目錄1. 根據(jù) Bean 名稱查找實(shí)時(shí)查找延時(shí)查找2. 根據(jù) Bean 類型查找單個(gè) Bean 對(duì)象集合 Bean 對(duì)象3. 根據(jù) Bean 類型 + 名稱查找

首先，我們創(chuàng)建一個(gè)包含 spring-context 依賴的 maven 項(xiàng)目，然后定義一個(gè) User.class

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 目錄下，創(chuàng)建 dependency-look-up.xml 配置文件

<?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/beanshttps://www.springframework.org/schema/beans/spring-beans.xsd'> <bean class='org.example.overview.dependency.domain.User'><property name='id' value='1'/><property name='name' value='彭于晏'/> </bean> <bean parent='user' primary='true'><property name='address' value='杭州'/> </bean> <bean class='org.springframework.beans.factory.config.ObjectFactoryCreatingFactoryBean'><property name='targetBeanName' value='user'/> </bean></beans>1. 根據(jù) Bean 名稱查找實(shí)時(shí)查找

實(shí)時(shí)查找的意思就是說(shuō)直接獲取 beanFactory, 通過(guò) beanFactory 獲取 user 對(duì)應(yīng)的 bean，代碼如下所示

BeanFactory beanFactory = new ClassPathXmlApplicationContext('classpath:/META-INF/dependency-look-up.xml');// 這里的 “user” 就是 xml 文件中的 id，即名稱實(shí)時(shí)查找User user = (User) beanFactory.getBean('user');System.out.println('實(shí)時(shí)加載: ' + bean);延時(shí)查找

這里的延遲就是說(shuō)，通過(guò)其他的對(duì)象來(lái)獲取 user 對(duì)應(yīng)的 Bean，代碼如下所示：

ObjectFactory<User> objectFactory = (ObjectFactory<User>) beanFactory.getBean('objectFactory');User user = objectFactory.getObject();System.out.println('延遲加載' + user);2. 根據(jù) Bean 類型查找

這里的類型指的就是 user.class

單個(gè) Bean 對(duì)象

User bean = beanFactory.getBean(User.class);集合 Bean 對(duì)象

if(beanFactory instanceof ListableBeanFactory){ ListableBeanFactory listableBeanFactory = (ListableBeanFactory)beanFactory; Map<String, User> beansOfType = listableBeanFactory.getBeansOfType(User.class); System.out.println('集合類型：' + beansOfType); }3. 根據(jù) Bean 類型 + 名稱查找4. 根據(jù) Java 注解查找

首先我們自定義一個(gè)注解 @Super

@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)public @interface Super {}

將注解表示到 superUser 類中，這里的 superUser 繼承了 user 類

@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(); }}

最后根據(jù) spring 提供的 api，獲取注解 bean

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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