写在前面

你还在为导入jar包而苦恼吗？常常找不到jar包，不知道从哪导入，就算导入了可能还会依赖冲突，目录杂乱，那么maven你值得拥有。
什么是jar包？jar [dʒɑː(r )] n.罐子…v.使烦躁…，~~让人烦躁的包~~
在这里插入图片描述
~~记录踩过的坑，被支配的恐惧😱~~

Maven

什么是Mavrn？
Maven 是专门用于构建和管理Java相关项目的工具。Maven把所有的jar包都放在本地仓库中，在pom.xml声明包名和版本号即可，避免新建项目时繁琐导入jar包，实现了jar包共享，使用Maven管理的项目具有相同的目录结构，便于统一管理。

下载安装

前往官网http://maven.apache.org/download.cgi下载
github下载
下载后解压到一个空文件夹(如D:\Maven)

配置环境变量

右键此电脑->属性->高级系统设置->环境设置
在这里插入图片描述

点击新建变量
变量名M2_HOME
变量值是解压目录(如D:\Maven)

编辑path，新建D:\Maven\bin

至此环境变量就配置好了，按下win+R输入cmd

输入mvn -v测试是否配置成功

配置settings.xml

打开解压目录/conf/settings.xml

修改< mirror >
使用默认的下载慢点就算了，关键还一直报错，这里直接修改成使用阿里云镜像
在< mirrors >中添加代码：

<mirror>      <id>nexus-aliyun</id>    <name>nexus-aliyun</name>  <url>http://maven.aliyun.com/nexus/content/groups/public</url>    <mirrorOf>central</mirrorOf>      
</mirror>

修改< profile >
设置jdk为1.8（或者自己使用的版本），避免新建和更新工程后一直变成默认的jdk1.5
在< profiles >中添加代码：

<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>

懒人一键复制替换：

<?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 athttp://www.apache.org/licenses/LICENSE-2.0Unless 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>--><!-- 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.|--><mirrors><!-- mirror| 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>-->
<mirror>      <id>nexus-aliyun</id>    <name>nexus-aliyun</name>  <url>http://maven.aliyun.com/nexus/content/groups/public</url>    <mirrorOf>central</mirrorOf>      
</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.||--><profiles><!-- profile| 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>-->
<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>

当然这里还可以配置一些其他东西，如本地仓库地址等等，我这里使用默认。

eclipse创建示例

设置maven相关

检查是否配置成功：
Windows->Show View->Maven Repositories

看到是我们之前配置阿里云镜像地址就成功了
新建maven工程
file->new->Maven Project

如果没有这一栏不要慌，选择other，搜索maven
生成web.xml
右键项目->Properties

勾上Dynamic Web Module，点击下方蓝色链接（如果已经勾过，取消勾中后Apply或Ok再勾就有链接了）
如果点开Project facets后没有下图所示复选框等，点击出现的链接，耐心等待进度条加载后即可。

输入src\main\webapp

4.配置pom.xml
最后就是申明你需要用的jar包，版本号等，可以去maven repository官网查询
比如spring jdbc相应jar包

选择你需要的版本

将对应代码加到pom.xml中即可，点击保存后，maven会自动下载导入jar包，maven就开始大显神通了