Tech Trek: A Software Engineer's Guide to Code and Beyond

The Basics - What is mod_jk? The mod_jk connector is an Apache HTTPD module that allows HTTPD to communicate with Apache Tomcat instances over the AJP protocol. Steps: 1. Download the latest apache connector from http://tomcat.apache.org/download-connectors.cgi . 2. Untar the download by           tar zxvf <filename> 3. Goto native directory of connector           cd <connector dir>/native/ 4. Run the buildconf.sh scripts        ./buildconf.sh Note : If you get any issue like "autocong" not installed then install following things:        yum install autoconf        yum install libtool 5. You need "httpd-devel" tools to build it. So make sure you have already installed it by          yum list installed | grep httpd-devel     else install it " yum install...

Overview A cluster is a group of servers running a Web application simultaneously, appearing to the world as if it were a single server. To balance server load, the system distributes requests to different nodes within the server cluster, with the goal of optimizing system performance. This results in higher availability and scalability -- necessities in an enterprise, Web-based application. High availability can be defined as redundancy. If a single Web server fails, then another server takes over, as transparently as possible, to process the request. Scalability is an application's ability to support a growing number of users. If it takes an application 10 milliseconds(ms) to respond to one request, then it should take 10 ms to respond to 10,000 concurrent requests. Of the many methods available to balance a server load, the main two are: DNS round robin and Hardware load balancers. DNS Round Robin To balance server loads using DNS, the DNS server ...

The most common approach of generating a self-signed certificate is using the  java keytool. There may be a situation when you want to create a self signed certificates programmatically One approach of programmatically generating these self-signed certificates is through the Bouncy Castle API. To start with this, you need to have the Bouncy Castle jar in your classpath.(You can download it from here ) Steps to generate self signed certificate key: 1. Create a public/private key pair for the new certificate           KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");         keyPairGenerator.initialize(1024, new SecureRandom());         KeyPair keyPair = keyPairGenerator.generateKeyPair();   2. Create new certificate Structure         // GENERATE THE X509 CERTIFICATE         X509V3Certi...

The example uses the keytool utility to create a new self signed certificate. Open the command console (Run as Administartor) on whatever operating system you are using and navigate to the directory where keytool.exe is located. Run the following command (where validity is the number of days before the certificate will expire): keytool -genkey -keyalg RSA -alias selfsigned -keystore keystore.jks  -keysize 1024 Fill in the prompts for your organization information.  This will create a keystore.jks file containing a private key and  self signed certificate. 

I have already updated about this in my previous  blog but that was from UI, In this tutorial You can do the same task from MySQL client itself. To configure this feature, you’ll need to update the mysql user table to allow access from any remote host, using the % wildcard. Open the command-line mysql client on the server using the root account. Then you will want to run the following two commands, to see what the root user host is set to already: use mysql; select host, user from user; Here’s an example of the output on my database. mysql> use mysql; Database changed mysql> select host,user from user; +-----------+------+ | host      | user | +-----------+------+ | localhost        | root | | 127.0.0.1 | root | | ::1       | root | | localhost |      | +-----------+------+ 4 rows in set (0.07 sec) Now I’ll update the localhost host to use the w...

What is Liquibase ? LiquiBase — available since 2006 — is an open source, freely available tool for migrating from one database version to another, It is an open source database-independent library for tracking, managing and applying database changes. A handful of other open source database-migration tools are on the scene as well, including openDBcopy and dbdeploy. LiquiBase supports 10 database types, including DB2, Apache Derby, MySQL, PostgreSQL, Oracle, Microsoft® SQL Server, Sybase, and HSQL. All changes to the database are stored in XML files and identified by a combination of an "id" and "author" tag as well as the name of the file itself. A list of all applied changes is stored in each database which is consulted on all database updates to determine what new changes need to be applied. LiquiBase executes changes based on this XML file to handle different revisions of database structures and data. When you first ...

/*         This Java example shows how to get reference of current thread using         currentThread method of Java Thread class. */   public class GetCurrentThread {           public static void main ( String [ ] args ) {                                 /*                  * To get the reference of currently running thread, use                  * Thread currentThread() method of Thread class.                  *                  * This is a static method.                  */                         ...