本文小编为大家详细介绍“Spring容器注入bean的方法有哪些”，内容详细，步骤清晰，细节处理妥当，希望这篇“Spring容器注入bean的方法有哪些”文章能帮助大家解决疑惑，下面跟着小编的思路慢慢深入，一起来学习新知识吧。
@ComponentScan+@Component
  @ComponentScan可以放在启动类上，指定要扫描的包路径；该包路径下被@Component修饰的类，都会被注入到Spring容器中。
import org.springframework.context.annotation.AnnotationConfigApplicationContext;import org.springframework.context.annotation.ComponentScan;@ComponentScan(basePackages = "com.gs.beanRegister")public class BootStrap { public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BootStrap.class); A bean = context.getBean(A.class); bean.say(); }}  com.gs.beanRegister包下：
import org.springframework.stereotype.Component;@Componentpublic class A { public void say() { System.out.println("这是a"); }}  注：在SpringBoot中，由于其自动装配的特性，所以@ComponentScan可以不加，只要@Component修饰的类和启动类在同一包下或者在启动类所在包的子包下。
@Configuration+@Bean
  @Configuration用来声明一个配置类，如果它的方法被@Bean修饰，那么该方法返回的对象也会被注入到Spring容器中。
  代码方面，BootStrap 类不动，A类的@Component去掉，com.gs.beanRegister包下建个配置类：
import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.Bean;@Configurationpublic class MyConfiguration { @Bean public A a() { return new A(); }}通过@Import注解
  这个注解可能平时大家接触得不多，它有好几种使用方式。
1.直接导入类的class
import org.springframework.context.annotation.Import;import org.springframework.context.annotation.AnnotationConfigApplicationContext;@Import(A.class)public class BootStrap { public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BootStrap.class); A bean = context.getBean(A.class); //B bean = context.getBean(B.class); bean.say(); }}  A类不用添加任何注解：
public class A { public void say() { System.out.println("这是a"); }}2.导入配置类
import org.springframework.context.annotation.AnnotationConfigApplicationContext;import org.springframework.context.annotation.Import;@Import(MyConfiguration.class)public class BootStrap { public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BootStrap.class); A bean = context.getBean(A.class); bean.say(); }}import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;// 使用@Import导入配置类时，@Configuration可以不加//@Configurationpublic class MyConfiguration { @Bean public A a() { return new A(); }}3.导入ImportSelector的实现类
import org.springframework.context.annotation.AnnotationConfigApplicationContext;import org.springframework.context.annotation.Import;@Import(MyImportSelector.class)public class BootStrap { public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BootStrap.class); A bean = context.getBean(A.class); bean.say(); }}import org.springframework.context.annotation.ImportSelector;import org.springframework.core.type.AnnotationMetadata;public class MyImportSelector implements ImportSelector { @Override public String[] selectImports(AnnotationMetadata metadata) { // 返回要注入的bean的全路径，A类不用任何注解修饰 // SpringBoot的自动装配，就用到了这种方式： // 返回配置类的全路径，配置类的@Bean方法返回的对象也能注入到容器中 return new String[] { A.class.getName() }; }}4.导入ImportBeanDefinitionRegistrar的实现类
import org.springframework.context.annotation.AnnotationConfigApplicationContext;import org.springframework.context.annotation.Import;@Import(MyImportBeanDefinitionRegistrar.class)public class BootStrap { public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BootStrap.class); A bean = context.getBean(A.class); bean.say(); }}import org.springframework.beans.factory.config.BeanDefinition;import org.springframework.beans.factory.support.BeanDefinitionRegistry;import org.springframework.beans.factory.support.RootBeanDefinition;import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;import org.springframework.core.type.AnnotationMetadata;public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar { @Override public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) { // 构建bean的元数据，A类不用任何注解修饰 // spring-mybatis扫描mapper接口，生成代理类，就是用的这种方式 BeanDefinition definition = new RootBeanDefinition(A.class); registry.registerBeanDefinition("a", definition); }}借助FactoryBean接口
  实现FactoryBean接口的类，除了本身会被注入外，getObject方法返回的对象也会被注入到Spring容器中。
import org.springframework.context.annotation.AnnotationConfigApplicationContext;import org.springframework.context.annotation.Import;@Import(MyFactoryBean.class)public class BootStrap { public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BootStrap.class); A bean = context.getBean(A.class); bean.say(); }}import org.springframework.beans.factory.FactoryBean;public class MyFactoryBean implements FactoryBean { @Override public Object getObject() throws Exception { return new A(); } @Override public Class<?> getObjectType() { return A.class; }}借助BeanDefinitionRegistryPostProcessor接口
  在Spring容器启动时，会调用该接口的postProcessBeanDefinitionRegistry方法，大概意思是等BeanDefinition(上面提到的bean的元数据)加载完成后，再对它进行后置处理。所以可以在此调整BeanDefinition，从而把对应的bean注入。
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class BootStrap { public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(); BeanDefinitionRegistryPostProcessor postProcessor = new MyBeanDefinitionRegistryPostProcessor(); context.addBeanFactoryPostProcessor(postProcessor); context.refresh(); A a = context.getBean(A.class); a.say(); }}import org.springframework.beans.BeansException;import org.springframework.beans.factory.config.BeanDefinition;import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;import org.springframework.beans.factory.support.BeanDefinitionRegistry;import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;import org.springframework.beans.factory.support.RootBeanDefinition;public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor { @Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException { BeanDefinition definition = new RootBeanDefinition(A.class); registry.registerBeanDefinition("a", definition); } @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { }}读到这里，这篇“Spring容器注入bean的方法有哪些”文章已经介绍完毕，想要掌握这篇文章的知识点还需要大家自己动手实践使用过才能领会，如果想了解更多相关内容的文章，欢迎关注编程网行业资讯频道。
