Changeset 28382 for main/trunk/greenstone3/src/java/org/greenstone/gsdl3/action/SystemAction.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/SystemAction.java (modified) (6 diffs)

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

@@ -4 +4 @@
 
 // XML classes
+import org.w3c.dom.Document;
 import org.w3c.dom.Node;
 import org.w3c.dom.Element;
@@ -28 +29 @@
     public Node process(Node message_node)
     {
-
         Element message = this.converter.nodeToElement(message_node);
-
+        Document doc = message.getOwnerDocument();
+        
         // assume only one request
         Element request = (Element) GSXML.getChildByTagName(message, GSXML.REQUEST_ELEM);
@@ -40 +41 @@
         HashMap<String, Serializable> params = GSXML.extractParams(cgi_param_list, false);
 
-        Element result = this.doc.createElement(GSXML.MESSAGE_ELEM);
+        Element result = doc.createElement(GSXML.MESSAGE_ELEM);
 
         String coll = (String) params.get(GSParams.SYSTEM_CLUSTER);
@@ -50 +51 @@
         }
 
-        Element mr_request_message = this.doc.createElement(GSXML.MESSAGE_ELEM);
-        Element mr_request = GSXML.createBasicRequest(this.doc, GSXML.REQUEST_TYPE_SYSTEM, to, userContext);
+        Element mr_request_message = doc.createElement(GSXML.MESSAGE_ELEM);
+        Element mr_request = GSXML.createBasicRequest(doc, GSXML.REQUEST_TYPE_SYSTEM, to, userContext);
         mr_request_message.appendChild(mr_request);
 
-        Element system = this.doc.createElement(GSXML.SYSTEM_ELEM);
+        Element system = doc.createElement(GSXML.SYSTEM_ELEM);
         mr_request.appendChild(system);
 
@@ -109 +110 @@
                 // for now just have an error
                 logger.error("bad subaction type");
-                Element page_response = this.doc.createElement(GSXML.RESPONSE_ELEM);
+                Element page_response = doc.createElement(GSXML.RESPONSE_ELEM);
                 result.appendChild(page_response);
 
@@ -118 +119 @@
         Node response_message = this.mr.process(mr_request_message);
 
-        Element response = GSXML.duplicateWithNewName(this.doc, (Element) GSXML.getChildByTagName(response_message, GSXML.RESPONSE_ELEM), GSXML.RESPONSE_ELEM, true);
+        Element response = GSXML.duplicateWithNewName(doc, (Element) GSXML.getChildByTagName(response_message, GSXML.RESPONSE_ELEM), GSXML.RESPONSE_ELEM, true);
         addSiteMetadata(response, userContext);
         addInterfaceOptions(response);