1.what is Maven?

Introduction

       Maven, a Yiddish word meaning accumulator
of knowledge, was originally started as an attempt to simplify the build processes in the Jakarta Turbine project. There were several projects each with their own Ant build files that were all slightly different and JARs were checked into CVS. We wanted
a standard way to build the projects, a clear definition of what the project consisted of, an easy way to publish project information and a way to share JARs across several projects.

      The result is a tool that can now be used for
building and managing any Java-based project. We hope that we have created something that will make the day-to-day work of Java developers easier and generally help with the comprehension of any Java-based project.

Maven's Objectives

Maven's primary goal is to allow a developer to comprehend the complete state of a development effort in the shortest period of time. In order to attain this goal there are several areas of concern that Maven attempts to deal with:

Making the build process easy

While using Maven doesn't eliminate(消除) the need to know about the underlying mechanisms, Maven does provide a lot of shielding from the details.

Providing a uniform build system

Maven allows a project to build using its
project object model (POM) and a set of plugins that are shared by all projects using Maven, providing a uniform build system. Once you familiarize yourself with how one Maven project builds you automatically know how all Maven projects
build saving you immense amounts （巨大的;浩瀚的）of time when trying to navigate many projects.

Providing quality project information
Maven provides plenty of useful project information that is in part taken from your POM and in part generated from your project's sources. For example, Maven can provide:

Change log document created directly from source control

Cross referenced sources

Mailing lists

Dependency list

Unit test reports including coverage
As Maven improves the information set provided will improve, all of which will be transparent to users of Maven.

Other products can also provide Maven plugins to allow their set of project information alongside some of the standard information given by Maven, all still based on the POM.

 

Providing guidelines for best practices development
Maven aims to gather current principles for best practices development, and make it easy to guide a project in that direction.

For example, specification, execution, and reporting of unit tests are part of the normal build cycle using Maven.
Current unit testing best practices were used as guidelines:

Keeping your test source code in a separate, but parallel source tree

Using test case naming conventions to locate and execute tests

Have test cases setup their environment and don't rely on customizing the build for test preparation.
Maven also aims to assist in project workflow such as release management and issue tracking.

Maven also suggests some guidelines on how to layout your project's directory structure so that once you learn the layout you can easily navigate any other project that uses Maven and the same defaults.

 

Allowing transparent migration(迁移) to new features
Maven provides an easy way for Maven clients to update their installations so that they can take advantage of any changes that been made to Maven itself.

Installation of new or updated plugins from third parties or Maven itself has been made trivial for this reason.