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Allow auto grow for entries w/o default constructor in SpEL

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Prior to this commit, The "auto grow" feature in SpEL expressions only
worked for element types with a default constructor. For example, auto
grow did not work for a list of BigDecimal elements.

This commit inserts a null value in the list when no default
constructor can be found for the element type.

Closes gh-25367
This commit is contained in:
Martin Knopf
2020-07-07 14:47:48 +02:00
committed by Sam Brannen
parent d2e1150c79
commit 35c0ae7b0c
3 changed files with 39 additions and 4 deletions
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13
spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java
View File

@@ -712,10 +712,10 @@ public class Indexer extends SpelNodeImpl {
}
TypeDescriptor elementType = this.collectionEntryDescriptor.getElementTypeDescriptor();
try {
Constructor<?> ctor = ReflectionUtils.accessibleConstructor(elementType.getType());
Constructor<?> ctor = getConstructor(elementType.getType());
int newElements = this.index - this.collection.size();
while (newElements >= 0) {
this.collection.add(ctor.newInstance());
this.collection.add(ctor == null ? null : ctor.newInstance());
newElements--;
}
}
@@ -725,6 +725,15 @@ public class Indexer extends SpelNodeImpl {
}
}
Constructor<?> getConstructor(Class<?> type) {
try {
return ReflectionUtils.accessibleConstructor(type);
}
catch (Throwable ex) {
return null;
}
}
@Override
public boolean isWritable() {
return true;

22
spring-expression/src/test/java/org/springframework/expression/spel/IndexingTests.java
View File

@@ -20,6 +20,7 @@ import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
@@ -199,6 +200,27 @@ public class IndexingTests {
}
}
public List<BigDecimal> decimals;
@Test
public void autoGrowWithoutDefaultConstructor() {
this.decimals = new ArrayList<>();
SpelExpressionParser parser = new SpelExpressionParser(new SpelParserConfiguration(true, true));
parser.parseExpression("decimals[0]").setValue(this, "123.4");
assertThat(decimals.get(0)).isEqualTo(BigDecimal.valueOf(123.4));
}
@Test
public void indexIntoPropertyContainingNullList() {
this.decimals = new ArrayList<>();
this.decimals.add(null);
this.decimals.add(BigDecimal.ONE);
SpelExpressionParser parser = new SpelExpressionParser(new SpelParserConfiguration(true, true));
parser.parseExpression("decimals[0]").setValue(this, "9876.5");
assertThat(decimals.get(0)).isEqualTo(BigDecimal.valueOf(9876.5));
assertThat(decimals.get(1)).isEqualTo(BigDecimal.ONE);
}
@Test
public void indexIntoPropertyContainingList() {
List<Integer> property = new ArrayList<>();