se.jiderhamn.classloader.leak.prevention

Class ClassLoaderLeakPreventor

java.lang.Object

se.jiderhamn.classloader.leak.prevention.ClassLoaderLeakPreventor

public class ClassLoaderLeakPreventor
extends Object

This class helps prevent classloader leaks.

Author:

Mattias Jiderhamn

Field Summary

Fields

Modifier and Type	Field and Description
static int	THREAD_WAIT_MS_DEFAULT Default no of milliseconds to wait for threads to finish execution

Constructor Summary

Constructors

Constructor and Description
ClassLoaderLeakPreventor(ClassLoader leakSafeClassLoader, ClassLoader classLoader, Logger logger, Collection<PreClassLoaderInitiator> preClassLoaderInitiators, Collection<ClassLoaderPreMortemCleanUp> cleanUps)

Method Summary

Modifier and Type	Method and Description
AccessControlContext	createAccessControlContext() Create AccessControlContext that is used in doInLeakSafeClassLoader(Runnable).
void	debug(String msg)
protected void	doInLeakSafeClassLoader(Runnable runnable) Perform action in the provided ClassLoader (normally system ClassLoader, that may retain references to the Thread.contextClassLoader.
void	error(String msg)
void	error(Throwable t)
Class<?>	findClass(String className)
Class<?>	findClass(String className, boolean trySystemCL)
Field	findField(Class<?> clazz, String fieldName)
Field	findFieldOfClass(String className, String fieldName)
Field	findFieldOfClass(String className, String fieldName, boolean trySystemCL)
Method	findMethod(Class<?> clazz, String methodName, Class... parameterTypes)
Method	findMethod(String className, String methodName, Class... parameterTypes)
static void	gc() Unlike System.gc() this method guarantees that garbage collection has been performed before returning.
Collection<Thread>	getAllThreads() Get a Collection with all Threads.
ClassLoader	getClassLoader()
<T> T	getFieldValue(Field field, Object obj)
<T> T	getFieldValue(Object obj, String fieldName)
ClassLoader	getLeakSafeClassLoader() Get ClassLoader to be used when invoking the PreClassLoaderInitiators.
String	getStackTrace(Thread thread) Get current stack trace or provided thread as string.
<E> E	getStaticFieldValue(Class<?> clazz, String fieldName)
<T> T	getStaticFieldValue(Field field)
<E> E	getStaticFieldValue(String className, String fieldName)
<E> E	getStaticFieldValue(String className, String fieldName, boolean trySystemCL)
void	info(String msg)
boolean	isClassLoaderOrChild(ClassLoader cl) Test if provided ClassLoader is the classLoader, or a child thereof
boolean	isJBoss() Override this method if you want to customize how we determine if we're running in JBoss WildFly (a.k.a JBoss AS).
boolean	isJvmShuttingDown() Is the JVM currently shutting down?
boolean	isLoadedByClassLoader(Class<?> clazz) Test if provided class is loaded wby classLoader
boolean	isLoadedInClassLoader(Object o) Test if provided object is loaded by classLoader
boolean	isOracleJRE() Are we running in the Oracle/Sun Java Runtime Environment?
boolean	isThreadInClassLoader(Thread thread) Is the Thread ties do the protected classloader, either by being a custom Thread class, having a custom ThreadGroup or having the protected classloader as its Thread.contextClassLoader?
void	removeDomainCombiner(String owner, AccessControlContext accessControlContext) Recursively unset our custom DomainCombiner (loaded in the web app) from the AccessControlContext and any parents or privilegedContext thereof.
void	removeDomainCombiner(Thread thread, AccessControlContext accessControlContext) Deprecated.
void	runCleanUps() Invoke all the registered ClassLoaderPreMortemCleanUps
void	runPreClassLoaderInitiators() Invoke all the registered PreClassLoaderInitiators in the leakSafeClassLoader
void	setFinalStaticField(Field field, Object newValue)
void	waitForThread(Thread thread, long waitMs, boolean interrupt) Make the provided Thread stop sleep(), wait() or join() and then give it the provided no of milliseconds to finish executing.
void	warn(String msg)
void	warn(Throwable t)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

THREAD_WAIT_MS_DEFAULT

public static final int THREAD_WAIT_MS_DEFAULT

Default no of milliseconds to wait for threads to finish execution

See Also:

Constant Field Values

Constructor Detail

ClassLoaderLeakPreventor

public ClassLoaderLeakPreventor(ClassLoader leakSafeClassLoader,
                                ClassLoader classLoader,
                                Logger logger,
                                Collection<PreClassLoaderInitiator> preClassLoaderInitiators,
                                Collection<ClassLoaderPreMortemCleanUp> cleanUps)

Method Detail

runPreClassLoaderInitiators

public void runPreClassLoaderInitiators()

Invoke all the registered PreClassLoaderInitiators in the leakSafeClassLoader

doInLeakSafeClassLoader

protected void doInLeakSafeClassLoader(Runnable runnable)

Perform action in the provided ClassLoader (normally system ClassLoader, that may retain references to the Thread.contextClassLoader. The motive for the custom AccessControlContext is to avoid spawned threads from inheriting all the ProtectionDomains of the running code, since that may include the classloader we want to avoid leaking. This however means the AccessControlContext will have a DomainCombiner referencing the classloader, which will be taken care of in runCleanUps().

createAccessControlContext

public AccessControlContext createAccessControlContext()

Create AccessControlContext that is used in doInLeakSafeClassLoader(Runnable). The motive is to avoid spawned threads from inheriting all the ProtectionDomains of the running code, since that will include the web app classloader.

removeDomainCombiner

@Deprecated
public void removeDomainCombiner(Thread thread,
                                              AccessControlContext accessControlContext)

Deprecated.

Recursively unset our custom DomainCombiner (loaded in the web app) from the AccessControlContext and any parents or privilegedContext thereof.

removeDomainCombiner

public void removeDomainCombiner(String owner,
                                 AccessControlContext accessControlContext)

Recursively unset our custom DomainCombiner (loaded in the web app) from the AccessControlContext and any parents or privilegedContext thereof.

runCleanUps

public void runCleanUps()

Invoke all the registered ClassLoaderPreMortemCleanUps

getClassLoader

public ClassLoader getClassLoader()

getLeakSafeClassLoader

public ClassLoader getLeakSafeClassLoader()

Get ClassLoader to be used when invoking the PreClassLoaderInitiators. This will normally be the ClassLoader.getSystemClassLoader(), but could be any other framework or app server classloader. Normally, but not necessarily, a parent of classLoader.

isLoadedInClassLoader

public boolean isLoadedInClassLoader(Object o)

Test if provided object is loaded by classLoader

isLoadedByClassLoader

public boolean isLoadedByClassLoader(Class<?> clazz)

Test if provided class is loaded wby classLoader

isClassLoaderOrChild

public boolean isClassLoaderOrChild(ClassLoader cl)

Test if provided ClassLoader is the classLoader, or a child thereof

isThreadInClassLoader

public boolean isThreadInClassLoader(Thread thread)

Is the Thread ties do the protected classloader, either by being a custom Thread class, having a custom ThreadGroup or having the protected classloader as its Thread.contextClassLoader?

waitForThread

public void waitForThread(Thread thread,
                          long waitMs,
                          boolean interrupt)

Make the provided Thread stop sleep(), wait() or join() and then give it the provided no of milliseconds to finish executing.

Parameters:

thread - The thread to wake up and wait for

waitMs - The no of milliseconds to wait. If <= 0 this method does nothing.

interrupt - Should Thread.interrupt() be called first, to make thread stop sleep(), wait() or join()?

getStackTrace

public String getStackTrace(Thread thread)

Get current stack trace or provided thread as string. Returns "unavailable" if stack trace could not be acquired.

getStaticFieldValue

public <E> E getStaticFieldValue(Class<?> clazz,
                                 String fieldName)

getStaticFieldValue

public <E> E getStaticFieldValue(String className,
                                 String fieldName)

getStaticFieldValue

public <E> E getStaticFieldValue(String className,
                                 String fieldName,
                                 boolean trySystemCL)

findFieldOfClass

public Field findFieldOfClass(String className,
                              String fieldName)

findFieldOfClass

public Field findFieldOfClass(String className,
                              String fieldName,
                              boolean trySystemCL)

findClass

public Class<?> findClass(String className)

findClass

public Class<?> findClass(String className,
                          boolean trySystemCL)

findField

public Field findField(Class<?> clazz,
                       String fieldName)

getStaticFieldValue

public <T> T getStaticFieldValue(Field field)

getFieldValue

public <T> T getFieldValue(Object obj,
                           String fieldName)

getFieldValue

public <T> T getFieldValue(Field field,
                           Object obj)

setFinalStaticField

public void setFinalStaticField(Field field,
                                Object newValue)

findMethod

public Method findMethod(String className,
                         String methodName,
                         Class... parameterTypes)

findMethod

public Method findMethod(Class<?> clazz,
                         String methodName,
                         Class... parameterTypes)

getAllThreads

public Collection<Thread> getAllThreads()

Get a Collection with all Threads. This method is heavily inspired by org.apache.catalina.loader.WebappClassLoader.getThreads()

isJBoss

public boolean isJBoss()

Override this method if you want to customize how we determine if we're running in JBoss WildFly (a.k.a JBoss AS).

isOracleJRE

public boolean isOracleJRE()

Are we running in the Oracle/Sun Java Runtime Environment? Override this method if you want to customize how we determine if this is a Oracle/Sun Java Runtime Environment.

gc

public static void gc()

Unlike System.gc() this method guarantees that garbage collection has been performed before returning.

isJvmShuttingDown

public boolean isJvmShuttingDown()

Is the JVM currently shutting down?

debug

public void debug(String msg)

warn

public void warn(Throwable t)

error

public void error(Throwable t)

warn

public void warn(String msg)

error

public void error(String msg)

info

public void info(String msg)