Detailed explanation of the technical principles of BYTE BUDDY in the Java class library

Byte Buddy is an unreasonable Java bytecode operation framework that can generate and modify the byte code during runtime.This framework provides a dynamic ability to create and modify the Java classes, which can realize the expansion or modification of the class without re -compilation. The technical principles of BYTE BUDDY can be divided into the following three aspects: bytecode generation, bytecode conversion, and byte code loading. 1. Bytecode generation: Byte Buddy uses a method called "Domain Specific Language" to generate the byte code.DSL is a high -level language, which provides a set of simple and easy -to -use syntax to describe the required bytecode structure.In Byte Buddy, you can use DSL syntax to create new Java classes and methods at runtime. Below is a sample code that generates a new methodless constructor method using BYTE BUDDDY: Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .defineConstructor(Modifier.PUBLIC) .intercept(MethodCall.construct(Object.class.getDeclaredConstructor())) .make() .load(getClass().getClassLoader()) .getLoaded(); Object instance = dynamicType.newInstance(); 2. bytecode conversion: Byte Buddy also provides a series of APIs that can be used to modify the bytecode of the existing Java class.Using BYTE Buddy's conversion API can enhance, rename, delete or replace methods without modifying the source code. Below is an example code that uses byte Buddy to add a method to the existing class: Class<?> dynamicType = new ByteBuddy() .redefine(ExistingClass.class) .defineMethod("newMethod", void.class, Modifier.PUBLIC) .intercept(MethodDelegation.to(MyInterceptor.class)) .make() .load(getClass().getClassLoader(), ClassReloadingStrategy.fromInstalledAgent()); dynamicType.getMethod("newMethod").invoke(dynamicType.newInstance()); 3. Bytecode loading: BYTE BUDDY uses Java's Instrumentation mechanism to load the generated or modified bytecode through Java Agent.Java Agent is a special Java program that can be converted into class and bytecode when JVM startup. Below is an example code that uses the byte code generated by BYTE BUDDY using Java Agent: import net.bytebuddy.agent.ByteBuddyAgent; public class AgentLoader { public static void premain(String agentArgs, Instrumentation inst) { inst.addTransformer((loader, className, classBeingRedefined, protectionDomain, classfileBuffer) -> new ByteBuddy() .redefine(classBeingRedefined, ClassFileLocator.Simple.of(classBeingRedefined.getName(), classfileBuffer)) .make() .getBytes() ); } public static void main(String[] args) { ByteBuddyAgent.attach(); } } Through the above principles, the BYTE BUDDY framework can generate and modify the byte code during runtime, so that developers can flexibly expand and modify the behavior of the Java class without re -compiling and deploying applications.This makes Byte Buddy a very useful and powerful tool in the Java field.