Java 9 - JEP 259：堆栈行走API

Question

我需要找到方法的调用者。是否可以使用堆栈跟踪或反射？

Answer 1

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。

StackTraceElement有getClassName()，getFileName()，getLineNumber()和getMethodName()。

您必须尝试确定所需的索引（可能是stackTraceElements[1]或[2]）。

Answer 2

可以在this request for enhancement的评论中找到替代解决方案。它使用自定义getClassContext()的{{1}}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SecurityManager中）：

SecurityManagerMethod

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

/**
 * 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.");
  }
}

内部Reflection方法很多比其他方法快。从新创建的Reflection: 10.195 ms. Current Thread StackTrace: 5886.964 ms. Throwable StackTrace: 4700.073 ms. SecurityManager: 1046.804 ms.获取堆栈跟踪比从当前Throwable获取堆栈跟踪要快。在查找调用者类的非内部方式中，自定义Thread似乎是最快的。

更新

正如 lyomi 在this comment中指出的那样，{7}更新40中默认禁用SecurityManager方法，并在Java 8中完全删除。在{8中详细了解此内容{3}}。

更新2

正如 zammbi 所发现的那样，Oracle this issue in the Java bug database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。

sun.reflect.Reflection.getCallerClass()

Answer 3

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。 重构更多OO设计甚至更好。您不需要知道调用者。如有必要，传递一个回调对象。

Answer 4

Java 9 - JEP 259：堆栈行走API

JEP 259为堆栈遍历提供了一个有效的标准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返回一个数组   StackTraceElement个对象，包含类名和方法   每个堆栈跟踪元素的名称。

SecurityManager::getClassContext是受保护的方法，允许使用   SecurityManager子类访问类上下文。

您不应该使用的JDK内部sun.reflect.Reflection::getCallerClass方法

使用这些API通常效率低下：

这些API要求VM急切地捕获整个快照 stack ，它们返回表示整个堆栈的信息。没有办法避免检查所有帧的成本调用者只对堆栈中的前几帧感兴趣。

为了找到直接来电者的班级，首先获得StackWalker：

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

然后调用getCallerClass()：

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

或walk StackFrame s并获取前一个StackFrame：

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

Answer 5

Oneliner ：

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

请注意，您可能需要将1替换为1。

Answer 6

这种方法做同样的事情，但更简单，可能更高效，如果您使用反射，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的运行时类中 - > 1.6。（重点是，它不是 public 类）。

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（）的包保护方法调用sun.reflect.Reflection.getCallerClass(3)，但是在我的帮助器实用程序类中，我使用了4，因为有一个辅助类调用的添加框架。

Answer 7

我以前做过这个。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，这是非常昂贵的 - 不要紧紧地做这件事。

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（性能很少重要，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。有趣的东西。

Answer 8

     /**
       * Get the method name for a depth in call stack. <br />
       * 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，仅用于说明潜在的StackTraceElement用法）

        /**
          * Returns the first "[class#method(line)]: " of the first class not equal to "StackTraceUtils". <br />
          * 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. <br />
          * 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. <br />
       * Stored in array of the callstack. <br />
       * 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;
      }

Answer 9

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() );
         }
      }
   }

Answer 10

以下是我在本主题中显示的提示中创建的代码的一部分。希望它有所帮助。

（请随意提出改进此代码的建议，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

    (...)



}

Answer 11

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);
    }
}

或者

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();
    }
}

Answer 12

使用此方法： -

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

方法示例的调用者代码在这里： -

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();
    }
}

如何使用堆栈跟踪或反射找到方法的调用者？

12 个答案:

更新

更新2

更新3

Java 9 - JEP 259：堆栈行走API

或者