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class="markdown_views prism-tomorrow-night">
1、ReflectASM 简介
1.1 什么是class="tags" href="/tags/FanShe.html" title=反射>反射？
一般情况下，我们使用某个类时已经知道它是什么类了，用来做什么的，所以我们直接将这个类 进行实例化，然后使用这个类对象进行操作
class="tags" href="/tags/FanShe.html" title=反射>反射就是在运行的过程中才知道要操作的类是什么。Java class="tags" href="/tags/FanShe.html" title=反射>反射实在运行的过程中，对任意一个类，都可以知道这个类的所有属性和方法，对一个对象，都能够调用任意一个方法和属性，这种动态获取的信息和调用对象方法的功能称为 class="tags" href="/tags/JAVA.html" title=java>java 的class="tags" href="/tags/FanShe.html" title=反射>反射机制。
我们可以使用class="tags" href="/tags/JAVA.html" title=java>java.lang.Class类，这个为了实现class="tags" href="/tags/FanShe.html" title=反射>反射体用的一个类，通过全类名获取到class="tags" href="/tags/FanShe.html" title=反射>反射的 Class 对象，然后通过 class 对象实现调用它的方法、获取属性、获取类信息等操作
1.2 什么是 reflectASM？
ASM 可以用来进行字节码操作，可以修改现有类或者以二进制形式动态生成类，ReflectASM 使用了 ASM，使用字节码生成的方式实现了更高效的class="tags" href="/tags/FanShe.html" title=反射>反射机制。执行时会生成一个存取类来 set/get 字段，访问方法或者创建实例。不是依赖于 Java 本身的class="tags" href="/tags/FanShe.html" title=反射>反射机制实现的，所以更快，而且避免了访问原始类型因自动装箱而产生的问题
ReflectASM 是一个非常小的 Java 类库，只有五个类，却提供了非常高性能的属性操作、方法调用、构造方法调用等，
2、maven 依赖
class="prism language-xml">class="token tag">class="token tag">class="token punctuation"><dependencyclass="token punctuation">>
class="token tag">class="token tag">class="token punctuation"><groupIdclass="token punctuation">>com.esotericsoftwareclass="token tag">class="token tag">class="token punctuation"></groupIdclass="token punctuation">>
class="token tag">class="token tag">class="token punctuation"><artifactIdclass="token punctuation">>reflectasmclass="token tag">class="token tag">class="token punctuation"></artifactIdclass="token punctuation">>
class="token tag">class="token tag">class="token punctuation"><versionclass="token punctuation">>1.11.0class="token tag">class="token tag">class="token punctuation"></versionclass="token punctuation">>
class="token tag">class="token tag">class="token punctuation"></dependencyclass="token punctuation">>
reflectASM 提供了根据匹配的字符串操作变量、函数的特性，reflectASM 中常用常用的类只有 MethodAccess，FieldAccess，Constructor 这几个
3、class="tags" href="/tags/FanShe.html" title=反射>反射调用测试
class="tags" href="/tags/FanShe.html" title=反射>反射对象
class="prism language-class="tags" href="/tags/JAVA.html" title=java>java">class="token annotation punctuation">@Data
class="token annotation punctuation">@Builder
class="token annotation punctuation">@NoArgsConstructor
class="token annotation punctuation">@AllArgsConstructor
class="token keyword">public class="token keyword">class class="token class-name">PlanBarCodeExcel class="token punctuation">{
class="token keyword">private class="token class-name">String barCodeclass="token punctuation">;
class="token keyword">public class="token class-name">String brandNameclass="token punctuation">;
class="token keyword">private class="token class-name">String packingNumclass="token punctuation">;
class="token keyword">private class="token class-name">String channelCodeclass="token punctuation">;
class="token punctuation">}
reflectASM 使用
class="prism language-class="tags" href="/tags/JAVA.html" title=java>java">class="token keyword">public class="token keyword">class class="token class-name">ReflectASMDemo class="token punctuation">{
class="token comment">/**
* jdk class="tags" href="/tags/FanShe.html" title=反射>反射调用方法
* @throws Exception
*/
class="token keyword">public class="token keyword">static class="token keyword">void class="token function">jdkReflectclass="token punctuation">(class="token punctuation">) class="token keyword">throws class="token class-name">Exception class="token punctuation">{
class="token class-name">PlanBarCodeExcel planBarCodeExcel class="token operator">= class="token keyword">new class="token class-name">PlanBarCodeExcelclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token class-name">Method setBarCode class="token operator">= planBarCodeExcelclass="token punctuation">.class="token function">getClassclass="token punctuation">(class="token punctuation">)class="token punctuation">.class="token function">getMethodclass="token punctuation">(class="token string">"setBarCode"class="token punctuation">, class="token class-name">Stringclass="token punctuation">.class="token keyword">classclass="token punctuation">)class="token punctuation">;
setBarCodeclass="token punctuation">.class="token function">invokeclass="token punctuation">(planBarCodeExcelclass="token punctuation">, class="token string">"barCode"class="token punctuation">)class="token punctuation">;
class="token punctuation">}
class="token comment">/**
* reflectASMclass="tags" href="/tags/FanShe.html" title=反射>反射调用方法
* 需要注意的是，reflectASM 提供的方法只能调用非私有的属性和方法，私有属性需要通过 get/set 方法调用
* @throws Exception
*/
class="token keyword">public class="token keyword">static class="token keyword">void class="token function">reflectASMByNameclass="token punctuation">(class="token punctuation">) class="token keyword">throws class="token class-name">Exception class="token punctuation">{
class="token comment">// 使用 MethodAccess class="tags" href="/tags/FanShe.html" title=反射>反射调用方法
class="token class-name">PlanBarCodeExcel planBarCodeExcel class="token operator">= class="token keyword">new class="token class-name">PlanBarCodeExcelclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token class-name">MethodAccess access class="token operator">= class="token class-name">MethodAccessclass="token punctuation">.class="token function">getclass="token punctuation">(class="token class-name">PlanBarCodeclass="token punctuation">.class="token keyword">classclass="token punctuation">)class="token punctuation">;
methodAccessclass="token punctuation">.class="token function">invokeclass="token punctuation">(planBarCodeExcelclass="token punctuation">, class="token string">"setBarCode"class="token punctuation">, class="token string">"barCode"class="token punctuation">)class="token punctuation">;
class="token class-name">String getBarCode class="token operator">= class="token punctuation">(class="token class-name">Stringclass="token punctuation">) methodAccessclass="token punctuation">.class="token function">invokeclass="token punctuation">(planBarCodeExcelclass="token punctuation">, class="token string">"getBarCode"class="token punctuation">)class="token punctuation">;
class="token class-name">Systemclass="token punctuation">.outclass="token punctuation">.class="token function">printlnclass="token punctuation">(getBarCodeclass="token punctuation">)class="token punctuation">;
class="token comment">// 如果方法重载有同名方法的话，找到方法的索引执行方法，相比通过名称访问成员，索引的方式会更快
class="token keyword">int setChannelCodeIndex class="token operator">= methodAccessclass="token punctuation">.class="token function">getIndexclass="token punctuation">(class="token string">"setChannelCode"class="token punctuation">, class="token class-name">Stringclass="token punctuation">.class="token keyword">classclass="token punctuation">)class="token punctuation">;
methodAccessclass="token punctuation">.class="token function">invokeclass="token punctuation">(planBarCodeExcelclass="token punctuation">, setChannelCodeIndexclass="token punctuation">, class="token string">"111"class="token punctuation">)class="token punctuation">;
class="token comment">// 使用 FieldAccess class="tags" href="/tags/FanShe.html" title=反射>反射 set/get 字段
class="token class-name">FieldAccess fieldAccess class="token operator">= class="token class-name">FieldAccessclass="token punctuation">.class="token function">getclass="token punctuation">(class="token class-name">PlanBarCodeclass="token punctuation">.class="token keyword">classclass="token punctuation">)class="token punctuation">;
fieldAccessclass="token punctuation">.class="token function">setclass="token punctuation">(planBarCodeExcelclass="token punctuation">, class="token string">"brandName"class="token punctuation">, class="token string">"brandName"class="token punctuation">)class="token punctuation">;
class="token class-name">String brandName class="token operator">= class="token punctuation">(class="token class-name">Stringclass="token punctuation">) fieldAccessclass="token punctuation">.class="token function">getclass="token punctuation">(planBarCodeExcelclass="token punctuation">, class="token string">"brandName"class="token punctuation">)class="token punctuation">;
class="token class-name">Systemclass="token punctuation">.outclass="token punctuation">.class="token function">printlnclass="token punctuation">(brandNameclass="token punctuation">)class="token punctuation">;
class="token comment">// ConstructorAccessclass="tags" href="/tags/FanShe.html" title=反射>反射调用构造方法
class="token class-name">ConstructorAccessclass="token generics">class="token punctuation"><class="token class-name">PlanBarCodeExcelclass="token punctuation">> planBarCodeExcelConstructorAccess class="token operator">= class="token class-name">ConstructorAccessclass="token punctuation">.class="token function">getclass="token punctuation">(class="token class-name">PlanBarCodeExcelclass="token punctuation">.class="token keyword">classclass="token punctuation">)class="token punctuation">;
class="token class-name">PlanBarCodeExcel planBarCodeExcel1 class="token operator">= planBarCodeExcelConstructorAccessclass="token punctuation">.class="token function">newInstanceclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token punctuation">}
class="token punctuation">}
4、reflectASM 原理解析
4.1 MethodAccess 源码
class="prism language-class="tags" href="/tags/JAVA.html" title=java>java">class="token keyword">public class="token keyword">abstract class="token keyword">class class="token class-name">MethodAccess class="token punctuation">{
class="token comment">// 这三个私有变量用来存储要class="tags" href="/tags/FanShe.html" title=反射>反射 Class 的方法名称、参数、返回值等信息
class="token keyword">private class="token class-name">Stringclass="token punctuation">[class="token punctuation">] methodNamesclass="token punctuation">;
class="token keyword">private class="token class-name">Classclass="token punctuation">[class="token punctuation">]class="token punctuation">[class="token punctuation">] parameterTypesclass="token punctuation">;
class="token keyword">private class="token class-name">Classclass="token punctuation">[class="token punctuation">] returnTypesclass="token punctuation">;
class="token keyword">static class="token keyword">public class="token class-name">MethodAccess get class="token punctuation">(class="token class-name">Class typeclass="token punctuation">) class="token punctuation">{
class="token comment">// 准备class="tags" href="/tags/FanShe.html" title=反射>反射信息
class="token class-name">ArrayListclass="token generics">class="token punctuation"><class="token class-name">Methodclass="token punctuation">> methods class="token operator">= class="token keyword">new class="token class-name">ArrayListclass="token generics">class="token punctuation"><class="token class-name">Methodclass="token punctuation">>class="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token keyword">boolean isInterface class="token operator">= typeclass="token punctuation">.class="token function">isInterfaceclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token keyword">if class="token punctuation">(class="token operator">!isInterfaceclass="token punctuation">) class="token punctuation">{ class="token comment">// 判断是否为接口
class="token class-name">Class nextClass class="token operator">= typeclass="token punctuation">;
class="token keyword">while class="token punctuation">(nextClass class="token operator">!= class="token class-name">Objectclass="token punctuation">.class="token keyword">classclass="token punctuation">) class="token punctuation">{
class="token comment">// 类中的公共非静态方法添加到 methods 中
class="token function">addDeclaredMethodsToListclass="token punctuation">(nextClassclass="token punctuation">, methodsclass="token punctuation">)class="token punctuation">;
nextClass class="token operator">= nextClassclass="token punctuation">.class="token function">getSuperclassclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token punctuation">}
class="token punctuation">} class="token keyword">else class="token punctuation">{
class="token function">recursiveAddInterfaceMethodsToListclass="token punctuation">(typeclass="token punctuation">, methodsclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
class="token keyword">int n class="token operator">= methodsclass="token punctuation">.class="token function">sizeclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token class-name">Stringclass="token punctuation">[class="token punctuation">] methodNames class="token operator">= class="token keyword">new class="token class-name">Stringclass="token punctuation">[nclass="token punctuation">]class="token punctuation">;
class="token class-name">Classclass="token punctuation">[class="token punctuation">]class="token punctuation">[class="token punctuation">] parameterTypes class="token operator">= class="token keyword">new class="token class-name">Classclass="token punctuation">[nclass="token punctuation">]class="token punctuation">[class="token punctuation">]class="token punctuation">;
class="token class-name">Classclass="token punctuation">[class="token punctuation">] returnTypes class="token operator">= class="token keyword">new class="token class-name">Classclass="token punctuation">[nclass="token punctuation">]class="token punctuation">;
class="token keyword">for class="token punctuation">(class="token keyword">int i class="token operator">= class="token number">0class="token punctuation">; i class="token operator">< nclass="token punctuation">; iclass="token operator">++class="token punctuation">) class="token punctuation">{
class="token class-name">Method method class="token operator">= methodsclass="token punctuation">.class="token function">getclass="token punctuation">(iclass="token punctuation">)class="token punctuation">;
methodNamesclass="token punctuation">[iclass="token punctuation">] class="token operator">= methodclass="token punctuation">.class="token function">getNameclass="token punctuation">(class="token punctuation">)class="token punctuation">;
parameterTypesclass="token punctuation">[iclass="token punctuation">] class="token operator">= methodclass="token punctuation">.class="token function">getParameterTypesclass="token punctuation">(class="token punctuation">)class="token punctuation">;
returnTypesclass="token punctuation">[iclass="token punctuation">] class="token operator">= methodclass="token punctuation">.class="token function">getReturnTypeclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token punctuation">}
class="token class-name">String className class="token operator">= typeclass="token punctuation">.class="token function">getNameclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token comment">// 类名进行拼接，准备要生成新类的名字
class="token class-name">String accessClassName class="token operator">= className class="token operator">+ class="token string">"MethodAccess"class="token punctuation">;
class="token keyword">if class="token punctuation">(accessClassNameclass="token punctuation">.class="token function">startsWithclass="token punctuation">(class="token string">"class="tags" href="/tags/JAVA.html" title=java>java."class="token punctuation">)class="token punctuation">) accessClassName class="token operator">= class="token string">"reflectasm." class="token operator">+ accessClassNameclass="token punctuation">;
class="token class-name">Class accessClassclass="token punctuation">;
class="token comment">// 获取该类的类加载器
class="token class-name">AccessClassLoader loader class="token operator">= class="token class-name">AccessClassLoaderclass="token punctuation">.class="token function">getclass="token punctuation">(typeclass="token punctuation">)class="token punctuation">;
class="token keyword">synchronized class="token punctuation">(loaderclass="token punctuation">) class="token punctuation">{
class="token keyword">try class="token punctuation">{
class="token comment">// 如果动态生成的类已经生成过了，第二次调用是不会操作字节码生成的
accessClass class="token operator">= loaderclass="token punctuation">.class="token function">loadClassclass="token punctuation">(accessClassNameclass="token punctuation">)class="token punctuation">;
class="token punctuation">} class="token keyword">catch class="token punctuation">(class="token class-name">ClassNotFoundException ignoredclass="token punctuation">) class="token punctuation">{
class="token class-name">String accessClassNameInternal class="token operator">= accessClassNameclass="token punctuation">.class="token function">replaceclass="token punctuation">(class="token string">'.'class="token punctuation">, class="token string">'/'class="token punctuation">)class="token punctuation">;
class="token class-name">String classNameInternal class="token operator">= classNameclass="token punctuation">.class="token function">replaceclass="token punctuation">(class="token string">'.'class="token punctuation">, class="token string">'/'class="token punctuation">)class="token punctuation">;
class="token class-name">ClassWriter cw class="token operator">= class="token keyword">new class="token class-name">ClassWriterclass="token punctuation">(class="token class-name">ClassWriterclass="token punctuation">.COMPUTE_MAXSclass="token punctuation">)class="token punctuation">;
class="token class-name">MethodVisitor mvclass="token punctuation">;
class="token comment">// 生成继承于 “com/esotericsoftware/reflectasm/MethodAccess” 类的子类
class="token comment">// 参数分别为：class="tags" href="/tags/JAVA.html" title=java>java Version、类修饰符、类名、参数类型、父类、接口
cwclass="token punctuation">.class="token function">visitclass="token punctuation">(V1_1class="token punctuation">, ACC_PUBLIC class="token operator">+ ACC_SUPERclass="token punctuation">, accessClassNameInternalclass="token punctuation">, class="token keyword">nullclass="token punctuation">, class="token string">"com/esotericsoftware/reflectasm/MethodAccess"class="token punctuation">,class="token keyword">nullclass="token punctuation">)class="token punctuation">;
class="token comment">// 下面这段代码生成构造方法
class="token punctuation">{
mv class="token operator">= cwclass="token punctuation">.class="token function">visitMethodclass="token punctuation">(ACC_PUBLICclass="token punctuation">, class="token string">"<init>"class="token punctuation">, class="token string">"()V"class="token punctuation">, class="token keyword">nullclass="token punctuation">, class="token keyword">nullclass="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitCodeclass="token punctuation">(class="token punctuation">)class="token punctuation">; class="token comment">// 开始生成方法
mvclass="token punctuation">.class="token function">visitVarInsnclass="token punctuation">(ALOADclass="token punctuation">, class="token number">0class="token punctuation">)class="token punctuation">;class="token comment">// 访问局部变量指令，加载或存储局部变量值的指令，从局部变量表 load 位置为 0 的变量到操作数栈
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKESPECIALclass="token punctuation">, class="token string">"com/esotericsoftware/reflectasm/MethodAccess"class="token punctuation">, class="token string">"<init>"class="token punctuation">, class="token string">"()V"class="token punctuation">)class="token punctuation">; class="token comment">// 访问方法时的指令
mvclass="token punctuation">.class="token function">visitInsnclass="token punctuation">(RETURNclass="token punctuation">)class="token punctuation">; class="token comment">// 访问一个字节码指令
mvclass="token punctuation">.class="token function">visitMaxsclass="token punctuation">(class="token number">0class="token punctuation">, class="token number">0class="token punctuation">)class="token punctuation">; class="token comment">// 方法的局部变量表和操作数栈的大小
mvclass="token punctuation">.class="token function">visitEndclass="token punctuation">(class="token punctuation">)class="token punctuation">; class="token comment">// 方法访问结束
class="token punctuation">}
class="token punctuation">{
class="token comment">// 动态生成方法，公共的可变参的 invoke 方法
mv class="token operator">= cwclass="token punctuation">.class="token function">visitMethodclass="token punctuation">(ACC_PUBLIC class="token operator">+ ACC_VARARGSclass="token punctuation">, class="token string">"invoke"class="token punctuation">,
class="token string">"(Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/Object;I[Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/Object;)Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/Object;"class="token punctuation">, class="token keyword">nullclass="token punctuation">, class="token keyword">nullclass="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitCodeclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token keyword">if class="token punctuation">(class="token operator">!methodsclass="token punctuation">.class="token function">isEmptyclass="token punctuation">(class="token punctuation">)class="token punctuation">) class="token punctuation">{
mvclass="token punctuation">.class="token function">visitVarInsnclass="token punctuation">(ALOADclass="token punctuation">, class="token number">1class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(CHECKCASTclass="token punctuation">, classNameInternalclass="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitVarInsnclass="token punctuation">(ASTOREclass="token punctuation">, class="token number">4class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitVarInsnclass="token punctuation">(ILOADclass="token punctuation">, class="token number">2class="token punctuation">)class="token punctuation">;
class="token class-name">Labelclass="token punctuation">[class="token punctuation">] labels class="token operator">= class="token keyword">new class="token class-name">Labelclass="token punctuation">[nclass="token punctuation">]class="token punctuation">;
class="token keyword">for class="token punctuation">(class="token keyword">int i class="token operator">= class="token number">0class="token punctuation">; i class="token operator">< nclass="token punctuation">; iclass="token operator">++class="token punctuation">)
labelsclass="token punctuation">[iclass="token punctuation">] class="token operator">= class="token keyword">new class="token class-name">Labelclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token class-name">Label defaultLabel class="token operator">= class="token keyword">new class="token class-name">Labelclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token comment">// label 代表的是跳转的字节码位置，对应一条指令
mvclass="token punctuation">.class="token function">visitTableSwitchInsnclass="token punctuation">(class="token number">0class="token punctuation">, labelsclass="token punctuation">.length class="token operator">- class="token number">1class="token punctuation">, defaultLabelclass="token punctuation">, labelsclass="token punctuation">)class="token punctuation">;
class="token class-name">StringBuilder buffer class="token operator">= class="token keyword">new class="token class-name">StringBuilderclass="token punctuation">(class="token number">128class="token punctuation">)class="token punctuation">;
class="token keyword">for class="token punctuation">(class="token keyword">int i class="token operator">= class="token number">0class="token punctuation">; i class="token operator">< nclass="token punctuation">; iclass="token operator">++class="token punctuation">) class="token punctuation">{ class="token comment">// n = methods.size();
class="token comment">// 跳转到指定字节码位置
mvclass="token punctuation">.class="token function">visitLabelclass="token punctuation">(labelsclass="token punctuation">[iclass="token punctuation">]class="token punctuation">)class="token punctuation">;
class="token keyword">if class="token punctuation">(i class="token operator">== class="token number">0class="token punctuation">)
mvclass="token punctuation">.class="token function">visitFrameclass="token punctuation">(class="token class-name">Opcodesclass="token punctuation">.F_APPENDclass="token punctuation">, class="token number">1class="token punctuation">, class="token keyword">new class="token class-name">Objectclass="token punctuation">[class="token punctuation">] class="token punctuation">{classNameInternalclass="token punctuation">}class="token punctuation">, class="token number">0class="token punctuation">, class="token keyword">nullclass="token punctuation">)class="token punctuation">;
class="token keyword">else
mvclass="token punctuation">.class="token function">visitFrameclass="token punctuation">(class="token class-name">Opcodesclass="token punctuation">.F_SAMEclass="token punctuation">, class="token number">0class="token punctuation">, class="token keyword">nullclass="token punctuation">, class="token number">0class="token punctuation">, class="token keyword">nullclass="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitVarInsnclass="token punctuation">(ALOADclass="token punctuation">, class="token number">4class="token punctuation">)class="token punctuation">;
bufferclass="token punctuation">.class="token function">setLengthclass="token punctuation">(class="token number">0class="token punctuation">)class="token punctuation">;
bufferclass="token punctuation">.class="token function">appendclass="token punctuation">(class="token string">'('class="token punctuation">)class="token punctuation">;
class="token class-name">Classclass="token punctuation">[class="token punctuation">] paramTypes class="token operator">= parameterTypesclass="token punctuation">[iclass="token punctuation">]class="token punctuation">;
class="token class-name">Class returnType class="token operator">= returnTypesclass="token punctuation">[iclass="token punctuation">]class="token punctuation">;
class="token keyword">for class="token punctuation">(class="token keyword">int paramIndex class="token operator">= class="token number">0class="token punctuation">; paramIndex class="token operator">< paramTypesclass="token punctuation">.lengthclass="token punctuation">; paramIndexclass="token operator">++class="token punctuation">) class="token punctuation">{
mvclass="token punctuation">.class="token function">visitVarInsnclass="token punctuation">(ALOADclass="token punctuation">, class="token number">3class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitIntInsnclass="token punctuation">(BIPUSHclass="token punctuation">, paramIndexclass="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitInsnclass="token punctuation">(AALOADclass="token punctuation">)class="token punctuation">;
class="token comment">// 获取到参数类型
class="token class-name">Type paramType class="token operator">= class="token class-name">Typeclass="token punctuation">.class="token function">getTypeclass="token punctuation">(paramTypesclass="token punctuation">[paramIndexclass="token punctuation">]class="token punctuation">)class="token punctuation">;
class="token comment">// 根据参数类型的 sort 使用 switch 判断是否为基本数据类型，避免基本数据类型的自动装箱操作，避免创建不必要的对象
class="token keyword">switch class="token punctuation">(paramTypeclass="token punctuation">.class="token function">getSortclass="token punctuation">(class="token punctuation">)class="token punctuation">) class="token punctuation">{
class="token keyword">case class="token class-name">Typeclass="token punctuation">.BOOLEANclass="token operator">:
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(CHECKCASTclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Boolean"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKEVIRTUALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Boolean"class="token punctuation">, class="token string">"booleanValue"class="token punctuation">, class="token string">"()Z"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.BYTEclass="token operator">:
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(CHECKCASTclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Byte"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKEVIRTUALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Byte"class="token punctuation">, class="token string">"byteValue"class="token punctuation">, class="token string">"()B"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.CHARclass="token operator">:
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(CHECKCASTclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Character"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKEVIRTUALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Character"class="token punctuation">, class="token string">"charValue"class="token punctuation">, class="token string">"()C"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.SHORTclass="token operator">:
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(CHECKCASTclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Short"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKEVIRTUALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Short"class="token punctuation">, class="token string">"shortValue"class="token punctuation">, class="token string">"()S"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.INTclass="token operator">:
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(CHECKCASTclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Integer"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKEVIRTUALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Integer"class="token punctuation">, class="token string">"intValue"class="token punctuation">, class="token string">"()I"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.FLOATclass="token operator">:
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(CHECKCASTclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Float"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKEVIRTUALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Float"class="token punctuation">, class="token string">"floatValue"class="token punctuation">, class="token string">"()F"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.LONGclass="token operator">:
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(CHECKCASTclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Long"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKEVIRTUALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Long"class="token punctuation">, class="token string">"longValue"class="token punctuation">, class="token string">"()J"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.DOUBLEclass="token operator">:
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(CHECKCASTclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Double"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKEVIRTUALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Double"class="token punctuation">, class="token string">"doubleValue"class="token punctuation">, class="token string">"()D"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.ARRAYclass="token operator">:
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(CHECKCASTclass="token punctuation">, paramTypeclass="token punctuation">.class="token function">getDescriptorclass="token punctuation">(class="token punctuation">)class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.OBJECTclass="token operator">:
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(CHECKCASTclass="token punctuation">, paramTypeclass="token punctuation">.class="token function">getInternalNameclass="token punctuation">(class="token punctuation">)class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token punctuation">}
class="token comment">// 拼接参数类型描述
bufferclass="token punctuation">.class="token function">appendclass="token punctuation">(paramTypeclass="token punctuation">.class="token function">getDescriptorclass="token punctuation">(class="token punctuation">)class="token punctuation">)class="token punctuation">;
class="token punctuation">}
bufferclass="token punctuation">.class="token function">appendclass="token punctuation">(class="token string">')'class="token punctuation">)class="token punctuation">;
class="token comment">// 拼接返回参数类型描述
bufferclass="token punctuation">.class="token function">appendclass="token punctuation">(class="token class-name">Typeclass="token punctuation">.class="token function">getDescriptorclass="token punctuation">(returnTypeclass="token punctuation">)class="token punctuation">)class="token punctuation">;
class="token keyword">int invokeclass="token punctuation">;
class="token keyword">if class="token punctuation">(isInterfaceclass="token punctuation">)
invoke class="token operator">= INVOKEINTERFACEclass="token punctuation">; class="token comment">// 调用接口方法
class="token keyword">else class="token keyword">if class="token punctuation">(class="token class-name">Modifierclass="token punctuation">.class="token function">isStaticclass="token punctuation">(methodsclass="token punctuation">.class="token function">getclass="token punctuation">(iclass="token punctuation">)class="token punctuation">.class="token function">getModifiersclass="token punctuation">(class="token punctuation">)class="token punctuation">)class="token punctuation">)
class="token comment">// 调用静态方法
invoke class="token operator">= INVOKESTATICclass="token punctuation">;
class="token keyword">else
class="token comment">// 调用普通方法
invoke class="token operator">= INVOKEVIRTUALclass="token punctuation">;
class="token comment">// 对字节码进行注入
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(invokeclass="token punctuation">, classNameInternalclass="token punctuation">, methodNamesclass="token punctuation">[iclass="token punctuation">]class="token punctuation">, bufferclass="token punctuation">.class="token function">toStringclass="token punctuation">(class="token punctuation">)class="token punctuation">)class="token punctuation">;
class="token comment">// 判断返回值与参数同操作
class="token keyword">switch class="token punctuation">(class="token class-name">Typeclass="token punctuation">.class="token function">getTypeclass="token punctuation">(returnTypeclass="token punctuation">)class="token punctuation">.class="token function">getSortclass="token punctuation">(class="token punctuation">)class="token punctuation">) class="token punctuation">{
class="token keyword">case class="token class-name">Typeclass="token punctuation">.VOIDclass="token operator">:
mvclass="token punctuation">.class="token function">visitInsnclass="token punctuation">(ACONST_NULLclass="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.BOOLEANclass="token operator">:
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKESTATICclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Boolean"class="token punctuation">, class="token string">"valueOf"class="token punctuation">, class="token string">"(Z)Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/Boolean;"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.BYTEclass="token operator">:
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKESTATICclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Byte"class="token punctuation">, class="token string">"valueOf"class="token punctuation">, class="token string">"(B)Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/Byte;"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.CHARclass="token operator">:
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKESTATICclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Character"class="token punctuation">, class="token string">"valueOf"class="token punctuation">, class="token string">"(C)Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/Character;"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.SHORTclass="token operator">:
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKESTATICclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Short"class="token punctuation">, class="token string">"valueOf"class="token punctuation">, class="token string">"(S)Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/Short;"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.INTclass="token operator">:
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKESTATICclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Integer"class="token punctuation">, class="token string">"valueOf"class="token punctuation">, class="token string">"(I)Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/Integer;"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.FLOATclass="token operator">:
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKESTATICclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Float"class="token punctuation">, class="token string">"valueOf"class="token punctuation">, class="token string">"(F)Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/Float;"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.LONGclass="token operator">:
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKESTATICclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Long"class="token punctuation">, class="token string">"valueOf"class="token punctuation">, class="token string">"(J)Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/Long;"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token keyword">case class="token class-name">Typeclass="token punctuation">.DOUBLEclass="token operator">:
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKESTATICclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/Double"class="token punctuation">, class="token string">"valueOf"class="token punctuation">, class="token string">"(D)Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/Double;"class="token punctuation">)class="token punctuation">;
class="token keyword">breakclass="token punctuation">;
class="token punctuation">}
mvclass="token punctuation">.class="token function">visitInsnclass="token punctuation">(ARETURNclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
mvclass="token punctuation">.class="token function">visitLabelclass="token punctuation">(defaultLabelclass="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitFrameclass="token punctuation">(class="token class-name">Opcodesclass="token punctuation">.F_SAMEclass="token punctuation">, class="token number">0class="token punctuation">, class="token keyword">nullclass="token punctuation">, class="token number">0class="token punctuation">, class="token keyword">nullclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
class="token comment">// 下面是一些新建和调用的操作
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(NEWclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/IllegalArgumentException"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitInsnclass="token punctuation">(DUPclass="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitTypeInsnclass="token punctuation">(NEWclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/StringBuilder"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitInsnclass="token punctuation">(DUPclass="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitLdcInsnclass="token punctuation">(class="token string">"Method not found: "class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKESPECIALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/StringBuilder"class="token punctuation">, class="token string">"<init>"class="token punctuation">, class="token string">"(Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/String;)V"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitVarInsnclass="token punctuation">(ILOADclass="token punctuation">, class="token number">2class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKEVIRTUALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/StringBuilder"class="token punctuation">, class="token string">"append"class="token punctuation">, class="token string">"(I)Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/StringBuilder;"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKEVIRTUALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/StringBuilder"class="token punctuation">, class="token string">"toString"class="token punctuation">, class="token string">"()Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/String;"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMethodInsnclass="token punctuation">(INVOKESPECIALclass="token punctuation">, class="token string">"class="tags" href="/tags/JAVA.html" title=java>java/lang/IllegalArgumentException"class="token punctuation">, class="token string">"<init>"class="token punctuation">, class="token string">"(Lclass="tags" href="/tags/JAVA.html" title=java>java/lang/String;)V"class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitInsnclass="token punctuation">(ATHROWclass="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitMaxsclass="token punctuation">(class="token number">0class="token punctuation">, class="token number">0class="token punctuation">)class="token punctuation">;
mvclass="token punctuation">.class="token function">visitEndclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token punctuation">}
class="token comment">// method 没有其它调用了，结束创建过程
cwclass="token punctuation">.class="token function">visitEndclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token comment">// 字节码生成，使用 ClassWriter 的 toByteArray() 方法，返回我们需要的代表这个类的 byte 数组
class="token keyword">byteclass="token punctuation">[class="token punctuation">] data class="token operator">= cwclass="token punctuation">.class="token function">toByteArrayclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token comment">// 我们将这个 class 文件进行加载
accessClass class="token operator">= loaderclass="token punctuation">.class="token function">defineClassclass="token punctuation">(accessClassNameclass="token punctuation">, dataclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
class="token punctuation">}
class="token keyword">try class="token punctuation">{
class="token comment">// 实例化并赋值返回结果
class="token class-name">MethodAccess access class="token operator">= class="token punctuation">(class="token class-name">MethodAccessclass="token punctuation">)accessClassclass="token punctuation">.class="token function">newInstanceclass="token punctuation">(class="token punctuation">)class="token punctuation">;
accessclass="token punctuation">.methodNames class="token operator">= methodNamesclass="token punctuation">;
accessclass="token punctuation">.parameterTypes class="token operator">= parameterTypesclass="token punctuation">;
accessclass="token punctuation">.returnTypes class="token operator">= returnTypesclass="token punctuation">;
class="token keyword">return accessclass="token punctuation">;
class="token punctuation">} class="token keyword">catch class="token punctuation">(class="token class-name">Throwable tclass="token punctuation">) class="token punctuation">{
class="token keyword">throw class="token keyword">new class="token class-name">RuntimeExceptionclass="token punctuation">(class="token string">"Error constructing method access class: " class="token operator">+ accessClassNameclass="token punctuation">, tclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
class="token punctuation">}
class="token comment">// 使用class="tags" href="/tags/FanShe.html" title=反射>反射获取到要class="tags" href="/tags/FanShe.html" title=反射>反射类的公有非静态方法后赋值给私有变量进行存储
class="token keyword">private class="token keyword">static class="token keyword">void addDeclaredMethodsToList class="token punctuation">(class="token class-name">Class typeclass="token punctuation">, class="token class-name">ArrayListclass="token generics">class="token punctuation"><class="token class-name">Methodclass="token punctuation">> methodsclass="token punctuation">) class="token punctuation">{
class="token class-name">Methodclass="token punctuation">[class="token punctuation">] declaredMethods class="token operator">= typeclass="token punctuation">.class="token function">getDeclaredMethodsclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token keyword">for class="token punctuation">(class="token keyword">int i class="token operator">= class="token number">0class="token punctuation">, n class="token operator">= declaredMethodsclass="token punctuation">.lengthclass="token punctuation">; i class="token operator">< nclass="token punctuation">; iclass="token operator">++class="token punctuation">) class="token punctuation">{
class="token class-name">Method method class="token operator">= declaredMethodsclass="token punctuation">[iclass="token punctuation">]class="token punctuation">;
class="token keyword">int modifiers class="token operator">= methodclass="token punctuation">.class="token function">getModifiersclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token comment">// 判断是否为私有方法
class="token keyword">if class="token punctuation">(class="token class-name">Modifierclass="token punctuation">.class="token function">isPrivateclass="token punctuation">(modifiersclass="token punctuation">)class="token punctuation">) class="token keyword">continueclass="token punctuation">;
methodsclass="token punctuation">.class="token function">addclass="token punctuation">(methodclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
class="token punctuation">}
class="token keyword">private class="token keyword">static class="token keyword">void recursiveAddInterfaceMethodsToList class="token punctuation">(class="token class-name">Class interfaceTypeclass="token punctuation">, class="token class-name">ArrayListclass="token generics">class="token punctuation"><class="token class-name">Methodclass="token punctuation">> methodsclass="token punctuation">) class="token punctuation">{
class="token function">addDeclaredMethodsToListclass="token punctuation">(interfaceTypeclass="token punctuation">, methodsclass="token punctuation">)class="token punctuation">;
class="token keyword">for class="token punctuation">(class="token class-name">Class nextInterface class="token operator">: interfaceTypeclass="token punctuation">.class="token function">getInterfacesclass="token punctuation">(class="token punctuation">)class="token punctuation">) class="token punctuation">{
class="token function">recursiveAddInterfaceMethodsToListclass="token punctuation">(nextInterfaceclass="token punctuation">, methodsclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
class="token punctuation">}
class="token punctuation">}
4.2 读源码后 了解到 MethodAccess 执行流程
- 通过 Java class="tags" href="/tags/FanShe.html" title=反射>反射获取 class 的公共非静态函数名、属性等
- 在私有变量内记录方法名称参数等信息
- 用 ASM 技术动态生成新的继承于 MethodAccess 的类（fileName + MethodAccess）
- 在类的 invoke 方法实现调用不同的方法
4.3 小结
-
class="tags" href="/tags/FanShe.html" title=反射>反射的核心是 getMethod 和 invoke，reflectASM 要生成文件然后加载到 JVM，所以 reflectASM 的 get 特别慢，
-
使用 jar 包要注意缓存生成的 class 对象，尽量少重复生成
-
reflectASM 借助class="tags" href="/tags/FanShe.html" title=反射>反射的 getDeclaredMethods 获取 class 的所有方法，然后动态生成一个继承于 MethodAccess 的子类 ，动态生成一个 class 文件并加载到 jvm 中。这个操作比较耗时，我们最好预先生成这个 MethodAccess 对象，将这个生成的对象缓存起来
-
子类中所有的方法名建立 index 索引，index 和方法名映射，根据方法名获取到 index，子类中的 switch 执行相应的代码，在 MethodAccess.invoke 的时候，是直接调用
-
如果class="tags" href="/tags/FanShe.html" title=反射>反射调用的类函数比较多，这个遍历也可能耗时较多，可以先通过 getIndex 方法先获取到索引，然后再进行调用，这样比使用函数的名字来进行调用快的多
