Changeset 28382 for main/trunk/greenstone3/src/java/org/greenstone/gsdl3/action/XMLDocumentAction.java

Timestamp:

2013-10-10T17:21:30+13:00 (11 years ago)

Author:

davidb

Message:

Elimination of the 'this.doc' field from the Action baseclass and the subclasses that rely on it. For Greenstone3 purposes it is unsafe to create this object in the constructor to the action and then store it for other methods to access. This is because the Greenstone 3 (and in particular calls to 'process' operate in a multi-threaded context, that is managed by the Servlet server (e.g. Tomcat by default). Calls to DOM methods are not guaranteed to be thread safe, this became apparent when we started looking in to an exception that was being thrown, and centred around use of the DOM method 'item(i)'. The change this commit makes is to remove 'this.doc' being stored as a field. A document is now created in the top level of a call to 'process()' and when a DOM reference is needed in a subsequent method an Element variable (typically passed in as a parameter to the method) is used (through 'Document doc = element.getOwnerDocument()') to gain access to the DOM

File:

• main/trunk/greenstone3/src/java/org/greenstone/gsdl3/action/XMLDocumentAction.java (modified) (4 diffs)

main/trunk/greenstone3/src/java/org/greenstone/gsdl3/action/XMLDocumentAction.java

@@ -28 +28 @@
     public Node process(Node message_node)
     {
-
         Element message = this.converter.nodeToElement(message_node);
-
+        Document doc = message.getOwnerDocument();
+        
         // get the request - assume there is only one
         Element request = (Element) GSXML.getChildByTagName(message, GSXML.REQUEST_ELEM);
 
         // create the return message
-        Element result = this.doc.createElement(GSXML.MESSAGE_ELEM);
-        Element page_response = this.doc.createElement(GSXML.RESPONSE_ELEM);
+        Element result = doc.createElement(GSXML.MESSAGE_ELEM);
+        Element page_response = doc.createElement(GSXML.RESPONSE_ELEM);
         result.appendChild(page_response);
 
@@ -75 +75 @@
 
         // make the request to the collection
-        Element mr_message = this.doc.createElement(GSXML.MESSAGE_ELEM);
+        Element mr_message = doc.createElement(GSXML.MESSAGE_ELEM);
 
-        Element ret_request = GSXML.createBasicRequest(this.doc, GSXML.REQUEST_TYPE_PROCESS, to, userContext);
+        Element ret_request = GSXML.createBasicRequest(doc, GSXML.REQUEST_TYPE_PROCESS, to, userContext);
         mr_message.appendChild(ret_request);
 
-        Element doc_list = this.doc.createElement(GSXML.DOC_NODE_ELEM + GSXML.LIST_MODIFIER);
+        Element doc_list = doc.createElement(GSXML.DOC_NODE_ELEM + GSXML.LIST_MODIFIER);
         ret_request.appendChild(doc_list);
-        Element doc = this.doc.createElement(GSXML.DOC_NODE_ELEM);
-        doc.setAttribute(GSXML.NODE_ID_ATT, doc_name);
-        doc_list.appendChild(doc);
+        Element docelem = doc.createElement(GSXML.DOC_NODE_ELEM);
+        docelem.setAttribute(GSXML.NODE_ID_ATT, doc_name);
+        doc_list.appendChild(docelem);
 
         // also add in a request for the Title metadata
         to = GSPath.appendLink(collection, "DocumentMetadataRetrieve");
-        Element meta_request = GSXML.createBasicRequest(this.doc, GSXML.REQUEST_TYPE_PROCESS, to, userContext);
+        Element meta_request = GSXML.createBasicRequest(doc, GSXML.REQUEST_TYPE_PROCESS, to, userContext);
         // copy the doc list
         meta_request.appendChild(doc_list.cloneNode(true));
         // add in a metadata param
-        Element param_list = this.doc.createElement(GSXML.PARAM_ELEM + GSXML.LIST_MODIFIER);
+        Element param_list = doc.createElement(GSXML.PARAM_ELEM + GSXML.LIST_MODIFIER);
         meta_request.appendChild(param_list);
-        Element param = GSXML.createParameter(this.doc, "metadata", "root_Title");
+        Element param = GSXML.createParameter(doc, "metadata", "root_Title");
         param_list.appendChild(param);
 
@@ -103 +103 @@
         String[] links = { GSXML.RESPONSE_ELEM, GSXML.DOC_NODE_ELEM + GSXML.LIST_MODIFIER, GSXML.DOC_NODE_ELEM };
         String path = GSPath.createPath(links);
-        Element doc_node = (Element) this.doc.importNode(GSXML.getNodeByPath(ret_response, path), true);
+        Element doc_node = (Element) doc.importNode(GSXML.getNodeByPath(ret_response, path), true);
         page_response.appendChild(doc_node);
 
@@ -114 +114 @@
         if (meta_list != null)
         {
-            doc_node.appendChild(this.doc.importNode(meta_list, true));
+            doc_node.appendChild(doc.importNode(meta_list, true));
         }
         return result;