanName" value="user"/> </bean></beans> |
1. 根据 Bean 名称查找
实时查找
实时查找的意思就是说直接获取 beanFactory, 通过 beanFactory 获取 user 对应的 bean，代码如下所示
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BeanFactory beanFactory = new ClassPathXmlApplicationContext("classpath:/META-INF/dependency-look-up.xml");// 这里的 “user” 就是 xml 文件中的 id，即名称实时查找 User user = (User) beanFactory.getBean("user");System.out.println("实时加载: " + bean); |
延时查找
这里的延迟就是说，通过其他的对象来获取 user 对应的 Bean，代码如下所示：
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ObjectFactory<User> objectFactory = (ObjectFactory<User>) beanFactory.getBean("objectFactory");User user = objectFactory.getObject();System.out.println("延迟加载" + user); |
2. 根据 Bean 类型查找
这里的类型指的就是 user.class
单个 Bean 对象
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User bean = beanFactory.getBean(User.class); |
集合 Bean 对象
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if(beanFactory instanceof ListableBeanFactory){ ListableBeanFactory listableBeanFactory = (ListableBeanFactory)beanFactory; Map<String, User> beansOfType = listableBeanFactory.getBeansOfType(User.class); System.out.println("集合类型：" + beansOfType); } |
3. 根据 Bean 类型 + 名称查找
4. 根据 Java 注解查找
首先我们自定义一个注解 @Super
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@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)public @interface Super {} |
将注解表示到 superUser 类中，这里的 superUser 继承了 user 类
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@Superpublic class SuperUser extends User { private String address; public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } @Override public String toString() { return "SuperUser{" + "address='" + address + '\'' + "} " + super.toString(); }} |
最后根据 spring 提供的 api，获取注解 bean
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if(beanFactory instanceof ListableBeanFactory){ ListableBeanFactory listableBeanFactory = (ListableBeanFactory)beanFactory; Map<String, Object> beansOfType = listableBeanFactory.getBeansWithAnnotation(Super.class); System.out.println("查找 @super 的：" + beansOfType);} |
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原文链接：https://blog.csdn.net/weixin_40007779/article/details/107969813
