使用ASM实现ParameterDiscover

本是古典何须时尚 2022-03-01 13:52 131阅读 0赞

import org.objectweb.asm.ClassReader;
    import org.objectweb.asm.ClassVisitor;
    import org.objectweb.asm.Label;
    import org.objectweb.asm.MethodVisitor;
    import org.objectweb.asm.Opcodes;
    import org.objectweb.asm.Type;
    
    import java.io.IOException;
    import java.lang.reflect.Method;
    import java.lang.reflect.Modifier;
    import java.util.Arrays;
    
    /**
     * @author <a href="wangte@meitaun.com">Te</a>
     * @date created at 2019/3/21
     */
    public class ParameterNameDiscover {
    
        public static void main(String[] args) throws Exception {
            Method method = EchoService.class.getMethod("echo", String.class, String.class);
            String[] methodParameterNames = getMethodParameterNames(method);
            System.out.println(Arrays.toString(methodParameterNames));
        }
    
    
        public static String[] getMethodParameterNames(final Method method) {
            final String[] paramNames = new String[method.getParameterTypes().length];
            final String n = method.getDeclaringClass().getName();
    
            ClassReader cr;
            try {
                cr = new ClassReader(n);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
            cr.accept(new ClassVisitor(Opcodes.ASM5) {
                @Override
                public MethodVisitor visitMethod(final int access,
                                                 final String name, final String desc,
                                                 final String signature, final String[] exceptions) {
    
                    final Type[] args = Type.getArgumentTypes(desc);
                    // 方法名相同并且参数个数相同
                    if (!name.equals(method.getName()) || !sameType(args, method.getParameterTypes())) {
                        return super.visitMethod(access, name, desc, signature, exceptions);
                    }
    
                    MethodVisitor v = super.visitMethod(access, name, desc, signature, exceptions);
                    return new MethodVisitor(Opcodes.ASM4, v) {
                        @Override
                        public void visitLocalVariable(String name, String desc,
                                                       String signature, Label start, Label end, int index) {
                            int i = index - 1;
                            // 如果是静态方法，则第一就是参数
                            // 如果不是静态方法，则第一个是"this"，然后才是方法的参数
                            if (Modifier.isStatic(method.getModifiers())) {
                                i = index;
                            }
                            if (i >= 0 && i < paramNames.length) {
                                paramNames[i] = name;
                            }
                            super.visitLocalVariable(name, desc, signature, start, end, index);
                        }
    
                    };
                }
            }, 0);
            return paramNames;
        }
    
        private static boolean sameType(Type[] types, Class<?>[] classes) {
            // 个数不同
            if (types.length != classes.length) {
                return false;
            }
    
            for (int i = 0; i < types.length; i++) {
                if (!Type.getType(classes[i]).equals(types[i])) {
                    return false;
                }
            }
            return true;
        }
    }