Correctly request primitive conversion in SpEL's Indexer

Prior to this commit, SpEL's Indexer incorrectly requested conversion
to wrappers instead of primitives when setting an element in a
primitive array.

This commit addresses this by requesting primitive conversion -- for
example, conversion to `int.class` instead of `Integer.class` when
setting a value in an `int[]` array.

For greater clarity, this commit also switches from using `TYPE`
constants in wrapper classes to primitive class literals -- for
example, from `Integer.TYPE` to `int.class`.

Closes gh-32147

Author: sbrannen

Diff for: spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -336,45 +336,45 @@ public String toStringAST() {
 	private void setArrayElement(TypeConverter converter, Object ctx, int idx, @Nullable Object newValue,
 			Class<?> arrayComponentType) throws EvaluationException {
 
-		if (arrayComponentType == Boolean.TYPE) {
+		if (arrayComponentType == boolean.class) {
 			boolean[] array = (boolean[]) ctx;
 			checkAccess(array.length, idx);
-			array[idx] = convertValue(converter, newValue, Boolean.class);
+			array[idx] = convertValue(converter, newValue, boolean.class);
 		}
-		else if (arrayComponentType == Byte.TYPE) {
+		else if (arrayComponentType == byte.class) {
 			byte[] array = (byte[]) ctx;
 			checkAccess(array.length, idx);
-			array[idx] = convertValue(converter, newValue, Byte.class);
+			array[idx] = convertValue(converter, newValue, byte.class);
 		}
-		else if (arrayComponentType == Character.TYPE) {
+		else if (arrayComponentType == char.class) {
 			char[] array = (char[]) ctx;
 			checkAccess(array.length, idx);
-			array[idx] = convertValue(converter, newValue, Character.class);
+			array[idx] = convertValue(converter, newValue, char.class);
 		}
-		else if (arrayComponentType == Double.TYPE) {
+		else if (arrayComponentType == double.class) {
 			double[] array = (double[]) ctx;
 			checkAccess(array.length, idx);
-			array[idx] = convertValue(converter, newValue, Double.class);
+			array[idx] = convertValue(converter, newValue, double.class);
 		}
-		else if (arrayComponentType == Float.TYPE) {
+		else if (arrayComponentType == float.class) {
 			float[] array = (float[]) ctx;
 			checkAccess(array.length, idx);
-			array[idx] = convertValue(converter, newValue, Float.class);
+			array[idx] = convertValue(converter, newValue, float.class);
 		}
-		else if (arrayComponentType == Integer.TYPE) {
+		else if (arrayComponentType == int.class) {
 			int[] array = (int[]) ctx;
 			checkAccess(array.length, idx);
-			array[idx] = convertValue(converter, newValue, Integer.class);
+			array[idx] = convertValue(converter, newValue, int.class);
 		}
-		else if (arrayComponentType == Long.TYPE) {
+		else if (arrayComponentType == long.class) {
 			long[] array = (long[]) ctx;
 			checkAccess(array.length, idx);
-			array[idx] = convertValue(converter, newValue, Long.class);
+			array[idx] = convertValue(converter, newValue, long.class);
 		}
-		else if (arrayComponentType == Short.TYPE) {
+		else if (arrayComponentType == short.class) {
 			short[] array = (short[]) ctx;
 			checkAccess(array.length, idx);
-			array[idx] = convertValue(converter, newValue, Short.class);
+			array[idx] = convertValue(converter, newValue, short.class);
 		}
 		else {
 			Object[] array = (Object[]) ctx;

Diff for: spring-expression/src/test/java/org/springframework/expression/spel/SetValueTests.java

@@ -21,16 +21,19 @@
 import java.util.Set;
 
 import org.assertj.core.api.ThrowableTypeAssert;
-import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 import org.springframework.expression.EvaluationException;
 import org.springframework.expression.Expression;
 import org.springframework.expression.ParseException;
 import org.springframework.expression.spel.testresources.PlaceOfBirth;
+import org.springframework.util.ObjectUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+import static org.springframework.expression.spel.SpelMessage.TYPE_CONVERSION_ERROR;
 
 /**
  * Tests for assignment, setValue(), and isWritable() expressions.
@@ -164,21 +167,19 @@ void setArrayElementToPrimitiveFromSingleElementWrapperList() {
 		setValue("arrayContainer.doubles[1]", List.of(42D), 42D);
 	}
 
-	@Disabled("Disabled due to bug in Indexer.setArrayElement() regarding primitive/wrapper types")
-	@Test
-	void setArrayElementToPrimitiveFromEmptyCollectionFails() {
-		List<Object> emptyList = List.of();
-		// TODO These fail because CollectionToObjectConverter returns null.
-		// It currently throws: java.lang.IllegalStateException: Null conversion result for index [[]].
-		// Whereas, it should throw a SpelEvaluationException.
-		setValueAndExpectError("arrayContainer.booleans[1]", emptyList);
-		setValueAndExpectError("arrayContainer.chars[1]", emptyList);
-		setValueAndExpectError("arrayContainer.shorts[1]", emptyList);
-		setValueAndExpectError("arrayContainer.bytes[1]", emptyList);
-		setValueAndExpectError("arrayContainer.ints[1]", emptyList);
-		setValueAndExpectError("arrayContainer.longs[1]", emptyList);
-		setValueAndExpectError("arrayContainer.floats[1]", emptyList);
-		setValueAndExpectError("arrayContainer.doubles[1]", emptyList);
+	@ParameterizedTest
+	@ValueSource(strings = {
+		"arrayContainer.booleans[1]",
+		"arrayContainer.chars[1]",
+		"arrayContainer.shorts[1]",
+		"arrayContainer.bytes[1]",
+		"arrayContainer.ints[1]",
+		"arrayContainer.longs[1]",
+		"arrayContainer.floats[1]",
+		"arrayContainer.doubles[1]"
+	})
+	void setArrayElementToPrimitiveFromEmptyCollectionFailsWithTypeConversionError(String expression) {
+		setValueAndExpectError(expression, List.of(), TYPE_CONVERSION_ERROR);
 	}
 
 	@Test
@@ -272,6 +273,40 @@ private void setValueAndExpectError(String expression, Object value) {
 		assertThatSpelEvaluationException().isThrownBy(() -> e.setValue(context, value));
 	}
 
+	/**
+	 * Call setValue() but expect it to fail.
+	 * @see #evaluateAndCheckError(org.springframework.expression.ExpressionParser, String, Class, SpelMessage, Object...)
+	 */
+	private void setValueAndExpectError(String expression, Object value, SpelMessage expectedMessage,
+			Object... otherProperties) {
+
+		Expression expr = parser.parseExpression(expression);
+		assertThat(expr).as("expression").isNotNull();
+
+		if (DEBUG) {
+			SpelUtilities.printAbstractSyntaxTree(System.out, expr);
+		}
+
+		assertThatSpelEvaluationException()
+			.isThrownBy(() -> expr.setValue(context, value))
+			.satisfies(ex -> {
+				assertThat(ex.getMessageCode()).isEqualTo(expectedMessage);
+				if (!ObjectUtils.isEmpty(otherProperties)) {
+					// first one is expected position of the error within the string
+					int pos = (Integer) otherProperties[0];
+					assertThat(ex.getPosition()).as("position").isEqualTo(pos);
+					if (otherProperties.length > 1) {
+						// Check inserts match
+						Object[] inserts = ex.getInserts();
+						assertThat(inserts).as("inserts").hasSizeGreaterThanOrEqualTo(otherProperties.length - 1);
+						Object[] expectedInserts = new Object[inserts.length];
+						System.arraycopy(otherProperties, 1, expectedInserts, 0, expectedInserts.length);
+						assertThat(inserts).as("inserts").containsExactly(expectedInserts);
+					}
+				}
+			});
+	}
+
 	private void setValue(String expression, Object value) {
 		Class<?> expectedType = value.getClass();
 		try {