一什么是 Maven
Maven是项目管理工具，开发者可以将自己的代码编写好之后打包成后缀名为.jar的文件，俗称jar包。在项目中引入jar包可以直接复用他人编写好的代码，从而实现相应功能。比如我们将要在开发中使用Spring Boot框架，其本质就是在使用该框架概念中的一系列jar包。在传统的方式中我们一般通过各种渠道手动下载jar包，这样产生的问题是获取和管理各类jar包都显得十分麻烦。在使用Maven之后，我们可以直接在其提供的pom.xml中编写标签内容，在网络通畅的前提下，Maven将直接访问网上的仓库并下载jar包到我们本地的仓库路径当中，同时自动将jar包添加进项目，可以说是非常方便了。
类似Python种的pip conda 之类的！！！
二 官网下载
其实现在的Eclipse中都集成的有maven，但是默认的maven很不好用，所以我们可以选择自己在官网下载，然后配置自己的maven本地仓库。
进入官网下载地址 http://maven.apache.org/download.cgi
上一篇：c#运行的三个net环境
五 在Eclipse中创建Maven项目
首先打开Eclipse，点击New 一个项目，选择other后选择 maven project
注意pom.xml文件
点击Apply后 再进入User Settings，点击Browse，添加setting.xml后点击Update Settings。
此时会发现Local Repository（本地仓库）就成为我们设置的存放地址了。
对于setting.xml注意：
1 文件中不能有任何中文字符，包括注释
2 路径用 / 而非windows下的
3 编码格式为 UTF-8
这里改好后也可以将setting.xml文件复制到D盘中的repository文件夹中的maven文件夹下，即跟以后下载的jar包放到一起，这样方便查看。
四 关联Eclipse和Maven
点击Windows菜单栏下的Preference，找到maven下的Installations，先点击Add，找到maven的安装路径添加，改好后如下图所示
用EditPlus打开
修改settings.xml文件如下：
<?xml version="1.0" encoding="UTF-8"?>
<!--
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements. See the NOTICE file
distributed with this work for additional information
regarding copyright ownership. The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
<!--
| This is the configuration file for Maven. It can be specified at two levels:
|
| 1. User Level. This settings.xml file provides configuration for a single user,
| and is normally provided in ${user.home}/.m2/settings.xml.
|
| NOTE: This location can be overridden with the CLI option:
|
| -s /path/to/user/settings.xml
|
| 2. Global Level. This settings.xml file provides configuration for all Maven
| users on a machine (assuming they're all using the same Maven
| installation). It's normally provided in
| ${maven.conf}/settings.xml.
|
| NOTE: This location can be overridden with the CLI option:
|
| -gs /path/to/global/settings.xml
|
| The sections in this sample file are intended to give you a running start at
| getting the most out of your Maven installation. Where appropriate, the default
| values (values used when the setting is not specified) are provided.
|
|-->
<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
<!-- localRepository
| The path to the local repository maven will use to store artifacts.
|
| Default: ${user.home}/.m2/repository
<localRepository>/path/to/local/repo</localRepository>
-->
<localRepository>D:/java bbs/tools/repository</localRepository>·
<!-- interactiveMode
| This will determine whether maven prompts you when it needs input. If set to false,
| maven will use a sensible default value, perhaps based on some other setting, for
| the parameter in question.
|
| Default: true
<interactiveMode>true</interactiveMode>
-->
<!-- offline
| Determines whether maven should attempt to connect to the network when executing a build.
| This will have an effect on artifact downloads, artifact deployment, and others.
|
| Default: false
<offline>false</offline>
-->
<!-- pluginGroups
| This is a list of additional group identifiers that will be searched when resolving plugins by their prefix, i.e.
| when invoking a command line like "mvn prefix:goal". Maven will automatically add the group identifiers
| "org.apache.maven.plugins" and "org.codehaus.mojo" if these are not already contained in the list.
|-->
<pluginGroups>
<!-- pluginGroup
| Specifies a further group identifier to use for plugin lookup.
<pluginGroup>com.your.plugins</pluginGroup>
-->
</pluginGroups>
<!-- proxies
| This is a list of proxies which can be used on this machine to connect to the network.
| Unless otherwise specified (by system property or command-line switch), the first proxy
| specification in this list marked as active will be used.
|-->
<proxies>
<!-- proxy
| Specification for one proxy, to be used in connecting to the network.
|
<proxy>
<id>optional</id>
<active>true</active>
<protocol>http</protocol>
<username>proxyuser</username>
<password>proxypass</password>
<host>proxy.host.net</host>
<port>80</port>
<nonProxyHosts>local.net|some.host.com</nonProxyHosts>
</proxy>
-->
</proxies>
<!-- servers
| This is a list of authentication profiles, keyed by the server-id used within the system.
| Authentication profiles can be used whenever maven must make a connection to a remote server.
|-->
<servers>
<!-- server
| Specifies the authentication information to use when connecting to a particular server, identified by
| a unique name within the system (referred to by the 'id' attribute below).
|
| NOTE: You should either specify username/password OR privateKey/passphrase, since these pairings are
| used together.
|
<server>
<id>deploymentRepo</id>
<username>repouser</username>
<password>repopwd</password>
</server>
-->
<!-- Another sample, using keys to authenticate.
<server>
<id>siteServer</id>
<privateKey>/path/to/private/key</privateKey>
<passphrase>optional; leave empty if not used.</passphrase>
</server>
-->
</servers>
<!-- mirrors
| This is a list of mirrors to be used in downloading artifacts from remote repositories.
|
| It works like this: a POM may declare a repository to use in resolving certain artifacts.
| However, this repository may have problems with heavy traffic at times, so people have mirrored
| it to several places.
|
| That repository definition will have a unique id, so we can create a mirror reference for that
| repository, to be used as an alternate download site. The mirror site will be the preferred
| server for that repository.
|-->
<!-- mirror
<mirrors>
| Specifies a repository mirror site to use instead of a given repository. The repository that
| this mirror serves has an ID that matches the mirrorOf element of this mirror. IDs are used
| for inheritance and direct lookup purposes, and must be unique across the set of mirrors.
|
<mirror>
<id>mirrorId</id>
<mirrorOf>repositoryId</mirrorOf>
<name>Human Readable Name for this Mirror.</name>
<url>http://my.repository.com/repo/path</url>
</mirror>
</mirrors>
-->
<!-- 阿里云仓库 -->
<mirrors>
<mirror>
<id>nexus-aliyun</id>
<mirrorOf>*</mirrorOf>
<name>Nexus aliyun</name>
<url>http://maven.aliyun.com/nexus/content/groups/public</url>
</mirror>
<!-- 中央仓库1 -->
<!-- 中央仓库2 -->
<mirror>
<id>repo2</id>
<mirrorOf>central</mirrorOf>
<name>Human Readable Name for this Mirror.</name>
<url>http://repo2.maven.org/maven2/</url>
</mirror>
</mirrors>
<!-- profiles
| This is a list of profiles which can be activated in a variety of ways, and which can modify
| the build process. Profiles provided in the settings.xml are intended to provide local machine-
| specific paths and repository locations which allow the build to work in the local environment.
|
| For example, if you have an integration testing plugin - like cactus - that needs to know where
| your Tomcat instance is installed, you can provide a variable here such that the variable is
| dereferenced during the build process to configure the cactus plugin.
|
| As noted above, profiles can be activated in a variety of ways. One way - the activeProfiles
| section of this document (settings.xml) - will be discussed later. Another way essentially
| relies on the detection of a system property, either matching a particular value for the property,
| or merely testing its existence. Profiles can also be activated by JDK version prefix, where a
| value of '1.4' might activate a profile when the build is executed on a JDK version of '1.4.2_07'.
| Finally, the list of active profiles can be specified directly from the command line.
|
| NOTE: For profiles defined in the settings.xml, you are restricted to specifying only artifact
| repositories, plugin repositories, and free-form properties to be used as configuration
| variables for plugins in the POM.
|
|-->
<!-- profile
<profiles>
| Specifies a set of introductions to the build process, to be activated using one or more of the
| mechanisms described above. For inheritance purposes, and to activate profiles via <activatedProfiles/>
| or the command line, profiles have to have an ID that is unique.
|
| An encouraged best practice for profile identification is to use a consistent naming convention
| for profiles, such as 'env-dev', 'env-test', 'env-production', 'user-jdcasey', 'user-brett', etc.
| This will make it more intuitive to understand what the set of introduced profiles is attempting
| to accomplish, particularly when you only have a list of profile id's for debug.
|
| This profile example uses the JDK version to trigger activation, and provides a JDK-specific repo.
<profile>
<id>jdk-1.4</id>
<activation>
<jdk>1.4</jdk>
</activation>
<repositories>
<repository>
<id>jdk14</id>
<name>Repository for JDK 1.4 builds</name>
<url>http://www.myhost.com/maven/jdk14</url>
<layout>default</layout>
<snapshotPolicy>always</snapshotPolicy>
</repository>
</repositories>
</profile>
-->
<!--
| Here is another profile, activated by the system property 'target-env' with a value of 'dev',
| which provides a specific path to the Tomcat instance. To use this, your plugin configuration
| might hypothetically look like:
|
| ...
| <plugin>
| <groupId>org.myco.myplugins</groupId>
| <artifactId>myplugin</artifactId>
|
| <configuration>
| <tomcatLocation>${tomcatPath}</tomcatLocation>
| </configuration>
| </plugin>
| ...
|
| NOTE: If you just wanted to inject this configuration whenever someone set 'target-env' to
| anything, you could just leave off the <value/> inside the activation-property.
|
<profile>
<id>env-dev</id>
<activation>
<property>
<name>target-env</name>
<value>dev</value>
</property>
</activation>
<properties>
<tomcatPath>/path/to/tomcat/instance</tomcatPath>
</properties>
</profile>
-->
<profiles>
<profile>
<id>jdk-1.8</id>
<activation>
<activeByDefault>true</activeByDefault>
<jdk>1.8</jdk>
</activation>
<properties>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
<maven.compiler.compilerVersion>1.8</maven.compiler.compilerVersion>
</properties>
</profile>
</profiles>
<!-- activeProfiles
| List of profiles that are active for all builds.
|
<activeProfiles>
<activeProfile>alwaysActiveProfile</activeProfile>
<activeProfile>anotherAlwaysActiveProfile</activeProfile>
</activeProfiles>
-->
</settings>
