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Jun 9, 2009
May 4, 2009
Welcom The close() method of ClassLoader in JDK7
The close() method of ClassLoader in JDK7 is revolutionary stuff in JDK history, because ClassLoader have no function of close, module programming is very difficult to manage java object.
Therefore, there is no need to kill application to close classloader (Known for App kill).
I am very expecting JDK7 release.
URL url = new URL("file:foo.jar");
URLClassLoader loader = new URLClassLoader (new URL[] {url});
Class cl = Class.forName ("Foo", true, loader);
Runnable foo = (Runnable) cl.newInstance();
foo.run();
loader.close ();
// foo.jar gets updated somehow
loader = new URLClassLoader (new URL[] {url});
cl = Class.forName ("Foo", true, loader);
foo = (Runnable) cl.newInstance();
// run the new implementation of Foo
foo.run();
Therefore, there is no need to kill application to close classloader (Known for App kill).
I am very expecting JDK7 release.
URL url = new URL("file:foo.jar");
URLClassLoader loader = new URLClassLoader (new URL[] {url});
Class cl = Class.forName ("Foo", true, loader);
Runnable foo = (Runnable) cl.newInstance();
foo.run();
loader.close ();
// foo.jar gets updated somehow
loader = new URLClassLoader (new URL[] {url});
cl = Class.forName ("Foo", true, loader);
foo = (Runnable) cl.newInstance();
// run the new implementation of Foo
foo.run();
java sources for ojdbc (odjbc14-10.0.2.zip, ojdbc14-9.2.zip) decompied by jad
Those sources are decompiled by jad decompiler. I can't source for ojdbc14.jar anywhere, so that I put sources to my blog.
Prior to see the source, you have to see the readme of ojdbc14.jar in oracle web site to understand jdbc specification and bug fixes.
Prior to see the source, you have to see the readme of ojdbc14.jar in oracle web site to understand jdbc specification and bug fixes.
odjbc14-10.0.2.zip
http://knight76.tistory.com/attachment/cfile4.uf@14432C1D49E8206A909F92.zip
ojdbc14-9.2.zip
http://knight76.tistory.com/attachment/cfile22.uf@1144E51D49E82072C532AE.zip
JavaOne 2008
To study or listen the sessions of java one 2008, visit "http://developers.sun.com/learning/javaoneonline/j1online.jsp?track=coolstuff&yr=2008" web site.
You may be requested to login by sun.com. If you are sdn's member, you can access and enjoy it.
Also, you can visit this site. "http://java.sun.com/javaone/sf/sessions/general/index.jsp"
You may be requested to login by sun.com. If you are sdn's member, you can access and enjoy it.
Also, you can visit this site. "http://java.sun.com/javaone/sf/sessions/general/index.jsp"
No SqlHandler log4j:ERROR problem
If you meet this log, you shoud take carefully a look at your log4j sqlhandler option, modify it.
log4j:ERROR JDBCAppender::configure(), No SqlHandler or sql, table, procedure option given !
log4j:ERROR JDBCAppender::append(), Not ready to append !
Thinking about saving error logs in web application based on web-work(or struts2)
You may meet java errors every day if you are a java developer. Especially if a lot of or critical error logs in web application get to meet, you will be panic. So, there is need to develop error log DB and error-collectiong log module.
I will introduce my idea about developing error log DB.
According to your company policies, methods are applied for error logging system.
Architecture of error logging system consists of
1) Error DB can be stored
2) Admin web application can show errors on error db
3) Java classes and log4j configuration to transfer logs to DB.
<Error DB>
In web application, there are many properties to save such as belows.
project-name, server-name, loginid(userid), access date-time, log level, url, form, cookie, referer, execpetionmessage
You can specify those more concisely. For example, exceptionmessage is divided to head and body according to java.lang.Exception.
I made error log db, table. Specially I made indexing in mysql. And in mysql DB, I made a batch script to rotate log db.
#!/bin/sh
TODAY=`date -d "-1 day" +%Y%m%d`
TO_DELETE_DAY=`date -d "-30 day" +%Y%m%d`
mysql -u userid -p password mysql db-schema-name << !
# rotate log table
alter table lgt_logdata rename logdata_${TODAY};
drop table if exists logdata_${TO_DELETE_DAY};
create table logdata (
logid int(11) NOT NULL auto_increment,
projectname varchar(30) ,
servername varchar(20) ,
....
KEY lgt_logdata_ix1 (projectname,loglevel)
)
<Error-collectiong>
Error-collecting log module is implemented by log4j in simple. You can change the properites to save several log-level like error, warning. So, you can make warning log DB as well.
Let us suppose to save the errors to mysql.
<Log4j.xml>
<appender name="ERROR-OUT" class="org.apache.log4j.jdbcplus.JDBCAppender">
<param name="Threshold" value="ERROR"/>
<param name="dbclass" value="com.mysql.jdbc.Driver"/>
<param name="url" value="jdbc:mysql://in.log.google.com"/>
<param name="username" value="error"/>
<param name="password" value="nobodynobodywantyou"/>
<param name="sqlhandler" value="com.google.kr.MySQLHandler"/>
<param name="Buffer" value="1"/>
</appender>
<logger name="com" additivity="false">
<level value="DEBUG"/>
<appender-ref ref="ERROR-OUT"/>
</logger>
You have to save error-loging policy in your web application.
I think every logs have to store error log DB, so, I have policy to save all tomcat logs. Because every any kinds of errors can affect the performance of web application.
I have three policies to store the DB. I think those are very important to design error DB.
1. Using Interceptor in web work or struts2, web data such as url, form have to save MDC. (MDC is api of log4j framework)
Before web application meet java exceptions, the interceptor save the web information and after invoking action it checks the result of invoking action are failed(or throw exception). If the action throws the exception, those errors will sqlhandler (ERROR-OUT)
MDC.put("projectname", projectname);
MDC.put("cookie",cookie);
2. Use Servlet in web.xml.
You may extend and implements extends javax.servlet.http.HttpServlet class. Through the implemented class to handle error, you can store errors.
<servlet>
<servlet-name>errorHandler</servlet-name>
<servlet-class>com.google.kr.ErrorHandlerServlet</servlet-class>
</servlet>
3. Adding some fuctions to sqlhandler.
Most of error cases occur in calling action from users, but in some case internal web application invoker can make errors. For example batch or cache or scheduling based on Thread could make fault, but belows method can not include saving error logs.
And then, when you implement sqlhandler, you can add those.
You've got to adds some exceptional case on the sqlhandler.
import org.apache.log4j.jdbcplus.JDBCSqlHandler;
public class ErrorHandler implements JDBCSqlHandler {
...
}
<web applicatiion for error log>
You can show the errors stored in DB in simple.
Dead lock using the evictor
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