如何使用堆栈跟踪或反射找到方法的调用者?

我需要找到一个方法的调用者 . 是否可以使用堆栈跟踪或反射?

回答(12)

3 years ago

StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace()

根据Javadocs:

数组的最后一个元素表示堆栈的底部,这是序列中最近的方法调用 .

StackTraceElementgetClassName()getFileName()getLineNumber()getMethodName() .

您将不得不尝试确定您想要的索引(可能是 stackTraceElements[1][2] ) .

3 years ago

可以在对this request for enhancement的评论中找到替代解决方案 . 它使用自定义 SecurityManagergetClassContext() 方法,并且似乎比堆栈跟踪方法更快 .

以下程序测试不同建议方法的速度(最有趣的位在内部类 SecurityManagerMethod ):

/**
 * Test the speed of various methods for getting the caller class name
 */
public class TestGetCallerClassName {

  /**
   * Abstract class for testing different methods of getting the caller class name
   */
  private static abstract class GetCallerClassNameMethod {
      public abstract String getCallerClassName(int callStackDepth);
      public abstract String getMethodName();
  }

  /**
   * Uses the internal Reflection class
   */
  private static class ReflectionMethod extends GetCallerClassNameMethod {
      public String getCallerClassName(int callStackDepth) {
          return sun.reflect.Reflection.getCallerClass(callStackDepth).getName();
      }

      public String getMethodName() {
          return "Reflection";
      }
  }

  /**
   * Get a stack trace from the current thread
   */
  private static class ThreadStackTraceMethod extends GetCallerClassNameMethod {
      public String  getCallerClassName(int callStackDepth) {
          return Thread.currentThread().getStackTrace()[callStackDepth].getClassName();
      }

      public String getMethodName() {
          return "Current Thread StackTrace";
      }
  }

  /**
   * Get a stack trace from a new Throwable
   */
  private static class ThrowableStackTraceMethod extends GetCallerClassNameMethod {

      public String getCallerClassName(int callStackDepth) {
          return new Throwable().getStackTrace()[callStackDepth].getClassName();
      }

      public String getMethodName() {
          return "Throwable StackTrace";
      }
  }

  /**
   * Use the SecurityManager.getClassContext()
   */
  private static class SecurityManagerMethod extends GetCallerClassNameMethod {
      public String  getCallerClassName(int callStackDepth) {
          return mySecurityManager.getCallerClassName(callStackDepth);
      }

      public String getMethodName() {
          return "SecurityManager";
      }

      /** 
       * A custom security manager that exposes the getClassContext() information
       */
      static class MySecurityManager extends SecurityManager {
          public String getCallerClassName(int callStackDepth) {
              return getClassContext()[callStackDepth].getName();
          }
      }

      private final static MySecurityManager mySecurityManager =
          new MySecurityManager();
  }

  /**
   * Test all four methods
   */
  public static void main(String[] args) {
      testMethod(new ReflectionMethod());
      testMethod(new ThreadStackTraceMethod());
      testMethod(new ThrowableStackTraceMethod());
      testMethod(new SecurityManagerMethod());
  }

  private static void testMethod(GetCallerClassNameMethod method) {
      long startTime = System.nanoTime();
      String className = null;
      for (int i = 0; i < 1000000; i++) {
          className = method.getCallerClassName(2);
      }
      printElapsedTime(method.getMethodName(), startTime);
  }

  private static void printElapsedTime(String title, long startTime) {
      System.out.println(title + ": " + ((double)(System.nanoTime() - startTime))/1000000 + " ms.");
  }
}

运行Java 1.6.0_17的2.4 GHz Intel Core 2 Duo MacBook的输出示例:

Reflection: 10.195 ms.
Current Thread StackTrace: 5886.964 ms.
Throwable StackTrace: 4700.073 ms.
SecurityManager: 1046.804 ms.

内部Reflection方法比其他方法快得多 . 从新创建的 Throwable 获取堆栈跟踪比从当前 Thread 获取堆栈跟踪更快 . 在查找调用者类的非内部方法中,自定义 SecurityManager 似乎是最快的 .

更新

正如this comment中的 lyomi 指出的那样, sun.reflect.Reflection.getCallerClass() 方法默认在Java 7更新40中被禁用,并在Java 8中完全删除 . 在this issue in the Java bug database中了解更多相关信息 .

更新2

正如 zammbi 所发现的那样,Oracle被forced to back out of the change删除了 sun.reflect.Reflection.getCallerClass() . 它仍然可以在Java 8中使用(但不推荐使用) .

更新3

3年后:使用当前JVM更新时序 .

> java -version
java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b132)
Java HotSpot(TM) 64-Bit Server VM (build 25.0-b70, mixed mode)
> java TestGetCallerClassName
Reflection: 0.194s.
Current Thread StackTrace: 3.887s.
Throwable StackTrace: 3.173s.
SecurityManager: 0.565s.

3 years ago

听起来你正试图避免将对 this 的引用传递给方法 . 传递 this 比通过当前堆栈跟踪查找调用方更好 . Refactoring to a more OO design is even better. 您不需要知道呼叫者 . 必要时传递回调对象 .

3 years ago

Java 9 - JEP 259:Stack-Walking API

JEP 259为堆栈遍历提供了一种有效的标准API,允许轻松过滤和延迟访问堆栈跟踪中的信息 . 在Stack-Walking API之前,访问堆栈帧的常用方法是:

Throwable :: getStackTrace和Thread :: getStackTrace返回一个StackTraceElement对象数组,其中包含每个stack-trace元素的类名和方法名 . SecurityManager :: getClassContext是一个受保护的方法,它允许SecurityManager子类访问类上下文 . JDK内部的sun.reflect.Reflection :: getCallerClass方法,你不应该使用它

使用这些API通常效率低下:

这些API要求VM急切地捕获整个堆栈的快照,并返回表示整个堆栈的信息 . 如果调用者只对堆栈中的前几帧感兴趣,则无法避免检查所有帧的成本 .

为了找到直接调用者的类,首先获取 StackWalker

StackWalker walker = StackWalker.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE);

然后调用 getCallerClass()

Class<?> callerClass = walker.getCallerClass();

walk StackFrame s并获得第一个前面的 StackFrame

walker.walk(frames -> frames.map(StackWalker.StackFrame::getDeclaringClass).skip(1).findFirst());

3 years ago

Oneliner

Thread.currentThread().getStackTrace()[2].getMethodName()

请注意,您可能需要将2替换为1 .

3 years ago

这种方法做了同样的事情,但更简单,可能更高效,如果你使用反射,它会自动跳过这些帧 . 唯一的问题是它可能不存在于非Sun JVM中,尽管它包含在JRockit 1.4的运行时类 - > 1.6中 . (重点是,它不是公共课) .

sun.reflect.Reflection

    /** Returns the class of the method <code>realFramesToSkip</code>
        frames up the stack (zero-based), ignoring frames associated
        with java.lang.reflect.Method.invoke() and its implementation.
        The first frame is that associated with this method, so
        <code>getCallerClass(0)</code> returns the Class object for
        sun.reflect.Reflection. Frames associated with
        java.lang.reflect.Method.invoke() and its implementation are
        completely ignored and do not count toward the number of "real"
        frames skipped. */
    public static native Class getCallerClass(int realFramesToSkip);

至于 realFramesToSkip 值应该是 java.lang.System 的Sun 1.5和1.6 VM版本,有一个名为getCallerClass()的包保护方法,它调用 sun.reflect.Reflection.getCallerClass(3) ,但在我的帮助实用程序类中,我使用了4,因为有一个添加的框架帮助程序类调用 .

3 years ago

/**
       * Get the method name for a depth in call stack. 
* Utility function * @param depth depth in the call stack (0 means current method, 1 means call method, ...) * @return method name */ public static String getMethodName(final int depth) { final StackTraceElement[] ste = new Throwable().getStackTrace(); //System. out.println(ste[ste.length-depth].getClassName()+"#"+ste[ste.length-depth].getMethodName()); return ste[ste.length - depth].getMethodName(); }

例如,如果您尝试将调用方法行用于调试目的,则需要通过Utility类来编写这些静态方法:
(旧的java1.4代码,只是为了说明潜在的StackTraceElement用法)

/**
          * Returns the first "[class#method(line)]: " of the first class not equal to "StackTraceUtils". 
* From the Stack Trace. * @return "[class#method(line)]: " (never empty, first class past StackTraceUtils) */ public static String getClassMethodLine() { return getClassMethodLine(null); } /** * Returns the first "[class#method(line)]: " of the first class not equal to "StackTraceUtils" and aclass.
* Allows to get past a certain class. * @param aclass class to get pass in the stack trace. If null, only try to get past StackTraceUtils. * @return "[class#method(line)]: " (never empty, because if aclass is not found, returns first class past StackTraceUtils) */ public static String getClassMethodLine(final Class aclass) { final StackTraceElement st = getCallingStackTraceElement(aclass); final String amsg = "[" + st.getClassName() + "#" + st.getMethodName() + "(" + st.getLineNumber() +")] <" + Thread.currentThread().getName() + ">: "; return amsg; } /** * Returns the first stack trace element of the first class not equal to "StackTraceUtils" or "LogUtils" and aClass.
* Stored in array of the callstack.
* Allows to get past a certain class. * @param aclass class to get pass in the stack trace. If null, only try to get past StackTraceUtils. * @return stackTraceElement (never null, because if aClass is not found, returns first class past StackTraceUtils) * @throws AssertionFailedException if resulting statckTrace is null (RuntimeException) */ public static StackTraceElement getCallingStackTraceElement(final Class aclass) { final Throwable t = new Throwable(); final StackTraceElement[] ste = t.getStackTrace(); int index = 1; final int limit = ste.length; StackTraceElement st = ste[index]; String className = st.getClassName(); boolean aclassfound = false; if(aclass == null) { aclassfound = true; } StackTraceElement resst = null; while(index < limit) { if(shouldExamine(className, aclass) == true) { if(resst == null) { resst = st; } if(aclassfound == true) { final StackTraceElement ast = onClassfound(aclass, className, st); if(ast != null) { resst = ast; break; } } else { if(aclass != null && aclass.getName().equals(className) == true) { aclassfound = true; } } } index = index + 1; st = ste[index]; className = st.getClassName(); } if(resst == null) { //Assert.isNotNull(resst, "stack trace should null"); //NO OTHERWISE circular dependencies throw new AssertionFailedException(StackTraceUtils.getClassMethodLine() + " null argument:" + "stack trace should null"); //$NON-NLS-1$ } return resst; } static private boolean shouldExamine(String className, Class aclass) { final boolean res = StackTraceUtils.class.getName().equals(className) == false && (className.endsWith("LogUtils" ) == false || (aclass !=null && aclass.getName().endsWith("LogUtils"))); return res; } static private StackTraceElement onClassfound(Class aclass, String className, StackTraceElement st) { StackTraceElement resst = null; if(aclass != null && aclass.getName().equals(className) == false) { resst = st; } if(aclass == null) { resst = st; } return resst; }

3 years ago

我之前做过这个 . 您可以创建一个新的异常并在其上抓取堆栈跟踪而不抛出它,然后检查堆栈跟踪 . 正如另一个答案所说的那样,它的成本非常高 - 不要在紧密的环路中进行 .

我之前已经完成了在应用程序上的日志实用程序,其中性能并不重要(性能很少,实际上 - 只要您将结果显示为快速按钮单击等操作) .

在您获得堆栈跟踪之前,异常只有.printStackTrace()所以我不得不将System.out重定向到我自己的创建流,然后(new Exception()) . printStackTrace();重定向System.out并解析流 . 好玩的东西 .

3 years ago

private void parseExceptionContents(
      final Exception exception,
      final OutputStream out)
   {
      final StackTraceElement[] stackTrace = exception.getStackTrace();
      int index = 0;
      for (StackTraceElement element : stackTrace)
      {
         final String exceptionMsg =
              "Exception thrown from " + element.getMethodName()
            + " in class " + element.getClassName() + " [on line number "
            + element.getLineNumber() + " of file " + element.getFileName() + "]";
         try
         {
            out.write((headerLine + newLine).getBytes());
            out.write((headerTitlePortion + index++ + newLine).getBytes() );
            out.write((headerLine + newLine).getBytes());
            out.write((exceptionMsg + newLine + newLine).getBytes());
            out.write(
               ("Exception.toString: " + element.toString() + newLine).getBytes());
         }
         catch (IOException ioEx)
         {
            System.err.println(
                 "IOException encountered while trying to write "
               + "StackTraceElement data to provided OutputStream.\n"
               + ioEx.getMessage() );
         }
      }
   }

3 years ago

以下是我在本主题中显示的提示中创建的代码的一部分 . 希望能帮助到你 .

(随意提出改进此代码的任何建议,请告诉我)

柜台:

public class InstanceCount{
    private static Map<Integer, CounterInstanceLog> instanceMap = new HashMap<Integer, CounterInstanceLog>();
private CounterInstanceLog counterInstanceLog;


    public void count() {
        counterInstanceLog= new counterInstanceLog();
    if(counterInstanceLog.getIdHashCode() != 0){
    try {
        if (instanceMap .containsKey(counterInstanceLog.getIdHashCode())) {
         counterInstanceLog= instanceMap .get(counterInstanceLog.getIdHashCode());
    }

    counterInstanceLog.incrementCounter();

            instanceMap .put(counterInstanceLog.getIdHashCode(), counterInstanceLog);
    }

    (...)
}

对象:

public class CounterInstanceLog{
    private int idHashCode;
    private StackTraceElement[] arrayStackTraceElements;
    private int instanceCount;
    private String callerClassName;

    private StackTraceElement getProjectClasses(int depth) {
      if(depth< 10){
        getCallerClassName(sun.reflect.Reflection.getCallerClass(depth).getName());
        if(getCallerClassName().startsWith("com.yourproject.model")){
            setStackTraceElements(Thread.currentThread().getStackTrace());
            setIdHashCode();
        return arrayStackTraceElements[depth];
        }
        //+2 because one new item are added to the stackflow
        return getProjectClasses(profundidade+2);           
      }else{
        return null;
      }
    }

    private void setIdHashCode() {
        if(getNomeClasse() != null){
            this.idHashCode = (getCallerClassName()).hashCode();
        }
    }

    public void incrementaContador() {
    this.instanceCount++;
}

    //getters and setters

    (...)



}

3 years ago

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintWriter;

class DBConnection {
    String createdBy = null;

    DBConnection(Throwable whoCreatedMe) {
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        PrintWriter pw = new PrintWriter(os);
        whoCreatedMe.printStackTrace(pw);
        try {
            createdBy = os.toString();
            pw.close();
            os.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

public class ThrowableTest {

    public static void main(String[] args) {

        Throwable createdBy = new Throwable(
                "Connection created from DBConnectionManager");
        DBConnection conn = new DBConnection(createdBy);
        System.out.println(conn.createdBy);
    }
}

public static interface ICallback<T> { T doOperation(); }


public class TestCallerOfMethod {

    public static <T> T callTwo(final ICallback<T> c){
        // Pass the object created at callee to the caller
        // From the passed object we can get; what is the callee name like below.
        System.out.println(c.getClass().getEnclosingMethod().getName());
        return c.doOperation();
    }

    public static boolean callOne(){
        ICallback callBackInstance = new ICallback(Boolean){
            @Override
            public Boolean doOperation() 
            {
                return true;
            }
        };
        return callTwo(callBackInstance);
    }

    public static void main(String[] args) {
         callOne();
    }
}

3 years ago

使用这种方法: -

StackTraceElement[] stacktrace = Thread.currentThread().getStackTrace();
 stackTraceElement e = stacktrace[2];//maybe this number needs to be corrected
 System.out.println(e.getMethodName());

方法示例代码的调用者在这里: -

public class TestString {

    public static void main(String[] args) {
        TestString testString = new TestString();
        testString.doit1();
        testString.doit2();
        testString.doit3();
        testString.doit4();
    }

    public void doit() {
        StackTraceElement[] stacktrace = Thread.currentThread().getStackTrace();
        StackTraceElement e = stacktrace[2];//maybe this number needs to be corrected
        System.out.println(e.getMethodName());
    }

    public void doit1() {
        doit();
    }

    public void doit2() {
        doit();
    }

    public void doit3() {
        doit();
    }

    public void doit4() {
        doit();
    }
}