ubuntu permission

sudo chmod -R 777 /* to give permission to the folder and all its contents recursively

installation of visual studio code for angular

1. download .deb 64 bit package for ubuntu  from https://code.visualstudio.com/download
2. open terminal and goto the location where the file exists
3. type the following
1. sudo dpkg -i code_1.27.2-1536736588_amd64.deb
4. goto search bar
5. type visual studio code
6. lock it to launcher

mysql docker container

1. https://severalnines.com/blog/mysql-docker-containers-understanding-basics
2. 
   

Enum

1. https://stackoverflow.com/questions/18883646/java-enum-methods/18883717
2. 
   

tag implementation

1. https://www.baeldung.com/jpa-tagging
2. https://www.nayuki.io/page/designing-better-file-organization-around-tags-not-hierarchies
3. 
   

domain driven design

1. books “Domain-driven Design” by Eric Evans and “Implementing Domain-driven Design” by Vaughn Vernon
2.  
3. value object is the object of a class whose constructor is private and which is constructed with the help of factory method inside it. they are not treated as entity. and two value objects having same state are considered to be equal.
4. https://deviq.com/value-object
5. they are small
6. they are immutable
7. https://martinfowler.com/bliki/ValueObject.html
8. https://enterprisecraftsmanship.com/2016/01/11/entity-vs-value-object-the-ultimate-list-of-differences/
9.  
10. value objects can be considered as @component
11. address is a good example of value object
12. value object should not be in a separate table.
13. value object should not have own identity
14. aggregates
1. https://medium.com/withbetterco/using-aggregates-and-factories-in-domain-driven-design-34e0dff220c3
2. https://www.infoq.com/news/2015/01/aggregates-value-objects-ddd
3.  

ubuntu

1. https://askubuntu.com/questions/278448/how-to-know-what-program-is-listening-on-a-given-port
2.