`maven`的`optional`用法

例子详细用法请参考链接
例子中demo-optional-plugin用于模拟第三方插件，demo-tester用于模拟第三方插件调用者。demo-optional-plugin中声明org.apache.commons:commons-lang3依赖的optional为true表示此依赖不传递，调用者需要手动引入org.apache.commons:commons-lang3依赖否则会报告NoClassDefFoundError。

demo-optional-plugin/pom.xml内容如下：

xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.future.demo</groupId>
    <artifactId>demo-optional-plugin</artifactId>
    <version>1.0.0</version>
    <packaging>jar</packaging>

    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.14.0</version>
            <!-- 默认的scope值compile -->
            <scope>compile</scope>
            <!--
                控制org.apache.commons:commons-lang3的依赖传递，optional=true时此依赖不会传递
                调用者需要手动引入此依赖，否则报告NoClassDefFoundError
            -->
            <optional>true</optional>
        </dependency>
    </dependencies>

</project>

demo-tester/pom.xml内容如下：

xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.future.demo</groupId>
    <artifactId>demo-tester</artifactId>
    <version>1.0.0</version>
    <packaging>jar</packaging>

    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>

        <!-- 引用com.future.demo:demo-optional-plugin插件 -->
        <dependency>
            <groupId>com.future.demo</groupId>
            <artifactId>demo-optional-plugin</artifactId>
            <version>1.0.0</version>
        </dependency>
        <!--
            因为插件中声明org.apache.commons:commons-lang3依赖为optional=true，
            所以需要手动引入依赖，否则报告NoClassDefFoundError错误
        -->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.14.0</version>
        </dependency>
    </dependencies>

</project>

测试演示步骤如下：

先在本地编译和安装demo-optional-plugin

bash

# 进入demo-optional-plugin目录
cd demo-optional-plugin

# 编译和安装插件
mvn package install

使用IntelliJ IDEA运行demo-tester中的测试

maven的optional用法 ​

`maven`的`optional`用法