Question

Kotlin无法在编译时注入注释，例如现有库Lombok。有没有什么好的方法可以在运行时为spring框架注入注释？

Answer 1

假设您正在尝试将注册器注释注入Spring应用程序。

这是注释类示例： Log.kt

package com.example.util
@Retention(AnnotationRetention.RUNTIME)
@Target(AnnotationTarget.FIELD)
@MustBeDocumented
annotation class Log

此类在运行时注入注释： LogInjector.kt

package com.example.util
import org.slf4j.LoggerFactory
import org.springframework.beans.BeansException
import org.springframework.beans.factory.config.BeanPostProcessor
import org.springframework.stereotype.Component
import org.springframework.util.ReflectionUtils
import java.lang.reflect.Field

@Component
class LogInjector: BeanPostProcessor {

  @Throws(BeansException::class)
  override fun postProcessAfterInitialization(bean: Any, beanName: String): Any {
    return bean
  }

  @Throws(BeansException::class)
  override fun postProcessBeforeInitialization(bean: Any, name: String): Any {
    ReflectionUtils.doWithFields(bean.javaClass,
      @Throws(IllegalArgumentException::class, IllegalAccessException::class) { field: Field ->
        // SAM conversion for Java interface 
        ReflectionUtils.makeAccessible(field)
        if (field.getAnnotation(Log::class.java) != null) {
          val log = LoggerFactory.getLogger(bean.javaClass)
          field.set(bean, log)
        }
      }
    )
    return bean
  }
}

然后，此类使用@Log注释： GreetingController.kt

package com.example.web
import org.slf4j.Logger
import org.springframework.web.bind.annotation.*

@RestController
class GreetingController {
  @Log lateinit private var logger: Logger

  @RequestMapping("/greeting")
  fun greeting(): String {
    logger.info("Greeting endpoint was called")
    return "Hello"
  }
}

为避免像logger?.info('...')那样在null-safe中调用logger，此示例使用the late-initialized modifier标记属性。

用Kotlin注入弹簧注射

1 个答案: