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authorDico200 <dico.karssiens@gmail.com>2018-07-25 01:53:02 +0100
committerDico200 <dico.karssiens@gmail.com>2018-07-25 01:53:02 +0100
commit5e168847c2624b767deb9da310ecfdf169e0f43c (patch)
tree56b76556a6837fff20b800d5a22218286a975581 /dicore3/core/src/main/java/io/dico/dicore/exceptions/ExceptionHandler.java
parent60503351a30a91985b95ee8aa64e163ef084b34b (diff)
Add dicore3-core, without really irrelevant packages
Diffstat (limited to 'dicore3/core/src/main/java/io/dico/dicore/exceptions/ExceptionHandler.java')
-rw-r--r--dicore3/core/src/main/java/io/dico/dicore/exceptions/ExceptionHandler.java203
1 files changed, 203 insertions, 0 deletions
diff --git a/dicore3/core/src/main/java/io/dico/dicore/exceptions/ExceptionHandler.java b/dicore3/core/src/main/java/io/dico/dicore/exceptions/ExceptionHandler.java
new file mode 100644
index 0000000..e95b65e
--- /dev/null
+++ b/dicore3/core/src/main/java/io/dico/dicore/exceptions/ExceptionHandler.java
@@ -0,0 +1,203 @@
+package io.dico.dicore.exceptions;
+
+import io.dico.dicore.exceptions.checkedfunctions.CheckedRunnable;
+import io.dico.dicore.exceptions.checkedfunctions.CheckedSupplier;
+import io.dico.dicore.exceptions.checkedfunctions.CheckedFunctionalObject;
+
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.sql.SQLException;
+import java.util.Objects;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+
+@FunctionalInterface
+public interface ExceptionHandler {
+
+ /**
+ * Handle the given exception according to this handler's implementation
+ *
+ * @param ex The exception to be handled
+ * @throws NullPointerException if ex is null, unless the implementation specifies otherwise
+ * @throws Error ex if ex is an instance of Error, unless the implementation specifies otherwise
+ */
+ void handle(Throwable ex);
+
+ /**
+ * Handle the given exception according to this handler's implementation
+ * This method is intended for use by {@link CheckedFunctionalObject} and subinterfaces.
+ * It supplies exception handlers the option to acquire more information, by overriding this method and calling it from {@link #handle(Throwable)}
+ *
+ * @param ex The exception to be handled
+ * @param args Any arguments passed, this is used by {@link CheckedFunctionalObject} and subinterfaces.
+ * @return {@code null} (unless specified otherwise by the implementation)
+ * @throws NullPointerException if ex is null, unless the implementation specifies otherwise
+ * @throws Error ex if ex is an instance of Error, unless the implementation specifies otherwise
+ */
+ default Object handleGenericException(Throwable ex, Object... args) {
+ handle(ex);
+ return null;
+ }
+
+ /**
+ * @return true if this {@link ExceptionHandler}'s {@link #handleGenericException(Throwable, Object...)} method is <b>never</b> expected to throw
+ * an unchecked exception other than {@link Error}
+ */
+ default boolean isSafe() {
+ return true;
+ }
+
+ /**
+ * Runs the given checked action, handling any thrown exceptions using this exception handler.
+ * <p>
+ * Any exceptions thrown by this handler are delegated to the caller.
+ *
+ * @param action The action to run
+ * @throws NullPointerException if action is null
+ */
+ default void runSafe(CheckedRunnable<? extends Throwable> action) {
+ Objects.requireNonNull(action);
+ try {
+ action.checkedRun();
+ } catch (Throwable ex) {
+ handle(ex);
+ }
+ }
+
+ /**
+ * Computes the result of the given checked supplier, handling any thrown exceptions using this exception handler.
+ * <p>
+ * Any exceptions thrown by this handler are delegated to the caller.
+ *
+ * @param action The supplier whose result to compute
+ * @param <T> generic type parameter for the supplier and the result type of this method
+ * @return The result of this computation, or null if an error occurred
+ * @throws NullPointerException if action is null
+ */
+
+ default <T> T supplySafe(CheckedSupplier<T, ? extends Throwable> action) {
+ Objects.requireNonNull(action);
+ try {
+ return action.checkedGet();
+ } catch (Throwable ex) {
+ handle(ex);
+ return null;
+ }
+ }
+
+ /**
+ * @param action The action to wrap
+ * @return A runnable that wraps the given action using this handler's {@link #runSafe(CheckedRunnable)} method.
+ * @see #runSafe(CheckedRunnable)
+ */
+ default Runnable safeRunnable(CheckedRunnable<? extends Throwable> action) {
+ return () -> runSafe(action);
+ }
+
+ /**
+ * @param supplier The computation to wrap
+ * @return A supplier that wraps the given computation using this handler's {@link #supplySafe(CheckedSupplier)} method.
+ * @see #supplySafe(CheckedSupplier)
+ */
+ default <T> Supplier<T> safeSupplier(CheckedSupplier<T, ? extends Throwable> supplier) {
+ return () -> supplySafe(supplier);
+ }
+
+ /**
+ * Logs the given exception as an error to {@code out}
+ * <p>
+ * Format: Error occurred while {@code failedActivityDescription}, followed by additional details and a stack trace
+ *
+ * @param out The consumer to accept the error message, for instance {@code {@link java.util.logging.Logger logger}::warning}.
+ * @param failedActivityDescription A description of the activity that was being executed when the exception was thrown
+ * @param ex The exception that was thrown
+ * @throws NullPointerException if any argument is null
+ */
+ static void log(Consumer<String> out, String failedActivityDescription, Throwable ex) {
+ if (out == null || failedActivityDescription == null || ex == null) {
+ throw new NullPointerException();
+ }
+
+ StringWriter msg = new StringWriter(1024);
+ msg.append("Error occurred while ").append(failedActivityDescription).append(':');
+
+ if (ex instanceof SQLException) {
+ SQLException sqlex = (SQLException) ex;
+ msg.append('\n').append("Error code: ").append(Integer.toString(sqlex.getErrorCode()));
+ msg.append('\n').append("SQL State: ").append(sqlex.getSQLState());
+ }
+
+ msg.append('\n').append("=======START STACK=======");
+ try (PrintWriter pw = new PrintWriter(msg)) {
+ ex.printStackTrace(pw);
+ }
+ msg.append('\n').append("========END STACK========");
+
+ out.accept(msg.toString());
+ }
+
+ /**
+ * @param activityDescription The activity description
+ * @return An ExceptionHandler that prints to {@link System#out}
+ * @see #log(Consumer, String)
+ */
+ static ExceptionHandler log(String activityDescription) {
+ // A method reference would cache the current value in System.out
+ // This would update if the value in System.out is changed (by for example, applying a PrintStream that handles colours).
+ return log(msg -> System.out.println(msg), activityDescription);
+ }
+
+ /**
+ * @param out The Consumer to be passed to {@link #log(Consumer, String, Throwable)}
+ * @param activityDescription The activity description to be passed to {@link #log(Consumer, String, Throwable)}
+ * @return An ExceptionHandler that passes exceptions with given arguments to {@link #log(Consumer, String, Throwable)}
+ * @see #log(Consumer, String, Throwable)
+ */
+ static ExceptionHandler log(Consumer<String> out, String activityDescription) {
+ return ex -> log(out, activityDescription, ex);
+ }
+
+ /**
+ * This ExceptionHandler turns any Throwable into an unchecked exception, then throws it again.
+ */
+ ExceptionHandler UNCHECKED = new ExceptionHandler() {
+ @Override
+ public void handle(Throwable ex) {
+ errorFilter(ex);
+ if (ex instanceof RuntimeException) {
+ throw (RuntimeException) ex;
+ }
+ throw new RuntimeException(ex);
+ }
+
+ @Override
+ public boolean isSafe() {
+ return false;
+ }
+ };
+
+ /**
+ * This ExceptionHandler suppresses all exceptions,
+ * apart from {@link Error} because that is not usually supposed to be caught
+ */
+ ExceptionHandler SUPPRESS = ExceptionHandler::errorFilter;
+
+ /**
+ * This ExceptionHandler calls {@link Throwable#printStackTrace()} unless it is a {@link NullPointerException} or {@link Error}.
+ */
+ ExceptionHandler PRINT_UNLESS_NP = ex -> {
+ errorFilter(ex);
+ if (!(ex instanceof NullPointerException)) {
+ ex.printStackTrace();
+ }
+ };
+
+ static void errorFilter(Throwable ex) {
+ if (ex instanceof Error) {
+ throw (Error) ex;
+ } else if (ex == null) {
+ throw new NullPointerException();
+ }
+ }
+
+}