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;
@Component
public 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;
@Configuration
public 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
//@Configuration
public 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 {
}
}