init

demo/pom.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<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">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.seele</groupId>
+    <artifactId>demo</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>

demo/src/main/java/com/seele/Main.java

@@ -0,0 +1,29 @@
+package com.seele;
+
+public class Main {
+
+    public int print(int i) {
+        System.out.println("i: " + i);
+        try {
+            Thread.sleep(1000);
+        }catch (InterruptedException e){
+            e.printStackTrace();
+        }
+        return i + 2;
+    }
+    public void run(){
+        int i = new Trans().getNumber();
+        while (i < 1000){
+            try{
+                i = print(i);
+            }catch (Exception e){
+                e.printStackTrace();
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        Main main = new Main();
+        main.run();
+    }
+}

demo/src/main/java/com/seele/Trans.java

@@ -0,0 +1,7 @@
+package com.seele;
+
+public class Trans {
+    public int getNumber() {
+        return 1;
+    }
+}

simple_agent/pom.xml

@@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<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">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.seele</groupId>
+    <artifactId>simple_agent</artifactId>
+    <version>1.0</version>
+
+    <properties>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <configuration>
+                    <descriptorRefs>
+                        <descriptorRef>jar-with-dependencies</descriptorRef>
+                    </descriptorRefs>
+                    <archive>
+<!--                        <manifest>-->
+<!--                            <addClasspath>true</addClasspath>-->
+<!--                        </manifest>-->
+                        <manifestEntries>
+                            <Built-By>neo</Built-By>
+                            <Premain-Class>com.seele.SimpleAgent</Premain-Class>
+                            <Agent-Class>com.seele.SimpleAgent</Agent-Class>
+<!--                            <Main-Class>com.janetfilter.core.Launcher</Main-Class>-->
+                            <Can-Redefine-Classes>true</Can-Redefine-Classes>
+                            <Can-Retransform-Classes>true</Can-Retransform-Classes>
+<!--                            <Can-Set-Native-Method-Prefix>true</Can-Set-Native-Method-Prefix>-->
+                        </manifestEntries>
+                    </archive>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>make-assembly</id>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>single</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+
+</project>

simple_agent/src/main/java/com/seele/AttachMain.java

@@ -0,0 +1,16 @@
+package com.seele;
+
+import com.sun.tools.attach.AgentInitializationException;
+import com.sun.tools.attach.AgentLoadException;
+import com.sun.tools.attach.AttachNotSupportedException;
+import com.sun.tools.attach.VirtualMachine;
+
+import java.io.IOException;
+
+public class AttachMain {
+
+    public static void main(String[] args) throws IOException, AttachNotSupportedException, AgentLoadException, AgentInitializationException {
+        VirtualMachine vm = VirtualMachine.attach("15168");
+        vm.loadAgent("D:\\Code\\learn\\java_agent\\simple_agent\\target\\simple_agent-1.0-jar-with-dependencies.jar");
+    }
+}

simple_agent/src/main/java/com/seele/SimpleAgent.java

@@ -0,0 +1,28 @@
+package com.seele;
+
+import java.lang.instrument.Instrumentation;
+
+public class SimpleAgent {
+
+    /**
+     * jvm 参数形式
+     *
+     * @param agentArgs
+     * @param inst
+     */
+    public static void premain(String agentArgs, Instrumentation inst) {
+        System.out.println("premain");
+        inst.addTransformer(new Transformer());
+    }
+
+    /**
+     * attach 方式形式
+     *
+     * @param agentArgs
+     * @param inst
+     */
+    public static void agentmain(String agentArgs, Instrumentation inst) {
+        System.out.println("agentmain");
+    }
+
+}

simple_agent/src/main/java/com/seele/Transformer.java

@@ -0,0 +1,46 @@
+package com.seele;
+
+import java.io.*;
+import java.lang.instrument.ClassFileTransformer;
+import java.lang.instrument.IllegalClassFormatException;
+import java.security.ProtectionDomain;
+
+public class Transformer implements ClassFileTransformer {
+
+    private static String classNumberReturn2 = "D:\\Code\\learn\\java_agent\\simple_agent\\src\\main\\java\\com\\seele\\Trans.class";
+
+    private static byte[] getBytesFromFile(String filename) {
+        try {
+            File file = new File(filename);
+            InputStream is = new FileInputStream(file);
+            long length = file.length();
+            byte[] bytes = new byte[(int) length];
+
+            int offset = 0;
+            int numRead = 0;
+            while (offset < bytes.length && (numRead = is.read(bytes, offset, bytes.length - offset)) >= 0) {
+                offset += numRead;
+            }
+
+            if (offset < bytes.length) {
+                throw new IOException("Could not completely read file." + filename);
+            }
+            is.close();
+            return bytes;
+        } catch (FileNotFoundException e) {
+            throw new RuntimeException(e);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    @Override
+    public byte[] transform(ClassLoader loader, String className,
+                            Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer)
+            throws IllegalClassFormatException {
+        if (!className.equals("com/seele/Trans")) {
+            return ClassFileTransformer.super.transform(loader, className, classBeingRedefined, protectionDomain, classfileBuffer);
+        }
+        return getBytesFromFile(classNumberReturn2);
+    }
+}