Javassistによる非侵襲的ログ・インジェクションの実装

序文

実装プロセス

private static void injectCode(StringBuffer body, String methodName /*元のメソッドのコード*/, boolean returnVoid,CtMethod mold) throws NotFoundException {
 String type = mold.getReturnType().getName();
 body.append("{ int res = 7;
");
 body.append(" long start = System.currentTimeMillis();
" +
 " long cost = -1;
" +
 " long end = start;
" +
 " boolean isSuccess = true;
" +
 " System.out.println(System.currentTimeMillis()); 
" );
 if (!type.equals("void")){
 if (type.equals("boolean")){
 body.append(type + " result = false;
");
 }
 else if (type.equals("String")){
 body.append(type + " result = null;
");
 }
 else if (type.equals("long")){
 body.append(type + " result = 0;
");
 }
 else if (type.equals("int")){
 body.append(type + " result = 0;
");
 }
 else{
 body.append(type + " result = null;
");
 }
 }
 body.append("
 try{" + "
");
 // method()と同様に、元のコードを呼び出す。;(?)クラス・ローダーのすべてのパラメーターは
 if (!"void".equals(type)){
 body.append("result = ");
 }
 body.append(methodName + "(?);
");
 body.append("}catch (Exception e){
" +
 " e.printStackTrace();" +
 " }finally {
" +
 " end = System.currentTimeMillis();
" +
 " cost = start - end;
" +
 " System.out.println(res + );"+
 " }");
 if (!"void".equals(type)){
 body.append("return result;
");
 }
 body.append("}");
 }

バイトコード置換

 private static void addLog(String methodName,CtClass ctClass) throws CannotCompileException, NotFoundException, IllegalAccessException, InstantiationException {
 CtMethod mold = ctClass.getDeclaredMethod(methodName);
 // 元のメソッド名を修正する
 String newName = methodName + "$impl";
 mold.setName(newName);
 //新しいメソッドを作り、元のメソッドをコピーする
 // メインのインジェクション・コード
 CtMethod mnew = CtNewMethod.copy(mold, methodName, ctClass, null);
 StringBuffer body = new StringBuffer();
 try {
 injectCode(body,newName,mold.getReturnType() == CtClass.voidType,mold);
 }catch (Exception e){
 e.printStackTrace();
 }
 // 新しいメソッド
 mnew.setBody(body.toString());
 // 新しいメソッドを追加する
 ctClass.addMethod(mnew);
 }

public class MyClassLoader extends ClassLoader{
 private String path;
 public MyClassLoader(String clazzPath){
 this.path = clazzPath;
 }
 @Override
 protected Class<?> findClass(String name) throws ClassNotFoundException {
 Class log = null;
 byte[] bytes = gatDate();
 if (bytes != null){
 log = defineClass(name,bytes,0,bytes.length);
 }
 return log;
 }
 private byte[] gatDate(){
 File file = new File(path);
 if (file.exists()){
 FileInputStream inputStream = null;
 ByteArrayOutputStream outputStream = null;
 try{
 inputStream = new FileInputStream(file);
 outputStream = new ByteArrayOutputStream();
 byte[] buffer = new byte;
 int size = 0;
 while ((size = inputStream.read(buffer)) != -1){
 outputStream.write(buffer,0,size);
 }
 }catch (Exception e){
 e.printStackTrace();
 }finally {
 try {
 inputStream.close();
 outputStream.close();
 }catch (Exception e){
 e.printStackTrace();
 }
 }
 return outputStream.toByteArray();
 }else{
 return null;
 }
 }
}

次のステップでは、具体的なビジネスについて、ニーズに応じて判断します。

 //  
 ClassPool pool = ClassPool.getDefault();
 CtClass ctClass = pool.get("redisson.RedissonTool");
 List<String> methodList = new ArrayList<>();
 URL path = Thread.currentThread().getContextClassLoader ().getResource("");
 MyClassLoader loader = new MyClassLoader(path.getPath() + "redisson/RedissonTool.class");
 Class<?>redissonTool = null;
 try {
 redissonTool = loader.findClass("redisson.RedissonTool");
 System.out.println(redissonTool.getClassLoader() + "");
 redissonTool.newInstance();
 }catch (Exception e){
 e.printStackTrace();
 }
 Method[] methods = redissonTool.getMethods();
 excludeObjectMethod(methods);
 for (Method i : methods){
 if (i != null){
 addLog(i.getName(),ctClass);
 }
 }
// addLog("set",ctClass);
 RedissonTool redissonTool1 = (RedissonTool) ctClass.toClass().newInstance();