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

I am working on one project where client/server response is in JSON format. It is easy to send object in JSON format but what if some exception occured and you want to send the Exception also in JSON format ? After n number of trial. I finally able to do the above task .  Step 1 : Add following annotation " AnnotationMethodHandlerExceptionResolver " in your <CONTROLLER>-servlet.xml file. <!-- JSON format support for Exception -->     <bean id="methodHandlerExceptionResolver"         class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerExceptionResolver">         <property name="messageConverters">             <list>                 <ref bean="jacksonMessageConverter" />             </list> ...

In a typical application, you perform lot of operations like instantiate objects, load object from the database and so on. Sometime in multiuser application you may face a situation in handling multiple call of databases. Hibernate offers caching functionality which is designed to reduces the amount of necessary database access. This is a very powerful feature if used correctly. It increases your application performance and works between your application and the database as it avoids the number of database hit as many as possible. Hibernate Cache Types : Hibernate uses different types of caches. Each type of cache is used for different purposes. Let us first have a look at this cache types. First level cache Second level cache Query level cache 1. First level cache : First-level cache is the session cache and is always Associates with the Session object. Hibernate uses this cache by default. The Session object keeps an object under its own cache before committing to th...

Generate a Java keystore and key pair : keytool -genkey -alias mycert -keyalg RSA -keystore keystore.jks -keysize 1024 Generate a keystore and self-signed certificate :  keytool -genkey -keyalg RSA -alias selfsigned -keystore keystore.jks -storepass password -validity 360 -keysize 2048 keytool command to view certificate details from keyStore : keytool -list -v -keystore keystore.jks Check a particular keystore entry using an alias: keytool -list -v -keystore keystore.jks -alias mydomain keytool command option is -printcert which prints details of a certificate stored in .cer file : keytool -printcert -file test.cer Export a certificate from a keystore: keytool -export -alias mydomain -file mydomain.crt -keystore keystore.jks   keytool -export -alias mydomain -keypass keypass -keystore keystore.jks -storepass jkspass -rfc -file keytool_crt.pem Note : "keytool -export" command uses DER format by default. The "-rfc" option is to...

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.