Add a new method to identify the invoked API

modules/core/src/main/java/org/apache/synapse/api/API.java

@@ -246,6 +246,10 @@ public Resource[] getResources() {
         return resources.values().toArray(new Resource[resources.size()]);
     }
 
+    public Map<String, Resource> getResourcesMap() {
+        return resources;
+    }
+
     public void addHandler(Handler handler) {
         handlers.add(handler);
     }
@@ -443,12 +447,7 @@ public void process(MessageContext synCtx) {
                     msgCtx.getIncomingTransportName() + "://" + hostHeader);
         }
 
-        Set<Resource> acceptableResources = new LinkedHashSet<Resource>();
-        for (Resource r : resources.values()) {
-            if (isBound(r, synCtx) && r.canProcess(synCtx)) {
-                acceptableResources.add(r);
-            }
-        }
+        Set<Resource> acceptableResources = ApiUtils.getAcceptableResources(resources, synCtx);
 
         boolean processed = false;
         if (!acceptableResources.isEmpty()) {
@@ -530,23 +529,6 @@ private void handleMethodNotAllowed(MessageContext synCtx) {
 
     }
 
-    /**
-     * Checks whether the provided resource is capable of processing the message from the provided message context.
-     * The resource becomes capable to do this when the it contains either the name of the api caller,
-     * or {@value ApiConstants#DEFAULT_BINDING_ENDPOINT_NAME}, in its binds-to.
-     *
-     * @param resource  Resource object
-     * @param synCtx    MessageContext object
-     * @return          Whether the provided resource is bound to the provided message context
-     */
-    private boolean isBound(Resource resource, MessageContext synCtx) {
-        Collection<String> bindings = resource.getBindsTo();
-        Object apiCaller = synCtx.getProperty(ApiConstants.API_CALLER);
-        if (apiCaller != null) {
-            return bindings.contains(apiCaller.toString());
-        }
-        return bindings.contains(ApiConstants.DEFAULT_BINDING_ENDPOINT_NAME);
-    }
 
     /**
      * Helper method to use when no matching resource found

modules/core/src/main/java/org/apache/synapse/api/ApiUtils.java

@@ -25,6 +25,9 @@
 import org.apache.synapse.MessageContext;
 import org.apache.synapse.SynapseConstants;
 import org.apache.synapse.SynapseException;
+import org.apache.synapse.api.version.ContextVersionStrategy;
+import org.apache.synapse.api.version.DefaultStrategy;
+import org.apache.synapse.api.version.URLBasedVersionStrategy;
 import org.apache.synapse.core.axis2.Axis2MessageContext;
 import org.apache.synapse.rest.RESTConstants;
 import org.apache.synapse.api.dispatch.DefaultDispatcher;
@@ -40,7 +43,11 @@
 import java.net.URL;
 import java.net.URLDecoder;
 import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Map;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Set;
 
 public class ApiUtils {
 
@@ -158,6 +165,89 @@ public static String getSubRequestPath(MessageContext synCtx) {
         return (String) synCtx.getProperty(RESTConstants.REST_SUB_REQUEST_PATH);
     }
 
+    /**
+     * Checks whether the provided resource is capable of processing the message from the provided message context.
+     * The resource becomes capable to do this when the it contains either the name of the api caller,
+     * or {@value ApiConstants#DEFAULT_BINDING_ENDPOINT_NAME}, in its binds-to.
+     *
+     * @param resource  Resource object
+     * @param synCtx    MessageContext object
+     * @return          Whether the provided resource is bound to the provided message context
+     */
+    public static boolean isBound(Resource resource, MessageContext synCtx) {
+        Collection<String> bindings = resource.getBindsTo();
+        Object apiCaller = synCtx.getProperty(ApiConstants.API_CALLER);
+        if (apiCaller != null) {
+            return bindings.contains(apiCaller.toString());
+        }
+        return bindings.contains(ApiConstants.DEFAULT_BINDING_ENDPOINT_NAME);
+    }
+
+    public static Set<Resource> getAcceptableResources(Map<String, Resource> resources, MessageContext synCtx) {
+        Set<Resource> acceptableResources = new LinkedHashSet<Resource>();
+        for (Resource r : resources.values()) {
+            if (isBound(r, synCtx) && r.canProcess(synCtx)) {
+                acceptableResources.add(r);
+            }
+        }
+        return acceptableResources;
+    }
+
+    public static API getSelectedAPI(MessageContext synCtx) {
+        API selectedApi;
+        //getting the API collection from the synapse configuration to find the invoked API
+        Collection<API> apiSet = synCtx.getEnvironment().getSynapseConfiguration().getAPIs();
+        //Since swapping elements are not possible with sets, Collection is converted to a List
+        List<API> defaultStrategyApiSet = new ArrayList<API>(apiSet);
+        //To avoid apiSet being modified concurrently
+        List<API> duplicateApiSet = new ArrayList<>(apiSet);
+        //identiy the api using canProcess method
+        for (API api : duplicateApiSet) {
+            if (identifySelectedAPI(api, synCtx, defaultStrategyApiSet)) {
+                selectedApi = api;
+                return selectedApi;
+            }
+        }
+        for (API api : defaultStrategyApiSet) {
+            api.setLogSetterValue();
+            if (api.canProcess(synCtx)) {
+                if (log.isDebugEnabled()) {
+                    log.debug("Located specific API: " + api.getName() + " for processing message");
+                }
+                selectedApi = api;
+                return selectedApi;
+            }
+        }
+        return null;
+    }
+
+    public static boolean identifySelectedAPI(API api, MessageContext synCtx, List defaultStrategyApiSet) {
+        API defaultAPI = null;
+        api.setLogSetterValue();
+        if ("/".equals(api.getContext())) {
+            defaultAPI = api;
+        } else if (api.getVersionStrategy().getClass().getName().equals(DefaultStrategy.class.getName())) {
+            //APIs whose VersionStrategy is bound to an instance of DefaultStrategy, should be skipped and processed at
+            // last.Otherwise they will be always chosen to process the request without matching the version.
+            defaultStrategyApiSet.add(api);
+        } else if (api.getVersionStrategy().getClass().getName().equals(ContextVersionStrategy.class.getName())
+                || api.getVersionStrategy().getClass().getName().equals(URLBasedVersionStrategy.class.getName())) {
+            api.setLogSetterValue();
+            if (api.canProcess(synCtx)) {
+                if (log.isDebugEnabled()) {
+                    log.debug("Located specific API: " + api.getName() + " for processing message");
+                }
+                return true;
+            }
+        } else if (api.canProcess(synCtx)) {
+            if (log.isDebugEnabled()) {
+                log.debug("Located specific API: " + api.getName() + " for processing message");
+            }
+            return true;
+        }
+        return false;
+    }
+
     public static List<RESTDispatcher> getDispatchers() {
         return dispatchers;
     }
@@ -177,10 +267,10 @@ private static void handleException(String msg, Throwable t) {
      * and false if the two values don't match
      */
     public static boolean matchApiPath(String path, String context) {
-        if (!path.startsWith(context + "/") && !path.startsWith(context + "?") &&
-                !context.equals(path) && !"/".equals(context)) {
+        if (!path.startsWith(context + "/") && !path.startsWith(context + "?")
+                && !context.equals(path) && !"/".equals(context)) {
             return false;
         }
         return true;
     }
-}
+}

modules/core/src/main/java/org/apache/synapse/api/dispatch/DefaultDispatcher.java

@@ -20,6 +20,7 @@
 
 import org.apache.synapse.MessageContext;
 import org.apache.synapse.api.Resource;
+import org.apache.synapse.rest.RESTConstants;
 
 import java.util.Collection;
 
@@ -28,6 +29,7 @@ public class DefaultDispatcher implements RESTDispatcher {
     public Resource findResource(MessageContext synCtx, Collection<Resource> resources) {
         for (Resource resource : resources) {
             if (resource.getDispatcherHelper() == null) {
+                synCtx.setProperty(RESTConstants.SELECTED_RESOURCE, resource);
                 return resource;
             }
         }

modules/core/src/main/java/org/apache/synapse/api/dispatch/URITemplateBasedDispatcher.java

@@ -35,12 +35,13 @@ public Resource findResource(MessageContext synCtx, Collection<Resource> resourc
             DispatcherHelper helper = r.getDispatcherHelper();
             if (helper instanceof URITemplateHelper) {
                 URITemplateHelper templateHelper = (URITemplateHelper) helper;
-                Map<String,String> variables = new HashMap<String,String>();
+                Map<String, String> variables = new HashMap<String, String>();
                 if (templateHelper.getUriTemplate().matches(url, variables)) {
-                    for (Map.Entry<String,String> entry : variables.entrySet()) {
+                    for (Map.Entry<String, String> entry : variables.entrySet()) {
                         synCtx.setProperty(RESTConstants.REST_URI_VARIABLE_PREFIX + entry.getKey(),
                                 entry.getValue());
                     }
+                    synCtx.setProperty(RESTConstants.SELECTED_RESOURCE, r);
                     return r;
                 }
             }

modules/core/src/main/java/org/apache/synapse/api/dispatch/URLMappingBasedDispatcher.java

@@ -23,6 +23,7 @@
 import org.apache.synapse.MessageContext;
 import org.apache.synapse.api.ApiUtils;
 import org.apache.synapse.api.Resource;
+import org.apache.synapse.rest.RESTConstants;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -55,6 +56,7 @@ public Resource findResource(MessageContext synCtx, Collection<Resource> resourc
                 if (log.isDebugEnabled()) {
                     log.debug("Found exact URL match for: " + url);
                 }
+                synCtx.setProperty(RESTConstants.SELECTED_RESOURCE, filteredResources.get(i));
                 return filteredResources.get(i);
             }
         }
@@ -72,6 +74,7 @@ public Resource findResource(MessageContext synCtx, Collection<Resource> resourc
             if (log.isDebugEnabled()) {
                 log.debug("Found path match for: " + url + " with matching length: " + maxLength);
             }
+            synCtx.setProperty(RESTConstants.SELECTED_RESOURCE, matchedResource);
             return matchedResource;
         }
 
@@ -80,6 +83,7 @@ public Resource findResource(MessageContext synCtx, Collection<Resource> resourc
                 if (log.isDebugEnabled()) {
                     log.debug("Found extension match for: " + url);
                 }
+                synCtx.setProperty(RESTConstants.SELECTED_RESOURCE, filteredResources.get(i));
                 return filteredResources.get(i);
             }
         }

modules/core/src/main/java/org/apache/synapse/rest/RESTConstants.java

@@ -91,5 +91,6 @@ public static enum METHODS {
      */
     public static final String IS_PROMETHEUS_ENGAGED = "IS_PROMETHEUS_ENGAGED";
     public static final String PROCESSED_API = "PROCESSED_API";
+    public static final String SELECTED_RESOURCE = "SELECTED_RESOURCE";
 
 }