@Configurable

AnnotationBeanConfigurerAspect

AnnotationBeanConfigurerAspect是一个AspectJ切面，使用AspectJ语言定义。
通过上下文获取该切面后，调用其实例方法configureBean()，可对一个使用new关键字创建的对象进行配置，实现自动连线。

AnnotationBeanConfigureAspect本身需要由Spring进行配置（以便获得用于配置新对象的bean工厂的引用）。@EnableSpringConfigured注解专门实现该需求。

该切面属于制品spring-aspects：

dependencies {
    implementation 'org.jetbrains.kotlin:kotlin-stdlib'
    implementation 'org.springframework:spring-context:5.2.0.RELEASE'
    implementation 'org.springframework:spring-aspects:5.2.0.RELEASE'
}

configureBean()：

package bean

import org.junit.jupiter.api.Test
import org.junit.jupiter.api.extension.ExtendWith
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.beans.factory.annotation.Configurable
import org.springframework.beans.factory.aspectj.AnnotationBeanConfigurerAspect
import org.springframework.context.ApplicationContext
import org.springframework.context.annotation.ComponentScan
import org.springframework.stereotype.Component
import org.springframework.test.context.junit.jupiter.SpringExtension
import org.springframework.test.context.junit.jupiter.SpringJUnitConfig

@Component
@Configurable(preConstruction = true)
open class A {
    @Autowired
    open var ctx: ApplicationContext? = null

    open fun foo() {
        println(ctx)
    }
}

@ExtendWith(SpringExtension::class)
@SpringJUnitConfig(ConfigurableTest::class)
@ComponentScan
@org.springframework.context.annotation.aspectj.EnableSpringConfigured
open class ConfigurableTest {
    @Autowired lateinit var ctx: ApplicationContext
    @Test fun main() {
        A().foo() // null
        ctx.getBean(A::class.java).foo() // not null

        val aspect = ctx.getBean(AnnotationBeanConfigurerAspect::class.java)
        val bean = A()
        bean.foo() // null
        aspect.configureBean(bean)
        bean.foo() // not null
    }
}

加载时编织

要启用Spring框架的LTW支持，你需要配置一个LoadTimeWeaver，通常通过使用@EnableLoadTimeWeaving注解完成。

@Configuration
@PropertySource("classpath:application.properties")
@ComponentScan
@org.springframework.context.annotation.aspectj.EnableSpringConfigured // AnnotationBeanConfigureAspect本身需要由Spring进行配置（以便获得用于配置新对象的bean工厂的引用）
//@EnableLoadTimeWeaving(aspectjWeaving = EnableLoadTimeWeaving.AspectJWeaving.ENABLED) // 要启用Spring框架的LTW支持，你需要配置一个LoadTimeWeaver，通常通过使用@EnableLoadTimeWeaving注解完成
//@EnableLoadTimeWeaving(aspectjWeaving = EnableLoadTimeWeaving.AspectJWeaving.DISABLED)
@EnableLoadTimeWeaving(aspectjWeaving = EnableLoadTimeWeaving.AspectJWeaving.AUTODETECT) // 自动检测META-INF/aop.xml配置文件是否存在
open class JavaConfig : LoadTimeWeavingConfigurer {
    // Implement LoadTimeWeavingConfigurer is optional. In default, DefaultContextLoadTimeWeaver will active.
    override fun getLoadTimeWeaver(): LoadTimeWeaver {
        return InstrumentationLoadTimeWeaver().apply {
            println("inject -> $this")
        }
    }
}

加载时编织需要修改jvm选项，设置代理为spring-instrument，可在Gradle脚本中设置：

dependencies {
    // AOP
    // https://mvnrepository.com/artifact/org.aspectj/aspectjrt
    implementation group: 'org.aspectj', name: 'aspectjrt', version: '1.9.6'
    // https://mvnrepository.com/artifact/org.aspectj/aspectjweaver
    implementation group: 'org.aspectj', name: 'aspectjweaver', version: '1.9.6'
    // Spring-instrument
    runtimeOnly 'org.springframework:spring-instrument:5.2.0.RELEASE'
}

test {
    // Setup the Java agent to Spring-instrument
    def file_spring_instrument = sourceSets.test.runtimeClasspath.find { it.name.matches("spring-instrument-.*\\.jar") }
    jvmArgs "-javaagent:$file_spring_instrument"

    useJUnitPlatform()
}

@See: https://docs.gradle.org/current/userguide/building_java_projects.html#sec:feature_preview

META-INF/aop.xml

META-INF/aop.xml定义需要扫描、配置的类，格式如下：

<!DOCTYPE aspectj PUBLIC "-//AspectJ//DTD//EN" "https://www.eclipse.org/aspectj/dtd/aspectj.dtd">
<aspectj>

    <weaver>
        <!-- only weave classes in our application-specific packages -->
        <include within="bean.*"/>
    </weaver>

</aspectj>

END