Sync MapAccessor implementations

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

@@ -34,6 +34,27 @@ import org.springframework.util.Assert;
  */
 class CompilableMapAccessor implements CompilablePropertyAccessor {
 
+	private final boolean allowWrite;
+
+	/**
+	 * Create a new map accessor for reading as well as writing.
+	 * @since 6.2
+	 * @see #CompilableMapAccessor(boolean)
+	 */
+	public CompilableMapAccessor() {
+		this(true);
+	}
+
+	/**
+	 * Create a new map accessor for reading and possibly also writing.
+	 * @param allowWrite whether to allow write operations on a target instance
+	 * @since 6.2
+	 * @see #canWrite
+	 */
+	public CompilableMapAccessor(boolean allowWrite) {
+		this.allowWrite = allowWrite;
+	}
+
 	@Override
 	public Class<?>[] getSpecificTargetClasses() {
 		return new Class<?>[] {Map.class};
@@ -57,7 +78,7 @@ class CompilableMapAccessor implements CompilablePropertyAccessor {
 
 	@Override
 	public boolean canWrite(EvaluationContext context, @Nullable Object target, String name) throws AccessException {
-		return true;
+		return (this.allowWrite && target instanceof Map);
 	}
 
 	@Override
@@ -65,7 +86,7 @@ class CompilableMapAccessor implements CompilablePropertyAccessor {
 	public void write(EvaluationContext context, @Nullable Object target, String name, @Nullable Object newValue)
 			throws AccessException {
 
-		Assert.state(target instanceof Map, "Target must be a Map");
+		Assert.state(target instanceof Map, "Target must be of type Map");
 		Map<Object, Object> map = (Map<Object, Object>) target;
 		map.put(name, newValue);
 	}