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https://issues.apache.org/jira/browse/IO-249?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Niall Pemberton updated IO-249:
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Attachment: CloseableHandler.java
I was thinking about Brent's suggestion and came up with an alternative - a
Closeable handler which does the closing - see attached example.
It has a number of features:
* Implements Closeable
* Can handle closing multiple Closeable objects
* Closeable objects can be added through the constructor
* Closeable objects can be added or an add() method that returns the
Closeable - removes the need e.g. to define the Closeable outside the try/catch
* Provides an easy way to relate which Closeable's close() method threw an
exception - which means e.g. logging can be improved
* Implements Iterable to provide and iterator of close exceptions
* provides a handle(Closeable, IOException) method that can be overriden to
create custom (e.g. logging) implementations
* provides convenience methods to store and re-throw an original exception
So for example you could use it in the following way to log all close exceptions
{code}
public void copy(InputStream input, OutputStream output) throws IOException {
CloseableHandler handler = new CloseableHandler(input, output);
try {
IOUtils.copy(input, output);
} finally {
handler.close();
for (IOException ioe : handler) {
logger.log(Level.SEVERE, "Close error", ioe);
}
}
}
{code}
...or you could create a custom implementation
{code}
public static class LoggingCloseableHandler extends CloseableHandler {
private final Logger logger;
public LoggingCloseableHandler(Logger logger, Closeable... delegates) {
super(delegates);
this.logger = logger;
}
protected void handle(Closeable closeable, IOException e) {
logger.log(Level.SEVERE, "Error closing " + closeable, e);
}
}
{code}
...and then use that implementation:
{code}
public void copy(InputStream input, OutputStream output) throws IOException {
Closeable closeables = new LoggingCloseableHandler(logger, input, output);
try {
IOUtils.copy(input, output);
} finally {
closeables.close();
}
}
{code}
Another example showing that the InputStream & OutputStream don't have to be
declared outside the try/catch. Also storing a caught exception - not used in
this example - but it tells the handler whether its a *normal* close or an
error has occurred.
{code}
public void copy(File fromFile, File toFile) throws IOException {
CloseableHandler handler = new CloseableHandler();
try {
InputStream input = handler.add(new FileInputStream(fromFile));
OutputStream output = handler.add(new FileOutputStream(toFile));
IOUtils.copy(input, output);
} catch(Exception e) {
handler.setCaughtException(e);
} finally {
handler.close();
for (IOException ioe : handler) {
logger.log(Level.SEVERE, "Close", ioe);
}
}
}
{code}
> Enhance closeQuietly to indicate success
> ----------------------------------------
>
> Key: IO-249
> URL: https://issues.apache.org/jira/browse/IO-249
> Project: Commons IO
> Issue Type: Improvement
> Components: Utilities
> Affects Versions: 2.0
> Reporter: Paul Benedict
> Assignee: Paul Benedict
> Priority: Minor
> Fix For: 2.x
>
> Attachments: CloseableHandler.java
>
>
> A convention of some programmers is to emit a log warning when a resource
> fails to close. Granted, such a condition is an error, but there's no
> reasonable recourse to the failure. Using IOUtils.closeQuietly() is very
> useful but all information about the success/failure is hidden. Returning
> Throwable will give insight into the error for diagnostic purposes. This
> change will be compatible with today's usage since the method currently
> returns void.
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