注解

简单注解很容易

val test = FunSpec.builder("test string equality")
  .addAnnotation(Test::class)
  .addStatement("assertThat(%1S).isEqualTo(%1S)", "foo")
  .build()

这会生成带有 @Test 注解的函数

@Test
fun `test string equality`() {
  assertThat("foo").isEqualTo("foo")
}

使用 AnnotationSpec.builder() 为注解设置属性

val logRecord = FunSpec.builder("recordEvent")
  .addModifiers(KModifier.ABSTRACT)
  .addAnnotation(
    AnnotationSpec.builder(Headers::class)
      .addMember("accept = %S", "application/json; charset=utf-8")
      .addMember("userAgent = %S", "Square Cash")
      .build()
  )
  .addParameter("logRecord", LogRecord::class)
  .returns(LogReceipt::class)
  .build()

这会生成带有 accept 和 userAgent 属性的注解

@Headers(
  accept = "application/json; charset=utf-8",
  userAgent = "Square Cash"
)
abstract fun recordEvent(logRecord: LogRecord): LogReceipt

当你需要更复杂的情况时，注解的值本身也可以是注解。使用 %L 表示嵌套注解

val headerList = ClassName("", "HeaderList")
val header = ClassName("", "Header")
val logRecord = FunSpec.builder("recordEvent")
  .addModifiers(KModifier.ABSTRACT)
  .addAnnotation(
    AnnotationSpec.builder(headerList)
      .addMember(
        "[\n⇥%L,\n%L⇤\n]",
        AnnotationSpec.builder(header)
          .addMember("name = %S", "Accept")
          .addMember("value = %S", "application/json; charset=utf-8")
          .build(),
        AnnotationSpec.builder(header)
          .addMember("name = %S", "User-Agent")
          .addMember("value = %S", "Square Cash")
          .build()
      )
      .build()
  )
  .addParameter("logRecord", logRecordName)
  .returns(logReceipt)
  .build()

这会生成

@HeaderList(
  [
    Header(name = "Accept", value = "application/json; charset=utf-8"),
    Header(name = "User-Agent", value = "Square Cash")
  ]
)
abstract fun recordEvent(logRecord: LogRecord): LogReceipt

KotlinPoet 支持注解的使用点目标

val utils = FileSpec.builder("com.example", "Utils")
  .addAnnotation(
    AnnotationSpec.builder(JvmName::class)
      .useSiteTarget(UseSiteTarget.FILE)
      .build()
  )
  .addFunction(
    FunSpec.builder("abs")
      .receiver(Int::class)
      .returns(Int::class)
      .addStatement("return if (this < 0) -this else this")
      .build()
  )
  .build()

将输出此内容

@file:JvmName

package com.example

import kotlin.Int
import kotlin.jvm.JvmName

fun Int.abs(): Int = if (this < 0) -this else this