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joplin notion extension/Web Development/Java/Spring/Intro.md

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+Intro
+
+https://www.youtube.com/watch?v=QuvS_VLbGko : crash course of 1hr
+
+https://www.baeldung.com/
+
+https://www.youtube.com/watch?v=Ch163VfHtvA&list=PLsyeobzWxl7oA8QOlMtQsRT_I7Rx2hoX4 : telusko playlist
+
+![Untitled](../../../../_resources/Untitled.png)
+
+### EJB (Enterprise java bean)
+- Three types of EJB
+   1. Session bean : Contains business logic that is invoked by local, remote or web service client
+   2. Message driven bean : Contains business logic that is invoked by passing message
+   3. Entity bean : Encapsulates state that can be persisted in database. it is deprecated and replaced by java persistent API
+
+
+POJO : Plain Old Java Object . Ordinary object which is not bound by special restriction. https://www.javatpoint.com/pojo-in-java
+
+
+Interface : multiple inheritance feature in java
+annotations : Java Annotation is a tag that represents the metadata i.e. attached with class, interface, methods or fields to indicate some additional information which can be used by java compiler and JVM.
+eg: `@Override`, `@Deprecated`
+ 
+
+**Spring**
+An open source  framework to build enterprise java applications on any deployment platform. It is a collection of subfraneworks called layers such as Spring AOP. Spring Object-Relational Mapping (Spring ORM). Spring Web Flow, and Spring Web MVC.
+Spring can integrate with other frameworks like hibernate and struts.
+ 
+**Spring boot**
+We need to work on configuration thouroughly instead of coding itself. Spring boot solves this issue as spring boot comes with built in configurations and dependencies so developers can focus on conventions. We can add additional configurations too on top of basic ones.
+Spring boot provides us with embedded server/tomcat so instead of needing a separate server, JVM is enough. So JAR file will have embedded tomcat. 
+There is no XML file so we can add properties in `application.properties`