@pragma('vm:entry-point')
在AOT編譯中趴酣,如果沒有被引用到的代碼會丟棄掉笙以,而AOP代碼是不會被引用,需要使用該方式告訴編譯器不要丟棄代碼
PointCut
/// Object carrying callsite information and methods which can enable you to
/// call the original implementation.
@pragma('vm:entry-point')
class PointCut {
/// PointCut default constructor.
@pragma('vm:entry-point')
PointCut(this.sourceInfos, this.target, this.function, this.stubKey,
this.positionalParams, this.namedParams);
/// Source infomation like file, linenum, etc for a call.
final Map<dynamic, dynamic> sourceInfos;
/// Target where a call is operating on, like x for x.foo().
final Object target;
/// Function name for a call, like foo for x.foo().
final String function;
/// Unique key which can help the proceed function to distinguish a
/// mocked call.
final String stubKey;
/// Positional parameters for a call.
final List<dynamic> positionalParams;
/// Named parameters for a call.
final Map<dynamic, dynamic> namedParams;
/// Unified entrypoint to call a original method,
/// the method body is generated dynamically when being transformed in
/// compile time.
@pragma('vm:entry-point')
Object proceed() {
return null;
}
}
該對象中包含一些我們要調(diào)用或執(zhí)行的代碼的信息壁肋。包括源代碼信息(如庫名揍诽、文件名、行號等)羡铲,方法調(diào)用對象蜂桶,方法名,位置參數(shù)也切,命名參數(shù)等
proceed()是調(diào)用原始方法的入口點扑媚,pointcut.proceed()可實現(xiàn)對原始邏輯的調(diào)用。原始定義中的proceed方法體只是個空殼雷恃,其內(nèi)容將會被在運行時動態(tài)生成
Aspect
/// Annotation indicating whether a class should be taken into consideration
/// when searching for aspectd implementations like AOP.
@pragma('vm:entry-point')
class Aspect {
/// Aspect default constructor
const factory Aspect() = Aspect._;
@pragma('vm:entry-point')
const Aspect._();
}
用來標記要進行AOP操作的類疆股,方便AOP進行識別和提取,也可以起到開關的作用倒槐,如果希望禁掉此段AOP邏輯旬痹,移除@Aspect注解即可。
Call
@Aspect()
@pragma("vm:entry-point")
class RegularCallDemo {
@pragma("vm:entry-point")
RegularCallDemo();
@Call("package:example/main.dart", "", "+appInit")
@pragma("vm:entry-point")
static dynamic appInit(PointCut pointcut) {
print('[KWLM1]: Before appInit!');
dynamic object = pointcut.proceed();
print('[KWLM1]: After appInit!');
return object;
}
@Call("package:example/main.dart", "MyApp", "+MyApp")
@pragma("vm:entry-point")
static dynamic myAppDefine(PointCut pointcut) {
print('[KWLM2]: MyApp default constructor!');
return pointcut.proceed();
}
@Call("package:example/main.dart", "MyHomePage", "+MyHomePage")
@pragma("vm:entry-point")
static dynamic myHomePage(PointCut pointcut) {
dynamic obj = pointcut.proceed();
print('[KWLM3]: MyHomePage named constructor!');
return obj;
}
}
@Call("package:example/main.dart", "MyApp", "+MyApp")中第一個參數(shù)表示的是包名讨越,第二個參數(shù)是類名两残,第三個參數(shù)是方法名。其中方法名可以有一個前綴(-或+)把跨,-表示的是實例方法人弓。而+表示的是靜態(tài)方法或類方法
需要注意的是:寫的aop方法的類型要和要注入的方法一致,即帶有+的着逐,方法前要有static崔赌。
Execute
@Aspect()
@pragma("vm:entry-point")
class RegularExecuteDemo {
@pragma("vm:entry-point")
RegularExecuteDemo();
@Execute("package:example/main.dart", "_MyHomePageState", "-_incrementCounter")
@pragma("vm:entry-point")
dynamic _incrementCounter(PointCut pointcut) {
dynamic obj = pointcut.proceed();
print('[KWLM21]:${pointcut.sourceInfos}:${pointcut.target}:${pointcut.function}!');
return obj;
}
@Execute("dart:math", "Random", "-next.*", isRegex: true)
@pragma("vm:entry-point")
static dynamic randomNext(PointCut pointcut) {
dynamic obj = pointcut.proceed();
print('[KWLM22]:randomNext!');
return obj;
}
}
Call和Execute的區(qū)別是插入代碼的位置不同,call是插入到調(diào)用的地方耸别,而Execute是插入到執(zhí)行的地方健芭。例如:在main方法中調(diào)用say方法,通過Call方式插入的代碼會插入到main方法中秀姐,而通過Execute方式插入的代碼會插入到say方法中慈迈。
Inject
@Aspect()
@pragma("vm:entry-point")
class InjectDemo{
@Inject("package:example/main.dart","","+injectDemo", lineNum:27)
@pragma("vm:entry-point")
static void onInjectDemoHook1() {
print('Aspectd:KWLM51');
}
@Inject("package:example/main.dart","C","+fc", lineNum:198)
@pragma("vm:entry-point")
static void onInjectDemoHook3() {
print('Aspectd:KWLM52++++');
}
}
inject就是往具體的行前插入代碼。
如何使修改代碼生效
對于不同位置的代碼省有,修改后讓其生效需要做的不同痒留。分為example、aspect_impl锥咸、aspectd下的lib
example中的代碼
當只修改了example中的代碼時狭瞎,可以直接運行就會生效
aspect_impl中的代碼
當修改了aspect_impl中的代碼時,需要分別在aspect_impl和example中執(zhí)行flutter clean和flutter pub get之后才能生效搏予。
aspectd下的lib下的代碼
當修改了這下面的代碼后熊锭,需要將flutter_frontend_server目錄下的frontend_server.dart.snapshot文件刪除掉,然后分別在aspect_impl和example中執(zhí)行flutter clean和flutter pub get之后才能生效雪侥。
當更改flutter版本
需要重新執(zhí)行如下:
git apply --3way path-for-aspectd-package/0001-aspectd.patch
rm bin/cache/flutter_tools.stamp
通過上一節(jié)分析我們知道碗殷,git apply之后,flutter源碼中會新增aspectd.dart文件速缨,該文件中會判斷frontend_server.dart.snapshot是否存在锌妻,存在就使用,不存在就通過代碼重新生成旬牲,所以當我們修改了lib下的代碼后需要刪掉frontend_server.dart.snapshot仿粹。