Query Params as Lists in SpEL, Groovy (#2789)

* Refactor query parameter handling: remove DuplicateKeyOrInvalidFormStrategy, update logic to support lists, and adjust affectd components and tests

* Refactor `URI` query parsing: simplify `DuplicateKeyOrInvalidFormStrategy` import, remove unused `ParamBuilder`, and clean up `TemplateInterceptorTest`.

* Refactor tests and parsing logic: update query parameter handling, remove unused tests and imports, add null checks, and improve YAML and JSON parsing.

* Remove unused `getBean` method from `GenericYamlParserTest.MockBeanRegistry`.

Author: predic8

README.md

@@ -347,7 +347,7 @@ api:
 # Requests with a query parameter city and value Paris
 api:
   port: 2000
-  test: params.city == 'Paris'
+  test: params.city?.[0] == 'Paris'
   flow:
     - response:
         - static:
@@ -676,7 +676,7 @@ api:
             contentType: application/json
             pretty: true
             src: |
-              { "answer": ${params.answer} }
+              { "answer": ${params.answer?[0]} }
     - return:
         status: 200
 ```

core/src/main/java/com/predic8/membrane/core/http/xml/URI.java

@@ -13,17 +13,15 @@
    limitations under the License. */
 package com.predic8.membrane.core.http.xml;
 
-import static com.predic8.membrane.core.util.URLParamUtil.parseQueryString;
+import com.predic8.membrane.core.config.*;
+import com.predic8.membrane.core.util.*;
 
-import java.io.UnsupportedEncodingException;
-import java.util.Map;
+import javax.xml.stream.*;
+import java.io.*;
+import java.util.*;
 
-import javax.xml.stream.XMLStreamException;
-import javax.xml.stream.XMLStreamReader;
-import javax.xml.stream.XMLStreamWriter;
-
-import com.predic8.membrane.core.config.AbstractXmlElement;
-import com.predic8.membrane.core.util.URLParamUtil;
+import static com.predic8.membrane.core.util.URLParamUtil.*;
+import static com.predic8.membrane.core.util.URLParamUtil.DuplicateKeyOrInvalidFormStrategy.MERGE_USING_COMMA;
 
 public class URI extends AbstractXmlElement {
 
@@ -85,11 +83,11 @@ public void setValue(String value) throws Exception {
 		parseQueryFromURI(jUri);
 	}
 
-	private void parseQueryFromURI(java.net.URI jUri) throws UnsupportedEncodingException {
+	private void parseQueryFromURI(java.net.URI jUri) {
 		if (jUri.getQuery() == null) return;
 
 		Query q = new Query();
-		for (Map.Entry<String, String> e : parseQueryString(jUri.getQuery(), URLParamUtil.DuplicateKeyOrInvalidFormStrategy.MERGE_USING_COMMA).entrySet()) {
+		for (Map.Entry<String, String> e : parseQueryString(jUri.getQuery(), MERGE_USING_COMMA).entrySet()) {
 			q.getParams().add(new Param(e.getKey(),e.getValue()));
 		}
 		setQuery(q);

core/src/main/java/com/predic8/membrane/core/interceptor/authentication/session/AbstractUserDataProvider.java

@@ -1,3 +1,17 @@
+/* Copyright 2026 predic8 GmbH, www.predic8.com
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License. */
+
 package com.predic8.membrane.core.interceptor.authentication.session;
 
 import com.predic8.membrane.annot.*;

core/src/main/java/com/predic8/membrane/core/interceptor/authentication/session/User.java

@@ -1,3 +1,17 @@
+/* Copyright 2026 predic8 GmbH, www.predic8.com
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License. */
+
 package com.predic8.membrane.core.interceptor.authentication.session;
 
 import java.util.*;

core/src/main/java/com/predic8/membrane/core/lang/ScriptingUtils.java

@@ -21,7 +21,6 @@
 import com.predic8.membrane.core.http.*;
 import com.predic8.membrane.core.interceptor.Interceptor.*;
 import com.predic8.membrane.core.lang.groovy.*;
-import com.predic8.membrane.core.lang.spel.spelable.*;
 import com.predic8.membrane.core.openapi.serviceproxy.*;
 import com.predic8.membrane.core.openapi.util.*;
 import com.predic8.membrane.core.router.*;
@@ -32,7 +31,6 @@
 import static com.predic8.membrane.core.interceptor.Interceptor.Flow.*;
 import static com.predic8.membrane.core.openapi.util.UriTemplateMatcher.*;
 import static com.predic8.membrane.core.util.FileUtil.*;
-import static com.predic8.membrane.core.util.URLParamUtil.DuplicateKeyOrInvalidFormStrategy.*;
 import static com.predic8.membrane.core.util.URLParamUtil.*;
 import static java.util.Collections.*;
 
@@ -68,7 +66,7 @@ public static Map<String, Object> createParameterBindings(Router router, Exchang
 
         if (flow == REQUEST) {
             try {
-                var qParams = getParams(router.getConfiguration().getUriFactory(), exc, MERGE_USING_COMMA);
+                var qParams = getParams(router.getConfiguration().getUriFactory(), exc);
                 params.put("params", qParams);
                 params.put("param", qParams);
             } catch (Exception e) {

core/src/main/java/com/predic8/membrane/core/lang/spel/SpELExchangeEvaluationContext.java

@@ -31,8 +31,7 @@
 import java.io.*;
 import java.util.*;
 
-import static com.predic8.membrane.annot.Constants.VERSION;
-import static com.predic8.membrane.core.util.URLParamUtil.DuplicateKeyOrInvalidFormStrategy.*;
+import static com.predic8.membrane.annot.Constants.*;
 
 public class SpELExchangeEvaluationContext extends StandardEvaluationContext {
 
@@ -120,7 +119,7 @@ private void extractFromRequest(Exchange exchange) {
         path = request.getUri();
         method = request.getMethod();
         try {
-            params = new SpELMap<>(URLParamUtil.getParams(new URIFactory(), exchange, ERROR));
+            params = new SpELMap<>(URLParamUtil.getParams(new URIFactory(), exchange));
         } catch (Exception e) {
             // Details are logged in URLParamUtil.getParams
             log.info("Error parsing query parameters for request '{} {}'", method, exchange.getOriginalRequestUri());

core/src/main/java/com/predic8/membrane/core/lang/spel/SpELExchangeExpression.java

@@ -29,9 +29,11 @@
 import org.springframework.expression.spel.*;
 import org.springframework.expression.spel.standard.*;
 
+import java.util.*;
+
 import static java.lang.Boolean.*;
 import static org.springframework.expression.spel.SpelCompilerMode.*;
-import static org.springframework.expression.spel.SpelMessage.METHOD_NOT_FOUND;
+import static org.springframework.expression.spel.SpelMessage.*;
 
 public class SpELExchangeExpression extends AbstractExchangeExpression {
 
@@ -77,6 +79,10 @@ public <T> T evaluate(Exchange exchange, Flow flow, Class<T> type) {
                 return type.cast(toBoolean(o));
             }
             if (String.class.isAssignableFrom(type)) {
+                // If a String is wanted and the type is List, return the first element of the list
+                if (o instanceof List<?> l && l.size() > 0) {
+                    return type.cast(l.getFirst());
+                }
                 return type.cast(toString(o));
             }
             if (Object.class.isAssignableFrom(type)) {