百度APP Android包体积优化实践（四）Dex注解优化

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前言

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Dex注解类型

Dex注解格式

.annotation [注解属性] <注解类名>    [注解字段 = 值].end annotation

.annotation build Landroid/annotation/SuppressLint;    value = {        "BanParcelableUsage"    }.end annotation

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优化目标

public List<JSONObject> jsonObjectList = new ArrayList<>()

.field public jsonObjectList:Ljava/util/List;    .annotation system Ldalvik/annotation/Signature;        value = {            "Ljava/util/List<",            "Lorg/json/JSONObject;",            ">;"        }    .end annotation.end field

java/lang/Class.getTypeParametersjava/lang/Class.getGenericSuperclassjava/lang/Class.getGenericInterfacesjava/lang/reflect/Field.getGenericTypejava/lang/reflect/Method.getGenericReturnTypejava/lang/reflect/Method.getTypeParametersjava/lang/reflect/Method.getGenericParameterTypesjava/lang/reflect/Method.getGenericExceptionTypesjava/lang/reflect/Constructor.getTypeParametersjava/lang/reflect/Constructor.getGenericParameterTypejava/lang/reflect/Constructor.getGenericExceptionTypes

public class OuterClass {    public String a;    public class InnerClass{        public String b;    }}

.class public Lcom/baidu/searchbox/OuterClass;.super Ljava/lang/Object;.source "OuterClass.java"
# annotations.annotation system Ldalvik/annotation/MemberClasses;    value = {        Lcom/baidu/searchbox/OuterClass$InnerClass;    }.end annotation
...

.class public Lcom/baidu/searchbox/OuterClass$InnerClass;.super Ljava/lang/Object;.source "OuterClass.java"

# annotations.annotation system Ldalvik/annotation/EnclosingClass;    value = Lcom/baidu/searchbox/OuterClass;.end annotation
.annotation system Ldalvik/annotation/InnerClass;    accessFlags = 0x1    name = "InnerClass".end annotation

com/google/gson/Gson.fromJson(Ljava/lang/String;Ljava/lang/Class;)Ljava/lang/Objectcom/google/gson/Gson.fromJson(Lcom/google/gson/JsonElement;Ljava/lang/Class;)Ljava/lang/Objectcom/google/gson/Gson.fromJson(Ljava/io/Reader;Ljava/lang/Class;)Ljava/lang/Object

优化方案

override fun visitClass(dcn: DexClassNode) {    val outDexClassNode = DexClassNode(dcn.type, dcn.accessFlags, dcn.superType, dcn.interfaces)    outDexClassPoolNode.addClass(outDexClassNode)    MarkedMultiDexSplitter.setDexIdForClassNode(outDexClassNode, dexId)    //遍历该Dex下面的所有类    dcn.accept(object : DexClassVisitor(outDexClassNode.asVisitor()) {        override fun visitAnnotation(annotationInfo: DexAnnotationVisitorInfo):                DexAnnotationVisitor? {            //检查类注解是否匹配删除规则            return if (removeAnnotation(annotationInfo, dcn.type.toTypeDescriptor())) {                null            } else super.visitAnnotation(annotationInfo)        }        override fun visitMethod(methodInfo: DexMethodVisitorInfo?): DexMethodVisitor {            val superMethodVisitor = super.visitMethod(methodInfo)            return object : DexMethodVisitor(superMethodVisitor) {                override fun visitAnnotation(annotationInfo: DexAnnotationVisitorInfo):                        DexAnnotationVisitor? {                    //检查方法注解是否匹配删除规则                    return if (removeAnnotation(annotationInfo, dcn.type.toTypeDescriptor())) {                        null                    } else super.visitAnnotation(annotationInfo)                }                override fun visitParameterAnnotation(parameter: Int, annotationInfo:                DexAnnotationVisitorInfo): DexAnnotationVisitor? {                    //检查方法参数的注解是否匹配删除规则                    return if (removeAnnotation(annotationInfo, dcn.type.toTypeDescriptor())) {                        null                    } else super.visitParameterAnnotation(parameter, annotationInfo)                }            }        }        override fun visitField(fieldInfo: DexFieldVisitorInfo?): DexFieldVisitor {            val superFiledVisitor = super.visitField(fieldInfo)            return object : DexFieldVisitor(superFiledVisitor) {                override fun visitAnnotation(annotationInfo: DexAnnotationVisitorInfo):                        DexAnnotationVisitor? {                    //检查类变量的注解是否匹配删除规则                    return if (removeAnnotation(annotationInfo, dcn.type.toTypeDescriptor())) {                        null                    } else super.visitAnnotation(annotationInfo)                }            }        }    })}

/** * 删除不必要的注解 * * @param annotationInfo * @param classType * @return Boolean */private fun removeAnnotation(annotationInfo: DexAnnotationVisitorInfo,                             classType: String): Boolean {    // build类型注解优化，仅根据配置开关决定    if (annotationInfo.visibility.name == ANNOTATION_TYPE_BUILD && optBuild) {        return true    }
    // system类型注解优化，根据开关与白名单决定    if (!optSystem) {        return false    }
    when (annotationInfo.type.toTypeDescriptor()) {        ANNOTATION_SIGNATURE,        ANNOTATION_INNERCLASS,        ANNOTATION_ENCLOSINGMETHOD,        ANNOTATION_ENCLOSINGCLASS,        ANNOTATION_MEMBERCLASS ->            if (classType !in whiteListSet) {                LogUtil.log("current classType", classType)                LogUtil.log("current annotationInfo.type", annotationInfo.type.toTypeDescriptor())                LogUtil.log("系统注解", "需要删除")                return true            }    }    return false}

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自动化检测和加白

com.baidu.searchbox.net.update.v2.AbstractCommandListener#superclasscom.google.gson.reflect.TypeToken#superclasscom.google.gson.annotations.SerializedName#annotationcom.google.gson.**#packagecom.alipay.**#packagecom.baidu.FinalDb#classname...

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总结