Java 如何获取cglib代理类实例的字节码?
我正在尝试使用BCEL以这种方式获取cglib增强对象的字节码:Java 如何获取cglib代理类实例的字节码?,java,bytecode,cglib,bcel,Java,Bytecode,Cglib,Bcel,我正在尝试使用BCEL以这种方式获取cglib增强对象的字节码: package app; import cglib.MyInterceptor; import net.sf.cglib.proxy.Enhancer; import org.apache.bcel.Repository; import org.apache.bcel.classfile.JavaClass; import org.apache.bcel.classfile.Method; import service.Tool
package app;
import cglib.MyInterceptor;
import net.sf.cglib.proxy.Enhancer;
import org.apache.bcel.Repository;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;
import service.Tool;
public class CgLibApp {
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException {
// target object
Tool tool = new Tool();
// proxying
Enhancer e = new Enhancer();
e.setSuperclass(tool.getClass());
e.setCallback(new MyInterceptor(tool));
Tool proxifiedTool = (Tool) e.create();
// trying to get proxy byte code
JavaClass clazz = Repository.lookupClass(proxifiedTool.getClass());
Method method = clazz.getMethod(Tool.class.getMethod("meth"));
System.out.println(method.getCode().toString());
}
}
但我得到了:
Exception in thread "main" java.lang.ClassNotFoundException: SyntheticRepository could not load service.Tool$$EnhancerByCGLIB$$22a3afcc
at org.apache.bcel.util.SyntheticRepository.loadClass(SyntheticRepository.java:174)
at org.apache.bcel.util.SyntheticRepository.loadClass(SyntheticRepository.java:158)
at org.apache.bcel.Repository.lookupClass(Repository.java:74)
at app.CgLibApp.main(CgLibApp.java:21)
如何从增强对象获取字节码?BCEL向类加载器查询
.class
文件,以获取表示该文件的字节数组。动态生成的类不存在这样的类文件
为了获得类文件,必须在创建类文件的过程中收集字节码。Cglib构建在ASM之上,它允许您注册自己的ClassVisitor
s来收集类文件
使用
增强器
,使用生成类(ClassVisitor)
方法,并将后一种方法交给类编写器
。调用该方法后,可以从传递的class writer对象中获取字节码。以下是打印生成的CGLIB类的伪代码的示例代码。
visitEnd方法以文本格式打印生成的类
package naga.cglib.demo;
import static org.objectweb.asm.Opcodes.ASM7;
import java.io.PrintWriter;
import java.lang.reflect.InvocationTargetException;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.util.TraceClassVisitor;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.FixedValue;
public class App {
public static void main(String[] args) throws Exception, IllegalArgumentException, InvocationTargetException {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(SampleClass.class);
enhancer.setCallback(new FixedValueImpl());
SampleClass proxy = (SampleClass) enhancer.create();
enhancer.generateClass(new CustomClassWriter());
System.out.println("Hello cglib!" + proxy.test(null));
}
}
class SampleClass {
public String test(String input) {
return "Hello world!";
}
}
class FixedValueImpl implements FixedValue {
@Override
public Object loadObject() throws Exception {
// TODO Auto-generated method stub
return "Hello cglib! from loadObject()";
}
}
class CustomClassWriter extends ClassVisitor {
TraceClassVisitor tracer;
PrintWriter pw = new PrintWriter(System.out);
public CustomClassWriter() {
super(ASM7);
tracer = new TraceClassVisitor(pw);
}
@Override
public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
System.out.println("method name is :" + name);
return tracer.visitMethod(access, name, desc, signature, exceptions);
}
@Override
public FieldVisitor visitField(int access, String name, String desc, String signature, Object value) {
System.out.println("field name is :" + name);
return tracer.visitField(access, name, desc, signature, value);
}
public void visitEnd() {
tracer.visitEnd();
System.out.println(tracer.p.getText());
}
}