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DataAccessUtils result accessors with Optional return value (#27735)
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Diff for: ‎spring-tx/src/main/java/org/springframework/dao/support/DataAccessUtils.java

+87
Original file line numberDiff line numberDiff line change
@@ -17,6 +17,10 @@
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package org.springframework.dao.support;
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import java.util.Collection;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Optional;
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import java.util.stream.Stream;
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import org.springframework.dao.DataAccessException;
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import org.springframework.dao.EmptyResultDataAccessException;
@@ -56,6 +60,89 @@ public static <T> T singleResult(@Nullable Collection<T> results) throws Incorre
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return results.iterator().next();
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}
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/**
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* Return a single result object from the given Stream.
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* <p>Returns {@code null} if 0 result objects found;
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* throws an exception if more than 1 element found.
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* @param results the result Stream (can be {@code null})
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* @return the single result object, or {@code null} if none
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* @throws IncorrectResultSizeDataAccessException if more than one
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* element has been found in the given Stream
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*/
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@Nullable
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public static <T> T singleResult(@Nullable Stream<T> results) throws IncorrectResultSizeDataAccessException {
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if (results == null) {
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return null;
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}
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try (results) {
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List<T> resultList = results.limit(2).toList();
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if (resultList.size() > 1) {
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throw new IncorrectResultSizeDataAccessException(1);
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}
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return CollectionUtils.isEmpty(resultList) ? null : resultList.get(0);
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}
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}
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/**
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* Return a single result object from the given Iterator.
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* <p>Returns {@code null} if 0 result objects found;
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* throws an exception if more than 1 element found.
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* @param results the result Iterator (can be {@code null})
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* @return the single result object, or {@code null} if none
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* @throws IncorrectResultSizeDataAccessException if more than one
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* element has been found in the given Iterator
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*/
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@Nullable
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public static <T> T singleResult(@Nullable Iterator<T> results) throws IncorrectResultSizeDataAccessException {
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if (results == null) {
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return null;
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}
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T result = results.hasNext() ? results.next() : null;
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if (results.hasNext()) {
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throw new IncorrectResultSizeDataAccessException(1);
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}
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return result;
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}
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/**
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* Return a single result object from the given Collection.
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* <p>Returns {@code Optional.empty()} if 0 result objects found;
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* throws an exception if more than 1 element found.
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* @param results the result Collection (can be {@code null})
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* @return the single optional result object, or {@code Optional.empty()} if none
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* @throws IncorrectResultSizeDataAccessException if more than one
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* element has been found in the given Collection
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*/
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public static <T> Optional<T> optionalResult(@Nullable Collection<T> results) throws IncorrectResultSizeDataAccessException {
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return Optional.ofNullable(singleResult(results));
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}
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/**
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* Return a single result object from the given Stream.
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* <p>Returns {@code Optional.empty()} if 0 result objects found;
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* throws an exception if more than 1 element found.
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* @param results the result Stream (can be {@code null})
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* @return the single optional result object, or {@code Optional.empty()} if none
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* @throws IncorrectResultSizeDataAccessException if more than one
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* element has been found in the given Stream
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*/
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public static <T> Optional<T> optionalResult(@Nullable Stream<T> results) throws IncorrectResultSizeDataAccessException {
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return Optional.ofNullable(singleResult(results));
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}
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/**
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* Return a single result object from the given Iterator.
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* <p>Returns {@code Optional.empty()} if 0 result objects found;
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* throws an exception if more than 1 element found.
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* @param results the result Iterator (can be {@code null})
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* @return the single optional result object, or {@code Optional.empty()} if none
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* @throws IncorrectResultSizeDataAccessException if more than one
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* element has been found in the given Iterator
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*/
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public static <T> Optional<T> optionalResult(@Nullable Iterator<T> results) throws IncorrectResultSizeDataAccessException {
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return Optional.ofNullable(singleResult(results));
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}
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/**
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* Return a single result object from the given Collection.
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* <p>Throws an exception if 0 or more than 1 element found.

Diff for: ‎spring-tx/src/test/java/org/springframework/dao/support/DataAccessUtilsTests.java

+63
Original file line numberDiff line numberDiff line change
@@ -23,6 +23,7 @@
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.Map;
26+
import java.util.Optional;
2627
import java.util.function.Consumer;
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import org.junit.jupiter.api.Test;
@@ -47,6 +48,13 @@ public void withEmptyCollection() {
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4849
assertThat(DataAccessUtils.uniqueResult(col)).isNull();
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51+
assertThat(DataAccessUtils.singleResult(col)).isNull();
52+
assertThat(DataAccessUtils.singleResult(col.stream())).isNull();
53+
assertThat(DataAccessUtils.singleResult(col.iterator())).isNull();
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assertThat(DataAccessUtils.optionalResult(col)).isEmpty();
55+
assertThat(DataAccessUtils.optionalResult(col.stream())).isEmpty();
56+
assertThat(DataAccessUtils.optionalResult(col.iterator())).isEmpty();
57+
5058
assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
5159
DataAccessUtils.requiredUniqueResult(col))
5260
.satisfies(sizeRequirements(1, 0));
@@ -89,6 +97,30 @@ public void withTooLargeCollection() {
8997
assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
9098
DataAccessUtils.longResult(col))
9199
.satisfies(sizeRequirements(1, 2));
100+
101+
assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
102+
DataAccessUtils.singleResult(col))
103+
.satisfies(sizeRequirements(1, 2));
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105+
assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
106+
DataAccessUtils.singleResult(col.stream()))
107+
.satisfies(sizeRequirements(1));
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109+
assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
110+
DataAccessUtils.singleResult(col.iterator()))
111+
.satisfies(sizeRequirements(1));
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113+
assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
114+
DataAccessUtils.optionalResult(col))
115+
.satisfies(sizeRequirements(1, 2));
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117+
assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
118+
DataAccessUtils.optionalResult(col.stream()))
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.satisfies(sizeRequirements(1));
120+
121+
assertThatExceptionOfType(IncorrectResultSizeDataAccessException.class).isThrownBy(() ->
122+
DataAccessUtils.optionalResult(col.iterator()))
123+
.satisfies(sizeRequirements(1));
92124
}
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94126
@Test
@@ -102,6 +134,12 @@ public void withInteger() {
102134
assertThat(DataAccessUtils.objectResult(col, String.class)).isEqualTo("5");
103135
assertThat(DataAccessUtils.intResult(col)).isEqualTo(5);
104136
assertThat(DataAccessUtils.longResult(col)).isEqualTo(5);
137+
assertThat(DataAccessUtils.singleResult(col)).isEqualTo(5);
138+
assertThat(DataAccessUtils.singleResult(col.stream())).isEqualTo(5);
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assertThat(DataAccessUtils.singleResult(col.iterator())).isEqualTo(5);
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assertThat(DataAccessUtils.optionalResult(col)).isEqualTo(Optional.of(5));
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assertThat(DataAccessUtils.optionalResult(col.stream())).isEqualTo(Optional.of(5));
142+
assertThat(DataAccessUtils.optionalResult(col.iterator())).isEqualTo(Optional.of(5));
105143
}
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107145
@Test
@@ -139,6 +177,12 @@ public void withLong() {
139177
assertThat(DataAccessUtils.objectResult(col, String.class)).isEqualTo("5");
140178
assertThat(DataAccessUtils.intResult(col)).isEqualTo(5);
141179
assertThat(DataAccessUtils.longResult(col)).isEqualTo(5);
180+
assertThat(DataAccessUtils.singleResult(col)).isEqualTo(Long.valueOf(5L));
181+
assertThat(DataAccessUtils.singleResult(col.stream())).isEqualTo(Long.valueOf(5L));
182+
assertThat(DataAccessUtils.singleResult(col.iterator())).isEqualTo(Long.valueOf(5L));
183+
assertThat(DataAccessUtils.optionalResult(col)).isEqualTo(Optional.of(5L));
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assertThat(DataAccessUtils.optionalResult(col.stream())).isEqualTo(Optional.of(5L));
185+
assertThat(DataAccessUtils.optionalResult(col.iterator())).isEqualTo(Optional.of(5L));
142186
}
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144188
@Test
@@ -149,6 +193,12 @@ public void withString() {
149193
assertThat(DataAccessUtils.uniqueResult(col)).isEqualTo("test1");
150194
assertThat(DataAccessUtils.requiredUniqueResult(col)).isEqualTo("test1");
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assertThat(DataAccessUtils.objectResult(col, String.class)).isEqualTo("test1");
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assertThat(DataAccessUtils.singleResult(col)).isEqualTo("test1");
197+
assertThat(DataAccessUtils.singleResult(col.stream())).isEqualTo("test1");
198+
assertThat(DataAccessUtils.singleResult(col.iterator())).isEqualTo("test1");
199+
assertThat(DataAccessUtils.optionalResult(col)).isEqualTo(Optional.of("test1"));
200+
assertThat(DataAccessUtils.optionalResult(col.stream())).isEqualTo(Optional.of("test1"));
201+
assertThat(DataAccessUtils.optionalResult(col.iterator())).isEqualTo(Optional.of("test1"));
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153203
assertThatExceptionOfType(TypeMismatchDataAccessException.class).isThrownBy(() ->
154204
DataAccessUtils.intResult(col));
@@ -167,6 +217,12 @@ public void withDate() {
167217
assertThat(DataAccessUtils.requiredUniqueResult(col)).isEqualTo(date);
168218
assertThat(DataAccessUtils.objectResult(col, Date.class)).isEqualTo(date);
169219
assertThat(DataAccessUtils.objectResult(col, String.class)).isEqualTo(date.toString());
220+
assertThat(DataAccessUtils.singleResult(col)).isEqualTo(date);
221+
assertThat(DataAccessUtils.singleResult(col.stream())).isEqualTo(date);
222+
assertThat(DataAccessUtils.singleResult(col.iterator())).isEqualTo(date);
223+
assertThat(DataAccessUtils.optionalResult(col)).isEqualTo(Optional.of(date));
224+
assertThat(DataAccessUtils.optionalResult(col.stream())).isEqualTo(Optional.of(date));
225+
assertThat(DataAccessUtils.optionalResult(col.iterator())).isEqualTo(Optional.of(date));
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171227
assertThatExceptionOfType(TypeMismatchDataAccessException.class).isThrownBy(() ->
172228
DataAccessUtils.intResult(col));
@@ -199,6 +255,13 @@ private <E extends IncorrectResultSizeDataAccessException> Consumer<E> sizeRequi
199255
};
200256
}
201257

258+
private <E extends IncorrectResultSizeDataAccessException> Consumer<E> sizeRequirements(
259+
int expectedSize) {
260+
return ex -> {
261+
assertThat(ex.getExpectedSize()).as("expected size").isEqualTo(expectedSize);
262+
};
263+
}
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202265
public static class MapPersistenceExceptionTranslator implements PersistenceExceptionTranslator {
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// in to out

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