ASM Sample Project (#2664)
* ASM Sample Project * Update Premain.java * Update pom.xml
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k0l0ssus
KevinGilmore
parent
6655ca0ba1
commit
815c66c9dd
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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>com.baeldung.examples</groupId>
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<artifactId>asm</artifactId>
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<version>1.0</version>
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<packaging>jar</packaging>
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<dependencies>
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<dependency>
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<groupId>org.ow2.asm</groupId>
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<artifactId>asm</artifactId>
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<version>5.2</version>
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</dependency>
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<dependency>
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<groupId>org.ow2.asm</groupId>
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<artifactId>asm-util</artifactId>
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<version>5.2</version>
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</dependency>
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</dependencies>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<maven.compiler.source>1.8</maven.compiler.source>
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<maven.compiler.target>1.8</maven.compiler.target>
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</properties>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-jar-plugin</artifactId>
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<version>2.4</version>
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<configuration>
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<archive>
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<manifestEntries>
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<Premain-Class>
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com.baeldung.examples.asm.instrumentation.Premain
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</Premain-Class>
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</manifestEntries>
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</archive>
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</configuration>
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</plugin>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-surefire-plugin</artifactId>
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<version>2.9</version>
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<configuration>
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<argLine>-javaagent:"C:\asm-1.0.jar"</argLine>
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</configuration>
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</plugin>
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</plugins>
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</build>
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</project>
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package com.baeldung.examples.asm;
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import java.io.IOException;
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import java.io.PrintWriter;
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import java.util.logging.Level;
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import java.util.logging.Logger;
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import org.objectweb.asm.ClassReader;
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import org.objectweb.asm.ClassVisitor;
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import org.objectweb.asm.ClassWriter;
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import org.objectweb.asm.FieldVisitor;
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import org.objectweb.asm.MethodVisitor;
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import static org.objectweb.asm.Opcodes.ACC_PUBLIC;
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import static org.objectweb.asm.Opcodes.ACC_STATIC;
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import static org.objectweb.asm.Opcodes.ASM4;
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import static org.objectweb.asm.Opcodes.V1_5;
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import org.objectweb.asm.Type;
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import org.objectweb.asm.util.TraceClassVisitor;
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/**
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*
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* @author baeldung
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* @param <String>
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*/
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public class CustomClassWriter {
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ClassReader reader;
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ClassWriter writer;
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AddFieldAdapter addFieldAdapter;
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AddInterfaceAdapter addInterfaceAdapter;
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PublicizeMethodAdapter pubMethAdapter;
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final static String CLASSNAME = "java.lang.Integer";
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final static String CLONEABLE = "java/lang/Cloneable";
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public CustomClassWriter() {
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try {
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reader = new ClassReader(CLASSNAME);
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writer = new ClassWriter(reader, 0);
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} catch (IOException ex) {
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Logger.getLogger(CustomClassWriter.class.getName()).log(Level.SEVERE, null, ex);
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}
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}
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public CustomClassWriter(byte[] contents) {
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reader = new ClassReader(contents);
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writer = new ClassWriter(reader, 0);
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}
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public static void main(String[] args) {
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CustomClassWriter ccw = new CustomClassWriter();
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ccw.publicizeMethod();
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}
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public byte[] addField() {
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addFieldAdapter = new AddFieldAdapter("aNewBooleanField", org.objectweb.asm.Opcodes.ACC_PUBLIC, writer);
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reader.accept(addFieldAdapter, 0);
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return writer.toByteArray();
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}
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public byte[] publicizeMethod() {
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pubMethAdapter = new PublicizeMethodAdapter(writer);
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reader.accept(pubMethAdapter, 0);
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return writer.toByteArray();
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}
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public byte[] addInterface() {
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addInterfaceAdapter = new AddInterfaceAdapter(writer);
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reader.accept(addInterfaceAdapter, 0);
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return writer.toByteArray();
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}
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public class AddInterfaceAdapter extends ClassVisitor {
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public AddInterfaceAdapter(ClassVisitor cv) {
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super(ASM4, cv);
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}
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@Override
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public void visit(int version, int access, String name,
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String signature, String superName, String[] interfaces) {
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String[] holding = new String[interfaces.length + 1];
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holding[holding.length - 1] = CLONEABLE;
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System.arraycopy(interfaces, 0, holding, 0, interfaces.length);
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cv.visit(V1_5, access, name, signature, superName, holding);
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}
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}
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public class PublicizeMethodAdapter extends ClassVisitor {
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final Logger logger = Logger.getLogger("PublicizeMethodAdapter");
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TraceClassVisitor tracer;
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PrintWriter pw = new PrintWriter(System.out);
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public PublicizeMethodAdapter(ClassVisitor cv) {
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super(ASM4, cv);
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this.cv = cv;
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tracer = new TraceClassVisitor(cv, pw);
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}
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@Override
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public MethodVisitor visitMethod(int access,
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String name,
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String desc,
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String signature,
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String[] exceptions) {
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if (name.equals("toUnsignedString0")) {
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logger.info("Visiting unsigned method");
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return tracer.visitMethod(ACC_PUBLIC + ACC_STATIC, name, desc, signature, exceptions);
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}
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return tracer.visitMethod(access, name, desc, signature, exceptions);
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}
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public void visitEnd() {
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tracer.visitEnd();
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System.out.println(tracer.p.getText());
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}
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}
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public class AddFieldAdapter extends ClassVisitor {
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String fieldName;
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int access;
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boolean isFieldPresent;
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public AddFieldAdapter(String fieldName, int access, ClassVisitor cv) {
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super(ASM4, cv);
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this.cv = cv;
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this.access = access;
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this.fieldName = fieldName;
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}
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@Override
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public FieldVisitor visitField(int access, String name, String desc,
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String signature, Object value) {
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if (name.equals(fieldName)) {
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isFieldPresent = true;
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}
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return cv.visitField(access, name, desc, signature, value);
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}
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@Override
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public void visitEnd() {
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if (!isFieldPresent) {
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FieldVisitor fv = cv.visitField(access, fieldName, Type.BOOLEAN_TYPE.toString(), null, null);
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if (fv != null) {
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fv.visitEnd();
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}
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}
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cv.visitEnd();
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}
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}
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}
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@ -0,0 +1,32 @@
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package com.baeldung.examples.asm.instrumentation;
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import com.baeldung.examples.asm.CustomClassWriter;
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import java.lang.instrument.ClassFileTransformer;
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import java.lang.instrument.IllegalClassFormatException;
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import java.lang.instrument.Instrumentation;
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import java.security.ProtectionDomain;
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/**
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*
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* @author baeldung
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*/
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public class Premain {
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public static void premain(String agentArgs, Instrumentation inst) {
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inst.addTransformer(new ClassFileTransformer() {
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@Override
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public byte[] transform(ClassLoader l, String name, Class c,
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ProtectionDomain d, byte[] b)
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throws IllegalClassFormatException {
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if (name.equals("java/lang/Integer")) {
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CustomClassWriter cr = new CustomClassWriter(b);
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return cr.addField();
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}
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return b;
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}
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});
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}
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}
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