我需要找到方法的调用者。是否可以使用堆栈跟踪或反射?
12 回答
StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace()
根据Javadocs:
数组的最后一个元素表示堆栈的底部,它是序列中最近的方法调用。
AStackTraceElement
有getClassName()
,和. getFileName()
_getLineNumber()
getMethodName()
您将不得不尝试确定您想要的索引(可能是stackTraceElements[1]
或[2]
)。
注意:如果您使用的是 Java 9 或更高版本,则应StackWalker.getCallerClass()
按照Ali Dehghani 的回答中所述使用。
由于历史原因,以下不同方法的比较主要是有趣的。
可以在对此增强请求的评论中找到替代解决方案。它使用getClassContext()
自定义的方法,SecurityManager
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(最有趣的是在内部类中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.
内部反射方法比其他方法快得多。从新创建Throwable
的获取堆栈跟踪比从当前获取更快Thread
。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lyomi在此评论中指出的那样,该sun.reflect.Reflection.getCallerClass()
方法在 Java 7 更新 40 中默认已禁用,并在 Java 8 中完全删除。在 Java 错误数据库中的此问题中阅读有关此问题的更多信息。
更新 2
正如zammbi发现的那样,甲骨文被迫退出删除sun.reflect.Reflection.getCallerClass()
. 它在 Java 8 中仍然可用(但已弃用)。
更新 3
3 年后:更新当前 JVM 的时间。
> 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.
Java 9 - JEP 259:Stack-Walking API
JEP 259为堆栈遍历提供了一个高效的标准 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有:
Throwable::getStackTrace
并Thread::getStackTrace
返回一个对象数组StackTraceElement
,其中包含每个堆栈跟踪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。
sun.reflect.Reflection::getCallerClass
无论如何都不应该使用的JDK 内部方法
使用这些 API 通常效率低下:
这些 API 要求 VM 急切地捕获整个堆栈的快照,并返回代表整个堆栈的信息。如果调用者只对堆栈上的前几帧感兴趣,则无法避免检查所有帧的成本。
为了找到直接调用者的类,首先获取一个StackWalker
:
StackWalker walker = StackWalker
.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE);
然后要么调用getCallerClass()
:
Class<?> callerClass = walker.getCallerClass();
或s 并获得walk
第StackFrame
一个前面的StackFrame
:
walker.walk(frames -> frames
.map(StackWalker.StackFrame::getDeclaringClass)
.skip(1)
.findFirst());
听起来您正试图避免将引用传递给this
该方法。传递this
比通过当前堆栈跟踪找到调用者要好得多。 重构为更面向对象的设计会更好。 您不需要知道来电者。如有必要,传递一个回调对象。
单线:
Thread.currentThread().getStackTrace()[2].getMethodName()
请注意,您可能需要将 2 替换为 1。
这个方法做同样的事情,但更简单一点,可能性能更高一点,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-->1.6 的运行时类中。(重点是,它不是公共课程)。
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
值应该是多少,Sun 1.5 和 1.6 VM 版本java.lang.System
,有一个名为 getCallerClass() 的包保护方法,它调用sun.reflect.Reflection.getCallerClass(3)
,但在我的辅助实用程序类中,我使用了 4,因为添加了辅助类的框架调用。
/**
* 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,如果您尝试获取用于调试目的的调用方法行,则需要通过在其中编写这些静态方法的 Utility 类:(
旧 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". <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;
}
我以前做过。您可以只创建一个新异常并在其上获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,它的成本非常高——不要在一个紧密的循环中进行。
我之前已经为性能无关紧要的应用程序上的日志实用程序完成了此操作(实际上,性能几乎不重要 - 只要您将结果显示为诸如快速单击按钮之类的操作)。
在您获得堆栈跟踪之前,异常只有 .printStackTrace() 所以我不得不将 System.out 重定向到我自己创建的流,然后 (new Exception()).printStackTrace(); 重定向 System.out 并解析流。好玩的东西。
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() );
}
}
}
这是我根据本主题中显示的提示编写的部分代码。希望能帮助到你。
(请随时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);
}
(...)
}
和对象:
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
(...)
}
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();
}
}
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();
}
}