IntelliJ IDEA Maven 編譯出錯run運行無反應

在使用IDEA的時候，出現過多次因爲maven環境原因，導致編譯出錯，找不到包或者找不到符號，或者點擊run無反應的情況。以下說明一些常見的情況，以及處理方式。

1.該項目未被識別爲maven項目

在pom.xml上，右鍵add as maven。

2.該項目的pom發生了更改，jar包未引入成功

在pom.xml上，右鍵maven reinport

3.jar無法下載下來

比如你設置了公司內網下的鏡像，導致無法下載，建議直接設置爲阿里雲和maven的倉庫。
jar包的查找順序：本地倉庫->公司或者團隊私有庫->阿里雲鏡像->maven鏡像。
maven 配置setting文件：（file->setting->build execution deployment）

一個可供參考的setting配置文件：

<?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.home}/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>C:\Users\Administrator\.m2\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.
     |-->
    <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>ibiblio</id>
          <mirrorOf>central</mirrorOf>
          <name>Human Readable Name for this Mirror.</name>
          <url>http://mirrors.ibiblio.org/maven2/</url>
        </mirror>
         -->

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

        <mirror>
            <id>nexus</id>
            <name>internal nexus repository</name>
            <url>http://repo.maven.apache.org/maven2</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>-->
            <!--<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>

4、jar包在本地倉庫已經存在，但是在maven項目上依然顯示紅線，或者引用不到

刪除本地庫中的對應jar包，然後maven reinport

5、重新編譯

（1）刪除項目下所有target文件，重新編譯。菜單欄Build ->Build Project。（也可以直接Rebuild Project，該操作會刪除target，重新編譯）。
（2）右側maven project->lifecycle->maven clean 也會刪除本地target，重新編譯。

6、點擊run或者debug後變灰色，無反應

（1）該問題在springcloud項目中出現的比較多。需要查看出錯模塊的pom是否有問題，測試方式是刪除某一個或者幾個jar包引用後，maven reimport，然後重新編譯項目是否報錯。如果依舊無任何反應，很可能是pom文件出現了問題，建議從其他正常模塊中拷貝一個pom文件（空的），逐個增加jar包引入，編譯，排查是哪個jar的問題。（我是這麼解決的）

7、項目使用的jdk版本是否一致

項目使用jdk版本

項目編譯的jdk版本

8、文件編碼

9、父子項目的編譯

父子項目的編譯，需要在父項目上進行maven compile或者package操作，父項目會確定項目編譯的先後順序，被依賴項目將會最先運行。
或者，在運行模塊前，先maven install其子模塊。（maven install操作會將本模塊打包註冊到本地倉庫）

10、invalidate and restart

羣途末路了，可以試下，將會清除ide緩存

題外話：
設置默認的setting或者project structure可以通過file->other setting進入設置。