Optimized for the case that there are no privacy lists (JM-762).

git-svn-id: http://svn.igniterealtime.org/svn/repos/wildfire/trunk@4289 b35dd754-fafc-0310-a699-88a17e54d16e

src/java/org/jivesoftware/wildfire/privacy/PrivacyListProvider.java

@@ -22,8 +22,10 @@ import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Collections;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.atomic.AtomicInteger;
 
 /**
  * Provider for the privacy lists system. Privacy lists are read and written
@@ -33,6 +35,8 @@ import java.util.concurrent.LinkedBlockingQueue;
  */
 public class PrivacyListProvider {
 
+    private static final String PRIVACY_LIST_COUNT =
+            "SELECT count(*) from jivePrivacyList";
     private static final String LOAD_LIST_NAMES =
             "SELECT name, isDefault FROM jivePrivacyList WHERE username=?";
     private static final String LOAD_PRIVACY_LIST =
@@ -53,12 +57,25 @@ public class PrivacyListProvider {
      */
     private BlockingQueue<SAXReader> xmlReaders = new LinkedBlockingQueue<SAXReader>();
 
+    /**
+     * Stores the total number of privacy lists.
+     */
+    private AtomicInteger privacyListCount;
+
     public PrivacyListProvider() {
         super();
         // Initialize the pool of sax readers
         for (int i=0; i<50; i++) {
             xmlReaders.add(new SAXReader());
         }
+
+        // Load the total number of privacy lists in the database. We're looking
+        // for the (very common) special case that there are no privacy lists stored.
+        // In that case, we can optimize away many database calls. In the future, a
+        // better general-case solution may be to cache all privacy lists defined
+        // if there are less than, say, 500.
+        privacyListCount = new AtomicInteger(0);
+        loadPrivacyListCount();
     }
 
     /**
@@ -69,6 +86,11 @@ public class PrivacyListProvider {
      * @return the names of the existing privacy lists with a default flag.
      */
     public Map<String, Boolean> getPrivacyLists(String username) {
+        // If there are no privacy lists stored, this method is a no-op.
+        if (privacyListCount.get() == 0) {
+            return Collections.emptyMap();
+        }
+
         Map<String, Boolean> names = new HashMap<String, Boolean>();
         Connection con = null;
         PreparedStatement pstmt = null;
@@ -101,36 +123,59 @@ public class PrivacyListProvider {
      *         with the specified name does not exist.
      */
     public PrivacyList loadPrivacyList(String username, String listName) {
-        PrivacyList privacyList = null;
-        java.sql.Connection con = null;
+        // If there are no privacy lists stored, this method is a no-op.
+        if (privacyListCount.get() == 0) {
+            return null;
+        }
+
+        boolean isDefault = false;
+        String listValue = null;
+
+        Connection con = null;
         PreparedStatement pstmt = null;
         ResultSet rs = null;
-        SAXReader xmlReader = null;
+
         try {
-            // Get a sax reader from the pool
-            xmlReader = xmlReaders.take();
             con = DbConnectionManager.getConnection();
             pstmt = con.prepareStatement(LOAD_PRIVACY_LIST);
             pstmt.setString(1, username);
             pstmt.setString(2, listName);
             rs = pstmt.executeQuery();
-            while (rs.next()) {
-                boolean isDefault = rs.getInt(1) == 1;
-                Element listElement =
-                        xmlReader.read(new StringReader(rs.getString(2))).getRootElement();
-                privacyList = new PrivacyList(username, listName, isDefault, listElement);
+            if (rs.next()) {
+                isDefault = rs.getInt(1) == 1;
+                listValue = rs.getString(2);
+            }
+            else {
+                return null;
             }
         }
         catch (Exception e) {
             Log.error("Error loading privacy list: " + listName + " of username: " + username, e);
+            return null;
+        }
+        finally {
+            DbConnectionManager.closeConnection(rs, pstmt, con);
+        }
+
+        PrivacyList privacyList = null;
+        SAXReader xmlReader = null;
+        try {
+            // Get a sax reader from the pool
+            xmlReader = xmlReaders.take();
+            Element listElement = xmlReader.read(new StringReader(listValue)).getRootElement();
+            privacyList = new PrivacyList(username, listName, isDefault, listElement);
+        }
+        catch (Exception e) {
+            Log.error(e);
         }
         finally {
             // Return the sax reader to the pool
             if (xmlReader != null) {
                 xmlReaders.add(xmlReader);
             }
-            DbConnectionManager.closeConnection(rs, pstmt, con);
         }
+
+
         return privacyList;
     }
 
@@ -142,35 +187,56 @@ public class PrivacyListProvider {
      * @return the default privacy list or <tt>null</tt> if no list was found.
      */
     public PrivacyList loadDefaultPrivacyList(String username) {
-        PrivacyList privacyList = null;
-        java.sql.Connection con = null;
+        // If there are no privacy lists stored, this method is a no-op.
+        if (privacyListCount.get() == 0) {
+            return null;
+        }
+
+        String listName = null;
+        String listValue = null;
+
+        Connection con = null;
         PreparedStatement pstmt = null;
         ResultSet rs = null;
-        SAXReader xmlReader = null;
         try {
-            // Get a sax reader from the pool
-            xmlReader = xmlReaders.take();
             con = DbConnectionManager.getConnection();
             pstmt = con.prepareStatement(LOAD_DEFAULT_PRIVACY_LIST);
             pstmt.setString(1, username);
             rs = pstmt.executeQuery();
-            while (rs.next()) {
-                String listName= rs.getString(1);
-                Element listElement =
-                        xmlReader.read(new StringReader(rs.getString(2))).getRootElement();
-                privacyList = new PrivacyList(username, listName, true, listElement);
+            if (rs.next()) {
+                listName = rs.getString(1);
+                listValue = rs.getString(2);
+            }
+            else {
+                return null;
             }
         }
         catch (Exception e) {
             Log.error("Error loading default privacy list of username: " + username, e);
+            return null;
+        }
+        finally {
+            DbConnectionManager.closeConnection(rs, pstmt, con);
+        }
+
+        PrivacyList privacyList = null;
+        SAXReader xmlReader = null;
+        try {
+            // Get a sax reader from the pool
+            xmlReader = xmlReaders.take();
+            Element listElement = xmlReader.read(new StringReader(listValue)).getRootElement();
+            privacyList = new PrivacyList(username, listName, true, listElement);
+        }
+        catch (Exception e) {
+            Log.error(e);
         }
         finally {
             // Return the sax reader to the pool
             if (xmlReader != null) {
                 xmlReaders.add(xmlReader);
             }
-            DbConnectionManager.closeConnection(rs, pstmt, con);
         }
+
         return privacyList;
     }
 
@@ -199,6 +265,9 @@ public class PrivacyListProvider {
         finally {
             DbConnectionManager.closeConnection(pstmt, con);
         }
+        // Set the privacy list count to -1. We don't know how many privacy lists there
+        // are, but it's not "0", which is the case we care about.
+        privacyListCount.set(-1);
     }
 
     /**
@@ -220,9 +289,8 @@ public class PrivacyListProvider {
             pstmt.executeUpdate();
         }
         catch (Exception e) {
-            Log.error(
-                    "Error updating privacy list: " + list.getName() + " of username: " + username,
-                    e);
+            Log.error("Error updating privacy list: " + list.getName() + " of username: " +
+                    username, e);
         }
         finally {
             DbConnectionManager.closeConnection(pstmt, con);
@@ -236,6 +304,10 @@ public class PrivacyListProvider {
      * @param listName the name of the PrivacyList to delete.
      */
     public void deletePrivacyList(String username, String listName) {
+        // If there are no privacy lists stored, this method is a no-op.
+        if (privacyListCount.get() == 0) {
+            return;
+        }
         Connection con = null;
         PreparedStatement pstmt = null;
         try {
@@ -251,6 +323,9 @@ public class PrivacyListProvider {
         finally {
             DbConnectionManager.closeConnection(pstmt, con);
         }
+        // Set the privacy list count to -1. We don't know how many privacy lists there
+        // are, but it's probably not "0", which is the case we care about.
+        privacyListCount.set(-1);
     }
 
     /**
@@ -259,6 +334,10 @@ public class PrivacyListProvider {
      * @param username the username of the user whose privacy lists are going to be deleted.
      */
     public void deletePrivacyLists(String username) {
+        // If there are no privacy lists stored, this method is a no-op.
+        if (privacyListCount.get() == 0) {
+            return;
+        }
         Connection con = null;
         PreparedStatement pstmt = null;
         try {
@@ -273,5 +352,30 @@ public class PrivacyListProvider {
         finally {
             DbConnectionManager.closeConnection(pstmt, con);
         }
+        // Set the privacy list count to -1. We don't know how many privacy lists there
+        // are, but it's probably not "0", which is the case we care about.
+        privacyListCount.set(-1);
+    }
+
+    /**
+     * Loads the total number of privacy lists stored in the database.
+     */
+    private void loadPrivacyListCount() {
+        Connection con = null;
+        PreparedStatement pstmt = null;
+        ResultSet rs = null;
+        try {
+            con = DbConnectionManager.getConnection();
+            pstmt = con.prepareStatement(PRIVACY_LIST_COUNT);
+            rs = pstmt.executeQuery();
+            rs.next();
+            privacyListCount.set(rs.getInt(1));
+        }
+        catch (Exception e) {
+            Log.error(e);
+        }
+        finally {
+            DbConnectionManager.closeConnection(rs, pstmt, con);
+        }
     }
 }