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Adding the Functions class as a helper for dealing with Java 8 Lambdas.

This commit is contained in:
Jochen Wiedmann (jwi) 2019-01-23 14:59:25 +01:00
parent b00e65686e
commit 11d9eb47a4
3 changed files with 377 additions and 0 deletions
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1
src/changes/changes.xml
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@ -46,6 +46,7 @@ The <action> type attribute can be add,update,fix,remove.
<body> <body>
<release version="3.9" date="????-??-??" description="??"> <release version="3.9" date="????-??-??" description="??">
<action type="add" dev="jochen">Adding the Functions class.</action>
<action issue="LANG-1416" type="update" dev="britter">Update to JUnit 5</action> <action issue="LANG-1416" type="update" dev="britter">Update to JUnit 5</action>
<action issue="LANG-1417" type="update" dev="britter">Add @FunctionalInterface to ThreadPredicate and ThreadGroupPredicate</action> <action issue="LANG-1417" type="update" dev="britter">Add @FunctionalInterface to ThreadPredicate and ThreadGroupPredicate</action>
<action issue="LANG-1415" type="update" dev="britter">Update Java Language requirement to 1.8</action> <action issue="LANG-1415" type="update" dev="britter">Update Java Language requirement to 1.8</action>

144
src/main/java/org/apache/commons/lang3/Functions.java Normal file
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@ -0,0 +1,144 @@
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.lang3;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.lang.reflect.Method;
import java.lang.reflect.UndeclaredThrowableException;
import java.util.ArrayList;
import org.apache.commons.lang3.exception.ExceptionUtils;
/** This class provides utility functions, and classes for working with the
* {@code java.util.function} package, or more generally, with Java 8
* lambdas.
* More specifically, it attempts to address the fact that lambdas are supposed
* not to throw Exceptions, at least not checked Exceptions, aka instances of
* {@link Exception}. This enforces the use of constructs like
* <pre>
* Consumer<java.lang.reflect.Method> consumer = (m) -> {
* try {
* m.invoke(o, args);
* } catch (Throwable t) {
* throw Functions.rethrow(t);
* }
* };
* </pre>
* By replacing a {@link Consumer Consumer<O>} with a
* {@link FailableConsumer FailableConsumer<O,? extends Throwable}, this can be
* written like follows:
* <pre>
* Functions.accept((m) -> m.invoke(o,args));
* </pre>
* Obviously, the second version is much more concise and the spirit of
* Lambda expressions is met better than the second version.
*/
public class Functions {
@FunctionalInterface
public interface FailableRunnable<T extends Throwable> {
public void run() throws T;
}
@FunctionalInterface
public interface FailableCallable<O,T extends Throwable> {
public O call() throws T;
}
@FunctionalInterface
public interface FailableConsumer<O,T extends Throwable> {
public void accept(O pObject) throws T;
}
@FunctionalInterface
public interface FailableBiConsumer<O1,O2,T extends Throwable> {
public void accept(O1 pObject1, O2 pObject2) throws T;
}
@FunctionalInterface
public interface FailableFunction<I,O,T extends Throwable> {
public O apply(I pInput) throws T;
}
@FunctionalInterface
public interface FailableBiFunction<I1,I2,O,T extends Throwable> {
public O apply(I1 pInput1, I2 pInput2) throws T;
}
public static <T extends Throwable> void run(FailableRunnable<T> pRunnable) {
try {
pRunnable.run();
} catch (Throwable t) {
throw rethrow(t);
}
}
public static <O,T extends Throwable> O call(FailableCallable<O,T> pCallable) {
try {
return pCallable.call();
} catch (Throwable t) {
throw rethrow(t);
}
}
public static <O,T extends Throwable> void accept(FailableConsumer<O,T> pConsumer, O pObject) {
try {
pConsumer.accept(pObject);
} catch (Throwable t) {
throw rethrow(t);
}
}
public static <O1,O2,T extends Throwable> void accept(FailableBiConsumer<O1,O2,T> pConsumer, O1 pObject1, O2 pObject2) {
try {
pConsumer.accept(pObject1, pObject2);
} catch (Throwable t) {
throw rethrow(t);
}
}
public static <I,O,T extends Throwable> O apply(FailableFunction<I,O,T> pFunction, I pInput) {
try {
return pFunction.apply(pInput);
} catch (Throwable t) {
throw rethrow(t);
}
}
public static <I1,I2,O,T extends Throwable> O apply(FailableBiFunction<I1,I2,O,T> pFunction, I1 pInput1, I2 pInput2) {
try {
return pFunction.apply(pInput1, pInput2);
} catch (Throwable t) {
throw rethrow(t);
}
}
public static RuntimeException rethrow(Throwable pThrowable) {
if (pThrowable == null) {
throw new NullPointerException("The Throwable must not be null.");
} else {
if (pThrowable instanceof RuntimeException) {
throw (RuntimeException) pThrowable;
} else if (pThrowable instanceof Error) {
throw (Error) pThrowable;
} else if (pThrowable instanceof IOException) {
throw new UncheckedIOException((IOException) pThrowable);
} else {
throw new UndeclaredThrowableException(pThrowable);
}
}
}
public static void test() throws Exception {
run(() -> ArrayList.class.newInstance());
}
}

232
src/test/java/org/apache/commons/lang3/FunctionsTest.java Normal file
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@ -0,0 +1,232 @@
package org.apache.commons.lang3;
import static org.junit.jupiter.api.Assertions.*;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.lang.reflect.UndeclaredThrowableException;
import org.junit.jupiter.api.Test;
class FunctionsTest {
public static class SomeException extends Exception {
private static final long serialVersionUID = -4965704778119283411L;
private Throwable t;
public SomeException(String pMsg) {
super(pMsg);
}
public void setThrowable(Throwable pThrowable) {
t = pThrowable;
}
public void test() throws Throwable {
if (t != null) {
throw t;
}
}
}
public static class Testable {
private Throwable t;
public Testable(Throwable pTh) {
t = pTh;
}
public void setThrowable(Throwable pThrowable) {
t = pThrowable;
}
public void test() throws Throwable {
test(t);
}
public void test(Throwable pThrowable) throws Throwable {
if (pThrowable != null) {
throw pThrowable;
}
}
public Integer testInt() throws Throwable {
return testInt(t);
}
public Integer testInt(Throwable pThrowable) throws Throwable {
if (pThrowable != null) {
throw pThrowable;
}
return 0;
}
}
public static class FailureOnOddInvocations {
private static int invocation;
public FailureOnOddInvocations() throws SomeException {
final int i = ++invocation;
if (i % 2 == 1) {
throw new SomeException("Odd Invocation: " + i);
}
}
}
@Test
void testRunnable() {
FailureOnOddInvocations.invocation = 0;
try {
Functions.run(() -> new FailureOnOddInvocations());
fail("Expected Exception");
} catch (UndeclaredThrowableException e) {
final Throwable cause = e.getCause();
assertNotNull(cause);
assertTrue(cause instanceof SomeException);
assertEquals("Odd Invocation: 1", cause.getMessage());
}
Functions.run(() -> new FailureOnOddInvocations());
}
@Test
void testCallable() {
FailureOnOddInvocations.invocation = 0;
try {
Functions.call(() -> new FailureOnOddInvocations());
fail("Expected Exception");
} catch (UndeclaredThrowableException e) {
final Throwable cause = e.getCause();
assertNotNull(cause);
assertTrue(cause instanceof SomeException);
assertEquals("Odd Invocation: 1", cause.getMessage());
}
final FailureOnOddInvocations instance = Functions.call(() -> new FailureOnOddInvocations());
assertNotNull(instance);
}
@Test
void testAcceptConsumer() {
final IllegalStateException ise = new IllegalStateException();
final Testable testable = new Testable(ise);
try {
Functions.accept((t) -> t.test(), testable);
fail("Expected Exception");
} catch (IllegalStateException e) {
assertSame(ise, e);
}
final Error error = new OutOfMemoryError();
testable.setThrowable(error);
try {
Functions.accept((t) -> t.test(), testable);
} catch (OutOfMemoryError e) {
assertSame(error, e);
}
final IOException ioe = new IOException("Unknown I/O error");
testable.setThrowable(ioe);
try {
Functions.accept((t) -> t.test(), testable);
fail("Expected Exception");
} catch (UncheckedIOException e) {
final Throwable t = e.getCause();
assertNotNull(t);
assertTrue(t instanceof IOException);
assertSame(ioe, t);
}
testable.setThrowable(null);
Functions.accept((t) -> t.test(), testable);
}
@Test
void testAcceptBiConsumer() {
final IllegalStateException ise = new IllegalStateException();
final Testable testable = new Testable(null);
try {
Functions.accept((t1,t2) -> t1.test(t2), testable, ise);
fail("Expected Exception");
} catch (IllegalStateException e) {
assertSame(ise, e);
}
final Error error = new OutOfMemoryError();
try {
Functions.accept((t1,t2) -> t1.test(t2), testable, error);
} catch (OutOfMemoryError e) {
assertSame(error, e);
}
final IOException ioe = new IOException("Unknown I/O error");
testable.setThrowable(ioe);
try {
Functions.accept((t1,t2) -> t1.test(t2), testable, ioe);
fail("Expected Exception");
} catch (UncheckedIOException e) {
final Throwable t = e.getCause();
assertNotNull(t);
assertTrue(t instanceof IOException);
assertSame(ioe, t);
}
testable.setThrowable(null);
Functions.accept((t1,t2) -> t1.test(t2), testable, (Throwable) null);
}
@Test
public void testApplyFunction() {
final IllegalStateException ise = new IllegalStateException();
final Testable testable = new Testable(ise);
try {
Functions.apply((t) -> t.testInt(), testable);
fail("Expected Exception");
} catch (IllegalStateException e) {
assertSame(ise, e);
}
final Error error = new OutOfMemoryError();
testable.setThrowable(error);
try {
Functions.apply((t) -> t.testInt(), testable);
} catch (OutOfMemoryError e) {
assertSame(error, e);
}
final IOException ioe = new IOException("Unknown I/O error");
testable.setThrowable(ioe);
try {
Functions.apply((t) -> t.testInt(), testable);
fail("Expected Exception");
} catch (UncheckedIOException e) {
final Throwable t = e.getCause();
assertNotNull(t);
assertTrue(t instanceof IOException);
assertSame(ioe, t);
}
testable.setThrowable(null);
final Integer i = Functions.apply((t) -> t.testInt(), testable);
assertNotNull(i);
assertEquals(0, i.intValue());
}
@Test
public void testApplyBiFunction() {
final IllegalStateException ise = new IllegalStateException();
final Testable testable = new Testable(null);
try {
Functions.apply((t1,t2) -> t1.testInt(t2), testable, ise);
fail("Expected Exception");
} catch (IllegalStateException e) {
assertSame(ise, e);
}
final Error error = new OutOfMemoryError();
try {
Functions.apply((t1,t2) -> t1.testInt(t2), testable, error);
} catch (OutOfMemoryError e) {
assertSame(error, e);
}
final IOException ioe = new IOException("Unknown I/O error");
try {
Functions.apply((t1,t2) -> t1.testInt(t2), testable, ioe);
fail("Expected Exception");
} catch (UncheckedIOException e) {
final Throwable t = e.getCause();
assertNotNull(t);
assertTrue(t instanceof IOException);
assertSame(ioe, t);
}
final Integer i = Functions.apply((t1,t2) -> t1.testInt(t2), testable, (Throwable) null);
assertNotNull(i);
assertEquals(0, i.intValue());
}
}