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://HdhCmsTestspringframework.org/schema/beans" xmlns:xsi = "http://HdhCmsTestw3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://HdhCmsTestspringframework.org/schema/beans https://HdhCmsTestspringframework.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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@Super public 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
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