SpringBoot自定义类加载器

讲解如何获取springBoot classLoader和如何往spring boot classLoader 添加包

获取spring boot classLoader

java 复制代码

 /**
     * SpringBoot打包模式下是SpringBoot的类加载器
     * @return
     */
    public static ClassLoader genClassLoader(){
        if (!SystemInfo.INSTANCE.isStandalone()) {
            return null;
        }
        AgentLogger.info("[SF Agent] Use springboot classloader.");
        try {
            // 检测是否SpringBoot打包方式
            Class launcherClass = Class.forName(STANDALONE_CLASS);
            if (launcherClass != null) {
                String jarfilePath = ClassUtils.getClassFilePath(launcherClass);
                if (null == jarfilePath) {
                    return null;
                }

                // 获取Manifest，并且获取Main-Class，可能是JarLauncher或者是WarLauncher
                Class jarFileArchiveClass = Class.forName("org.springframework.boot.loader.archive.JarFileArchive");
                Object jarFileArchiveObj = jarFileArchiveClass.getDeclaredConstructor(File.class).newInstance(new File(jarfilePath));
                Method manifestMethod = jarFileArchiveClass.getDeclaredMethod("getManifest");
                Manifest manifest = (Manifest)manifestMethod.invoke(jarFileArchiveObj);
                String mainClass = manifest.getMainAttributes().getValue("Main-Class");

                // 反射调用Launcer，获取可以加载SpringBoot依赖的类加载器
                Class launcher = Class.forName(mainClass);
                Map<String, Method> methods = getClassLoadderMethod(launcher);
                Method classLoaderMethod = methods.get("classLoader");
                Method archivesMethod = methods.get("archive");
                if (null == classLoaderMethod || null == archivesMethod) {
                    AgentLogger.error("No class loader found.");
                    return null;
                }

                archivesMethod.setAccessible(true);
                classLoaderMethod.setAccessible(true);
                Object launcherObj = launcher.getDeclaredConstructor().newInstance();
                Object classPathArchives = archivesMethod.invoke(launcherObj);
                return (ClassLoader)classLoaderMethod.invoke(launcherObj, classPathArchives);
            }
        } catch (Exception e) {
  
        }
        return null;
    }

通过字节码增强往spring boot classLoader 添加包

java 复制代码

public abstract class AbstractEnhanceModel {

    public abstract byte[] enhance(String className, byte[] source);

}

java 复制代码

import enhance.AbstractEnhanceModel;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;



public class SpringBootEnhance extends AbstractEnhanceModel {

    public static final SpringBootEnhance INSTANCE = new SpringBootEnhance();
    private SpringBootEnhance(){}

    @Override
    public byte[] enhance(String className, byte[] source) {
        ClassWriter classWriter = new ClassWriter(ClassWriter.COMPUTE_MAXS);
        ClassReader classReader = new ClassReader(source);

        AgentJarEnhance agentInitEnhance = new AgentJarEnhance(classWriter);
        classReader.accept(agentInitEnhance, ClassReader.SKIP_DEBUG);
        return classWriter.toByteArray();
    }
}

java 复制代码

import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

import static org.objectweb.asm.Opcodes.*;


public class AgentJarEnhance extends ClassVisitor {

    private ClassVisitor cv;

    public AgentJarEnhance(ClassVisitor classVisitor) {
        super(ASM4, classVisitor);
        this.cv = classVisitor;
    }

    @Override
    public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
        // 新版接口转换为旧版接口
        if ("isPostProcessingClassPathArchives".equals(name)) {
            return null;
        }
        if ("postProcessClassPathArchives".equals(name)) {
            return null;
        }
        if ("genArchive".equals(name)) {
            return null;
        }
        return cv.visitMethod(access, name, descriptor, signature, exceptions);
    }

    @Override
    public void visitEnd(){
        isPostProcessingClassPathArchives();
        postProcessClassPathArchives();
        cv.visitEnd();
    }

    private void isPostProcessingClassPathArchives(){
        MethodVisitor methodVisitor = cv.visitMethod(ACC_PUBLIC, "isPostProcessingClassPathArchives", "()Z", null, null);
        methodVisitor.visitCode();
        Label label0 = new Label();
        methodVisitor.visitLabel(label0);
        methodVisitor.visitLineNumber(14, label0);
        methodVisitor.visitInsn(ICONST_1);
        methodVisitor.visitInsn(IRETURN);
        Label label1 = new Label();
        methodVisitor.visitLabel(label1);
        methodVisitor.visitLocalVariable("this", "Lorg/springframework/boot/loader/JarLauncher;", null, label0, label1, 0);
        methodVisitor.visitMaxs(1, 1);
        methodVisitor.visitEnd();
    }

    private void postProcessClassPathArchives(){
        MethodVisitor methodVisitor = cv.visitMethod(ACC_PROTECTED, "postProcessClassPathArchives", "(Ljava/util/List;)V", "(Ljava/util/List<Lorg/springframework/boot/loader/archive/Archive;>;)V", new String[]{"java/lang/Exception"});
        methodVisitor.visitCode();
        Label label0 = new Label();
        methodVisitor.visitLabel(label0);
        methodVisitor.visitLineNumber(42, label0);
        methodVisitor.visitVarInsn(ALOAD, 1);
        methodVisitor.visitInsn(ICONST_0);
        methodVisitor.visitVarInsn(ALOAD, 0);
        methodVisitor.visitMethodInsn(INVOKEVIRTUAL, "org/springframework/boot/loader/JarLauncher", "getArchive", "()Lorg/springframework/boot/loader/archive/Archive;", false);
        methodVisitor.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(ILjava/lang/Object;)V", true);
        Label label1 = new Label();
        methodVisitor.visitLabel(label1);
        methodVisitor.visitLineNumber(43, label1);
        // 往classLoader添加jar包
        methodVisitor.visitMethodInsn(INVOKESTATIC, "agent/config/SupportConfig", "getAll", "()Ljava/util/List;", false);
        methodVisitor.visitVarInsn(ASTORE, 2);
        Label label2 = new Label();
        methodVisitor.visitLabel(label2);
        methodVisitor.visitLineNumber(44, label2);
        methodVisitor.visitVarInsn(ALOAD, 2);
        methodVisitor.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "iterator", "()Ljava/util/Iterator;", true);
        methodVisitor.visitVarInsn(ASTORE, 3);
        Label label3 = new Label();
        methodVisitor.visitLabel(label3);
        methodVisitor.visitFrame(Opcodes.F_APPEND, 2, new Object[]{"java/util/List", "java/util/Iterator"}, 0, null);
        methodVisitor.visitVarInsn(ALOAD, 3);
        methodVisitor.visitMethodInsn(INVOKEINTERFACE, "java/util/Iterator", "hasNext", "()Z", true);
        Label label4 = new Label();
        methodVisitor.visitJumpInsn(IFEQ, label4);
        methodVisitor.visitVarInsn(ALOAD, 3);
        methodVisitor.visitMethodInsn(INVOKEINTERFACE, "java/util/Iterator", "next", "()Ljava/lang/Object;", true);
        methodVisitor.visitTypeInsn(CHECKCAST, "java/lang/String");
        methodVisitor.visitVarInsn(ASTORE, 4);
        Label label5 = new Label();
        methodVisitor.visitLabel(label5);
        methodVisitor.visitLineNumber(45, label5);
        methodVisitor.visitTypeInsn(NEW, "org/springframework/boot/loader/jar/JarFile");
        methodVisitor.visitInsn(DUP);
        methodVisitor.visitTypeInsn(NEW, "java/io/File");
        methodVisitor.visitInsn(DUP);
        methodVisitor.visitVarInsn(ALOAD, 4);
        methodVisitor.visitMethodInsn(INVOKESPECIAL, "java/io/File", "<init>", "(Ljava/lang/String;)V", false);
        methodVisitor.visitMethodInsn(INVOKESPECIAL, "org/springframework/boot/loader/jar/JarFile", "<init>", "(Ljava/io/File;)V", false);
        methodVisitor.visitVarInsn(ASTORE, 5);
        Label label6 = new Label();
        methodVisitor.visitLabel(label6);
        methodVisitor.visitLineNumber(46, label6);
        methodVisitor.visitVarInsn(ALOAD, 1);
        methodVisitor.visitTypeInsn(NEW, "org/springframework/boot/loader/archive/JarFileArchive");
        methodVisitor.visitInsn(DUP);
        methodVisitor.visitVarInsn(ALOAD, 5);
        methodVisitor.visitMethodInsn(INVOKESPECIAL, "org/springframework/boot/loader/archive/JarFileArchive", "<init>", "(Lorg/springframework/boot/loader/jar/JarFile;)V", false);
        methodVisitor.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true);
        methodVisitor.visitInsn(POP);
        Label label7 = new Label();
        methodVisitor.visitLabel(label7);
        methodVisitor.visitLineNumber(47, label7);
        methodVisitor.visitJumpInsn(GOTO, label3);
        methodVisitor.visitLabel(label4);
        methodVisitor.visitLineNumber(48, label4);
        methodVisitor.visitFrame(Opcodes.F_CHOP, 1, null, 0, null);
        methodVisitor.visitInsn(RETURN);
        Label label8 = new Label();
        methodVisitor.visitLabel(label8);
        methodVisitor.visitLocalVariable("jarFile", "Lorg/springframework/boot/loader/jar/JarFile;", null, label6, label7, 5);
        methodVisitor.visitLocalVariable("path", "Ljava/lang/String;", null, label5, label7, 4);
        methodVisitor.visitLocalVariable("this", "Lorg/springframework/boot/loader/JarLauncher;", null, label0, label8, 0);
        methodVisitor.visitLocalVariable("archives", "Ljava/util/List;", "Ljava/util/List<Lorg/springframework/boot/loader/archive/Archive;>;", label0, label8, 1);
        methodVisitor.visitLocalVariable("paths", "Ljava/util/List;", "Ljava/util/List<Ljava/lang/String;>;", label2, label8, 2);
        methodVisitor.visitMaxs(5, 6);
        methodVisitor.visitEnd();
    }
}

java 复制代码

import java.util.ArrayList;
import java.util.List;

public class SupportConfig {

    private static final String KEY = "Governance.SupportConfig";
    private static final String SPLIT = ";";

    public static void add(String support) {
        String value = System.getProperty(KEY);
        if (null == value || value.length() < 1) {
            value = support;
        }else {
            value = value + SPLIT + support;
        }
        System.setProperty(KEY, value);
    }

    public static List<String> getAll(){
        String value = System.getProperty(KEY);
        if (null == value || value.length() < 1) {
            return new ArrayList<>();
        }
        List<String> list = new ArrayList<>();
        String[] values = value.split(SPLIT);
        for(String row : values) {
            list.add(row);
        }
        return list;
    }
}