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

What is Semaphore? Semaphore is used to control access to common resource for completing multiple resources . It guards a critical section against entry by more than N threads at a time. The  java.util.concurrent.Semaphore   class was first introduced by Java in V 1.5. It has two main methods(): ·          acquire() ·          release() Semaphore is initialized with a given number of "permits” i.e. counter which keeps track of the number of resources available. When a request comes to resources, Semaphore checks the counter and if it is less than total count then it grant access to resources and subsequently reduces the counter. Similarly while releasing a resources, it increments the count. Thus, at most N threads can access the acquire method without any release() calls where N is number of permits the semaphore was initialized with. If the permits is in ON|OFF mode i....

Requirement : I was working on shell script where I need to get Id value from JSON and I tried so many thing but unable to get it without using any other tools. So, After trying so many failure attempt, I end up with this site (A big thanks to you) which resolved my issue. Here is how I fetched value from JSON, JSON = <YOUR_JSON> PROPERTY_TO_FETCH="<VALUE>" (In my case, it was "id") ID = `echo $JSON| sed 's/\\\\\//\//g' | sed 's/[{}]//g' | awk -v k="text" '{n=split($0,a,","); for (i=1; i<=n; i++) print a[i]}' | sed 's/\"\:\"/\|/g' | sed 's/[\,]/ /g' | sed 's/\"//g' | grep -w $PROPERTY_TO_FETCH` echo ${ID ##*|} Which will print the value of 'id' from JSON.

I am working on multi module maven project and If I define any plugin in the parent pom.xml file, It get executed for all the child build as well. In simple language, I wanted to use one plugin in parent pom.xml file which read properties file from the base directory but whenever I executes it, all the sub pom.xml tries to read the properties file from their base directory and its ends up in maven failed. To resolve the above issue, We just need to add "inherit' attributes in the plugin. Example : <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>properties-maven-plugin</artifactId> <version>1.0-alpha-2</version> <inherited>false</inherited> <executions> <execution> <phase>initialize</phase> <goals> <goal>read-project-properties</goal> </goals> <configuration> <files> ...

Yesterday while working on my project, I got one requirement where I need to store list of Array into the database, I checked on Google, went through various site but didn't get much information. Everyone talks about creating new entity and do onetomany relationship BUT I wanted to create a collection of basic types. Finally I come across @ElementCollection annotation provided by JPA 2.0 which resolves my problem. Problem : Input JSON which we need to store in DB: { "schemas": ["urn:scim:schemas:core:1.0", "urn:scim:schemas:extension:enterprise:1.0"] }            Where schemas is Array of String. Solution : Just add following annotation in your POJO i,e @ElementCollection @CollectionTable(name = "SCIM_SCHEMAS", joinColumns = @JoinColumn(name = "SCHEMA_ID")) @Column(name = "SCIM_SCHEMA") private List<String> schemas; It will create the table named "SCIM_SCHEMAS" having columns 'SCHE...

This tutorial will demonstrate how can you generate Java Objects from XML documents using xjc tool. The tool “xjc” is used to generate the annotated Java classes from the XSD schema Suppose I am using below XML file to generate Java Objects i,e <?xml version="1.0" encoding="UTF-8"?> <adaptorapp id="application"> <instance id="instance1"> <connectiondetails> <accesskey>abcde</accesskey> <secretkey>fghij</secretkey> </connectiondetails> </instance> <instance id="instance2"> <connectiondetails> <accesskey>klmnop</accesskey> <secretkey>qrstuvwxyz</secretkey> </connectiondetails> </instance> </adaptorapp> Now  to generate Java Objects we need to create one xsd file(say "connection.xsd") : <?xml version="1.0"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema...

In hibernate, You cannot have two classes with the same name in the same or different packages else you will get an error at runtime like " Caused by: org.hibernate.DuplicateMappingException: duplicate import: ....(try using auto-import="false ")" I have resolved this issue by adding property name on the Entity annotation. Let us suppose I have Meta class in two different packages "com.database.user" and "com.database.group', you can resolve it as : package com.database.user @Entity( name= "com.database.user" ) @Table(name="USER_META") public class Meta package com.database.group @Entity( name= "com.database.group" ) @Table(name="GROUP_META") public class Meta There must be some other ways too to resolve this issue, So please feel free to share it :)

To upgrade the ANT into the Eclipse, First you need to download the latest version of ANT anywhere on you machine. Once you are done with the download then go to Eclipse → Windows → Preferences → Ant → Runtime → Ant Home and Select the downloaded folder. Now your Eclipse will use the latest version of ANT :)