pom.xml maven 中的属性标记是什么意思？

Question

我在 spring 引导下工作，我在 pom.xml 文件中看到 properties 标记，但我没有不明白这是什么意思，我们可以在这个标签里做什么。

属性标签例如

   <properties>
        <java.version>1.8</java.version>
   </properties>

properties 标签是什么意思？

我还可以在 properties 标签中添加什么？

Answer 1

属性标签是什么意思？

来自官方 Maven 文档：

Properties are the last required piece to understand POM basics. Maven properties are value placeholders, like properties in Ant. Their values are accessible anywhere within a POM by using the notation ${X}, where X is the property. Or they can be used by plugins as default values, for example:

在您的情况下，您已将属性定义为 java.

的版本

现在这个属性(java.version) 以后可以在 maven pom 文件中重复使用。

来自官方 Maven 文档：

They come in five different styles:

env.X: Prefixing a variable with "env." will return the shell's environment variable. For example, ${env.PATH} contains the PATH environment variable. Note: While environment variables themselves are case-insensitive on Windows, lookup of properties is case-sensitive. In other words, while the Windows shell returns the same value for %PATH% and %Path%, Maven distinguishes between ${env.PATH} and ${env.Path}. The names of environment variables are normalized to all upper-case for the sake of reliability.

project.x: A dot (.) notated path in the POM will contain the corresponding element's value. For example: 1.0 is accessible via ${project.version}.

settings.x: A dot (.) notated path in the settings.xml will contain the corresponding element's value. For example: false is accessible via ${settings.offline}.

Java System Properties: All properties accessible via java.lang.System.getProperties() a-re available as POM properties, such as ${java.home}.

x: Set within a element in the POM. The value of value may be used as ${someVar}.

我还可以在属性标签中添加什么？

您可以在您的 maven pom 文件中添加您以后需要重用的所有变量。

例如下面的 POM 片段重用了 jackson.version 4 次。

<properties>
    <jackson.version>2.10.2</jackson.version>
    <dropwizard.version>2.0.1</dropwizard.version>
    <websocket.version>1.4.0</websocket.version>
    <apachehttp.version>4.5.10</apachehttp.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <version>${apachehttp.version}</version>
    </dependency>
    <dependency>
        <groupId>org.java-websocket</groupId>
        <artifactId>Java-WebSocket</artifactId>
        <version>${websocket.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-annotations</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.dataformat</groupId>
        <artifactId>jackson-dataformat-yaml</artifactId>
        <version>${jackson.version}</version>
    </dependency>
 <dependencies>

参考资料：

Maven Pom Properties

pom.xml maven 中的属性标记是什么意思？

What does properties tag mean in pom.xml maven?

pom.xml

maven

spring-boot