Author: rchapin

Most OO programers are familiar with packages.  This enables programmers to group like classes together in a logical order and provide some namespace to avoid class name collisions.

I have seen a variety of JavaScript sugar implementations that are mostly unintelligible.

I like things that are simple and easy to understand.

So, if you have a JavaScript class that looks like:

/**
 * Constructor
 */
com.ryanchapin.Base = function() {

    //
    // Constructor does something here . . .
    //
}→ Continue reading “Simple Solution for JavaScript Object Packages and Namespaces”

When first installing NXServer I have seen a number of occastions when the initial run of

# /usr/NX/bin/nxserver –install

Does not necessarily work correctly and simply running the following commands has worked.

# /usr/NX/bin/nxsetup –uninstall –purge –clean

then

# /usr/NX/bin/nxsetup –install –setup-nomachine-key

If the previous uninstall/install command doesn’t work, try rpm -e nx*.rpms and reinstalling the rpms before trying to run the nxserver –install command again.→ Continue reading “Solution for ‘NX service is not available’”

Following are some good articles/tutorial on OO JavaScript:

• http://killdream.github.com/blog/2011/10/understanding-javascript-oop/
• http://mckoss.com/jscript/object.htm
• http://nefariousdesigns.co.uk/archive/2006/05/object-oriented-javascript/
• http://msdn.microsoft.com/en-us/magazine/cc163419.aspx

→ Continue reading “Resources for Understanding Object-Oriented JavaScript”

http://javascript.crockford.com/→ Continue reading “JavaScript Resources”

Very handy ECMAScript 5 compatibility table for the JavaScript programmer:

http://kangax.github.com/es5-compat-table/→ Continue reading “ECMAScript 5 Compatibility Table”

Following is a quick example of how to generate an MD5 Hash (SHA-256, SHA-512 or any other supported hash algorithm) of either a String or the byte value of a long.  You should be able to adapt for your particular application:

package com.ryanchapin.util;

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class HashGenerator {

    public static String createHash(long input, String hashAlgorithm) {
        // Generate a byte array from the long
        // Extract the byte value → Continue reading “Creating a MD5 Hash in Java From Either a String or the Byte Value of a Long”

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”