Notes

When you run the maven install command

for the very first time you would have

seen that may when downloads quite a few

plugins and jars from a central location

on the Internet maven is very small when

we install it and it downloads what is

required to do the build from the

central repository on the fly the

default maven repository location is the

following repo dot maven dot Apache dot

org /maven2 you can google for it and

if it changes in the future again you

should be able to Google for it and find

this central location or when maven

builds it will output this location for

you the artifacts are stored under a

certain folder structure on this server

the folder structure is derived from the

maven coordinates in the pom dot XML of

a project for example the maven

coordinates the J unit developers would

have used his group ID J unit artifact

ID is J unit version in our case is

3.8.1 that is the

version we are using and scope is test

if you go to the central repository the

repo dot maven dot Apache dot org slash

maven2 you will find all the libraries

that are available publicly under

maven and maven repository and you

should be able to use them by declaring

them as dependencies in your project do

a ctrl f search for j unit and you will

see that there is a j unit here so maven

when it builds it uses the group ID to

create a folder under the repository so

click on that j unit it creates a

subfolder again with the artifact ID if

you go to the pom dot xml for

j unit both the group ID and artifact

id are j unit they haven't used any

domain name or a URL in the group ID so

j unit another sub folder under it j

unit and one more folder using the

version information so whatever version

the j unit developers would have defined

in their pom dot XML maven uses that

version there are different versions

here click on 3.8.1

and you will find all the

artifacts under it that is how maven

will put the final output into the

repository here the j unit jar again the

artifact ID is used to name this jar

file hyphen the version information is

used dot the jar or war depending on the

project type in the maven dot XML for

example in our case we have defined it

as a jar if we want certain libraries

that are not available in the central

repository then we'll have to use a

enterprise level repository there are

several free products and also

commercial products that are available

that will create a local repository

within our enterprise that can mirror

the central repository and we can add

whatever jars we want in this case for

example Oracle dot jar if it is not

available in the open public repository

we can create a repository locally on a

server running in our enterprise and we

can put it there and then all the

projects in our all the projects or the

teams or the developers we think who are

within our enterprise should be able to

use it also we can push all the project

jars that are local to our enterprise

into this central repository and all the

teams will be able to use those jars

from that point maven also creates a

local repository on a developer's

machine it's not going to fetch these

plugins and jars every time we run maven

install it will pull these charts

the very first time and then it will

locate or put them into our local

repository on your machine the location

of it is under your user directory on

windows go to your users directory under

documents and browse to your user

directory you will find a folder called

dot m2 on Mac go to finder hit ctrl

shift H that is the shortcut to get to

the user directory under my user

directory or ever use a directory you

will find a dot M to folder which is the

hidden

folder click on that and you will find

the repository folder double-click and

you will see all the dependencies are

all the jars here so whatever is

required maven will download them and

put them here under the repository let's

browse to the j unit portion j unit j

unit you will see the version

information and then the j unit dot jar

in your case you might see only certain

versions because i have been using j

unit and different versions of it I see

all these folders if you don't see all

of them that's okay but what is key is

that you should know under your users

directory there is a dot m to folder

which maven creates and it also creates

a folder called repository under which

it will pull and place all the jar files

using the group ID artifact ID version

and then the jar file if it is a war it

will place the war file here you can

also see the project you have created

the hello maven project for me under

dot m2 repository com bharath hello

maven if you have used a different group

ID your folder will be different and

hello under hello maven it uses the one

dot o hyphen snapshot which is the

version information from our forum if

you see com dot bharath is the group ID

so it has created com and then Bharath

similar to how packaging works in Java

and then hello maven when is the artifact

ID it has created one more folder the

version information one more folder this

way we can uniquely place a project into

its sub directories and finally the jar

file which uses the artifact ID the

version information and then the dot jar

is derived from the packaging.