WW-2963 default-action-ref fails to find wildcard named actions

core/src/main/java/org/apache/struts2/config/impl/DefaultConfiguration.java

@@ -609,26 +609,39 @@ private boolean shouldFallbackToEmptyNamespace(String namespace) {
         }
 
         private ActionConfig findActionConfigInNamespace(String namespace, String name) {
-            ActionConfig config = null;
             if (namespace == null) {
                 namespace = "";
             }
             Map<String, ActionConfig> actions = namespaceActionConfigs.get(namespace);
-            if (actions != null) {
-                config = actions.get(name);
-                // Check wildcards
-                if (config == null) {
-                    config = namespaceActionConfigMatchers.get(namespace).match(name);
-                    // fail over to default action
-                    if (config == null) {
-                        String defaultActionRef = namespaceConfigs.get(namespace);
-                        if (defaultActionRef != null) {
-                            config = actions.get(defaultActionRef);
-                        }
-                    }
-                }
+            if (actions == null) {
+                return null;
             }
-            return config;
+
+            ActionConfig config = actions.get(name);
+            if (config != null) {
+                return config;
+            }
+
+            config = namespaceActionConfigMatchers.get(namespace).match(name);
+            if (config != null) {
+                return config;
+            }
+
+            return findDefaultActionConfig(namespace, actions);
+        }
+
+        private ActionConfig findDefaultActionConfig(String namespace, Map<String, ActionConfig> actions) {
+            String defaultActionRef = namespaceConfigs.get(namespace);
+            if (defaultActionRef == null) {
+                return null;
+            }
+
+            ActionConfig config = actions.get(defaultActionRef);
+            if (config != null) {
+                return config;
+            }
+
+            return namespaceActionConfigMatchers.get(namespace).match(defaultActionRef);
         }
 
         /**

core/src/test/java/org/apache/struts2/config/ConfigurationTest.java

@@ -337,6 +337,38 @@ public void testPackageExtension() {
     }
 
 
+    public void testDefaultActionRefWithWildcard() {
+        RuntimeConfiguration configuration = configurationManager.getConfiguration().getRuntimeConfiguration();
+
+        // "unknown-action" doesn't exist in /wildcard-default, so default-action-ref "movie-input" should be used
+        // "movie-input" matches wildcard "movie-*", so it should resolve via wildcard matching
+        ActionConfig config = configuration.getActionConfig("/wildcard-default", "unknown-action");
+
+        assertNotNull("Default action ref should resolve via wildcard matching", config);
+        assertEquals("org.apache.struts2.SimpleAction", config.getClassName());
+        assertEquals("input", config.getMethodName());
+    }
+
+    public void testDefaultActionRefWithExactMatch() {
+        RuntimeConfiguration configuration = configurationManager.getConfiguration().getRuntimeConfiguration();
+
+        // default-action-ref "home" matches an exact action, so it should resolve without wildcard matching
+        ActionConfig config = configuration.getActionConfig("/exact-default", "unknown-action");
+
+        assertNotNull("Default action ref should resolve via exact match", config);
+        assertEquals("org.apache.struts2.SimpleAction", config.getClassName());
+        assertEquals("execute", config.getMethodName());
+    }
+
+    public void testDefaultActionRefWithWildcardNoMatch() {
+        RuntimeConfiguration configuration = configurationManager.getConfiguration().getRuntimeConfiguration();
+
+        // default-action-ref "no-match-anywhere" matches neither an exact action nor wildcard "movie-*"
+        ActionConfig config = configuration.getActionConfig("/wildcard-default-nomatch", "unknown-action");
+
+        assertNull("Should return null when default-action-ref matches neither exact nor wildcard", config);
+    }
+
     @Override
     protected void setUp() throws Exception {
         super.setUp();

core/src/test/resources/xwork-sample.xml

@@ -304,5 +304,26 @@
         <!--  default-class-ref is expected to be inherited -->
     </package>
 
+    <package name="wildcardDefault" extends="default" namespace="/wildcard-default">
+        <default-action-ref name="movie-input"/>
+        <action name="movie-*" class="org.apache.struts2.SimpleAction" method="{1}">
+            <result name="success" type="mock"/>
+        </action>
+    </package>
+
+    <package name="exactDefault" extends="default" namespace="/exact-default">
+        <default-action-ref name="home"/>
+        <action name="home" class="org.apache.struts2.SimpleAction" method="execute">
+            <result name="success" type="mock"/>
+        </action>
+    </package>
+
+    <package name="wildcardDefaultNoMatch" extends="default" namespace="/wildcard-default-nomatch">
+        <default-action-ref name="no-match-anywhere"/>
+        <action name="movie-*" class="org.apache.struts2.SimpleAction" method="{1}">
+            <result name="success" type="mock"/>
+        </action>
+    </package>
+
     <include file="includeTest.xml"/>
 </struts>

thoughts/shared/research/2026-03-06-WW-2963-default-action-ref-wildcard-fallback.md

@@ -0,0 +1,138 @@
+---
+date: 2026-03-06T12:00:00+01:00
+topic: "default-action-ref fails to find wildcard named actions"
+tags: [research, codebase, default-action-ref, wildcard, action-mapping, DefaultConfiguration]
+status: complete
+---
+
+# Research: WW-2963 — default-action-ref fails to find wildcard named actions
+
+**Date**: 2026-03-06
+**Ticket**: [WW-2963](https://issues.apache.org/jira/browse/WW-2963)
+
+## Research Question
+
+When `<default-action-ref name="movie-list"/>` is configured and the only matching action uses a wildcard pattern `<action name="movie-*" ...>`, Struts returns a 404 instead of resolving the default action through wildcard matching.
+
+## Summary
+
+The bug is in `DefaultConfiguration.RuntimeConfigurationImpl.findActionConfigInNamespace()`. When the default-action-ref fallback triggers (step 3 of the resolution chain), it only performs an **exact map lookup** (`actions.get(defaultActionRef)`) for the default action name. It does NOT attempt wildcard matching. This means if the default action name (e.g., "movie-list") is only matchable via a wildcard pattern (e.g., "movie-*"), the lookup returns `null` and the request fails with a 404.
+
+The fix is to also try the wildcard matcher when the exact lookup for the default action ref fails.
+
+## Detailed Findings
+
+### Action Resolution Order (within a namespace)
+
+In [`DefaultConfiguration.java:611-632`](https://github.com/apache/struts/blob/4c94c4f89a15b3102c3822dfc64dca15ee42a731/core/src/main/java/org/apache/struts2/config/impl/DefaultConfiguration.java#L611-L632):
+
+```java
+private ActionConfig findActionConfigInNamespace(String namespace, String name) {
+    ActionConfig config = null;
+    if (namespace == null) {
+        namespace = "";
+    }
+    Map<String, ActionConfig> actions = namespaceActionConfigs.get(namespace);
+    if (actions != null) {
+        config = actions.get(name);                                    // 1. Exact match
+        if (config == null) {
+            config = namespaceActionConfigMatchers.get(namespace).match(name);  // 2. Wildcard match
+            if (config == null) {
+                String defaultActionRef = namespaceConfigs.get(namespace);
+                if (defaultActionRef != null) {
+                    config = actions.get(defaultActionRef);            // 3. Default (EXACT ONLY — BUG)
+                }
+            }
+        }
+    }
+    return config;
+}
+```
+
+Steps 1 and 2 correctly try exact then wildcard matching for the **incoming request name**. But step 3 (the default-action-ref fallback) only does `actions.get(defaultActionRef)` — an exact map lookup. It never tries wildcard matching for the default action name.
+
+### The Bug Scenario
+
+Configuration:
+```xml
+<package name="default" namespace="/" extends="struts-default">
+    <default-action-ref name="movie-list"/>
+    <action name="movie-*" class="MovieAction" method="{1}"/>
+</package>
+```
+
+When a request hits an unknown action in namespace `/`:
+1. `actions.get("unknownAction")` → `null` (no exact match)
+2. `namespaceActionConfigMatchers.get("/").match("unknownAction")` → `null` (doesn't match `movie-*`)
+3. `defaultActionRef` = `"movie-list"` from `namespaceConfigs`
+4. `actions.get("movie-list")` → `null` ← **BUG**: "movie-list" is not a key in the actions map; it's only matchable via the wildcard pattern "movie-*"
+5. Result: `null` → 404
+
+### The Fix
+
+After the exact lookup fails for the default action ref, also try the wildcard matcher:
+
+```java
+if (config == null) {
+    String defaultActionRef = namespaceConfigs.get(namespace);
+    if (defaultActionRef != null) {
+        config = actions.get(defaultActionRef);
+        if (config == null) {
+            config = namespaceActionConfigMatchers.get(namespace).match(defaultActionRef);
+        }
+    }
+}
+```
+
+This adds one line: try `namespaceActionConfigMatchers.get(namespace).match(defaultActionRef)` when `actions.get(defaultActionRef)` returns null, mirroring the same exact→wildcard fallback pattern already used for the request name.
+
+### How `actions` Map Is Built
+
+In [`DefaultConfiguration.java:440-478`](https://github.com/apache/struts/blob/4c94c4f89a15b3102c3822dfc64dca15ee42a731/core/src/main/java/org/apache/struts2/config/impl/DefaultConfiguration.java#L440-L478), `buildRuntimeConfiguration()` iterates all `PackageConfig` instances and populates:
+
+- `namespaceActionConfigs`: `Map<String, Map<String, ActionConfig>>` — namespace → (action pattern name → ActionConfig). Keys are the literal declared names (e.g., `"movie-*"`), NOT expanded names.
+- `namespaceConfigs`: `Map<String, String>` — namespace → default action ref name (e.g., `"movie-list"`).
+
+The `ActionConfigMatcher` is then built from the action names in each namespace, compiling only non-literal (wildcard-containing) names into patterns.
+
+### How Wildcard Matching Works
+
+The matching chain is:
+1. `ActionConfigMatcher.match(name)` → inherited from `AbstractMatcher.match()` ([`AbstractMatcher.java:131-148`](https://github.com/apache/struts/blob/4c94c4f89a15b3102c3822dfc64dca15ee42a731/core/src/main/java/org/apache/struts2/config/impl/AbstractMatcher.java#L131-L148))
+2. Uses `WildcardHelper.match()` (default `PatternMatcher` impl) to match the input against compiled patterns
+3. On match, `ActionConfigMatcher.convert()` clones the `ActionConfig` substituting `{1}`, `{2}`, etc. with captured groups
+
+### Key Classes
+
+| Concern | Class | File |
+|---|---|---|
+| Resolution order (exact→wildcard→default) | `RuntimeConfigurationImpl` | [`DefaultConfiguration.java:611-632`](https://github.com/apache/struts/blob/4c94c4f89a15b3102c3822dfc64dca15ee42a731/core/src/main/java/org/apache/struts2/config/impl/DefaultConfiguration.java#L611-L632) |
+| Runtime config build | `DefaultConfiguration` | [`DefaultConfiguration.java:440-478`](https://github.com/apache/struts/blob/4c94c4f89a15b3102c3822dfc64dca15ee42a731/core/src/main/java/org/apache/struts2/config/impl/DefaultConfiguration.java#L440-L478) |
+| Wildcard pattern storage/matching | `AbstractMatcher` | [`AbstractMatcher.java:95-148`](https://github.com/apache/struts/blob/4c94c4f89a15b3102c3822dfc64dca15ee42a731/core/src/main/java/org/apache/struts2/config/impl/AbstractMatcher.java#L95-L148) |
+| ActionConfig wildcard cloning | `ActionConfigMatcher` | [`ActionConfigMatcher.java:58-152`](https://github.com/apache/struts/blob/4c94c4f89a15b3102c3822dfc64dca15ee42a731/core/src/main/java/org/apache/struts2/config/impl/ActionConfigMatcher.java#L58-L152) |
+| Default `*`/`**` matcher | `WildcardHelper` | [`WildcardHelper.java`](https://github.com/apache/struts/blob/4c94c4f89a15b3102c3822dfc64dca15ee42a731/core/src/main/java/org/apache/struts2/util/WildcardHelper.java) |
+| PackageConfig default-action-ref storage | `PackageConfig` | [`PackageConfig.java:52, 262-273`](https://github.com/apache/struts/blob/4c94c4f89a15b3102c3822dfc64dca15ee42a731/core/src/main/java/org/apache/struts2/config/entities/PackageConfig.java#L262-L273) |
+| XML parsing of default-action-ref | `XmlDocConfigurationProvider` | [`XmlDocConfigurationProvider.java:833-840`](https://github.com/apache/struts/blob/4c94c4f89a15b3102c3822dfc64dca15ee42a731/core/src/main/java/org/apache/struts2/config/providers/XmlDocConfigurationProvider.java#L833-L840) |
+
+## Code References
+
+- `core/src/main/java/org/apache/struts2/config/impl/DefaultConfiguration.java:626` — The buggy line: `config = actions.get(defaultActionRef)` without wildcard fallback
+- `core/src/main/java/org/apache/struts2/config/impl/DefaultConfiguration.java:621` — How wildcard matching IS correctly done for the request name (just above the buggy code)
+- `core/src/main/java/org/apache/struts2/config/impl/DefaultConfiguration.java:440-478` — `buildRuntimeConfiguration()` where action maps and default refs are built
+
+## Existing Test Coverage
+
+- **No tests exist** for WW-2963 or the combination of default-action-ref with wildcard actions
+- Wildcard tests exist in `ConfigurationTest.java:91-116` (testWildcardName, testWildcardNamespace)
+- Default-action-ref is used in production XML (showcase, tiles, etc.) but never tested with wildcards
+- Best place to add a test: `ConfigurationTest.java` or a new test using a dedicated test XML config
+
+## Architecture Insights
+
+The resolution chain (exact → wildcard → default) was designed so that default-action-ref is a last resort. However, the implementation assumed the default action ref name would always correspond to a literally-declared action. The fix is minimal and consistent with the existing pattern — just add a wildcard match attempt for the default action ref name, the same way it's already done for the request name.
+
+## Open Questions
+
+1. Should there be a validation at configuration load time that warns if `default-action-ref` doesn't resolve to any action (neither exact nor wildcard)?
+2. Should the wildcard-matched default action also support `{1}` substitution (e.g., "movie-list" matching "movie-*" with `{1}` = "list")? The current `ActionConfigMatcher.convert()` already handles this.
+3. Does the same issue exist in the namespace-level wildcard fallback at `getActionConfig()` lines 581-605? (Likely no — namespace matching uses `NamespaceMatcher` which already does wildcard matching.)