Add IndexAccessor support to SpEL's SimpleEvaluationContext

Closes gh-32702

Author: sbrannen

spring-expression/src/main/java/org/springframework/expression/spel/support/SimpleEvaluationContext.java

@@ -27,6 +27,7 @@
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.expression.BeanResolver;
 import org.springframework.expression.EvaluationContext;
+import org.springframework.expression.IndexAccessor;
 import org.springframework.expression.MethodResolver;
 import org.springframework.expression.OperatorOverloader;
 import org.springframework.expression.PropertyAccessor;
@@ -107,6 +108,8 @@ public final class SimpleEvaluationContext implements EvaluationContext {
 
 	private final List<PropertyAccessor> propertyAccessors;
 
+	private final List<IndexAccessor> indexAccessors;
+
 	private final List<MethodResolver> methodResolvers;
 
 	private final TypeConverter typeConverter;
@@ -118,10 +121,11 @@ public final class SimpleEvaluationContext implements EvaluationContext {
 	private final Map<String, Object> variables = new HashMap<>();
 
 
-	private SimpleEvaluationContext(List<PropertyAccessor> accessors, List<MethodResolver> resolvers,
-			@Nullable TypeConverter converter, @Nullable TypedValue rootObject) {
+	private SimpleEvaluationContext(List<PropertyAccessor> propertyAccessors, List<IndexAccessor> indexAccessors,
+			List<MethodResolver> resolvers, @Nullable TypeConverter converter, @Nullable TypedValue rootObject) {
 
-		this.propertyAccessors = accessors;
+		this.propertyAccessors = propertyAccessors;
+		this.indexAccessors = indexAccessors;
 		this.methodResolvers = resolvers;
 		this.typeConverter = (converter != null ? converter : new StandardTypeConverter());
 		this.rootObject = (rootObject != null ? rootObject : TypedValue.NULL);
@@ -145,6 +149,16 @@ public List<PropertyAccessor> getPropertyAccessors() {
 		return this.propertyAccessors;
 	}
 
+	/**
+	 * Return the specified {@link IndexAccessor} delegates, if any.
+	 * @since 6.2
+	 * @see Builder#withIndexAccessors(IndexAccessor...)
+	 */
+	@Override
+	public List<IndexAccessor> getIndexAccessors() {
+		return this.indexAccessors;
+	}
+
 	/**
 	 * Return the specified {@link MethodResolver} delegates, if any.
 	 * @see Builder#withMethodResolvers
@@ -289,7 +303,9 @@ public static Builder forReadWriteDataBinding() {
 	 */
 	public static final class Builder {
 
-		private final List<PropertyAccessor> accessors;
+		private final List<PropertyAccessor> propertyAccessors;
+
+		private List<IndexAccessor> indexAccessors = Collections.emptyList();
 
 		private List<MethodResolver> resolvers = Collections.emptyList();
 
@@ -299,8 +315,20 @@ public static final class Builder {
 		@Nullable
 		private TypedValue rootObject;
 
+
 		private Builder(PropertyAccessor... accessors) {
-			this.accessors = Arrays.asList(accessors);
+			this.propertyAccessors = Arrays.asList(accessors);
+		}
+
+
+		/**
+		 * Register the specified {@link IndexAccessor} delegates.
+		 * @param indexAccessors the index accessors to use
+		 * @since 6.2
+		 */
+		public Builder withIndexAccessors(IndexAccessor... indexAccessors) {
+			this.indexAccessors = Arrays.asList(indexAccessors);
+			return this;
 		}
 
 		/**
@@ -381,7 +409,8 @@ public Builder withTypedRootObject(Object rootObject, TypeDescriptor typeDescrip
 		}
 
 		public SimpleEvaluationContext build() {
-			return new SimpleEvaluationContext(this.accessors, this.resolvers, this.typeConverter, this.rootObject);
+			return new SimpleEvaluationContext(this.propertyAccessors, this.indexAccessors,
+					this.resolvers, this.typeConverter, this.rootObject);
 		}
 	}
 

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

@@ -43,6 +43,7 @@
 import org.springframework.expression.PropertyAccessor;
 import org.springframework.expression.TypedValue;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.expression.spel.support.SimpleEvaluationContext;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
 import org.springframework.expression.spel.testresources.Person;
 import org.springframework.lang.Nullable;
@@ -696,6 +697,31 @@ void readAndWriteIndex() {
 			assertThat(expr.getValue(context, arrayNode)).isNull();
 		}
 
+		@Test
+		void readAndWriteIndexWithSimpleEvaluationContext() {
+			ObjectMapper objectMapper = new ObjectMapper();
+			SimpleEvaluationContext context = SimpleEvaluationContext.forReadWriteDataBinding()
+					.withIndexAccessors(new JacksonArrayNodeIndexAccessor(objectMapper))
+					.build();
+			SpelExpressionParser parser = new SpelExpressionParser();
+
+			TextNode node0 = new TextNode("node0");
+			TextNode node1 = new TextNode("node1");
+			ArrayNode arrayNode = objectMapper.createArrayNode();
+			arrayNode.addAll(List.of(node0, node1));
+
+			Expression expr = parser.parseExpression("[0]");
+			assertThat(expr.getValue(context, arrayNode)).isSameAs(node0);
+
+			TextNode nodeX = new TextNode("nodeX");
+			expr.setValue(context, arrayNode, nodeX);
+			// We use isEqualTo() instead of isSameAs(), since ObjectMapper.convertValue()
+			// converts the supplied TextNode to an equivalent JsonNode.
+			assertThat(expr.getValue(context, arrayNode)).isEqualTo(nodeX);
+
+			expr = parser.parseExpression("[1]");
+			assertThat(expr.getValue(context, arrayNode)).isSameAs(node1);
+		}
 
 		/**
 		 * {@link IndexAccessor} that knows how to read and write indexes in a