最近看到有人问Retrofit的原理，然后就研究了一下，发现内部是用java的动态代理实现的，真的很巧妙，动态代理在android端的应用场景不多，retrofit算是一个，就想着能不能自己写一个简化版的Retrofit。
只拿get做演示
定义GET注解：
@Documented
@Target(METHOD)
@Retention(RUNTIME)
public @interface GET {
String value() default "";
}
定义接口：
interface ServiceApi {
/**
* 获取公众号列表
* 基于 玩android开放api
*/
@GET("/wxarticle/chapters/json")
fun getPublicList():Call
}
核心retrofit类，利用建造者模式：
@Suppress("UNCHECKED_CAST")
class Retrofit(var callFactory: Call.Factory, var baseUrl: String) {
fun <T> create(service: Class<T>): T {
return Proxy.newProxyInstance(
service.classLoader, arrayOf(service)
) { _, method, _ ->
//解析注解
val annotations = method.annotations
if (annotations.isEmpty()) {
throw IllegalStateException("annotation required.")
}
annotations.forEach {
Logger.d(it.toString())
Logger.d(it is GET)
return@newProxyInstance when (it) {
is GET -> {
handlerGet(it.value)
}
is POST -> {
//不处理，只模拟GET
}
else -> {
}
}
}
} as T
}
/**
* 处理get请求
*/
private fun handlerGet(url: String): Call {
val request = Request.Builder()
.url(baseUrl + url)
.get()
.build()
//这里没有做返回类型转换，默认都返回call
return callFactory.newCall(request)
}
class Builder {
private var baseUrl: String? = null
private var callFactory: Call.Factory? = null
/**
* 模拟传入baseUrl
*/
fun baseUrl(baseUrl: String): Builder {
this.baseUrl = baseUrl
return this
}
/**
* 模拟传入client
*/
fun client(client: OkHttpClient): Builder {
this.callFactory = client
return this
}
fun build(): Retrofit {
if (baseUrl == null) {
throw IllegalStateException("Base URL required.")
}
if (callFactory == null) {
callFactory = OkHttpClient()
}
return Retrofit(callFactory!!, baseUrl!!)
}
}
}
使用：
//初始化retrofit
val api = Retrofit
.Builder()
.baseUrl("https://wanandroid.com")
.client(OkHttpClient())
.build()
.create(ServiceApi::class.java)
//按钮点击（这里利用kotlin的扩展函数，做的防重点）
bt_net.singleClick {
api.getPublicList()
.enqueue(object : Callback {
override fun onFailure(call: Call, e: IOException) {
Logger.d(e.message)
}
override fun onResponse(call: Call, response: Response) {
val res = response.body()?.source()?.readUtf8()
Logger.d(res)
}
})
}
返回结果：
{
"data": [{
"children": [],
"courseId": 13,
"id": 408,
"name": "鸿洋",
"order": 190000,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 409,
"name": "郭霖",
"order": 190001,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 410,
"name": "玉刚说",
"order": 190002,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 411,
"name": "承香墨影",
"order": 190003,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 413,
"name": "Android群英传",
"order": 190004,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 414,
"name": "code小生",
"order": 190005,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 415,
"name": "谷歌开发者",
"order": 190006,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 416,
"name": "奇卓社",
"order": 190007,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 417,
"name": "美团技术团队",
"order": 190008,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 420,
"name": "GcsSloop",
"order": 190009,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 421,
"name": "互联网侦察",
"order": 190010,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 427,
"name": "susion随心",
"order": 190011,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 428,
"name": "程序亦非猿",
"order": 190012,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}, {
"children": [],
"courseId": 13,
"id": 434,
"name": "Android达摩院",
"order": 190013,
"parentChapterId": 407,
"userControlSetTop": false,
"visible": 1
}],
"errorCode": 0,
"errorMsg": ""
}
只是一个简单的模拟，很多深入的功能如果有时间的话再完善~
github传送门
完工 撒花~
