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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.yolean;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.NoSuchFileException;
import java.util.Optional;
/**
* Helper methods for handling exceptions
*
* @author bratseth
*/
public class Exceptions {
/**
* <p>Returns a user friendly error message string which includes information from all nested exceptions.</p>
*
* <p>The form of this string is
* <code>e.getMessage(): e.getCause().getMessage(): e.getCause().getCause().getMessage()...</code>
* In addition, some heuristics are used to clean up common cases where exception nesting causes bad messages.
*/
public static String toMessageString(Throwable t) {
StringBuilder b = new StringBuilder();
String lastMessage = null;
String message;
for (; t != null; t = t.getCause()) {
message = getMessage(t);
if (message == null) continue;
if (message.equals(lastMessage)) continue;
if (b.length() > 0) {
b.append(": ");
}
b.append(message);
lastMessage = message;
}
return b.toString();
}
/** Returns a useful message from *this* exception, or null if there is nothing useful to return */
private static String getMessage(Throwable t) {
String message = t.getMessage();
if (t.getCause() == null) {
if (message == null) return t.getClass().getSimpleName();
} else {
if (message == null) return null;
if (message.equals(t.getCause().getClass().getName() + ": " + t.getCause().getMessage())) return null;
}
return message;
}
/**
* Wraps any IOException thrown from a runnable in an UncheckedIOException.
*/
public static void uncheck(RunnableThrowingIOException runnable) {
try {
runnable.run();
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}
/**
* Wraps any IOException thrown from a runnable in an UncheckedIOException w/message.
*/
public static void uncheck(RunnableThrowingIOException runnable, String format, String... args) {
try {
runnable.run();
} catch (IOException e) {
String message = String.format(format, (Object[]) args);
throw new UncheckedIOException(message, e);
}
}
/** Similar to uncheck() except NoSuchFileException is silently ignored. */
public static void ifExists(RunnableThrowingIOException runnable) {
try {
runnable.run();
} catch (NoSuchFileException e) {
// Do nothing - OK
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}
@FunctionalInterface
public interface RunnableThrowingIOException {
void run() throws IOException;
}
/**
* Wraps any IOException thrown from a supplier in an UncheckedIOException.
*/
public static <T> T uncheck(SupplierThrowingIOException<T> supplier) {
try {
return supplier.get();
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}
/**
* Wraps any IOException thrown from a supplier in an UncheckedIOException w/message.
*/
public static <T> T uncheck(SupplierThrowingIOException<T> supplier, String format, String... args) {
try {
return supplier.get();
} catch (IOException e) {
String message = String.format(format, (Object[]) args);
throw new UncheckedIOException(message, e);
}
}
/** Similar to uncheck() except the return value is wrapped in an Optional, and empty is returned on NoSuchFileException. */
public static <T> Optional<T> ifExists(SupplierThrowingIOException<T> supplier) {
try {
return Optional.ofNullable(supplier.get());
} catch (NoSuchFileException e) {
return Optional.empty();
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}
@FunctionalInterface
public interface SupplierThrowingIOException<T> {
T get() throws IOException;
}
}
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