Maven“前”和“后”阶段

Question

当我执行关联的阶段时，pre和post阶段是否总是被执行？例如，如果我这样做mvn clean，这是否也会执行该mvn post-clean阶段？

我在看https://maven.apache.org/guides/introduction/introduction-to-the-lifecycle.html#Lifecycle_Reference，其中说：

下面列出了默认、清理和站点生命周期的所有构建阶段，它们按照指定的时间点之前的顺序执行。

所以严格来说，既然post-clean是在之后clean，那么我就应该不执行mvn clean。但是我的直觉是不同的 - 虽然，我没有找到一种方法来验证这一点，因为 Maven 标准输出不打印它正在执行的阶段。

任何人都可以权衡答案以及您如何验证？

Answer 1

您可以将插件（例如echo-maven-plugin）绑定到clean生命周期的各个阶段，以帮助验证是否/何时执行每个阶段。

例如，给定以下插件定义：

<plugin>
    <groupId>com.github.ekryd.echo-maven-plugin</groupId>
    <artifactId>echo-maven-plugin</artifactId>
    <version>1.2.0</version>
    <executions>
        <execution>
            <id>pre-clean</id>
            <phase>pre-clean</phase>
            <goals>
                <goal>echo</goal>
            </goals>
            <configuration>
                <message>In 'pre-clean'</message>
            </configuration>
        </execution>
        <execution>
            <id>clean</id>
            <phase>clean</phase>
            <goals>
                <goal>echo</goal>
            </goals>
            <configuration>
                <message>In 'clean'</message>
            </configuration>
        </execution>
        <execution>
            <id>post-clean</id>
            <phase>post-clean</phase>
            <goals>
                <goal>echo</goal>
            </goals>
            <configuration>
                <message>In 'post-clean'</message>
            </configuration>
        </execution>
    </executions>
</plugin>

调用mvn clean将导致以下输出：

$ mvn clean
[INFO] Scanning for projects...
[INFO] 
[INFO] --- echo-maven-plugin:1.2.0:echo (pre-clean) @ sandbox ---
[INFO] In 'pre-clean'
[INFO] 
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ sandbox ---
[INFO] Deleting target
[INFO] 
[INFO] --- echo-maven-plugin:1.2.0:echo (clean) @ sandbox ---
[INFO] In 'clean'

所以，那里没有调用post-clean阶段。

调用mvn clean compile将导致以下输出：

$ mvn clean compile
[INFO] Scanning for projects...
[INFO] 
[INFO] --- echo-maven-plugin:1.2.0:echo (pre-clean) @ sandbox ---
[INFO] In 'pre-clean'
[INFO] 
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ sandbox ---
[INFO] 
[INFO] --- echo-maven-plugin:1.2.0:echo (clean) @ sandbox ---
[INFO] In 'clean'
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ sandbox ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 1 resource
[INFO] 
[INFO] --- maven-compiler-plugin:3.5.1:compile (default-compile) @ sandbox ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 5 source files to ...

同样，那里没有调用post-clean阶段。这意味着 maven-clean-plugin（也许没有别的）没有绑定到post-clean.

调用mvn post-clean 将导致调用post-clean阶段...

$ mvn post-clean
[INFO] Scanning for projects...
[INFO] 
[INFO] --- echo-maven-plugin:1.2.0:echo (pre-clean) @ sandbox ---
[INFO] In 'pre-clean'
[INFO] 
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ sandbox ---
[INFO] Deleting target
[INFO] 
[INFO] --- echo-maven-plugin:1.2.0:echo (clean) @ sandbox ---
[INFO] In 'clean'
[INFO] 
[INFO] --- echo-maven-plugin:1.2.0:echo (post-clean) @ sandbox ---
[INFO] In 'post-clean'

因此，基于上述测试，我认为以下陈述是正确的：

• post-clean是不是当你调用调用clean
• post-clean是只叫你时，明确调用post-clean（注：调用pre-和post-阶段直接异常）