Add new variable mediator

modules/core/src/main/java/org/apache/synapse/MessageContext.java

@@ -457,4 +457,27 @@ public interface MessageContext {
      * @param tracingState Set whether the message flowtracing is enabled or not
      */
     public void setMessageFlowTracingState(int tracingState);
+
+    /**
+     * Get the value of a variable on the message instance
+     *
+     * @param key key to look up variable
+     * @return value for the given key
+     */
+    public Object getVariable(String key);
+
+    /**
+     * Set a variable with the given name on the message instance
+     *
+     * @param key   key to be used
+     * @param value value to be saved
+     */
+    public void setVariable(String key, Object value);
+
+    /**
+     * Returns the Set of keys over the variables on this message context
+     *
+     * @return a Set of keys over message variables
+     */
+    public Set getVariableKeySet();
 }

modules/core/src/main/java/org/apache/synapse/config/xml/AbstractMediatorFactory.java

@@ -65,6 +65,8 @@ public abstract class AbstractMediatorFactory implements MediatorFactory {
         = new QName(XMLConfigConstants.STATISTICS_ATTRIB_NAME);
     protected static final QName PROP_Q
         = new QName(XMLConfigConstants.SYNAPSE_NAMESPACE, "property");
+    protected static final QName VARIABLE_Q
+            = new QName(XMLConfigConstants.SYNAPSE_NAMESPACE, "variable");
     protected static final QName PROPERTY_GROUP_Q
             = new QName(XMLConfigConstants.SYNAPSE_NAMESPACE, "propertyGroup");
     protected static final QName FEATURE_Q

modules/core/src/main/java/org/apache/synapse/config/xml/MediatorFactoryFinder.java

@@ -102,7 +102,8 @@ public class MediatorFactoryFinder implements XMLToObjectMapper {
             CommentMediatorFactory.class,
             ForEachMediatorFactory.class,
             JSONTransformMediatorFactory.class,
-            NTLMMediatorFactory.class
+            NTLMMediatorFactory.class,
+            VariableMediatorFactory.class
     };
 
     private final static MediatorFactoryFinder instance  = new MediatorFactoryFinder();

modules/core/src/main/java/org/apache/synapse/config/xml/MediatorSerializerFinder.java

@@ -76,7 +76,8 @@ public class MediatorSerializerFinder {
             CommentMediatorSerializer.class,
             ForEachMediatorSerializer.class,
             JSONTransformMediatorSerializer.class,
-            NTLMMediatorSerializer.class
+            NTLMMediatorSerializer.class,
+            VariableMediatorSerializer.class
     };
 
     private final static MediatorSerializerFinder instance = new MediatorSerializerFinder();

modules/core/src/main/java/org/apache/synapse/config/xml/VariableMediatorFactory.java

@@ -0,0 +1,95 @@
+/*
+ *  Copyright (c) 2024, WSO2 LLC. (http://www.wso2.org) All Rights Reserved.
+ *
+ *  WSO2 LLC. 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.synapse.config.xml;
+
+import org.apache.axiom.om.OMAttribute;
+import org.apache.axiom.om.OMElement;
+import org.apache.synapse.Mediator;
+import org.apache.synapse.SynapseException;
+import org.apache.synapse.mediators.v2.VariableMediator;
+import org.jaxen.JaxenException;
+
+import java.util.Properties;
+import javax.xml.namespace.QName;
+
+/**
+ * Creates a variable mediator through the supplied XML configuration
+ * <p/>
+ * <pre>
+ * &lt;variable name="string" [action=set/remove] (value="literal" | expression="expression") type="string|integer|JSON"/&gt;
+ * </pre>
+ */
+public class VariableMediatorFactory extends AbstractMediatorFactory {
+
+    private static final QName ATT_ACTION = new QName("action");
+    private static final QName ATT_TYPE = new QName("type");
+
+    public Mediator createSpecificMediator(OMElement elem, Properties properties) {
+
+        VariableMediator variableMediator = new VariableMediator();
+        OMAttribute name = elem.getAttribute(ATT_NAME);
+        OMAttribute value = elem.getAttribute(ATT_VALUE);
+        OMAttribute expression = elem.getAttribute(ATT_EXPRN);
+        OMAttribute action = elem.getAttribute(ATT_ACTION);
+        OMAttribute type = elem.getAttribute(ATT_TYPE);
+
+        if (name == null || name.getAttributeValue().isEmpty()) {
+            String msg = "The 'name' attribute is required for the configuration of a variable mediator";
+            log.error(msg);
+            throw new SynapseException(msg);
+        } else if ((value == null && expression == null) &&
+                !(action != null && "remove".equals(action.getAttributeValue()))) {
+            String msg = "'value' or 'expression' attributes is required for a variable mediator when action is SET";
+            log.error(msg);
+            throw new SynapseException(msg);
+        }
+        variableMediator.setName(name.getAttributeValue());
+
+        String dataType = null;
+        if (type != null) {
+            dataType = type.getAttributeValue();
+        }
+
+        if (value != null) {
+            variableMediator.setValue(value.getAttributeValue(), dataType);
+        } else if (expression != null) {
+            try {
+                variableMediator.setExpression(SynapsePathFactory.getSynapsePath(elem, ATT_EXPRN),
+                        dataType);
+            } catch (JaxenException e) {
+                String msg = "Invalid expression for attribute 'expression' : " +
+                        expression.getAttributeValue();
+                log.error(msg);
+                throw new SynapseException(msg);
+            }
+        }
+
+        if (action != null && "remove".equals(action.getAttributeValue())) {
+            variableMediator.setAction(VariableMediator.ACTION_REMOVE);
+        }
+        processAuditStatus(variableMediator, elem);
+        addAllCommentChildrenToList(elem, variableMediator.getCommentsList());
+        return variableMediator;
+    }
+
+    public QName getTagQName() {
+
+        return VARIABLE_Q;
+    }
+}

modules/core/src/main/java/org/apache/synapse/config/xml/VariableMediatorSerializer.java

@@ -0,0 +1,77 @@
+/*
+ *  Copyright (c) 2024, WSO2 LLC. (http://www.wso2.org) All Rights Reserved.
+ *
+ *  WSO2 LLC. 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.synapse.config.xml;
+
+import org.apache.axiom.om.OMElement;
+import org.apache.synapse.Mediator;
+import org.apache.synapse.mediators.v2.VariableMediator;
+
+/**
+ * <pre>
+ * &lt;variable name="string" [action=set/remove] (value="literal" | expression="expression") type="string|integer|JSON"/&gt;
+ * </pre>
+ */
+public class VariableMediatorSerializer extends AbstractMediatorSerializer {
+
+    public OMElement serializeSpecificMediator(Mediator m) {
+
+        if (!(m instanceof VariableMediator)) {
+            handleException("Unsupported mediator passed in for serialization : " + m.getType());
+        }
+
+        VariableMediator mediator = (VariableMediator) m;
+        OMElement variable = fac.createOMElement("variable", synNS);
+        saveTracingState(variable, mediator);
+
+        if (mediator.getName() != null) {
+            variable.addAttribute(fac.createOMAttribute(
+                    "name", nullNS, mediator.getName()));
+        } else {
+            handleException("Invalid variable mediator. Name is required");
+        }
+
+        if (mediator.getValue() != null) {
+            variable.addAttribute(fac.createOMAttribute(
+                    "value", nullNS, mediator.getValue().toString()));
+        } else if (mediator.getExpression() != null) {
+            SynapsePathSerializer.serializePath((SynapsePath) mediator.getExpression(),
+                    variable, "expression");
+        } else if (mediator.getAction() == VariableMediator.ACTION_SET) {
+            handleException("Invalid variable mediator. Value or expression is required if " +
+                    "action is SET");
+        }
+
+        if (mediator.getAction() == VariableMediator.ACTION_REMOVE) {
+            variable.addAttribute(fac.createOMAttribute(
+                    "action", nullNS, "remove"));
+        } else if (mediator.getType() != null) {
+            variable.addAttribute(fac.createOMAttribute(
+                    "type", nullNS, mediator.getType()));
+        }
+
+        serializeComments(variable, mediator.getCommentsList());
+
+        return variable;
+    }
+
+    public String getMediatorClassName() {
+
+        return VariableMediator.class.getName();
+    }
+}

modules/core/src/main/java/org/apache/synapse/core/axis2/Axis2MessageContext.java

@@ -68,6 +68,11 @@ public class Axis2MessageContext implements MessageContext {
      */
     private final Map<String, Object> properties = new HashMap<String, Object>();
 
+    /**
+     * Synapse Message Context variables
+     */
+    private final Map<String, Object> variables = new HashMap<>();
+
     /**
      * Local entries fetched from the configuration or from the registry for the transactional
      * resource access
@@ -725,4 +730,22 @@ public HashMap<String, Object> getAnalyticsMetadata() {
         //noinspection unchecked
         return (HashMap<String, Object>) getProperty(SynapseConstants.ANALYTICS_METADATA);
     }
+
+    @Override
+    public Object getVariable(String key) {
+        return variables.get(key);
+    }
+
+    @Override
+    public void setVariable(String key, Object value) {
+        if (value == null) {
+            return;
+        }
+        variables.put(key, value);
+    }
+
+    @Override
+    public Set getVariableKeySet() {
+        return variables.keySet();
+    }
 }