From e915feb1602a7d88c39623da055fe68af422d27c Mon Sep 17 00:00:00 2001
From: "David A. Madore" <david+git@madore.org>
Date: Sun, 5 Oct 2014 01:13:30 +0200
Subject: Introduce at least a semblance of thread-safety.

---
 org/madore/damlengine/DamlEngine.java              |  5 +++-
 .../damlengine/WeblogDatabaseConnection.java       |  5 +++-
 org/madore/damlengine/WeblogServlet.java           | 35 +++++++++++-----------
 org/madore/damlengine/WeblogSummary.java           |  2 +-
 4 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/org/madore/damlengine/DamlEngine.java b/org/madore/damlengine/DamlEngine.java
index 9ac0c08..cffd589 100644
--- a/org/madore/damlengine/DamlEngine.java
+++ b/org/madore/damlengine/DamlEngine.java
@@ -81,8 +81,10 @@ public final class DamlEngine {
     }
 
     public static final class IncantDOM {
-	static DOMImplementation domi;
+	static ThreadLocal<DOMImplementation> pdomi
+	    = new ThreadLocal<DOMImplementation>();
 	public static DOMImplementation getDOMI() {
+	    DOMImplementation domi = pdomi.get();
 	    if ( domi == null ) {
 		DOMImplementationSource source
 		    = new DOMImplementationSourceImpl();
@@ -90,6 +92,7 @@ public final class DamlEngine {
 		if ( domi == null )
 		    throw new MissingResourceException("failed to obtain DOM implementation",
 						       "org.w3c.dom.ls.DOMImplementationLS", "");
+		pdomi.set(domi);
 	    }
 	    return domi;
 	}
diff --git a/org/madore/damlengine/WeblogDatabaseConnection.java b/org/madore/damlengine/WeblogDatabaseConnection.java
index fc485a6..16d0973 100644
--- a/org/madore/damlengine/WeblogDatabaseConnection.java
+++ b/org/madore/damlengine/WeblogDatabaseConnection.java
@@ -15,10 +15,12 @@ public final class WeblogDatabaseConnection {
 	throw new AssertionError("WeblogDatabaseConnection cannot be instantiated");
     }
 
-    public static Connection conn;
+    public static ThreadLocal<Connection> pconn
+	= new ThreadLocal<Connection>();
 
     public static Connection getConnection()
         throws SQLException {
+	Connection conn = pconn.get();
 	if ( conn == null ) {
 	    String dbHost = null;
 	    if ( ! DamlEngine.runAsServlet )
@@ -106,6 +108,7 @@ public final class WeblogDatabaseConnection {
 	    dbProps.setProperty("sslfactory", "org.postgresql.ssl.NonValidatingFactory");
 	    conn = (new Driver()).connect(dbUrl, dbProps);
 	    conn.createStatement().execute("SET TIME ZONE 0");
+	    pconn.set(conn);
 	}
 	return conn;
     }
diff --git a/org/madore/damlengine/WeblogServlet.java b/org/madore/damlengine/WeblogServlet.java
index 6b9b738..9cf1a75 100644
--- a/org/madore/damlengine/WeblogServlet.java
+++ b/org/madore/damlengine/WeblogServlet.java
@@ -28,7 +28,7 @@ import javax.servlet.http.HttpServletResponse;
 
 public class WeblogServlet extends HttpServlet {
 
-    private static final long serialVersionUID = 2014100406L;
+    private static final long serialVersionUID = 2014100407L;
 
     @Override
     public void doGet(HttpServletRequest request,
@@ -36,22 +36,23 @@ public class WeblogServlet extends HttpServlet {
         throws IOException, ServletException
     {
 
-	DamlEngine.runAsServlet = true;
-	DamlEngine.appProps = new Properties();
-	ServletConfig cfg = getServletConfig();
-	for (Enumeration<String> e = cfg.getInitParameterNames() ; e.hasMoreElements() ; ) {
-	    String k = e.nextElement();
-	    DamlEngine.appProps.setProperty(k, cfg.getInitParameter(k));
-	}
-
-	if ( DamlEngine.appProps.getProperty("base_path") != null )
-	    DamlEngine.basePath = Paths.get(DamlEngine.appProps.getProperty("base_path"));
-	if ( DamlEngine.basePath == null )
-	    DamlEngine.basePath = Paths.get(getServletContext().getRealPath("/"));
-	if ( DamlEngine.appProps.getProperty("template_path") != null )
-	    DamlEngine.templatePath = Paths.get(DamlEngine.appProps.getProperty("template_path"));
-	if ( DamlEngine.templatePath == null )
-	    DamlEngine.templatePath = DamlEngine.basePath.resolve("templates");
+	synchronized ( DamlEngine.class ) { if ( DamlEngine.appProps == null ) {
+	    DamlEngine.runAsServlet = true;
+	    DamlEngine.appProps = new Properties();
+	    ServletConfig cfg = getServletConfig();
+	    for (Enumeration<String> e = cfg.getInitParameterNames() ; e.hasMoreElements() ; ) {
+		String k = e.nextElement();
+		DamlEngine.appProps.setProperty(k, cfg.getInitParameter(k));
+	    }
+	    if ( DamlEngine.appProps.getProperty("base_path") != null )
+		DamlEngine.basePath = Paths.get(DamlEngine.appProps.getProperty("base_path"));
+	    if ( DamlEngine.basePath == null )
+		DamlEngine.basePath = Paths.get(getServletContext().getRealPath("/"));
+	    if ( DamlEngine.appProps.getProperty("template_path") != null )
+		DamlEngine.templatePath = Paths.get(DamlEngine.appProps.getProperty("template_path"));
+	    if ( DamlEngine.templatePath == null )
+		DamlEngine.templatePath = DamlEngine.basePath.resolve("templates");
+	}  }
 
         response.setContentType("text/html; charset=utf-8");
 	response.setCharacterEncoding("UTF-8");
diff --git a/org/madore/damlengine/WeblogSummary.java b/org/madore/damlengine/WeblogSummary.java
index 50ab143..b067987 100644
--- a/org/madore/damlengine/WeblogSummary.java
+++ b/org/madore/damlengine/WeblogSummary.java
@@ -37,7 +37,7 @@ public final class WeblogSummary {
 	this.entries = new HashMap<Integer,EntrySummary>();
     }
 
-    public static WeblogSummary getSummary() {
+    public static synchronized WeblogSummary getSummary() {
 	if ( singleton != null )
 	    return singleton;
 	singleton = new WeblogSummary();
-- 
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