Some remarks after a little investigation.
1) Using the ServletContext logger doesn't seem to be a widespread
practice among slf4j folks. There is a slf4j-servletcontext
implementation on github, but it is not referenced on the official slf4j
site. Moreover, I tested it, and it does not support deserialization (I
had some doubts about it, because deserialization may happen before
ServletContext initialization), so it cannot be used as is. Plus, it
needs to be declared as context's listener in the deployment file.
It's possible to solve those two problems (alas not from our own codebase):
- The logger object can be a proxy to a transcient implementation that
waits for the servlet context to be initialized.
- Since J2EE API v3.0, there is no need to declare the listener in the
deployment descriptor, as it can be done using Java annotations, which
would fit slf4j 'jar'-only binding strategy far more than the current
state of the project.
But not using the ServletContext logger is not necessarily a bad idea.
Of course, "it's here", so why not use it, but:
- In practice, container logger and webapp logger serve rather
different purposes, as container logs won't be active but at
initialization or destruction.
- They're not formatted the same way.
- It's not so cumbersome to watch several log files at once (I mean,
on a real O.S. with a proper command line, of course) when you need to
see both at the same time.
- It's much easier to configure a per-webapp logging (and consequently
to ease webapp deployment).
- Gathering logs is always doable at the container level, which can
also use slf4j (or one of its many bridges), bypassing ServletContext
(which is just a proxy).
Anyhow, even it's a little drawback for some people, it can not weight
as much in the balance as being freed of all logging
2) We can -and should- keep our logger injection mechanism, since it not
only helps separating different instances logs, but also permits
unifying log line prefixes. No more need to define the logger in
velocity.properties, by default it will be a static logger named
"Velocity". The only constraint when trying to separate instances logs
is to explicitly give different names to each logger (since the
underlying LoggerFactory mechanism remains static). Not a big deal.
Without any other objection, I'll start this drastic simplification very
soon. We don't even need to keep the o.a.v.runtime.log package. And four
sub-modules can disappear...
Claude
On 21/08/2015 17:25, Nathan Bubna wrote:
I like simple. :)
On Fri, Aug 21, 2015 at 2:18 AM, Claude Brisson<cla...@renegat.net> wrote:
It looks like that with slf4j, we could keep loggers injection even in
session tools, so no need to go static:
"As of SLF4J version 1.5.3, logger instances survive serialization. Thus,
serialization of the host class no longer requires any special action, even
when loggers are declared as instance variables. In previous versions,
logger instances needed to be declared as transient in the host class."
(http://www.slf4j.org/faq.html#declared_static )
So it looks like the perfect solution, and will simplify many things.
Claude
On 20/08/2015 21:32, Sergiu Dumitriu wrote:
A recent discussion was proposing to switch to slf4j as the façade.
On Aug 20, 2015 3:12 PM, "Claude Brisson"<cla...@renegat.net> wrote:
Thanks for the review.
Yes, we should be using Velocity logging facade, but I just don't see for
now how we should do this while preserving tools serialization.
For now I just mimicked a behavior present in some deprecated classes,
re-introducing the dependency of velocity-tools-view on commons-logging.
I agree that we should try to do better, but if a logger cannot be
statically reached from a session tool, and if it cannot be passed at
initialization because of serialization, there's a problem...
Let say for instance that we use transient weak references on
non-serializable Velocity loggers, fed up at initialization time. Then
the
tool could detect it has lost its logger at deserialization, and ask a
new
one, but to whom? It's a bad idea either to keep a static reference on
the
servlet context.
I'm open to suggestions...
Claude
On 20/08/2015 20:45, Sergiu Dumitriu wrote:
Isn't the logging framework supposed to be pluggable, meaning that all
calls go through org.apache.velocity.runtime.log.Log which is then
passed to the actual logging library in use, be it log4j, slf4j, jcl or
commons-logging?
On 08/20/2015 01:16 PM,cbris...@apache.org wrote:
Author: cbrisson
Date: Thu Aug 20 17:16:02 2015
New Revision: 1696822
URL:http://svn.apache.org/r1696822
Log:
J2EE containers session serialization implies static logging from
session scoped tools
Modified:
velocity/tools/trunk/src/site/xdoc/changes.xml
velocity/tools/trunk/velocity-tools-struts/src/main/java/org/apache/velocity/tools/struts/TilesTool.java
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/AbstractSearchTool.java
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/BrowserTool.java
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/ImportSupport.java
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/tools/ImportTool.java
Modified: velocity/tools/trunk/src/site/xdoc/changes.xml
URL:
http://svn.apache.org/viewvc/velocity/tools/trunk/src/site/xdoc/changes.xml?rev=1696822&r1=1696821&r2=1696822&view=diff
==============================================================================
--- velocity/tools/trunk/src/site/xdoc/changes.xml (original)
+++ velocity/tools/trunk/src/site/xdoc/changes.xml Thu Aug 20 17:16:02
2015
@@ -35,6 +35,7 @@
<li>Reflect Velocity Engine dependency shading of
commons-lang
and commons-collections (cb)</li>
<li>Removed deprecated class
org.apache.velocity.tools.generic.log.LogSystemCommonsLog (cb)</li>
<li>MathTool: fixed result type calculations and added
bitwise
operations (cb)</li>
+ <li>have session scoped tools use a static logger to fix J2EE
containers session serialization (cb)</li>
</ul>
</subsection>
Modified:
velocity/tools/trunk/velocity-tools-struts/src/main/java/org/apache/velocity/tools/struts/TilesTool.java
URL:
http://svn.apache.org/viewvc/velocity/tools/trunk/velocity-tools-struts/src/main/java/org/apache/velocity/tools/struts/TilesTool.java?rev=1696822&r1=1696821&r2=1696822&view=diff
==============================================================================
---
velocity/tools/trunk/velocity-tools-struts/src/main/java/org/apache/velocity/tools/struts/TilesTool.java
(original)
+++
velocity/tools/trunk/velocity-tools-struts/src/main/java/org/apache/velocity/tools/struts/TilesTool.java
Thu Aug 20 17:16:02 2015
@@ -101,7 +101,6 @@ public class TilesTool extends ImportSup
setRequest(ctx.getRequest());
setResponse(ctx.getResponse());
setServletContext(ctx.getServletContext());
- setLog(ctx.getVelocityEngine().getLog());
}
}
Modified:
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/AbstractSearchTool.java
URL:
http://svn.apache.org/viewvc/velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/AbstractSearchTool.java?rev=1696822&r1=1696821&r2=1696822&view=diff
==============================================================================
---
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/AbstractSearchTool.java
(original)
+++
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/AbstractSearchTool.java
Thu Aug 20 17:16:02 2015
@@ -22,7 +22,8 @@ package org.apache.velocity.tools.view;
import java.util.Collections;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
-import org.apache.velocity.runtime.log.Log;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
import org.apache.velocity.tools.Scope;
import org.apache.velocity.tools.config.DefaultKey;
import org.apache.velocity.tools.config.InvalidScope;
@@ -129,19 +130,11 @@ public abstract class AbstractSearchTool
protected static final String STORED_RESULTS_KEY =
StoredResults.class.getName();
- protected Log LOG;
+ protected static final Log LOG =
LogFactory.getLog(AbstractSearchTool.class);
+
private String criteriaKey = DEFAULT_CRITERIA_KEY;
private Object criteria;
- public void setLog(Log log)
- {
- if (log == null)
- {
- throw new NullPointerException("log should not be set to
null");
- }
- this.LOG = log;
- }
-
/**
* Sets the criteria *if* it is set in the request parameters.
*/
Modified:
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/BrowserTool.java
URL:
http://svn.apache.org/viewvc/velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/BrowserTool.java?rev=1696822&r1=1696821&r2=1696822&view=diff
==============================================================================
---
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/BrowserTool.java
(original)
+++
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/BrowserTool.java
Thu Aug 20 17:16:02 2015
@@ -24,7 +24,8 @@ import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
import java.util.*;
import javax.servlet.http.HttpServletRequest;
-import org.apache.velocity.runtime.log.Log;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
import org.apache.velocity.tools.Scope;
import org.apache.velocity.tools.ConversionUtils;
import org.apache.velocity.tools.generic.FormatConfig;
@@ -73,8 +74,8 @@ import org.apache.velocity.tools.config.
public class BrowserTool extends FormatConfig implements
java.io.Serializable
{
private static final long serialVersionUID =
1734529350532353339L;
-
- protected Log LOG;
+
+ protected static final Log LOG =
LogFactory.getLog(BrowserTool.class);
/* User-Agent header variables */
private String userAgent = null;
@@ -187,19 +188,6 @@ public class BrowserTool extends FormatC
}
/**
- * Set log.
- */
- public void setLog(Log log)
- {
- if (log == null)
- {
- throw new NullPointerException("log should not be set to
null");
- }
- this.LOG = log;
- }
-
-
- /**
* Sets the User-Agent string to be parsed for info. If null,
the
string
* will be empty and everything will return false or null.
Otherwise,
* it will set the whole string to lower case before storing to
simplify
Modified:
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/ImportSupport.java
URL:
http://svn.apache.org/viewvc/velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/ImportSupport.java?rev=1696822&r1=1696821&r2=1696822&view=diff
==============================================================================
---
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/ImportSupport.java
(original)
+++
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/ImportSupport.java
Thu Aug 20 17:16:02 2015
@@ -39,12 +39,17 @@ import javax.servlet.ServletOutputStream
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
-import org.apache.velocity.runtime.log.Log;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
/**
* <p>Provides methods to import arbitrary local or remote resources
as strings.</p>
* <p>Based on ImportSupport from the JSTL taglib by Shawn
Bayern</p>
*
+ * <p>If you wish to take profit of your J2EE container session
serialization,
+ * inheriting tools should always be in the request scope.</p>
+ *
* @author <a href="mailto:mari...@centrum.is";>Marino A.
Jonsson</a>
* @since VelocityTools 2.0
* @version $Revision$ $Date$
@@ -57,7 +62,8 @@ public abstract class ImportSupport
/** Default character encoding for response. */
protected static final String DEFAULT_ENCODING = "ISO-8859-1";
- protected Log LOG;
+ protected static final Log LOG =
LogFactory.getLog(ImportSupport.class);
+
protected ServletContext application;
protected HttpServletRequest request;
protected HttpServletResponse response;
@@ -65,15 +71,6 @@ public abstract class ImportSupport
// --------------------------------------- Setup Methods
-------------
- public void setLog(Log log)
- {
- if (log == null)
- {
- throw new NullPointerException("log should not be set to
null");
- }
- this.LOG = log;
- }
-
/**
* Sets the current {@link HttpServletRequest}. This is required
* for this tool to operate and will throw a
NullPointerException
Modified:
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/tools/ImportTool.java
URL:
http://svn.apache.org/viewvc/velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/tools/ImportTool.java?rev=1696822&r1=1696821&r2=1696822&view=diff
==============================================================================
---
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/tools/ImportTool.java
(original)
+++
velocity/tools/trunk/velocity-tools-view/src/main/java/org/apache/velocity/tools/view/tools/ImportTool.java
Thu Aug 20 17:16:02 2015
@@ -36,7 +36,6 @@ public class ImportTool extends org.apac
setRequest(ctx.getRequest());
setResponse(ctx.getResponse());
setServletContext(ctx.getServletContext());
- setLog(ctx.getVelocityEngine().getLog());
}
}
}
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