Add new custom juel function: list (#3783)

activiti-core-common/activiti-expression-language/src/main/java/org/activiti/core/el/ELContextBuilder.java

@@ -16,6 +16,7 @@
 package org.activiti.core.el;
 
 import static org.activiti.core.el.DateResolverHelper.addDateFunctions;
+import static org.activiti.core.el.ListResolverHelper.addListFunctions;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
@@ -54,13 +55,14 @@ public class ELContextBuilder {
         return new ActivitiElContext(elResolver);
     }
 
-    public ELContext buildWithDateFunctions() {
+    public ELContext buildWithCustomFunctions() {
         CompositeELResolver elResolver = createCompositeResolver();
         ActivitiElContext elContext = new ActivitiElContext(elResolver);
         try {
             addDateFunctions(elContext);
+            addListFunctions(elContext);
         } catch (NoSuchMethodException e) {
-            logger.error("Error setting up EL date functions", e);
+            logger.error("Error setting up EL custom functions", e);
         }
         return elContext;
     }

activiti-core-common/activiti-expression-language/src/main/java/org/activiti/core/el/JuelExpressionResolver.java

@@ -58,6 +58,6 @@ public class JuelExpressionResolver implements ExpressionResolver {
                 beanResolver()
             )
             .withVariables(variables)
-            .buildWithDateFunctions();
+            .buildWithCustomFunctions();
     }
 }

activiti-core-common/activiti-expression-language/src/main/java/org/activiti/core/el/ListResolverHelper.java

+/*
+ * Copyright 2010-2020 Alfresco Software, Ltd.
+ *
+ * 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 org.activiti.core.el;
+
+import java.util.List;
+
+public class ListResolverHelper {
+
+    private static final String LIST_FUNCTION_NAME = "list";
+    private static final String LIST_INVOKE_METHOD = "list";
+
+    public static List<Object> list(Object... objects) {
+        return List.of(objects);
+    }
+
+    private ListResolverHelper() {
+    }
+
+    public static void addListFunctions(ActivitiElContext elContext) throws NoSuchMethodException {
+        elContext.setFunction("", LIST_FUNCTION_NAME, ListResolverHelper.class.getMethod(LIST_INVOKE_METHOD, Object[].class));
+    }
+}

activiti-core-common/activiti-expression-language/src/test/java/org/activiti/core/el/JuelResolverTest.java

@@ -21,6 +21,7 @@ import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.notNullValue;
 import java.util.Collections;
 import java.util.Date;
+import java.util.List;
 import java.util.Map;
 import javax.el.ELException;
 import javax.el.PropertyNotFoundException;
@@ -121,4 +122,17 @@ public class JuelResolverTest {
             .isThrownBy(() -> expressionResolver.resolveExpression(expressionString, Collections.emptyMap(), Date.class))
             .withMessage("Could not resolve function 'current'");
     }
+
+    @Test
+    public void should_returnList_when_expressionIsListFunction() {
+        //given
+        String expressionString = "${list(1,'item',3)}";
+        ExpressionResolver expressionResolver = new JuelExpressionResolver();
+
+        //when
+        List result = expressionResolver.resolveExpression(expressionString, Collections.emptyMap(), List.class);
+
+        //then
+        assertThat(result).contains(1l, "item", 3l);
+    }
 }

activiti-core/activiti-engine/src/main/java/org/activiti/engine/impl/el/ExpressionManager.java

@@ -108,7 +108,7 @@ public class ExpressionManager {
     }
 
     protected ActivitiElContext createElContext(VariableScope variableScope) {
-        return (ActivitiElContext) new ELContextBuilder().withResolvers(createElResolver(variableScope)).buildWithDateFunctions();
+        return (ActivitiElContext) new ELContextBuilder().withResolvers(createElResolver(variableScope)).buildWithCustomFunctions();
     }
 
     protected ELResolver createElResolver(VariableScope variableScope) {
@@ -150,6 +150,6 @@ public class ExpressionManager {
     public ELContext getElContext(Map<String, Object> availableVariables) {
         CompositeELResolver elResolver = new CompositeELResolver();
         addBaseResolvers(elResolver);
-        return new ELContextBuilder().withResolvers(elResolver).withVariables(availableVariables).buildWithDateFunctions();
+        return new ELContextBuilder().withResolvers(elResolver).withVariables(availableVariables).buildWithCustomFunctions();
     }
 }