I see, interesting! So Class.newInstance can throw, say, an SQLException even though the signature does not declare that exception.
So if you have fine-grained exception handling (separate catch blocks for InstantiationException, IllegalAccessException, SecurityException etc) then you might might not catch that SQLException. I guess I've never run into this because I always use a single (catch Exception ex) block, and if reflection failed (for any reason) then I either fall back to plan B or just fail. So I guess it doesn't make much difference in our case. But I did learn something new today, thanks! :-) Remko Sent from my iPhone > On 2014/04/17, at 8:00, Matt Sicker <[email protected]> wrote: > > From the docs for Class.newInstance: > > Note that this method propagates any exception thrown by the nullary > constructor, including a checked exception. Use of this method effectively > bypasses the compile-time exception checking that would otherwise be > performed by the compiler. The Constructor.newInstance method avoids this > problem by wrapping any exception thrown by the constructor in a (checked) > InvocationTargetException. > > >> On 16 April 2014 17:40, Remko Popma <[email protected]> wrote: >> Out of interest, what is the advantage of calling >> clazz.getConstructor().newInstance(); >> vs >> clazz.newInstance(); ? >> >> Until now all the code I've seen simply uses newInstance unless the >> constructor needs parameters. >> And it is shorter. :-) >> So just wondering if I missed something... >> >> >> >>> On Tue, Apr 15, 2014 at 4:03 PM, <[email protected]> wrote: >>> Author: mattsicker >>> Date: Tue Apr 15 07:03:55 2014 >>> New Revision: 1587455 >>> >>> URL: http://svn.apache.org/r1587455 >>> Log: >>> Add fallback to Class.newInstance. >>> >>> - In some scenarios, if a class doesn't have a constructor defined, >>> Class.getConstructor() will fail, but Class.newInstance() won't fail. Not >>> sure on the logic behind that one, Java. >>> >>> 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=1587455&r1=1587454&r2=1587455&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 07:03:55 2014 >>> @@ -21,6 +21,7 @@ import java.lang.ClassCastException; >>> import java.lang.reflect.InvocationTargetException; >>> import java.net.URL; >>> >>> +import org.apache.logging.log4j.Level; >>> import org.apache.logging.log4j.Logger; >>> import org.apache.logging.log4j.status.StatusLogger; >>> import org.apache.logging.log4j.util.PropertiesUtil; >>> @@ -248,7 +249,7 @@ public final class Loader { >>> // 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.catching(Level.DEBUG, e); >>> LOGGER.trace("TCCL didn't work. Trying Class.forName({}).", >>> className); >>> return loadClassWithDefaultClassLoader(className); >>> } >>> @@ -283,7 +284,7 @@ public final class Loader { >>> try { >>> return Class.forName(className, true, >>> ClassLoader.getSystemClassLoader()); >>> } catch (final Throwable t) { >>> - LOGGER.catching(t); >>> + LOGGER.catching(Level.DEBUG, t); >>> LOGGER.trace("Couldn't use SystemClassLoader. Trying >>> Class.forName({}).", className); >>> return Class.forName(className); >>> } >>> @@ -306,7 +307,13 @@ public final class Loader { >>> InstantiationException, >>> NoSuchMethodException, >>> InvocationTargetException { >>> - return loadClass(className).getConstructor().newInstance(); >>> + final Class<?> clazz = loadClass(className); >>> + try { >>> + return clazz.getConstructor().newInstance(); >>> + } catch (final NoSuchMethodException e) { >>> + //noinspection ClassNewInstance >>> + return clazz.newInstance(); >>> + } >>> } >>> >>> /** >>> @@ -342,7 +349,7 @@ public final class Loader { >>> try { >>> final Class<?> clazz = loadClass(className); >>> return clazz != null; >>> - } catch (final Exception ignored) { >>> + } catch (final Throwable ignored) { >>> return false; >>> } >>> } > > > > -- > Matt Sicker <[email protected]>
