java 在 exec-maven-plugin 中设置 systemProperty 不起作用
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set systemProperty in exec-maven-plugin does not work
提问by Tran Ngu Dang
Here is my pom.xml file:
这是我的 pom.xml 文件：
<project>
<modelVersion>4.0.0</modelVersion>
<groupId>com.test</groupId>
<artifactId>test</artifactId>
<version>1.0-SNAPSHOT</version>
<profiles>
<profile>
<id>my_proj</id>
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.4.0</version>
<executions>
<execution>
<phase>install</phase>
<goals>
<goal>exec</goal>
</goals>
</execution>
</executions>
<configuration>
<executable>java</executable>
<arguments>
<argument>-classpath</argument>
<classpath />
<argument>com.test.Main</argument>
</arguments>
<systemProperties>
<systemProperty>
<key>someKey</key>
<value>someValue</value>
</systemProperty>
</systemProperties>
<environmentVariables>
<someKey>
someValue
</someKey>
</environmentVariables>
</configuration>
</plugin>
</plugins>
</build>
</profile>
</profiles>
</project>
and in Main.java
并在 Main.java 中
public static void main(String[] args) {
System.out.println("hello world" + System.getenv("someKey") + " " + System.getProperty("someKey"));
}
the output when I run
我运行时的输出
mvn install -Pmy_proj
is
是
hello worldsomeValue null
I cannot seem to get the systemProperty value. What did I do wrong ?
我似乎无法获得 systemProperty 值。我做错了什么 ？
回答by A_Di-Matteo
The systemPropertydoes not work simply because it is not an expected element of the execgoal of the exec-maven-plugin.
的systemProperty，因为它不是的预期元素不只是工作exec的目标exec-maven-plugin。
Check the official execgoal page, no systemPropertieselement is specified. As such, your configuration is still valid for Maven simply because is well-formed XML, but it is ignored by the exec-maven-plugin.
检查官方exec目标页面，没有systemProperties指定元素。因此，您的配置对 Maven 仍然有效，因为它是格式良好的 XML，但它被exec-maven-plugin.
From official Maven Pom Referenceconcerning the plugin configurationelement:
来自关于插件元素的官方Maven Pom 参考configuration：
It may be good to note that all configuration elements, wherever they are within the POM, are intended to pass values to another underlying system, such as a plugin. In other words: values within a configuration element are never explicitly required by the POM schema, but a plugin goal has every right to require configuration values.
最好注意所有配置元素，无论它们位于 POM 中的哪个位置，都旨在将值传递给另一个底层系统，例如插件。换句话说：POM 模式从不明确要求配置元素中的值，但插件目标完全有权要求配置值。
You are making confusion with the systemPropertiesconfiguration entry foreseen by its javagoal. This option is available there because of its context: it's crafted for java executions. On the other hand, the execgoal is much more generic and as such cannot foresee an option required only by java programs.
您正在混淆systemProperties其java目标所预见的配置条目。这个选项在那里可用是因为它的上下文：它是为 java 执行而设计的。另一方面，exec目标更加通用，因此无法预见仅 Java 程序需要的选项。
To pass system properties to a Java execution via the execgoal, you can use the argumentsconfiguration entry and use the -Dnotation
要通过exec目标将系统属性传递给 Java 执行，您可以使用arguments配置条目并使用-D符号
-Dproperty=valueSets a system property value.
-Dproperty=value设置系统属性值。
Further note, as per official Running Java programs with the exec goaldocumentation, the -Darguments should go first:
进一步注意，根据带有 exec 目标文档的官方运行 Java 程序，-D参数应该放在最前面：
<configuration>
<executable>java</executable>
<arguments>
<argument>-DsomeKey2=someValue2</argument>
<argument>-classpath</argument>
<classpath />
<argument>com.test.Main</argument>
</arguments>
<environmentVariables>
<someKey>someValue</someKey>
</environmentVariables>
</configuration>
Moreover, you should not set the same variable name for environment and as system property, the system property would not be set otherwise.
此外，您不应该为环境和系统属性设置相同的变量名，否则系统属性将不会被设置。
