最近学习注解，于是实现一个kotlin版本的加载配置项注解。

注解代码 :

/**
 * property annotate
 * use those to easy use property
 */

@Target(AnnotationTarget.CLASS)
@Retention(AnnotationRetention.RUNTIME)
annotation class PropertyBase(val filePath: String)

@Target(AnnotationTarget.FIELD)
@Retention(AnnotationRetention.RUNTIME)
annotation class IntProperty(val propertyName: String, val defValue: Int)

@Target(AnnotationTarget.FIELD)
@Retention(AnnotationRetention.RUNTIME)
annotation class DoubleProperty(val propertyName: String, val defValue: Double)

@Target(AnnotationTarget.FIELD)
@Retention(AnnotationRetention.RUNTIME)
annotation class StringProperty(val propertyName: String, val defValue: String)

注解处理器 :

import java.io.BufferedInputStream
import java.io.FileInputStream
import java.lang.Exception
import java.util.*

class PropertyUtil {
    companion object {
        fun loadProperty(obj: Any)  {
            if(!obj.javaClass.isAnnotationPresent(PropertyBase::class.java))    {
                throw Exception("$obj have no annotation for property")
            }

            val pp = Properties().apply {
                val pb = obj.javaClass.getAnnotation(PropertyBase::class.java)
                load(BufferedInputStream(FileInputStream(pb.filePath)))
            }

            obj.javaClass.declaredFields.forEach {
                    when {
                        it.isAnnotationPresent(IntProperty::class.java) -> {
                            it.getAnnotation(IntProperty::class.java).let { ia ->
                                it.isAccessible = true
                                it.setInt(obj, pp.getProperty(ia.propertyName)?.toInt() ?: ia.defValue)
                            }
                        }

                        it.isAnnotationPresent(DoubleProperty::class.java) -> {
                            it.getAnnotation(DoubleProperty::class.java).let { da ->
                                it.isAccessible = true
                                it.setDouble(obj, pp.getProperty(da.propertyName)?.toDouble() ?: da.defValue)
                            }
                        }

                        it.isAnnotationPresent(StringProperty::class.java) -> {
                            it.getAnnotation(StringProperty::class.java).let { sa ->
                                it.isAccessible = true
                                it.set(obj, pp.getProperty(sa.propertyName) ?: sa.defValue)
                            }
                        }
                    }
            }
        }
    }
}

单元测试类 ：

import twsLib.util.propertAnnotate.DoubleProperty
import twsLib.util.propertAnnotate.IntProperty
import twsLib.util.propertAnnotate.PropertyBase
import twsLib.util.propertAnnotate.StringProperty

@PropertyBase("src/test/resources/test.properties")
class TestProperty {
    @IntProperty("test.intProp", 1)
    var intProp = 1

    @DoubleProperty("test.doubleProp", 2.toDouble())
    var doubleProp = 2.toDouble()

    @StringProperty("test.stringProp", "def")
    var stringProp = "def"
}

JUnit4单元测试代码 ：

import org.junit.Assert
import org.junit.Test
import twsLib.util.propertAnnotate.PropertyUtil

class PropertyUtilTest {
    @Test
    fun testProp() {
        val tp = TestProperty()
        PropertyUtil.loadProperty(tp)

        Assert.assertEquals(2, tp.intProp)
        Assert.assertEquals(3.14, tp.doubleProp, 0.0001)
        Assert.assertEquals("pi", tp.stringProp)
    }
}

最后，测试用配置文件（test.properties）：

test.intProp = 2
test.doubleProp = 3.14
test.stringProp = pi

单元测试通过 ：

捕获.PNG