jio.ExceptionFun Maven / Gradle / Ivy
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package jio;
import java.io.EOFException;
import java.net.ConnectException;
import java.net.SocketException;
import java.util.Objects;
import java.util.Optional;
import java.util.function.Function;
import java.util.function.Predicate;
/**
* The {@code ExceptionFun} class provides utility methods for working with exceptions in Java, offering functionalities
* to find the ultimate cause in an exception chain and to filter exceptions based on specific criteria.
*/
public final class ExceptionFun {
private ExceptionFun() {
}
/**
* Returns the ultimate cause in the exception chain or the exception if the cause is null.
*
* @param exception The initial exception to start the search from.
* @return The ultimate cause in the exception chain.
*/
public static Throwable findUltimateCause(Throwable exception) {
var ultimateCause = Objects.requireNonNull(exception);
while (ultimateCause.getCause() != null) {
ultimateCause = ultimateCause.getCause();
}
return ultimateCause;
}
/**
* Returns a function that finds the cause in the exception chain that satisfies the given predicate.
*
* @param predicate The predicate to test each cause in the chain.
* @return A function that finds the cause such that the predicate is satisfied.
* @throws NullPointerException If the provided predicate is {@code null}.
*/
public static Function> findCauseRecursively(Predicate predicate) {
Objects.requireNonNull(predicate);
return e -> {
var cause = Objects.requireNonNull(e);
while (cause != null && !predicate.test(cause)) {
cause = cause.getCause();
}
return Optional.ofNullable(cause);
};
}
/**
* Predicate to check if the given exception indicates a connection refused error. This predicate can be used to
* filter or handle exceptions related to connection errors.
*
* The predicate checks if the ultimate cause of the given exception is an instance of {@link ConnectException}
* and if the message of the {@link ConnectException} is "Connection refused".
*
* @see ConnectException
*/
public static final Predicate IS_CONNECTION_REFUSE =
e -> findConnectionExcRecursively("connection refused"::equalsIgnoreCase).apply(e)
.isPresent();
/**
* Returns a function that finds the cause in the exception chain that satisfies the given predicate, specifically for
* {@link ConnectException} instances.
*
* The function traverses the exception chain recursively starting from the provided exception,
* identifying instances of {@link ConnectException} and filtering them based on the provided message predicate. If a
* matching {@link ConnectException} is found, it is returned as an optional.
*
* @param messagePredicate The predicate to test each message in the chain.
* @return A function that finds the {@link ConnectException} cause satisfying the predicate.
* @throws NullPointerException If the provided predicate is {@code null}.
* @see ConnectException
*/
public static Function> findConnectionExcRecursively(Predicate messagePredicate) {
return e -> findConnectionExcRecursively.apply(e)
.filter(it -> messagePredicate.test(it.getMessage()));
}
/**
* Returns a function that finds the cause in the exception chain that satisfies the given predicate, specifically for
* {@link SocketException} instances.
*
* The function traverses the exception chain recursively starting from the provided exception,
* identifying instances of {@link SocketException} and filtering them based on the provided message predicate. If a
* matching {@link SocketException} is found, it is returned as an optional.
*
* @param messagePredicate The predicate to test each message in the chain.
* @return A function that finds the {@link SocketException} cause satisfying the predicate.
* @throws NullPointerException If the provided predicate is {@code null}.
* @see SocketException
*/
public static Function> findSocketExcRecursively(Predicate messagePredicate) {
return e -> findSocketExcRecursively.apply(e)
.filter(it -> messagePredicate.test(it.getMessage()));
}
/**
* Returns a function that finds the cause in the exception chain that is an instance of {@link ConnectException}.
*
* @see SocketException
*/
public static Function> findConnectionExcRecursively =
e -> findCauseRecursively(exc -> exc instanceof ConnectException).apply(e)
.map(it -> ((ConnectException) it));
/**
* Returns a function that finds the cause in the exception chain that is an instance of {@link SocketException}.
*
* @see SocketException
*/
public static Function> findSocketExcRecursively =
e -> findCauseRecursively(exc -> exc instanceof SocketException).apply(e)
.map(it -> ((SocketException) it));
/**
* Returns a function that finds the cause in the exception chain that is an instance of {@link EOFException}.
*
* @see EOFException
*/
public static Function> findEndOfStreamExcRecursively =
e -> findCauseRecursively(exc -> exc instanceof EOFException).apply(e)
.map(it -> ((EOFException) it));
/**
* A predefined function to find instances of {@link SocketException} in the exception chain with a message indicating
* a "Connection reset" error.
*
* @see SocketException
*/
public static final Predicate IS_CONNECTION_RESET =
e -> findSocketExcRecursively("connection reset"::equalsIgnoreCase).apply(e)
.isPresent();
/**
* A predefined function to find instances of {@link EOFException} in the exception chain.
*
* @see EOFException
*/
public static final Predicate IS_END_OF_STREAM =
e -> findEndOfStreamExcRecursively.apply(e)
.isPresent();
}