Apache Maven

Welcome to Apache Maven

Apache Maven is a software project management and comprehension tool. Based on the concept of a project object model (POM), Maven can manage a project's build, reporting and documentation from a central piece of information.

If you think that Maven could help your project, you can find out more information about in the "About Maven" section of the navigation. This includes an in-depth description of what Maven is, a list of some of its main features, and a set of frequently asked questions about what Maven is.

This site is separated into the following sections, depending on how you'd like to use Maven:

Use	Download, Install, Run Maven	Configure, Use Maven and Maven Plugins
	Information for those needing to build a project that uses Maven	Information for those wanting to use Maven to build their project, including a "10 minute test" that gives a practical overview of Maven's main features in just 10 minutes and plugin list for more information on each plugin
Extend	Write Maven Plugins	Improve the Maven Central Repository
	Information for those who want to provide a Maven plugin for shared functionality or to accompany their own product or toolset	Information for those who may or may not use Maven, but are interested in getting project metadata into the central repository
Contribute	Help Maven	Develop Maven
	Information if you'd like to get involved: Maven is an open source community and welcomes contributions.	Information for those who are currently developers, or who are interested in contributing to the Maven project itself

Each guide is divided into a number of trails to get you started on a particular topic, and includes a reference area and a "cookbook" of common examples.

You can access the guides at any time from the left navigation. If you are looking for a quick reference, you can use the documentation index.

GIT

DESCRIPTION

Git is a fast distributed revision control system.

This manual is designed to be readable by someone with basic UNIX command-line skills, but no previous knowledge of Git.

This tutorial explains how to import a new project into Git, make changes to it, and share changes with other developers.

If you are instead primarily interested in using Git to fetch a project, for example, to test the latest version, you may prefer to start with the first two chapters of The Git User’s Manual.

First, note that you can get documentation for a command such as git log --graph with:

$ man git-log

or:

$ git help log

With the latter, you can use the manual viewer of your choice; see git-help[1] for more information.

It is a good idea to introduce yourself to Git with your name and public email address before doing any operation. The easiest way to do so is:

$ git config --global user.name "Your Name Comes Here"
$ git config --global user.email you@yourdomain.example.com

Importing a new project

Assume you have a tarball project.tar.gz with your initial work. You can place it under Git revision control as follows.

$ tar xzf project.tar.gz
$ cd project
$ git init

Git will reply

Initialized empty Git repository in .git/

You’ve now initialized the working directory—​you may notice a new directory created, named ".git".

Next, tell Git to take a snapshot of the contents of all files under the current directory (note the .), with git add:

$ git add .

This snapshot is now stored in a temporary staging area which Git calls the "index". You can permanently store the contents of the index in the repository with git commit:

$ git commit

This will prompt you for a commit message. You’ve now stored the first version of your project in Git.

Making changes

Modify some files, then add their updated contents to the index:

$ git add file1 file2 file3

You are now ready to commit. You can see what is about to be committed using git diff with the --cached option:

$ git diff --cached

(Without --cached, git diff will show you any changes that you’ve made but not yet added to the index.) You can also get a brief summary of the situation with git status:

$ git status
On branch master
Changes to be committed:
Your branch is up to date with 'origin/master'.
  (use "git reset HEAD <file>..." to unstage)

 modified:   file1
 modified:   file2
 modified:   file3

If you need to make any further adjustments, do so now, and then add any newly modified content to the index. Finally, commit your changes with:

$ git commit

This will again prompt you for a message describing the change, and then record a new version of the project.

Alternatively, instead of running git add beforehand, you can use

$ git commit -a

which will automatically notice any modified (but not new) files, add them to the index, and commit, all in one step.

A note on commit messages: Though not required, it’s a good idea to begin the commit message with a single short (less than 50 character) line summarizing the change, followed by a blank line and then a more thorough description. The text up to the first blank line in a commit message is treated as the commit title, and that title is used throughout Git. For example, git-format-patch[1] turns a commit into email, and it uses the title on the Subject line and the rest of the commit in the body.

Git tracks content not files

Many revision control systems provide an add command that tells the system to start tracking changes to a new file. Git’s add command does something simpler and more powerful: git add is used both for new and newly modified files, and in both cases it takes a snapshot of the given files and stages that content in the index, ready for inclusion in the next commit.

Viewing project history

At any point you can view the history of your changes using

$ git log

If you also want to see complete diffs at each step, use

$ git log -p

Often the overview of the change is useful to get a feel of each step

$ git log --stat --summary

Managing branches

A single Git repository can maintain multiple branches of development. To create a new branch named "experimental", use

$ git branch experimental

If you now run

$ git branch

you’ll get a list of all existing branches:

  experimental
* master

The "experimental" branch is the one you just created, and the "master" branch is a default branch that was created for you automatically. The asterisk marks the branch you are currently on; type

$ git checkout experimental

to switch to the experimental branch. Now edit a file, commit the change, and switch back to the master branch:

(edit file)
$ git commit -a
$ git checkout master

Check that the change you made is no longer visible, since it was made on the experimental branch and you’re back on the master branch.

You can make a different change on the master branch:

(edit file)
$ git commit -a

at this point the two branches have diverged, with different changes made in each. To merge the changes made in experimental into master, run

$ git merge experimental

If the changes don’t conflict, you’re done. If there are conflicts, markers will be left in the problematic files showing the conflict;

$ git diff

will show this. Once you’ve edited the files to resolve the conflicts,

$ git commit -a

will commit the result of the merge. Finally,

$ gitk

will show a nice graphical representation of the resulting history.

At this point you could delete the experimental branch with

$ git branch -d experimental

This command ensures that the changes in the experimental branch are already in the current branch.

If you develop on a branch crazy-idea, then regret it, you can always delete the branch with

$ git branch -D crazy-idea

Branches are cheap and easy, so this is a good way to try something out.

Using Git for collaboration

Suppose that Alice has started a new project with a Git repository in /home/alice/project, and that Bob, who has a home directory on the same machine, wants to contribute.

Bob begins with:

bob$ git clone /home/alice/project myrepo

This creates a new directory "myrepo" containing a clone of Alice’s repository. The clone is on an equal footing with the original project, possessing its own copy of the original project’s history.

Bob then makes some changes and commits them:

(edit files)
bob$ git commit -a
(repeat as necessary)

When he’s ready, he tells Alice to pull changes from the repository at /home/bob/myrepo. She does this with:

alice$ cd /home/alice/project
alice$ git pull /home/bob/myrepo master

This merges the changes from Bob’s "master" branch into Alice’s current branch. If Alice has made her own changes in the meantime, then she may need to manually fix any conflicts.

The "pull" command thus performs two operations: it fetches changes from a remote branch, then merges them into the current branch.

Note that in general, Alice would want her local changes committed before initiating this "pull". If Bob’s work conflicts with what Alice did since their histories forked, Alice will use her working tree and the index to resolve conflicts, and existing local changes will interfere with the conflict resolution process (Git will still perform the fetch but will refuse to merge --- Alice will have to get rid of her local changes in some way and pull again when this happens).

Alice can peek at what Bob did without merging first, using the "fetch" command; this allows Alice to inspect what Bob did, using a special symbol "FETCH_HEAD", in order to determine if he has anything worth pulling, like this:

alice$ git fetch /home/bob/myrepo master
alice$ git log -p HEAD..FETCH_HEAD

This operation is safe even if Alice has uncommitted local changes. The range notation "HEAD..FETCH_HEAD" means "show everything that is reachable from the FETCH_HEAD but exclude anything that is reachable from HEAD". Alice already knows everything that leads to her current state (HEAD), and reviews what Bob has in his state (FETCH_HEAD) that she has not seen with this command.

If Alice wants to visualize what Bob did since their histories forked she can issue the following command:

$ gitk HEAD..FETCH_HEAD

This uses the same two-dot range notation we saw earlier with git log.

Alice may want to view what both of them did since they forked. She can use three-dot form instead of the two-dot form:

$ gitk HEAD...FETCH_HEAD

This means "show everything that is reachable from either one, but exclude anything that is reachable from both of them".

Please note that these range notation can be used with both gitk and "git log".

After inspecting what Bob did, if there is nothing urgent, Alice may decide to continue working without pulling from Bob. If Bob’s history does have something Alice would immediately need, Alice may choose to stash her work-in-progress first, do a "pull", and then finally unstash her work-in-progress on top of the resulting history.

When you are working in a small closely knit group, it is not unusual to interact with the same repository over and over again. By defining remote repository shorthand, you can make it easier:

alice$ git remote add bob /home/bob/myrepo

With this, Alice can perform the first part of the "pull" operation alone using the git fetch command without merging them with her own branch, using:

alice$ git fetch bob

Unlike the longhand form, when Alice fetches from Bob using a remote repository shorthand set up with git remote, what was fetched is stored in a remote-tracking branch, in this case bob/master. So after this:

alice$ git log -p master..bob/master

shows a list of all the changes that Bob made since he branched from Alice’s master branch.

After examining those changes, Alice could merge the changes into her master branch:

alice$ git merge bob/master

This merge can also be done by pulling from her own remote-tracking branch, like this:

alice$ git pull . remotes/bob/master

Note that git pull always merges into the current branch, regardless of what else is given on the command line.

Later, Bob can update his repo with Alice’s latest changes using

bob$ git pull

Note that he doesn’t need to give the path to Alice’s repository; when Bob cloned Alice’s repository, Git stored the location of her repository in the repository configuration, and that location is used for pulls:

bob$ git config --get remote.origin.url
/home/alice/project

(The complete configuration created by git clone is visible using git config -l, and the git-config[1]man page explains the meaning of each option.)

Git also keeps a pristine copy of Alice’s master branch under the name "origin/master":

bob$ git branch -r
  origin/master

If Bob later decides to work from a different host, he can still perform clones and pulls using the ssh protocol:

bob$ git clone alice.org:/home/alice/project myrepo

Alternatively, Git has a native protocol, or can use http; see git-pull[1] for details.

Git can also be used in a CVS-like mode, with a central repository that various users push changes to; see git-push[1] and gitcvs-migration[7].

Exploring history

Git history is represented as a series of interrelated commits. We have already seen that the git logcommand can list those commits. Note that first line of each git log entry also gives a name for the commit:

$ git log
commit c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
Author: Junio C Hamano <junkio@cox.net>
Date:   Tue May 16 17:18:22 2006 -0700

    merge-base: Clarify the comments on post processing.

We can give this name to git show to see the details about this commit.

$ git show c82a22c39cbc32576f64f5c6b3f24b99ea8149c7

But there are other ways to refer to commits. You can use any initial part of the name that is long enough to uniquely identify the commit:

$ git show c82a22c39c # the first few characters of the name are
   # usually enough
$ git show HEAD  # the tip of the current branch
$ git show experimental # the tip of the "experimental" branch

Every commit usually has one "parent" commit which points to the previous state of the project:

$ git show HEAD^  # to see the parent of HEAD
$ git show HEAD^^ # to see the grandparent of HEAD
$ git show HEAD~4 # to see the great-great grandparent of HEAD

Note that merge commits may have more than one parent:

$ git show HEAD^1 # show the first parent of HEAD (same as HEAD^)
$ git show HEAD^2 # show the second parent of HEAD

You can also give commits names of your own; after running

$ git tag v2.5 1b2e1d63ff

you can refer to 1b2e1d63ff by the name "v2.5". If you intend to share this name with other people (for example, to identify a release version), you should create a "tag" object, and perhaps sign it; see git-tag[1]for details.

Any Git command that needs to know a commit can take any of these names. For example:

$ git diff v2.5 HEAD  # compare the current HEAD to v2.5
$ git branch stable v2.5 # start a new branch named "stable" based
    # at v2.5
$ git reset --hard HEAD^ # reset your current branch and working
    # directory to its state at HEAD^

Be careful with that last command: in addition to losing any changes in the working directory, it will also remove all later commits from this branch. If this branch is the only branch containing those commits, they will be lost. Also, don’t use git reset on a publicly-visible branch that other developers pull from, as it will force needless merges on other developers to clean up the history. If you need to undo changes that you have pushed, use git revert instead.

The git grep command can search for strings in any version of your project, so

$ git grep "hello" v2.5

searches for all occurrences of "hello" in v2.5.

If you leave out the commit name, git grep will search any of the files it manages in your current directory. So

$ git grep "hello"

is a quick way to search just the files that are tracked by Git.

Many Git commands also take sets of commits, which can be specified in a number of ways. Here are some examples with git log:

$ git log v2.5..v2.6            # commits between v2.5 and v2.6
$ git log v2.5..                # commits since v2.5
$ git log --since="2 weeks ago" # commits from the last 2 weeks
$ git log v2.5.. Makefile       # commits since v2.5 which modify
    # Makefile

You can also give git log a "range" of commits where the first is not necessarily an ancestor of the second; for example, if the tips of the branches "stable" and "master" diverged from a common commit some time ago, then

$ git log stable..master

will list commits made in the master branch but not in the stable branch, while

$ git log master..stable

will show the list of commits made on the stable branch but not the master branch.

The git log command has a weakness: it must present commits in a list. When the history has lines of development that diverged and then merged back together, the order in which git log presents those commits is meaningless.

Most projects with multiple contributors (such as the Linux kernel, or Git itself) have frequent merges, and gitk does a better job of visualizing their history. For example,

$ gitk --since="2 weeks ago" drivers/

allows you to browse any commits from the last 2 weeks of commits that modified files under the "drivers" directory. (Note: you can adjust gitk’s fonts by holding down the control key while pressing "-" or "+".)

Finally, most commands that take filenames will optionally allow you to precede any filename by a commit, to specify a particular version of the file:

$ git diff v2.5:Makefile HEAD:Makefile.in

You can also use git show to see any such file:

$ git show v2.5:Makefile

Next Steps

This tutorial should be enough to perform basic distributed revision control for your projects. However, to fully understand the depth and power of Git you need to understand two simple ideas on which it is based:

• The object database is the rather elegant system used to store the history of your project—​files, directories, and commits.
• The index file is a cache of the state of a directory tree, used to create commits, check out working directories, and hold the various trees involved in a merge.

Part two of this tutorial explains the object database, the index file, and a few other odds and ends that you’ll need to make the most of Git. You can find it at gittutorial-2[7].

If you don’t want to continue with that right away, a few other digressions that may be interesting at this point are:

• git-format-patch[1], git-am[1]: These convert series of git commits into emailed patches, and vice versa, useful for projects such as the Linux kernel which rely heavily on emailed patches.
• git-bisect[1]: When there is a regression in your project, one way to track down the bug is by searching through the history to find the exact commit that’s to blame. Git bisect can help you perform a binary search for that commit. It is smart enough to perform a close-to-optimal search even in the case of complex non-linear history with lots of merged branches.
• gitworkflows[7]: Gives an overview of recommended workflows.
• giteveryday[7]: Everyday Git with 20 Commands Or So.
• gitcvs-migration[7]: Git for CVS users.

SEE ALSO

gittutorial-2[7], gitcvs-migration[7], gitcore-tutorial[7], gitglossary[7], git-help[1], gitworkflows[7],giteveryday[7], The Git User’s Manual

GIT

Reference

Quick reference guides: GitHub Cheat Sheet (PDF)  |  Visual Git Cheat Sheet (SVG | PNG)

Setup and Config

• git
• config
• help

Getting and Creating Projects

• init
• clone

Basic Snapshotting

• add
• status
• diff
• commit
• reset
• rm
• mv

Branching and Merging

• branch
• checkout
• merge
• mergetool
• log
• stash
• tag

Sharing and Updating Projects

• fetch
• pull
• push
• remote
• submodule

Inspection and Comparison

• show
• log
• diff
• shortlog
• describe

Patching

• apply
• cherry-pick
• diff
• rebase
• revert

Debugging

• bisect
• blame
• grep

Guides

• gitattributes
• Everyday Git
• Glossary
• gitignore
• gitmodules
• Revisions
• Tutorial
• Workflows

Email

• am
• apply
• format-patch
• send-email
• request-pull

External Systems

• svn
• fast-import

Administration

• clean
• gc
• fsck
• reflog
• filter-branch
• instaweb
• archive
• bundle

Server Admin

• daemon
• update-server-info

Plumbing Commands

• cat-file
• check-ignore
• checkout-index
• commit-tree
• count-objects
• diff-index
• for-each-ref
• hash-object
• ls-files
• merge-base
• read-tree
• rev-list
• rev-parse
• show-ref
• symbolic-ref
• update-index
• update-ref
• verify-pack
• write-tree

Configuration Management Tools

 

   

Continuous Integration Tools

 

  

Continuous Monitoring Tools

 

 

Testing Tools

 

Version Control Tools

 

  

Nexus

Sonatype Nexus on Amazon EC2

12 MAY 2014

Nexus OSS from Sonatype is a Maven artifact repository server.

We currently use Nexus to store the Maven artifacts of private libs and modified 3rd party open source libraries for the Yoyo App's.

It's also handy as a proxy as we can define proxing routes as know where certain projects are hosted, which alows us to speed up dependency resolution in Maven/Gradle Projects.

Hopefully following steps will help you to install Sonatype Nexus OSS on a EC2 instance on AWS.
We currently use a EC2 micro instance, we have found it's more than enough.

Login into the AWS Management Console and go to EC2
https://console.aws.amazon.com/ec2/v2/home

Create a new Security Group called Deployment.
Allow the following inbound services:

22 (SSH) 0.0.0.0/0
80 (HTTP) 0.0.0.0/0
443 (HTTPS) 0.0.0.0/0
4000 0.0.0.0/0
8080 (HTTP*) 0.0.0.0/0
8081 0.0.0.0/0 (Nexus OSS)

Launch a new EC2 instance

• Amazon Machine Image: Amazon Linux AMI – 64 bit
• Instance Type: t1.micro (micro should be plenty unless you have GB's of deps)
• Security Group: Deployment

Connect

Download KeyPair into your SSH folder (~/.ssh):

$ ~/.ssh/YOUR_KEY_PAIR.pem.

Then update the access permissions:

chmod 400 ~/.ssh/YOUR_KEY_PAIR.pem

Connect with your favourite SSH tool to your EC2 instance, find the address of your EC2 instance by selecting it in the Management Console (something like ec2-XX-XXX-XXX-XXX.compute-1.amazonaws.com).

Your cmd will look similar, if using shell/bash/zsh:

ssh -i ~/.ssh/YOUR_KEY_PAIR.pem ubuntu@ec2-XX-XXX-XXX-XXX.compute-1.amazonaws.com

Install Nexus

Once connected, download and unzip Nexus OSS.

cd /usr/local
sudo wget http://www.sonatype.org/downloads/nexus-latest-bundle.tar.gz
sudo tar -xvzf nexus-latest-bundle.tar.gz
sudo rm nexus-latest-bundle.tar.gz

Create a virtual link to the actual nexus-VERSION folder (replace nexus-2.5.1-01 with your nexus installed version)

sudo ln -s nexus-2.5.1-01/ nexus

Create NEXUS_HOME environment variable.

export NEXUS_HOME=/usr/local/nexus

Create nexus user with restricted permissions.

sudo useradd -m nexus

Change ownership of nexus folder to the nexus user and nexus group.

sudo chown -R nexus:nexus /usr/local/nexus-2.5.1-01/
sudo chown -R nexus:nexus /usr/local/sonatype-work

Edit the nexus executable (necessary for the nexus user and to run nexus as a service).
I’m using the nano editor since it’s already installed on Ubuntu.

sudo nano /usr/local/nexus/bin/nexus

Change the following lines:

NEXUS_HOME="/usr/local/nexus"
#...
RUN_AS_USER="nexus"
#...
PIDDIR="/home/nexus"

CTRL + X then Y, Enter will save the file.

Launch Nexus

Starting Nexus

cd /usr/local/nexus/bin
sudo ./nexus console

If starting fails, make sure you have a vaild JVM installed, e.g. sudo apt-get install openjdk-7-jre.

Stopping Nexus

cd /usr/local/nexus/bin
sudo ./nexus stop

Start nexus as a service

Copy the nexus starting script to /etc/init.d:

sudo cp /usr/local/nexus/bin/nexus /etc/init.d/nexus

Make the nexus script executable:

sudo chmod 755 /etc/init.d/nexus

Enable the Nexus Service settings, (You may need to install chkconfig, sudo apt-get install chkconfig):

cd /etc/init.d
chkconfig --add nexus
sudo chkconfig --level 345 nexus on

If chkconfig --add fails, link insserv, sudo ln -s /usr/lib/insserv/insserv /sbin/insserv.

Now you nexus should start automatically at each OS startup.

You can still start/stop nexus as a service manually:

sudo service nexus start|stop

Access Nexus web dashboard

Once nexus is running should be able to connect to the Nexus Dashboard using the EC2 address followed by the 8081 port and /nexus path:

http://ec2-XX-XXX-XXX-XXX.com:8081/nexus

Login into Nexus and change the default credentials.

Login using the default credentials:

username: admin password: admin123

Once you are loggedin change your admin password, OR, create a new admin account and delete the default admin credentials using the Security -> Users screen accessible through the menu on the left.

Ref:https://help.sonatype.com/display/NXRM2/Adding+Repositories+for+Missing+Dependencies