BAEL-6865, implemented review comments

core-java-modules/core-java-streams-5/src/main/java/com/baeldung/aggregateEx/CustomCollector.java

@@ -1,31 +1,34 @@
 package com.baeldung.aggregateEx;
 
+import com.baeldung.aggregateEx.entity.ExceptionAggregator;
+
 import java.util.ArrayList;
 import java.util.List;
 import java.util.function.Function;
 import java.util.stream.Collector;
 
-public class ExceptionCollector<T, R> {
+public class CustomCollector<T, R> {
     private final List<R> results = new ArrayList<>();
-    private final List<Exception> exceptions = new ArrayList<>();
+    private final List<Throwable> exceptions = new ArrayList<>();
 
-    private ExceptionCollector() {
+    private final ExceptionAggregator exceptionAggregator = new ExceptionAggregator("Exceptions occurred");
-    }
 
-    public static <T, R> Collector<T, ?, ExceptionCollector<T, R>> of(Function<T, R> mapper) {
+    public static <T, R> Collector<T, ?, CustomCollector<T, R>> of(Function<T, R> mapper) {
         return Collector.of(
-                ExceptionCollector::new,
+                CustomCollector::new,
                 (collector, item) -> {
                     try {
                         R result = mapper.apply(item);
                         collector.results.add(result);
                     } catch (Exception e) {
                         collector.exceptions.add(e);
+                        collector.exceptionAggregator.addException(e);
                     }
                 },
                 (left, right) -> {
                     left.results.addAll(right.results);
                     left.exceptions.addAll(right.exceptions);
+                    left.exceptionAggregator.addExceptions(right.exceptions);
                     return left;
                 }
         );
@@ -35,7 +38,11 @@ public class ExceptionCollector<T, R> {
         return results;
     }
 
-    public List<Exception> getExceptions() {
+    public List<Throwable> getExceptions() {
         return exceptions;
     }
+
+    public ExceptionAggregator getExceptionAggregator() {
+        return exceptionAggregator;
+    }
 }

core-java-modules/core-java-streams-5/src/main/java/com/baeldung/aggregateEx/CustomMapper.java

@@ -5,7 +5,7 @@ import com.baeldung.aggregateEx.entity.Result;
 import java.util.function.Function;
 
 public class CustomMapper {
-    public static <T, R> Function<T, Result<R>> mapper(Function<T, R> func) {
+    public static <T, R> Function<T, Result<R, Throwable>> mapper(Function<T, R> func) {
         return arg -> {
             try {
                 return new Result(func.apply(arg));

core-java-modules/core-java-streams-5/src/main/java/com/baeldung/aggregateEx/entity/ExceptionAggregator.java

@@ -4,24 +4,24 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class ExceptionAggregator extends RuntimeException {
-    private List<Exception> exceptions;
+    private List<Throwable> exceptions;
 
     public ExceptionAggregator(String message) {
         super(message);
         exceptions = new ArrayList<>();
     }
 
-    public List<Exception> getExceptions() {
+    public List<Throwable> getExceptions() {
         return exceptions;
     }
 
-    public Exception addException(Exception e) {
+    public Throwable addException(Throwable e) {
         this.addSuppressed(e);
         exceptions.add(e);
         return e;
     }
 
-    public void addExceptions(List<Exception> exceptions) {
+    public void addExceptions(List<Throwable> exceptions) {
         exceptions.forEach(this::addException);
     }
 }

core-java-modules/core-java-streams-5/src/main/java/com/baeldung/aggregateEx/entity/Result.java

@@ -2,16 +2,16 @@ package com.baeldung.aggregateEx.entity;
 
 import java.util.Optional;
 
-public class Result<R> {
+public class Result<R, E extends Throwable> {
     private Optional<R> result;
-    private Optional<Exception> exception;
+    private Optional<E> exception;
 
     public Result(R result) {
         this.result = Optional.of(result);
         this.exception = Optional.empty();
     }
 
-    public Result(Exception exception) {
+    public Result(E exception) {
         this.exception = Optional.of(exception);
         this.result = Optional.empty();
     }
@@ -20,8 +20,7 @@ public class Result<R> {
         return result;
     }
 
-    public Optional<Exception> getException() {
+    public Optional<E> getException() {
         return exception;
     }
-
 }

core-java-modules/core-java-streams-5/src/test/java/com/baeldung/aggregateEx/AggregateExceptionHandlerUnitTest.java

@@ -5,6 +5,8 @@ import com.baeldung.aggregateEx.entity.Result;
 import io.vavr.control.Either;
 import io.vavr.control.Try;
 import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.Arrays;
 import java.util.List;
@@ -12,172 +14,138 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.stream.Collectors;
 
-import static org.junit.Assert.*;
+import static org.junit.Assert.assertEquals;
+
 
 public class AggregateExceptionHandlerUnitTest {
-
+    static Logger logger = LoggerFactory.getLogger(AggregateExceptionHandlerUnitTest.class);
-    private static RuntimeException process(String str) {
-        try {
-            Integer.parseInt(str);
-            return null;
-        } catch (NumberFormatException e) {
-            return new RuntimeException(e);
-        }
-    }
-
-    private static Object transform(String str) {
-        try {
-            return Integer.parseInt(str);
-        } catch (NumberFormatException e) {
-            return new RuntimeException(e);
-        }
-    }
 
     @Test
-    public void givenExtractedMethod_whenFoundNonInt_thenSuppressExIntoRuntimeEx() {
+    public void givenExtractedMethod_whenFoundEx_thenSuppressExIntoRuntimeEx() {
         String[] strings = {"1", "2", "3", "a", "b", "c"};
-        RuntimeException runEx = Arrays.stream(strings)
+        Throwable runEx = Arrays.stream(strings)
-                .map(AggregateExceptionHandlerUnitTest::process)
+                .map(str -> callProcessThrowsExAndNoOutput(str))
                 .filter(Objects::nonNull)
                 .reduce(new RuntimeException("Errors Occurred"), (o1, o2) -> {
                     o1.addSuppressed(o2);
                     return o1;
                 });
+        processExceptions(runEx);
         assertEquals("Errors Occurred", runEx.getMessage());
         assertEquals(3, runEx.getSuppressed().length);
     }
-
     @Test
-    public void givenTryCatchInPipeline_whenFoundNonInts_thenSuppressExIntoRuntimeEx() {
+    public void givenTryCatchInPipeline_whenFoundEx_thenSuppressExIntoRuntimeEx() {
         String[] strings = {"1", "2", "3", "a", "b", "c"};
-        RuntimeException runEx = Arrays.stream(strings)
+        RuntimeException runEx = Arrays.stream(strings).map(str -> {
-                .map(str -> {
                     try {
-                        Integer.parseInt(str);
+                        processThrowsExAndNoOutput(str);
                         return null;
-                    } catch (NumberFormatException e) {
+                    } catch (RuntimeException e) {
-                        return new RuntimeException(e);
+                        return e;
                     }
-                })
+                }).filter(Objects::nonNull)
-                .filter(Objects::nonNull)
+                .collect(Collectors.collectingAndThen(Collectors.toList(), list -> {
-                .reduce(new RuntimeException("Errors Occurred"), (o1, o2) -> {
+                    RuntimeException runtimeException = new RuntimeException("Errors Occurred");
-                    o1.addSuppressed(o2);
+                    list.forEach(runtimeException::addSuppressed);
-                    return o1;
+                    return runtimeException;
-                });
+                }));
+        processExceptions(runEx);
         assertEquals("Errors Occurred", runEx.getMessage());
         assertEquals(3, runEx.getSuppressed().length);
     }
 
     @Test
-    public void givenExtractedMethodReturnOutputAndEx_whenFoundNonInts_thenSuppressExIntoRuntimeEx() {
+    public void givenProcessMethod_whenStreamResultHasExAndOutput_thenHandleExceptionListAndOutputList() {
-        String[] strings = {"1", "2", "3", "a", "b", "c"};
+        List<String> strings = List.of("1", "2", "3", "a", "b", "c");
-        Map resultMap = Arrays.stream(strings)
+        Map map = strings.stream()
-                .map(AggregateExceptionHandlerUnitTest::transform)
+                .map(s -> processReturnsExAndOutput(s))
                 .collect(Collectors.partitioningBy(o -> o instanceof RuntimeException, Collectors.toList()));
-
+        assert(map.containsKey(Boolean.TRUE) && map.containsKey(Boolean.FALSE));
-        RuntimeException ex = null;
+        handleExceptionsAndOutputs((List<RuntimeException>) map.get(Boolean.TRUE), (List<Integer>)map.get(Boolean.FALSE));
-
-        assertTrue(resultMap.containsKey(Boolean.TRUE));
-
-        List<RuntimeException> exs = (List<RuntimeException>) resultMap.get(Boolean.TRUE);
-        ex = exs.stream()
-                .reduce(
-                        new RuntimeException("Errors Occurred"), (o1, o2) -> {
-                            o1.addSuppressed(o2);
-                            return o1;
-                        });
-
-        assertEquals("Errors Occurred", ex.getMessage());
-        assertEquals(3, ex.getSuppressed().length);
     }
 
     @Test
-    public void givenWrapFunction_whenFoundNonInts_thenUseExAggregator() throws ExceptionAggregator {
+    public void givenCustomMapper_whenStreamResultHasExAndSuccess_thenHandleExceptionListAndOutputList() {
-        String[] strings = {"1", "2", "3", "a", "b", "c"};
+        List<String> strings = List.of("1", "2", "3", "a", "b", "c");
-        Map<Boolean, List<Result<Integer>>> resultmap = Arrays.stream(strings)
+        strings.stream()
                 .map(CustomMapper.mapper(Integer::parseInt))
-                .collect(Collectors.partitioningBy(r -> r.getException().isEmpty(), Collectors.toList()));
+                .collect(Collectors.collectingAndThen(Collectors.toList(), list -> handleErrorsAndOutPutForResult(list)));
-
-        assertTrue(resultmap.containsKey(Boolean.TRUE));
-
-        List<Result<Integer>> resultList = resultmap.get(Boolean.FALSE);
-        List<Exception> exceptionList = resultList.stream()
-                .map(opex -> opex.getException().get())
-                .collect(Collectors.toList());
-
-        assertThrows(ExceptionAggregator.class, () -> handleExceptions(exceptionList));
-
-    }
-
-    private void handleExceptions(List<Exception> exceptions) throws ExceptionAggregator {
-        ExceptionAggregator exceptionAggregator = new ExceptionAggregator("Errors occurred");
-        exceptionAggregator.addExceptions(exceptions);
-        throw exceptionAggregator;
     }
 
     @Test
-    public void givenExCollector_whenFoundNonInts_thenAggregateExInCustomCollector() throws ExceptionAggregator {
+    public void givenCustomCollector_whenStreamResultHasExAndSuccess_thenHandleAggrExceptionAndResults() {
         String[] strings = {"1", "2", "3", "a", "b", "c"};
-        ExceptionCollector exCollector = Arrays.stream(strings)
+        Arrays.stream(strings)
-                .collect(ExceptionCollector.of(Integer::parseInt));
+                .collect(Collectors.collectingAndThen(CustomCollector.of(Integer::parseInt), col -> {
-        List<Integer> output = exCollector.getResults();
+                    handleExAndResults(col.getExceptionAggregator(), col.getResults());
-        List<RuntimeException> runEx = exCollector.getExceptions();
+                    return col;
-        assertEquals(3, runEx.size());
+                }));
-    }
-
-    private static Either<RuntimeException, Integer> processAndReturnEither(String str) {
-        try {
-            return Either.right(Integer.parseInt(str));
-        } catch (NumberFormatException e) {
-            return Either.left(new RuntimeException(e));
-        }
     }
 
     @Test
-    public void givenVavrEither_whenFoundNonInts_thenSuppressExIntoRuntimeEx() {
+    public void givenVavrEitherAndTry_whenStreamResultHasExAndSuccess_thenHandleExceptionListAndOutputList() {
         List<String> strings = List.of("1", "2", "3", "a", "b", "c");
-        Map<Boolean, List<Either<RuntimeException, Integer>>> map = strings.stream()
+        strings.stream()
-                .map(str -> processAndReturnEither(str))
-                .collect(Collectors.partitioningBy(t -> t.isLeft(), Collectors.toList()));
-
-        assertTrue(map.containsKey(Boolean.TRUE));
-
-        RuntimeException runEx = map.get(Boolean.TRUE)
-                .stream().map(either -> either.getLeft())
-                .reduce(new RuntimeException("Errors Occurred"), (o1, o2) -> {
-                    o1.addSuppressed(o2);
-                    return o1;
-                });
-        assertEquals(3, runEx.getSuppressed().length);
-    }
-
-    @Test
-    public void givenVavrTry_whenFoundNonInts_thenSuppressExIntoRuntimeEx() {
-        List<String> strings = List.of("1", "2", "3", "a", "b", "c");
-        Map<Boolean, List<Try<Integer>>> map = strings.stream()
-                .map(str -> Try.of(() -> Integer.parseInt(str)))
-                .collect(Collectors.partitioningBy(t -> t.isFailure(), Collectors.toList()));
-        Throwable runEx = map.get(Boolean.TRUE).stream()
-                .map(t -> t.getCause())
-                .reduce(new RuntimeException("Errors Occurred"), (o1, o2) -> {
-                    o1.addSuppressed(o2);
-                    return o1;
-                });
-        assertEquals(3, runEx.getSuppressed().length);
-    }
-
-    @Test
-    public void givenVavrEitherAndTry_whenFoundNonInts_thenSuppressExIntoRuntimeEx() {
-        List<String> strings = List.of("1", "2", "3", "a", "b", "c");
-        Map<Boolean, List<Either<Throwable, Integer>>> map = strings.stream()
                 .map(str -> Try.of(() -> Integer.parseInt(str)).toEither())
-                .collect(Collectors.partitioningBy(Either::isLeft, Collectors.toList()));
+                .collect(Collectors.collectingAndThen(Collectors.partitioningBy(Either::isLeft, Collectors.toList()), map -> {
-        Throwable runEx = map.get(Boolean.TRUE).stream()
+                    handleErrorsAndOutPutForEither(map);
-                .map(either -> either.getLeft())
+                    return map;
-                .reduce(new RuntimeException("Errors Occurred"), (o1, o2) -> {
+                }));
-                    o1.addSuppressed(o2);
+    }
-                    return o1;
+
+    private static void processThrowsExAndNoOutput(String input) {
+        //return exception when input is "a", "b", "c"
+        if (input.matches("[a-c]")) {
+            throw new RuntimeException("Downstream method throws exception for " + input);
+        }
+    }
+    private static Throwable callProcessThrowsExAndNoOutput(String input) {
+        try {
+            processThrowsExAndNoOutput(input);
+            return null;
+        } catch (RuntimeException e) {
+            return e;
+        }
+    }
+
+    private static Object processReturnsExAndOutput(String input) {
+        logger.info("call a downstream method that returns an Integer");
+        try {
+            return Integer.parseInt(input);
+        } catch (Exception e) {
+            return new RuntimeException("Exception in processWithReturnOutput for " + input, e);
+        }
+    }
+
+    private static void processExceptions(Throwable throwable) {
+        logger.error("Process Exception" + throwable.getMessage());
+    }
+
+    private static void handleExceptionsAndOutputs(List<RuntimeException> exs, List output) {
+        logger.info("handle exceptions and output");
+    }
+
+    private static void handleExAndResults(ExceptionAggregator exAgg, List<Integer> results ) {
+        logger.info("handle aggregated exceptions and results" + exAgg.getExceptions().size() + " " + results.size());
+    }
+
+    private static void handleErrorsAndOutPutForEither(Map<Boolean, List<Either<Throwable, Integer>>> map) {
+        logger.info("handle errors and output");
+        map.get(Boolean.TRUE).forEach(either -> logger.error("Process Exception " + either.getLeft()));
+
+        map.get(Boolean.FALSE).forEach(either -> logger.info("Process Result " + either.get()));
+    }
+
+    private static String handleErrorsAndOutPutForResult(List<Result<Integer, Throwable>> successAndErrors) {
+        logger.info("handle errors and output");
+        successAndErrors.forEach(result -> {
+            if (result.getException().isPresent()) {
+                logger.error("Process Exception " + result.getException().get());
+            } else {
+                logger.info("Process Result" + result.getResult());
+            }
         });
-        assertEquals(3, runEx.getSuppressed().length);
+        return "Errors and Output Handled";
     }
 }