Class StackLocator
Background
This method, available only in the Oracle/Sun/OpenJDK implementations of the Java Virtual Machine, is a much more
efficient mechanism for determining the Class
of the caller of a particular method. When it is not available,
a SecurityManager
is the second-best option. When this is also not possible, the StackTraceElement[]
returned by Throwable.getStackTrace()
must be used, and its String
class name converted to a
Class
using the slow Class.forName(java.lang.String)
(which can add an extra microsecond or more for each invocation
depending on the runtime ClassLoader hierarchy).
During Java 8 development, the sun.reflect.Reflection.getCallerClass(int)
was removed from OpenJDK, and this
change was back-ported to Java 7 in version 1.7.0_25 which changed the behavior of the call and caused it to be off
by one stack frame. This turned out to be beneficial for the survival of this API as the change broke hundreds of
libraries and frameworks relying on the API which brought much more attention to the intended API removal.
After much community backlash, the JDK team agreed to restore getCallerClass(int)
and keep its existing
behavior for the rest of Java 7. However, the method is deprecated in Java 8, and current Java 9 development has not
addressed this API. Therefore, the functionality of this class cannot be relied upon for all future versions of Java.
It does, however, work just fine in Sun JDK 1.6, OpenJDK 1.6, Oracle/OpenJDK 1.7, and Oracle/OpenJDK 1.8. Other Java
environments may fall back to using Throwable.getStackTrace()
which is significantly slower due to
examination of every virtual frame of execution.
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate static final Class
<?> TODO: Use Object.class.private static final Method
private static final StackLocator
(package private) static final int
TODO Consider removing now that we require Java 8. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptioncalcLocation
(String fqcnOfLogger) Class
<?> getCallerClass
(int depth) Gets the Class of the method that called this method at the location up the call stack by the given stack frame depth.Class
<?> getCallerClass
(Class<?> anchor) Class
<?> getCallerClass
(Class<?> sentinelClass, Predicate<Class<?>> callerPredicate) Class
<?> getCallerClass
(String fqcn, String pkg) static StackLocator
Gets the singleton instance.getStackTraceElement
(int depth) private boolean
isValid
(StackTraceElement element)
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Field Details
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JDK_7U25_OFFSET
static final int JDK_7U25_OFFSETTODO Consider removing now that we require Java 8. -
GET_CALLER_CLASS_METHOD
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INSTANCE
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DEFAULT_CALLER_CLASS
TODO: Use Object.class.
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Constructor Details
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StackLocator
private StackLocator()
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Method Details
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getInstance
Gets the singleton instance.- Returns:
- the singleton instance.
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getCallerClass
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getCallerClass
Gets the Class of the method that called this method at the location up the call stack by the given stack frame depth.This method returns
null
if:sun.reflect.Reflection.getCallerClass(int)
is not present.- An exception is caught calling
sun.reflect.Reflection.getCallerClass(int)
.
- Parameters:
depth
- The stack frame count to walk.- Returns:
- A class or null.
- Throws:
IndexOutOfBoundsException
- if depth is negative.
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getCallerClass
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getCallerClass
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getCurrentStackTrace
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calcLocation
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getStackTraceElement
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isValid
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