BridgeLi's Blog

一般我们在公司工作中，很少有人就负责一个项目，而负责不同的项目，由于各种原因使用的 JDK 版本可能并不相同，如果存在不兼容的情况，那么本地 mvn clean compile 的时候就会报错，这个时候就需要我们去修改我们设置的环境变量，如果多个项目同时开发，那么就需要时不时切来切去，特别烦人，其实这个问题 maven 早就替大家考虑过了，我们只需要：

1. 修改 maven 的 toolchains.xml 文件

<?xml version="1.0" encoding="UTF-8"?>

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    http://www.apache.org/licenses/LICENSE-2.0

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specific language governing permissions and limitations
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<!--
 | This is the toolchains file for Maven. It can be specified at two levels:
 |
 |  1. User Level. This toolchains.xml file provides configuration for a single user,
 |                 and is normally provided in ${user.home}/.m2/toolchains.xml.
 |
 |                 NOTE: This location can be overridden with the CLI option:
 |
 |                 -t /path/to/user/toolchains.xml
 |
 |  2. Global Level. This toolchains.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}/toolchains.xml.
 |
 |                 NOTE: This location can be overridden with the CLI option:
 |
 |                 -gt /path/to/global/toolchains.xml
 |
 | The sections in this sample file are intended to give you a running start at
 | getting the most out of your Maven installation.
 |-->
<toolchains xmlns="http://maven.apache.org/TOOLCHAINS/1.1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/TOOLCHAINS/1.1.0 http://maven.apache.org/xsd/toolchains-1.1.0.xsd">

  <!-- 
   | With toolchains you can refer to installations on your system. This 
   | way you don't have to hardcode paths in your pom.xml. 
   | 
   | Every toolchain consist of 3 elements: 
   | * type: the type of tool. An often used value is 'jdk'. Toolchains-aware 
   |   plugins should document which type you must use. 
   | 
   | * provides: A list of key/value-pairs. 
   |   Based on the toolchain-configuration in the pom.xml Maven will search for 
   |   matching <provides/> configuration. You can decide for yourself which key-value 
   |   pairs to use. Often used keys are 'version', 'vendor' and 'arch'. By default 
   |   the version has a special meaning. If you configured in the pom.xml '1.5' 
   |   Maven will search for 1.5 and above.
   |   
   | * configuration: Additional configuration for this tool.
   |   Look for documentation of the toolchains-aware plugin which configuration elements
   |   can be used.   
   |
   | See also https://maven.apache.org/guides/mini/guide-using-toolchains.html
   |
   | General example

  <toolchain>
    <type/>
    <provides> 
      <version>1.0</version> 
    </provides> 
    <configuration/>
  </toolchain>
   
   | JDK examples

  <toolchain>
    <type>jdk</type>
    <provides>
      <version>1.5</version>
      <vendor>sun</vendor>
    </provides>
    <configuration>
      <jdkHome>/path/to/jdk/1.5</jdkHome>
    </configuration>
  </toolchain>
  <toolchain>
    <type>jdk</type>
    <provides>
      <version>1.6</version>
      <vendor>sun</vendor>
    </provides>
    <configuration>
      <jdkHome>/path/to/jdk/1.6</jdkHome>
    </configuration>
  </toolchain>
   
  -->

  <toolchain>
    <type>jdk</type>
    <provides>
      <version>17</version>
    </provides>
    <configuration>
      <jdkHome>D:\J2EE\Java\jdk-17</jdkHome>
    </configuration>
  </toolchain>
  <toolchain>
    <type>jdk</type>
    <provides>
      <version>8</version>
    </provides>
    <configuration>
      <jdkHome>D:\J2EE\Java\jdk1.8.0_311</jdkHome>
    </configuration>
  </toolchain>

</toolchains>

2. 修改项目的 pom.xml 文件

    <profiles>
        <profile>
            <id>dev</id>
            <activation>
                <activeByDefault>false</activeByDefault>
            </activation>
            <build>
                <plugins>
                    <plugin>
                        <groupId>org.apache.maven.plugins</groupId>
                        <artifactId>maven-toolchains-plugin</artifactId>
                        <version>3.1.0</version>
                        <executions>
                            <execution>
                                <goals>
                                    <goal>toolchain</goal>
                                </goals>
                            </execution>
                        </executions>
                        <configuration>
                            <toolchains>
                                <jdk>
                                    <version>8</version>
                                </jdk>
                            </toolchains>
                        </configuration>
                    </plugin>
                </plugins>
            </build>
        </profile>
    </profiles>

3. 修改完我们在编译的时候只需要运行：

mvn clean compile -Pdev

即可，这样编译就会自动用 jdk8 也不是系统环境变量配置的，当然还有更简单的，我们可以修改 pom.xml 中的配置，只需要把：

<activeByDefault>false</activeByDefault>

修改成

<activeByDefault>true</activeByDefault>

这样我们只需要运行：

mvn clean compile

即可。