JAVA

Java is a high level, robust, secured, object oriented, plateform independent programing language. Java, Servlet, JSP, EJB, Struts2, Hibernate, Spring are important topics comes under java.


Sping Modules:

 

Apache Struts Framework: 

Struts 2.5.10 is the stable version as of March 2017. Its free, open-source, mvc framework for creating java EE web application.



Comparision of Web Frameworks:
https://en.wikipedia.org/wiki/Comparison_of_web_frameworks


EJB:
Enterprise JavaBeans (EJB) is a server-side software component that encapsulates the business logic of an application. The EJB specification is a subset of the Java EE specification. An EJB web container provides a runtime environment for web related software components.

Must Know about below Topics:

• jar (java archieve)    - It contains a group of .class files.

• war (web archieve)  - it contais a group of jsps, servlets, html, css, js, xml etc. Only web related technologies like jsp and servlets.

• ear (enterprise archieve) - it represents one enterprise application. it contains java 2e technologies. like jsps + ejb+ jms etc.

   

• web application:

• enterprise application:

• web server - provides environment to run web application. JSPs + SERVLT + HTML + js + css

• application server - provides environment to run enterprise application. Any technology from j2ee. Application Server = Web Server + EJBs + JMS + other J2EE technology.

   

• classpath - tells applications, including jdk tools, where to look for user classes.

• path - tells where the executables exists.

• jdk - java development kit. provides environment to development and run java application site.

• jre - java runtime environment - provies an environment to run java application.

• jvm - in jre jvm is reponsible to run program. it is an interpreter which is responsible to run java program line by line.

• jdk= jre (jvm + liberary classes) + development tools

• jre= jvm + liberary classes

JVM Architecture:

test.java - java source/ java file => java  compiler (javac) => will generate java class file (.class)

Class Loader Sub System =>
1. Loading => bootstrap class loader, extension class loader, application class loader
2. Linking => verify, prepare, resolve
3. Initialization => Initialization