Spring应用中注入Spring bean的情况总结

素颜马尾好姑娘i 2022-06-09 00:56 380阅读 0赞

1.在一个应用类（也是一个Spring bean）中，通过Spring bean注入接口的实现类

*  接口定义如下：

public interface AnInterface {
        String getMessage();
    }

1) 只定义了接口的一个实现类（这也是最常见的一种情况）

*  实现类定义如下：

@Component
    public class AnImpl implements AnInterface {
    	...

*  则应用类中的依赖注入定义如下：

@Configuration
    @ComponentScan
    class MyRunner {
    	@Autowired
    	private AnInterface aReference;
            ...

2) 定义了接口的多个实现类（注入时需要指出注入哪个实现类）

*  定义一个默认实现类

@Component("aDefaultImpl")
    @Primary
    public class ADefaultImpl implements AnInterface {
    	...

注意，这里的**@Primary，表明主实现类（即默认实现类）**。

*  定义其他非默认实现类

@Component("aNonDefaultImpl")
    public class ANonDefaultImpl implements AnInterface {
    	...

注意，这就是个基本Spring bean。

*  在应用类中注入默认实现类

@Configuration
    @ComponentScan
    class MyRunner {
    	@Autowired
    	private AnInterface aReference;
            ...

注意，注入默认实现类时，用法等同于只有一个主实现类。

*  应用类中注入非默认实现类时（需要给出实现类的Spring bean名称）

@Configuration
    @ComponentScan
    class MyRunner {
    	@Autowired
    	@Qualifier("aNonDefaultImpl")
    	private AnInterface aReference;
    	...

注意，这里的**@Qualifier，给出了要注入的实现类的Spring bean名称**。

除此之外，还可以使用@javax.annotation.Resource如下：

@Configuration
    @ComponentScan
    class MyRunner {
    	@javax.annotation.Resource(name="aNonDefaultImpl")
    	private AnInterface aReference;
    	...

2.在应用类（不是一个Spring bean）中，通过Spring bean注入接口的实现类

*  接口定义同上AnInterface
 *  定义接口的实现类同上AnImpl
 *  在应用类中引用接口的实现类

@Configurable
    public class ANoneSpringBean {
    	@Autowired
    	private AnInterface aReference;
            ...

注意，这里的**@Configurable**，表明该类虽然不是Spring bean，但是还是希望能够借助于Spring来注入必要对象。

*  在另一个应用类（该应用类是Spring bean）中，为非Spring bean的ANoneSpringBean注入必要对象依赖对象

@Configuration
    @ComponentScan
    @EnableSpringConfigured
    @EnableLoadTimeWeaving
    public class MyApplication {
    	public aMethod() {
    		ApplicationContext context = new AnnotationConfigApplicationContext(MyApplication.class);//Spring context中有被注入的实现类对象
    		public ANoneSpringBean aNoneSpringBean = new ANonSpringBean();//为ANoneSpringBean注入AnInterface对象
    		...//后续就可以访问ANoneSpringBean中的aReference对象

注意，在new ANoneSpringBean()之前，必须初始化Spring的ApplicationCentext，并且AnImpl类必须能够被加入到该ApplicationCentext。

此外，如果是Maven项目，必须有如下依赖：

<dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.9.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>4.3.9.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>4.3.9.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aspects</artifactId>
            <version>4.3.9.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-instrument</artifactId>
            <version>4.3.9.RELEASE</version>
        </dependency>
        <dependency>
          <groupId>org.aspectj</groupId>
          <artifactId>aspectjrt</artifactId>
          <version>1.8.9</version>
        </dependency>

运行时，还需要设置如下JVM启动参数：

-javaagent:C:\Users\myname\.m2\repository\org\springframework\spring-instrument\4.3.9.RELEASE\spring-instrument-4.3.9.RELEASE.jar

运行结果如下：

Aug 23, 2017 5:26:52 PM org.springframework.context.annotation.AnnotationConfigApplicationContext prepareRefresh
    INFO: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@1a6c5a9e: startup date [Wed Aug 23 17:26:52 CST 2017]; root of context hierarchy
    Aug 23, 2017 5:26:53 PM org.springframework.context.weaving.DefaultContextLoadTimeWeaver setBeanClassLoader
    INFO: Found Spring's JVM agent for instrumentation
    Aug 23, 2017 5:26:53 PM org.springframework.context.weaving.DefaultContextLoadTimeWeaver setBeanClassLoader
    INFO: Found Spring's JVM agent for instrumentation
    [AppClassLoader@18b4aac2] error can't determine superclass of missing type org.springframework.transaction.interceptor.TransactionAspectSupport
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.aop.scope.ScopedProxyUtils
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.aop.scope.ScopedProxyUtils
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.aop.scope.ScopedProxyUtils
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.aop.scope.ScopedObject
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.aop.RawTargetAccess
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.context.event.EventListenerMethodProcessor$1
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.core.MethodIntrospector
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.core.MethodIntrospector$1
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.context.event.EventListener
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.context.MessageSourceResolvable
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.util.ErrorHandler
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.context.support.DefaultLifecycleProcessor
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.context.ApplicationContextException
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.context.event.AbstractApplicationEventMulticaster$ListenerCacheKey
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.context.support.LiveBeansView
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.context.support.LiveBeansViewMBean
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.util.ConcurrentReferenceHashMap$EntrySet
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.util.ConcurrentReferenceHashMap$EntryIterator
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type com.ericsson.tao5.spring.nonbean_beans.ANoneSpringBean
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.beans.factory.aspectj.ConfigurableObject
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type com.sun.proxy.$Proxy25
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    [AppClassLoader@18b4aac2] error can't determine annotations of missing type org.springframework.transaction.annotation.Transactional
    when weaving type org.springframework.beans.factory.wiring.BeanWiringInfo
    when weaving classes 
    when weaving 
     [Xlint:cantFindType]
    ANoneSpringBean
    ANonDefaultImpl

参考链接：

http://docs.spring.io/spring/docs/current/spring-framework-reference/htmlsingle/

https://github.com/ahmedbhaila/non-managed-beans

http://docs.spring.io/spring-framework/docs/current/javadoc-api/overview-summary.html