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Merged
merged 11 commits into from
Jul 14, 2023
Merged

DataAccessUtils result accessors with Optional return value #27735

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f86cf08
extend DataAccessUtils
KaidosGH Nov 26, 2021
ff503c7
cleanup
KaidosGH Nov 26, 2021
b98e7ad
optimize imports, refactor iterator usage
KaidosGH Nov 26, 2021
8a5fc7d
close streams properly with try-with-resource
KaidosGH Nov 27, 2021
1e7d103
Update spring-tx/src/main/java/org/springframework/dao/support/DataAc…
KaidosGH Nov 28, 2021
6522003
Update spring-tx/src/main/java/org/springframework/dao/support/DataAc…
KaidosGH Nov 28, 2021
4ee08be
Update spring-tx/src/main/java/org/springframework/dao/support/DataAc…
KaidosGH Nov 28, 2021
3017beb
fix closing bracket
KaidosGH Nov 28, 2021
9206303
Update spring-tx/src/main/java/org/springframework/dao/support/DataAc…
KaidosGH Nov 28, 2021
7c096e0
Update spring-tx/src/main/java/org/springframework/dao/support/DataAc…
KaidosGH Nov 28, 2021
1891fa4
update tests to correctly assert the thrown exception
KaidosGH Nov 28, 2021
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108 changes: 108 additions & 0 deletions spring-tx/src/main/java/org/springframework/dao/support/DataAccessUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,11 @@
package org.springframework.dao.support;

import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import org.springframework.dao.DataAccessException;
import org.springframework.dao.EmptyResultDataAccessException;
Expand Down Expand Up @@ -56,6 +61,109 @@ public static <T> T singleResult(@Nullable Collection<T> results) throws Incorre
return results.iterator().next();
}

/**
* Return a single result object from the given Stream.
* <p>Returns {@code null} if 0 result objects found;
* throws an exception if more than 1 element found.
* @param results the result Stream (can be {@code null})
* @return the single result object, or {@code null} if none
* @throws IncorrectResultSizeDataAccessException if more than one
* element has been found in the given Stream
*/
@Nullable
public static <T> T singleResult(@Nullable Stream<T> results) throws IncorrectResultSizeDataAccessException {
if (results == null) {
return null;
}
List<T> resultList = results.toList();
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Wouldn't it be better to do a

.limit(2).toList()

and then avoid opening the second stream and instead do

resultList.get(0)

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Hi @marschall,

thanks for reviewing, sounds good, i refactored this. Does it make more sense now?

throw new IncorrectResultSizeDataAccessException(1, resultList.size());
as we limited the resultList size with .limit, this would not report the original passed Stream results size though but instead a maximum of 2... is that an issue?

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Yes, looks better to me.

if (resultList.size() > 1) {
throw new IncorrectResultSizeDataAccessException(1, resultList.size());
}
return resultList.stream().findFirst().orElse(null);
}

/**
* Return a single result object from the given Iterator.
* <p>Returns {@code null} if 0 result objects found;
* throws an exception if more than 1 element found.
* @param results the result Iterator (can be {@code null})
* @return the single result object, or {@code null} if none
* @throws IncorrectResultSizeDataAccessException if more than one
* element has been found in the given Iterator
*/
@Nullable
public static <T> T singleResult(@Nullable Iterator<T> results) throws IncorrectResultSizeDataAccessException {
if (results == null) {
return null;
}
Iterable<T> iterable = () -> results;
List<T> resultList = StreamSupport.stream(iterable.spliterator(), false).toList();
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Why a stream instead of just

results.next()

if (resultList.size() > 1) {
throw new IncorrectResultSizeDataAccessException(1, resultList.size());
}
return resultList.stream().findFirst().orElse(null);
}

/**
* Return a single result object from the given Collection.
* <p>Returns {@code Optional.empty()} if 0 result objects found;
* throws an exception if more than 1 element found.
* @param results the result Collection (can be {@code null})
* @return the single optional result object, or {@code Optional.empty()} if none
* @throws IncorrectResultSizeDataAccessException if more than one
* element has been found in the given Collection
*/
public static <T> Optional<T> optionalResult(@Nullable Collection<T> results) throws IncorrectResultSizeDataAccessException {
if (CollectionUtils.isEmpty(results)) {
return Optional.empty();
}
if (results.size() > 1) {
throw new IncorrectResultSizeDataAccessException(1, results.size());
}
return results.stream().findFirst();
}

/**
* Return a single result object from the given Stream.
* <p>Returns {@code Optional.empty()} if 0 result objects found;
* throws an exception if more than 1 element found.
* @param results the result Stream (can be {@code null})
* @return the single optional result object, or {@code Optional.empty()} if none
* @throws IncorrectResultSizeDataAccessException if more than one
* element has been found in the given Stream
*/
public static <T> Optional<T> optionalResult(@Nullable Stream<T> results) throws IncorrectResultSizeDataAccessException {
if (results == null) {
return Optional.empty();
}
List<T> resultList = results.toList();
if (resultList.size() > 1) {
throw new IncorrectResultSizeDataAccessException(1, resultList.size());
}
return resultList.stream().findFirst();
}

/**
* Return a single result object from the given Iterator.
* <p>Returns {@code Optional.empty()} if 0 result objects found;
* throws an exception if more than 1 element found.
* @param results the result Iterator (can be {@code null})
* @return the single optional result object, or {@code Optional.empty()} if none
* @throws IncorrectResultSizeDataAccessException if more than one
* element has been found in the given Iterator
*/
public static <T> Optional<T> optionalResult(@Nullable Iterator<T> results) throws IncorrectResultSizeDataAccessException {
if (results == null) {
return Optional.empty();
}
Iterable<T> iterable = () -> results;
List<T> resultList = StreamSupport.stream(iterable.spliterator(), false).toList();
if (resultList.size() > 1) {
throw new IncorrectResultSizeDataAccessException(1, resultList.size());
}
return resultList.stream().findFirst();
}

/**
* Return a single result object from the given Collection.
* <p>Throws an exception if 0 or more than 1 element found.
Expand Down
63 changes: 56 additions & 7 deletions spring-tx/src/test/java/org/springframework/dao/support/DataAccessUtilsTests.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -16,13 +16,7 @@

package org.springframework.dao.support;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.*;
import java.util.function.Consumer;

import org.junit.jupiter.api.Test;
Expand All @@ -47,6 +41,13 @@ public void withEmptyCollection() {

assertThat(DataAccessUtils.uniqueResult(col)).isNull();

assertThat(DataAccessUtils.singleResult(col)).isNull();
assertThat(DataAccessUtils.singleResult(col.stream())).isNull();
assertThat(DataAccessUtils.singleResult(col.iterator())).isNull();
assertThat(DataAccessUtils.optionalResult(col)).isEmpty();
assertThat(DataAccessUtils.optionalResult(col.stream())).isEmpty();
assertThat(DataAccessUtils.optionalResult(col.iterator())).isEmpty();

assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
DataAccessUtils.requiredUniqueResult(col))
.satisfies(sizeRequirements(1, 0));
Expand Down Expand Up @@ -89,6 +90,30 @@ public void withTooLargeCollection() {
assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
DataAccessUtils.longResult(col))
.satisfies(sizeRequirements(1, 2));

assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
DataAccessUtils.singleResult(col))
.satisfies(sizeRequirements(1, 2));

assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
DataAccessUtils.singleResult(col.stream()))
.satisfies(sizeRequirements(1, 2));

assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
DataAccessUtils.singleResult(col.iterator()))
.satisfies(sizeRequirements(1, 2));

assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
DataAccessUtils.optionalResult(col))
.satisfies(sizeRequirements(1, 2));

assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
DataAccessUtils.optionalResult(col.stream()))
.satisfies(sizeRequirements(1, 2));

assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
DataAccessUtils.optionalResult(col.iterator()))
.satisfies(sizeRequirements(1, 2));
}

@Test
Expand All @@ -102,6 +127,12 @@ public void withInteger() {
assertThat(DataAccessUtils.objectResult(col, String.class)).isEqualTo("5");
assertThat(DataAccessUtils.intResult(col)).isEqualTo(5);
assertThat(DataAccessUtils.longResult(col)).isEqualTo(5);
assertThat(DataAccessUtils.singleResult(col)).isEqualTo(5);
assertThat(DataAccessUtils.singleResult(col.stream())).isEqualTo(5);
assertThat(DataAccessUtils.singleResult(col.iterator())).isEqualTo(5);
assertThat(DataAccessUtils.optionalResult(col)).isEqualTo(Optional.of(5));
assertThat(DataAccessUtils.optionalResult(col.stream())).isEqualTo(Optional.of(5));
assertThat(DataAccessUtils.optionalResult(col.iterator())).isEqualTo(Optional.of(5));
}

@Test
Expand Down Expand Up @@ -139,6 +170,12 @@ public void withLong() {
assertThat(DataAccessUtils.objectResult(col, String.class)).isEqualTo("5");
assertThat(DataAccessUtils.intResult(col)).isEqualTo(5);
assertThat(DataAccessUtils.longResult(col)).isEqualTo(5);
assertThat(DataAccessUtils.singleResult(col)).isEqualTo(Long.valueOf(5L));
assertThat(DataAccessUtils.singleResult(col.stream())).isEqualTo(Long.valueOf(5L));
assertThat(DataAccessUtils.singleResult(col.iterator())).isEqualTo(Long.valueOf(5L));
assertThat(DataAccessUtils.optionalResult(col)).isEqualTo(Optional.of(5L));
assertThat(DataAccessUtils.optionalResult(col.stream())).isEqualTo(Optional.of(5L));
assertThat(DataAccessUtils.optionalResult(col.iterator())).isEqualTo(Optional.of(5L));
}

@Test
Expand All @@ -149,6 +186,12 @@ public void withString() {
assertThat(DataAccessUtils.uniqueResult(col)).isEqualTo("test1");
assertThat(DataAccessUtils.requiredUniqueResult(col)).isEqualTo("test1");
assertThat(DataAccessUtils.objectResult(col, String.class)).isEqualTo("test1");
assertThat(DataAccessUtils.singleResult(col)).isEqualTo("test1");
assertThat(DataAccessUtils.singleResult(col.stream())).isEqualTo("test1");
assertThat(DataAccessUtils.singleResult(col.iterator())).isEqualTo("test1");
assertThat(DataAccessUtils.optionalResult(col)).isEqualTo(Optional.of("test1"));
assertThat(DataAccessUtils.optionalResult(col.stream())).isEqualTo(Optional.of("test1"));
assertThat(DataAccessUtils.optionalResult(col.iterator())).isEqualTo(Optional.of("test1"));

assertThatExceptionOfType(TypeMismatchDataAccessException.class).isThrownBy(() ->
DataAccessUtils.intResult(col));
Expand All @@ -167,6 +210,12 @@ public void withDate() {
assertThat(DataAccessUtils.requiredUniqueResult(col)).isEqualTo(date);
assertThat(DataAccessUtils.objectResult(col, Date.class)).isEqualTo(date);
assertThat(DataAccessUtils.objectResult(col, String.class)).isEqualTo(date.toString());
assertThat(DataAccessUtils.singleResult(col)).isEqualTo(date);
assertThat(DataAccessUtils.singleResult(col.stream())).isEqualTo(date);
assertThat(DataAccessUtils.singleResult(col.iterator())).isEqualTo(date);
assertThat(DataAccessUtils.optionalResult(col)).isEqualTo(Optional.of(date));
assertThat(DataAccessUtils.optionalResult(col.stream())).isEqualTo(Optional.of(date));
assertThat(DataAccessUtils.optionalResult(col.iterator())).isEqualTo(Optional.of(date));

assertThatExceptionOfType(TypeMismatchDataAccessException.class).isThrownBy(() ->
DataAccessUtils.intResult(col));
Expand Down