Ryan Chapin's Website

http://plsql-tutorial.com/→ Continue reading “Great PL/SQL Overview and Tutorial”

Here is a query with which you can see all of the active sessions on an Oracle database:

SELECT SID, Serial#, UserName, Status, SchemaName, Logon_Time
FROM V$Session
WHERE
Status=’ACTIVE’ AND
UserName IS NOT NULL;→ Continue reading “List All Active Sessions in Oracle 11g”

If you do not want to hard-code your file upload servlet with the @MultipartConfig annotation but would rather add it to your <servlet> configuration element in web.xml, following is the syntax (add this as a child element of <servlet>):

<multipart-config>
      <location>/tmp</location>
      <max-file-size>20848820</max-file-size>
      <max-request-size>418018841</max-request-size>
      <file-size-threshold>1048576</file-size-threshold>
</multipart-config>→ Continue reading “Adding MultipartConfig Configuration to web.xml in JBoss 6.x for a Servlet 3.0 File Upload Servlet”

This one requires a bit of explaination.

When writing a Servlet that will enable users to upload files from a form you need to be able to limit both the size of the file(s) and the entire multipart/form-data request.  The Servlet 3.0 spec now includes a @MultipartConfig annotation (which can also be specified in web.xml, see other post in this blog).

Based on the Servlet 3.0 spec here is what is supposed to happen.

1. The user submits a multi-part

→ Continue reading “Invocation of request.getParts() in a Servlet 3.0 doPost Method Will Not Throw IllegalStateException”

The following is a tutorial on how to create a empty file on the filesystem:

// Destination directory
File destinationDir = new File(“/some/path”);

// The ‘touched’ file
File doneFile = new File(destinationDir, “some_file_name”);

// The JVM will only ‘touch’ the file if you instantiate a
// FileOutputStream instance for the file in question.
// You don’t actually write any data to the file through
// the FileOutputStream.  Just instantiate it and close it.
FileOutputStream doneFOS = null;
try {
    doneFOS → Continue reading “Touching a File in Java”

When I attempted to install the Web Developer Add-on in Firefox I was presented with the error in the title of this post.

After some searching it seems that the least intrusive way to go about fixing it is to update the Firefox configuration for your user profile.

If you are on WinXP look in C:\Documents and Settings\UID\Application Data\Mozilla\Firefox\Profiles\fxlme5ka.default.  On my install the following preference was in prefs.js

Change:

user_pref(“xpinstall.enabled”, false);

to:

user_pref(“xpinstall.enabled”, true);

Save the file and restart Firefox.→ Continue reading “Fixing "Software installation has been disabled by your system administrator" Notice When Attempting to Install An Addon for Firefox”

This tutorial makes the following assumptions:

• That you are running JBoss under a ‘jboss’ user whose home directory is /home/jboss/

For the following examples the string “<server-name/ip>” should be replaced with the domain name, or ip address from which the site will be accessed via https.  Also the path to your installed JDK is likely different.

• Create a new keystore using the jdk provided binary:

# /usr/lib/jvm/java-1.6.0-openjdk/bin/keytool -genkey -alias your_alias -keyalg RSA -keystore keystore.jks

Enter keystore password:
Re-enter new password:→ Continue reading “Configuring JBoss 6.x for HTTPS with a Self-Signed Cert”

If you ever see the following when attempting to start up an instance of JBoss 6.x:

15:41:15,740 ERROR [AbstractKernelController] Error installing to Start: name=IIOPInvoker state=Create: java.net.UnknownHostException: some_host_name: some_host_name
        at java.net.InetAddress.getLocalHost(InetAddress.java:1426)
        [:1.6.0_17] at org.jboss.invocation.iiop.IIOPInvoker.start(IIOPInvoker.java:233) [:6.0.0.Final]

It is because JBoss cannot resolve the host name of the machine on which it is running.  To fix:

 

• Edit /etc/hosts and add the name of the box pointing to an ip address.
• Set up a proper DNS entry for the host name of the machine.

→ Continue reading “Fixing JBoss Error installing to Start: name=IIOPInvoker state=Create: java.net.UnknownHostException:”

The following is a howto for installing Jboss under Red Hat Enterprise Linux or CentOS.  The steps are most likely the same under any other Linux distro.

• Unpack your jboss.zip (or .tar)
• Jboss requires a ‘place’ to store data as it runs.  Out of the box it uses org.jboss.jdbc.HypersonicDatabase which is horribly inefficient and should never be used in a production system.  So we’ll set up MySQL such that jboss can write to it (installing and configuring MySQL is an

→ Continue reading “Installing Jboss 6.1.0-Final under RHEL or CentOS”

In most cases you will want to run JBoss as a non-privileged user.  For this example we will set up a jboss user (adding the user is an excersize for the user).  This example covers jboss-6.1.0-Final.

• Add $JAVA_HOME and $JBOSS_HOME environmental vars to .bash_profile for your jboss user.  $JAVA_HOME points to your install of the JDK and $JBOSS_HOME points to your jboss installation directory.
  

  JAVA_HOME=/usr/lib/jvm/java-1.6.0-openjdk.x86_64
  export JAVA_HOME
  PATH=$JAVA_HOME/bin:$PATH
  export PATH
  

JBOSS_HOME=/opt/jboss/
export JBOSS_HOME

• Once you have done the basic JBoss

→ Continue reading “Configuring JBoss 6.x to Run as a Service Under RHEL and CentOS”