core: improve expression definition to ease the integration with DSLs

core/camel-core-model/src/main/java/org/apache/camel/model/ExpressionSubElementDefinition.java

@@ -30,13 +30,17 @@
  */
 @XmlRootElement(name = "expression") // must be named expression
 @XmlAccessorType(XmlAccessType.FIELD)
-public class ExpressionSubElementDefinition {
+public class ExpressionSubElementDefinition implements HasExpressionType {
     @XmlElementRef
     private ExpressionDefinition expressionType;
 
     public ExpressionSubElementDefinition() {
     }
 
+    public ExpressionSubElementDefinition(ExpressionDefinition expressionType) {
+        this.expressionType = expressionType;
+    }
+
     public ExpressionSubElementDefinition(Expression expression) {
         this.expressionType = new ExpressionDefinition(expression);
     }
@@ -45,10 +49,12 @@ public ExpressionSubElementDefinition(Predicate predicate) {
         this.expressionType = new ExpressionDefinition(predicate);
     }
 
+    @Override
     public ExpressionDefinition getExpressionType() {
         return expressionType;
     }
 
+    @Override
     public void setExpressionType(ExpressionDefinition expressionType) {
         this.expressionType = expressionType;
     }

core/camel-core-model/src/main/java/org/apache/camel/model/HasExpressionType.java

@@ -0,0 +1,29 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.apache.camel.model;
+
+import org.apache.camel.model.language.ExpressionDefinition;
+
+/**
+ * Marker interface to mark a {@link ProcessorDefinition} that supports expressions.
+ */
+public interface HasExpressionType {
+
+    ExpressionDefinition getExpressionType();
+
+    void setExpressionType(ExpressionDefinition expressionType);
+}

core/camel-core-model/src/main/java/org/apache/camel/model/language/ExpressionDefinition.java

@@ -34,6 +34,7 @@
 import org.apache.camel.ExpressionFactory;
 import org.apache.camel.Predicate;
 import org.apache.camel.PredicateFactory;
+import org.apache.camel.model.HasExpressionType;
 import org.apache.camel.model.ModelCamelContext;
 import org.apache.camel.spi.ExpressionFactoryAware;
 import org.apache.camel.spi.Metadata;
@@ -49,7 +50,8 @@
 @XmlAccessorType(XmlAccessType.FIELD)
 @SuppressWarnings("rawtypes")
 public class ExpressionDefinition
-        implements Expression, Predicate, ExpressionFactory, ExpressionFactoryAware, PredicateFactory, PredicateFactoryAware {
+        implements Expression, Predicate, ExpressionFactory, ExpressionFactoryAware, PredicateFactory, PredicateFactoryAware,
+        HasExpressionType {
     @XmlAttribute
     @XmlID
     private String id;
@@ -149,10 +151,20 @@ protected void setExpressionValue(Expression expressionValue) {
         this.expressionValue = expressionValue;
     }
 
+    @Override
     public ExpressionDefinition getExpressionType() {
         return expressionType;
     }
 
+    /**
+     * Allows derived classes and DSLs to set a lazily created expressionType instance such as if using the
+     * {@link org.apache.camel.builder.ExpressionClause}
+     */
+    @Override
+    public void setExpressionType(ExpressionDefinition expressionType) {
+        this.expressionType = expressionType;
+    }
+
     public String getTrim() {
         return trim;
     }
@@ -181,14 +193,6 @@ public String getLabel() {
         return exp != null ? exp : "";
     }
 
-    /**
-     * Allows derived classes to set a lazily created expressionType instance such as if using the
-     * {@link org.apache.camel.builder.ExpressionClause}
-     */
-    protected void setExpressionType(ExpressionDefinition expressionType) {
-        this.expressionType = expressionType;
-    }
-
     //
     // ExpressionFactory
     //