codeconsole commented on code in PR #15732:
URL: https://github.com/apache/grails-core/pull/15732#discussion_r3416488630
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grails-web-core/src/main/groovy/org/grails/web/servlet/HttpServletRequestExtension.groovy:
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@@ -251,4 +252,26 @@ class HttpServletRequestExtension {
static Date date(HttpServletRequest request, String name,
Collection<String> formats) {
TypeConverters.toDate(request.getAttribute(name), formats)
}
+ /**
+ * Null-safe, typed read of an attribute. Returns the attribute when it is
an
+ * instance of {@code type}; otherwise {@code null}. No coercion is
attempted —
+ * use the named converters ({@code string}, {@code int}, ...) for type
conversion.
+ */
+ static <T> T getAttribute(HttpServletRequest request, String name,
Class<T> type) {
+ if (type == null) {
+ throw new IllegalArgumentException('type must not be null - use
getAttribute(name) for an untyped read')
+ }
+ Object value = request.getAttribute(name)
+ Class<T> resolvedType = (Class<T>)
ClassUtils.resolvePrimitiveIfNecessary(type)
+ resolvedType.isInstance(value) ? resolvedType.cast(value) : null
Review Comment:
Proxies are fine with `isInstance` — added a test covering both mechanisms:
a JDK dynamic proxy (its runtime-generated class implements the interface, so
`isInstance(interface)` is true) and a subclass (the relationship CGLIB /
ByteBuddy / Hibernate-lazy proxies use — `isInstance` walks the class hierarchy
the same way whether the subclass is generated at runtime or declared). Both
resolve; a wrong-type request still reads as `null` rather than an unsafe cast.
`value.class.isAssignableFrom(type)` would actually break the proxy case — a
proxy's class is a *subtype* of the proxied type, so it returns false even when
the value is a valid instance.
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