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?
当前回答
使用方法:-
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();
}
}
其他回答
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);
}
}
OR
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();
}
}
简单回答ReflectionUtils.getCallingClass(0)
长答案(代码，Groovy)
package my
import org.codehaus.groovy.reflection.ReflectionUtils
import java.lang.reflect.Field
import java.lang.reflect.Method
trait Reflector {
static String[] fieldNames() {
List<String> names = []
Arrays.asList(naturalFields()).forEach { Field fl -> names.add(fl.name) }
return names.toArray() as String[]
}
static Field[] naturalFields() {
return finalClass().getDeclaredFields().findAll { Field fl -> !fl.synthetic }.collect()
}
static Method[] naturalMethods() {
return finalClass().getDeclaredMethods().findAll { Method md -> !md.synthetic }.collect()
}
static Class finalClass() {
return ReflectionUtils.getCallingClass(0)
}
}
class Demo implements Reflector {
int archived = 0
int demo = 100
static void playToo() {
println finalClass()
}
}
println Demo.finalClass() // class my.Demo
println Demo.naturalFields() // [private int my.Demo.archived, private int my.Demo.demo]
println Demo.fieldNames() // [archived, demo]
注意:如果你使用Java 9或更高版本，你应该使用Ali Dehghani的回答中描述的StackWalker.getCallerClass()。
由于历史原因，下面不同方法的比较非常有趣。
可以在此请求的注释中找到替代解决方案。 它使用自定义SecurityManager的getClassContext()方法，似乎比堆栈跟踪方法快。
下面的程序测试了不同建议方法的速度(最有趣的部分是内部类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英特尔酷睿2双核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。从新创建的Throwable中获取堆栈跟踪比从当前线程中获取堆栈跟踪要快。在寻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在这条评论中指出的那样，sun.reflect. reflect. getcallerclass()方法在Java 7 update 40中默认被禁用，在Java 8中被完全删除。有关这方面的更多信息，请参阅本期Java错误数据库。
更新2
正如zammbi所发现的，Oracle被迫退出删除sun.reflect. reflect. getcallerclass()的更改。在Java 8中仍然可用(但已弃用)。
更新3
3年后:更新当前JVM的计时。
> 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.
下面是我根据本主题中显示的提示制作的部分代码。 希望能有所帮助。
(请随时提出任何建议来改进此代码，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);
}
(...)
}
对象是:
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
(...)
}
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() );
}
}
}
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