Author: mattsicker
Date: Tue Apr 15 04:56:12 2014
New Revision: 1587412
URL: http://svn.apache.org/r1587412
Log:
Add several methods to Loader.
Modified:
logging/log4j/log4j2/trunk/log4j-core/src/main/java/org/apache/logging/log4j/core/helpers/Loader.java
Modified:
logging/log4j/log4j2/trunk/log4j-core/src/main/java/org/apache/logging/log4j/core/helpers/Loader.java
URL:
http://svn.apache.org/viewvc/logging/log4j/log4j2/trunk/log4j-core/src/main/java/org/apache/logging/log4j/core/helpers/Loader.java?rev=1587412&r1=1587411&r2=1587412&view=diff
==============================================================================
---
logging/log4j/log4j2/trunk/log4j-core/src/main/java/org/apache/logging/log4j/core/helpers/Loader.java
(original)
+++
logging/log4j/log4j2/trunk/log4j-core/src/main/java/org/apache/logging/log4j/core/helpers/Loader.java
Tue Apr 15 04:56:12 2014
@@ -17,6 +17,8 @@
package org.apache.logging.log4j.core.helpers;
import java.io.InputStream;
+import java.lang.ClassCastException;
+import java.lang.reflect.InvocationTargetException;
import java.net.URL;
import org.apache.logging.log4j.Logger;
@@ -234,22 +236,117 @@ public final class Loader {
* @return The Class.
* @throws ClassNotFoundException if the Class could not be found.
*/
+ // FIXME: should we do lazy class loading or eager class loading by
default?
public static Class<?> loadClass(final String className) throws
ClassNotFoundException {
// Just call Class.forName(className) if we are instructed to ignore
the TCL.
if (ignoreTCL) {
LOGGER.trace("Ignoring TCCL. Trying Class.forName({}).",
className);
- return Class.forName(className);
+ return loadClassWithDefaultClassLoader(className);
}
try {
LOGGER.trace("Trying TCCL for class {}.", className);
- return getTCL().loadClass(className);
+ // using the TCCL should work the same as the default ClassLoader
(i.e., init or not)
+ return Class.forName(className, true, getTCL());
} catch (final Throwable e) {
LOGGER.catching(e);
LOGGER.trace("TCCL didn't work. Trying Class.forName({}).",
className);
+ return loadClassWithDefaultClassLoader(className);
+ }
+ }
+
+ private static Class<?> loadClassWithDefaultClassLoader(final String
className) throws ClassNotFoundException {
+ return Class.forName(className);
+ }
+
+ /**
+ * Loads and initializes a named Class using a given ClassLoader.
+ *
+ * @param className The class name.
+ * @param loader The class loader.
+ * @return The class.
+ * @throws ClassNotFoundException if the class could not be found.
+ */
+ public static Class<?> initializeClass(final String className, final
ClassLoader loader)
+ throws ClassNotFoundException {
+ return Class.forName(className, true, loader);
+ }
+
+ /**
+ * Load a Class in the {@code java.*} namespace by name. Useful for
peculiar scenarios typically involving
+ * Google App Engine.
+ *
+ * @param className The class name.
+ * @return The Class.
+ * @throws ClassNotFoundException if the Class could not be found.
+ */
+ public static Class<?> loadSystemClass(final String className) throws
ClassNotFoundException {
+ try {
+ return Class.forName(className, true,
ClassLoader.getSystemClassLoader());
+ } catch (final Throwable t) {
+ LOGGER.catching(t);
+ LOGGER.trace("Couldn't use SystemClassLoader. Trying
Class.forName({}).", className);
return Class.forName(className);
}
}
+ /**
+ * Loads and instantiates a Class using the default constructor.
+ *
+ * @param className The class name.
+ * @return new instance of the class.
+ * @throws ClassNotFoundException if the class isn't available to the
usual ClassLoaders
+ * @throws IllegalAccessException if the class can't be instantiated
through a public constructor
+ * @throws InstantiationException if there was an exception whilst
instantiating the class
+ * @throws NoSuchMethodException if there isn't a no-args constructor on
the class
+ * @throws InvocationTargetException if there was an exception whilst
constructing the class
+ */
+ public static Object newInstanceOf(final String className)
+ throws ClassNotFoundException,
+ IllegalAccessException,
+ InstantiationException,
+ NoSuchMethodException,
+ InvocationTargetException {
+ return loadClass(className).getConstructor().newInstance();
+ }
+
+ /**
+ * Loads, instantiates, and casts a Class using the default constructor.
+ *
+ * @param className The class name.
+ * @param clazz The class to cast it to.
+ * @param <T> The type to cast it to.
+ * @return new instance of the class cast to {@code T}
+ * @throws ClassNotFoundException if the class isn't available to the
usual ClassLoaders
+ * @throws IllegalAccessException if the class can't be instantiated
through a public constructor
+ * @throws InstantiationException if there was an exception whilst
instantiating the class
+ * @throws NoSuchMethodException if there isn't a no-args constructor on
the class
+ * @throws InvocationTargetException if there was an exception whilst
constructing the class
+ * @throws ClassCastException if the constructed object isn't type
compatible with {@code T}
+ */
+ public static <T> T newCheckedInstanceOf(final String className, final
Class<T> clazz)
+ throws ClassNotFoundException,
+ NoSuchMethodException,
+ IllegalAccessException,
+ InvocationTargetException,
+ InstantiationException {
+ return clazz.cast(newInstanceOf(className));
+ }
+
+ /**
+ * Determines if a named Class can be loaded or not.
+ *
+ * @param className The class name.
+ * @return {@code true} if the class could be found or {@code false}
otherwise.
+ */
+ public static boolean isClassAvailable(final String className) {
+ try {
+ final Class<?> clazz = loadClass(className);
+ return clazz != null;
+ } catch (final Exception ignored) {
+ return false;
+ }
+ }
+
private Loader() {
}
}
