Maven - 在执行"mvn clean"之后，为什么需要在执行"mvn package"之前执行"Maven Update Project"?

Question

我正在进行一些测试，并且想要了解为什么在执行命令mvn clean后，需要在运行mvn package之前执行“Maven > 更新项目”，否则在打包期间的某个依赖项中会出现编译错误。

看起来我的项目在运行“Maven > 更新项目”之前不能正确编译我的项目，但我不确定。这是正常的吗？

• 我使用Eclipse并通过“Run as > Maven Build”运行{mvn clean}和{mvn package}命令。

这是我的pom.xml：

<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.project</groupId>
    <artifactId>myProject</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>

    <properties>
        <jmockit.version>0.0.1</jmockit.version>
    </properties>

    <build>
        <testSourceDirectory>src/test/java/junit</testSourceDirectory>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <excludes>
                    <exclude>**/*.java</exclude>
                </excludes>
            </resource>
        </resources>

        <testResources>
            <testResource>
                <directory>src/test/java/selenium</directory>
                <excludes>
                    <exclude>**/*.java</exclude>
                </excludes>
            </testResource>
        </testResources>

        <pluginManagement>
            <plugins>
                <!-- Need Java 5, which is the default since v2.3 of the maven-compiler-plugin. -->
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>2.5.1</version>
                </plugin>
            </plugins>
        </pluginManagement>

        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                </configuration>
            </plugin>
            <plugin>
                <artifactId>maven-war-plugin</artifactId>
                <version>2.2</version>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                    <warSourceExcludes>src/main/resources/conf_development</warSourceExcludes>
                    <webResources>
                        <resource>
                            <directory>src/main/resources/conf_production</directory>
                            <targetPath>WEB-INF/classes/</targetPath>
                            <includes>
                                <include>**/*</include>
                            </includes>
                        </resource>
                        <resource>
                            <directory>src/main/resources/conf</directory>
                            <targetPath>WEB-INF/classes/</targetPath>
                            <includes>
                                <include>**/*</include>
                            </includes>
                        </resource>
                    </webResources>
                </configuration>
            </plugin>

            <plugin>
                <artifactId>maven-surefire-plugin</artifactId>
                <configuration>
                    <argLine>
                        -javaagent:"${settings.localRepository}"/mockit/jmockit/${jmockit.version}/jmockit-${jmockit.version}.jar
                    </argLine>
                </configuration>
            </plugin>
        </plugins>
    </build>


<dependencies>
    <dependency>
        <groupId>asm</groupId>
        <artifactId>asm</artifactId>
        <version>1.5.3</version>
    </dependency>
    <dependency>
        <groupId>bouncycastle</groupId>
        <artifactId>bcprov-jdk14</artifactId>
        <version>140</version>
    </dependency>
    <dependency>
        <groupId>c3p0</groupId>
        <artifactId>c3p0</artifactId>
        <version>0.9.1</version>
    </dependency>
    <dependency>
        <groupId>c3p0</groupId>
        <artifactId>c3p0-oracle-thin-extras</artifactId>
        <version>0.9.0.2</version>
    </dependency>
    <dependency>
        <groupId>commons-betwixt</groupId>
        <artifactId>commons-betwixt</artifactId>
        <version>0.7</version>
    </dependency>
    <dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>1.4</version>
    </dependency>
    <dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-email</artifactId>
        <version>1.2</version>
    </dependency>
    <dependency>
        <groupId>net.sf.ehcache</groupId>
        <artifactId>ehcache-core</artifactId>
        <version>2.4.2</version>
    </dependency>
    <dependency>
        <groupId>com.googlecode.ehcache-spring-annotations</groupId>
        <artifactId>ehcache-spring-annotations</artifactId>
        <version>1.1.3</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-annotations</artifactId>
        <version>3.4.0.GA</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>3.4.0.GA</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>3.3.2.GA</version>
    </dependency>
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <version>4.1.2</version>
    </dependency>
    <dependency>
        <groupId>net.sf.json-lib</groupId>
        <artifactId>json-lib</artifactId>
        <version>2.4</version>
        <type>pom</type>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc</artifactId>
        <version>2.5.6</version>
    </dependency>
    <dependency>
        <groupId>net.fckeditor</groupId>
        <artifactId>java-core</artifactId>
        <version>2.4</version>
    </dependency>
    <dependency>
        <groupId>backport-util-concurrent</groupId>
        <artifactId>backport-util-concurrent</artifactId>
        <version>3.1</version>
    </dependency>
    <dependency>
        <groupId>com.oracle</groupId>
        <artifactId>ojdbc14</artifactId>
        <version>10.2.0.1.0</version>
    </dependency>
    <dependency>
        <groupId>com.ibm.icu</groupId>
        <artifactId>icu4j</artifactId>
        <version>3.8</version>
    </dependency>
    <dependency>
        <groupId>mockit</groupId>
        <artifactId>jmockit</artifactId>
        <version>${jmockit.version}</version>
    </dependency>
    <dependency>
        <groupId>joda-time</groupId>
        <artifactId>joda-time</artifactId>
        <version>2.0</version>
    </dependency>
    <dependency>
        <groupId>com.lowagie</groupId>
        <artifactId>itext</artifactId>
        <version>2.1.0</version>
    </dependency>
    <dependency>
        <groupId>atg.taglib.json</groupId>
        <artifactId>json-taglib</artifactId>
        <version>0.4.1</version>
    </dependency>
    <dependency>
        <groupId>commons-httpclient</groupId>
        <artifactId>commons-httpclient</artifactId>
        <version>3.1</version>
    </dependency>
    <dependency>
        <groupId>net.sourceforge.jexcelapi</groupId>
        <artifactId>jxl</artifactId>
        <version>2.6</version>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.17</version>
    </dependency>
    <dependency>
        <groupId>org.mockito</groupId>
        <artifactId>mockito-all</artifactId>
        <version>1.8.5</version>
    </dependency>
    <dependency>
        <groupId>org.quartz-scheduler</groupId>
        <artifactId>quartz</artifactId>
        <version>1.8.4</version>
    </dependency>
    <dependency>
        <groupId>org.seleniumhq.selenium</groupId>
        <artifactId>selenium-server</artifactId>
        <version>2.25.0</version>
        <type>pom</type>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring</artifactId>
        <version>2.5.6.SEC03</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-agent</artifactId>
        <version>2.5.6.SEC03</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-test</artifactId>
        <version>2.5.6.SEC03</version>
    </dependency>
    <dependency>
        <groupId>org.apache.struts</groupId>
        <artifactId>struts2-config-browser-plugin</artifactId>
        <version>2.2.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.struts</groupId>
        <artifactId>struts2-convention-plugin</artifactId>
        <version>2.2.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.struts</groupId>
        <artifactId>struts2-core</artifactId>
        <version>2.2.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.struts</groupId>
        <artifactId>struts2-jasperreports-plugin</artifactId>
        <version>2.2.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.struts</groupId>
        <artifactId>struts2-jfreechart-plugin</artifactId>
        <version>2.2.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.struts</groupId>
        <artifactId>struts2-json-plugin</artifactId>
        <version>2.2.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.struts</groupId>
        <artifactId>struts2-spring-plugin</artifactId>
        <version>2.2.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.velocity</groupId>
        <artifactId>velocity</artifactId>
        <version>1.6.3</version>
    </dependency>
    <dependency>
        <groupId>org.apache.velocity</groupId>
        <artifactId>velocity-tools</artifactId>
        <version>1.3</version>
    </dependency>
    <dependency>
        <groupId>com.yahoo.platform.yui</groupId>
        <artifactId>yuicompressor</artifactId>
        <version>2.4.6</version>
    </dependency>
    <dependency>
        <groupId>commons-lang</groupId>
        <artifactId>commons-lang</artifactId>
        <version>2.5</version>
    </dependency>
    <dependency>
        <groupId>net.sf.jodreports</groupId>
        <artifactId>jodreports</artifactId>
        <version>2.4.0</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.ws</groupId>
        <artifactId>spring-oxm</artifactId>
        <version>1.5.9</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.ws</groupId>
        <artifactId>spring-ws-core</artifactId>
        <version>1.5.9</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.ws</groupId>
        <artifactId>spring-oxm-tiger</artifactId>
        <version>1.5.9</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.ws</groupId>
        <artifactId>spring-ws-core-tiger</artifactId>
        <version>1.5.9</version>
    </dependency>
    <dependency>
        <groupId>javax.xml.bind</groupId>
        <artifactId>jaxb-api</artifactId>
        <version>2.1</version>
    </dependency>
    <dependency>
        <groupId>com.sun.xml.bind</groupId>
        <artifactId>jaxb-xjc</artifactId>
        <version>2.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.ws.commons.axiom
        </groupId>
        <artifactId>axiom-api</artifactId>
        <version>1.2.5</version>
    </dependency>
    <dependency>
        <groupId>org.apache.ws.commons.axiom
        </groupId>
        <artifactId>axiom-impl</artifactId>
        <version>1.2.5</version>
    </dependency>
    <dependency>
        <groupId>javax.xml</groupId>
        <artifactId>jaxrpc-api</artifactId>
        <version>1.1</version>
    </dependency>
    <dependency>
        <groupId>org.seleniumhq.selenium.client-drivers</groupId>
        <artifactId>selenium-java-client-driver</artifactId>
        <version>1.0.1</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.11</version>
    </dependency>
    <dependency>
        <groupId>org.acegisecurity</groupId>
        <artifactId>acegi-security</artifactId>
        <version>1.0.7</version>
    </dependency>
    <dependency>
        <groupId>citizen</groupId>
        <artifactId>citizen</artifactId>
        <version>citizen</version>
    </dependency>
    <dependency>
        <groupId>jstl</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>servlet-api</artifactId>
        <version>2.4</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>javax.servlet.jsp</groupId>
        <artifactId>jsp-api</artifactId>
        <version>2.0</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>jasperreports</groupId>
        <artifactId>jasperreports</artifactId>
        <version>3.5.3</version>
    </dependency>
</dependencies>
</project>

错误：

（记得这个出错的库是一个内部库，在“Maven > 更新项目”之后它能够正常工作）

[INFO] Compiling 2595 source files to C:\Users\user\Documents\Dev\workspace\project\target\classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR : 
[INFO] -------------------------------------------------------------
[ERROR] C:\Users\user\Documents\Dev\workspace\project\src\main\java\com\project\jobs\citizen\model\service\CitizenService.java:[38
,34] cannot access org.apache.axis.client.Service
class file for org.apache.axis.client.Service not found
        Resolution2Locator r2 = new Resolution2Locator ();
[INFO] 1 error
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2:09.448s
[INFO] Finished at: Fri Mar 22 11:55:14 BRT 2013
[INFO] Final Memory: 25M/274M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.5.1:compile (default-compile) on project project: Compilation failure
[ERROR] C:\Users\user\Documents\Dev\workspace\project
\src\main\java\com\project\jobs\citizen\model\service\CitizenService.java:[38
,34] cannot access org.apache.axis.client.Service
[ERROR] class file for org.apache.axis.client.Service not found
[ERROR] Resolution2Locator r2 = new Resolution2Locator();
[ERROR] -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.5.1:compile (default-compile) on project u
nico: Compilation failure
C:\Users\user\Documents\Dev\workspace\project\src\main\java\com\project\jobs\citizen\model\service\CitizenService.java:[38,34] can
not access org.apache.axis.client.Service
class file for org.apache.axis.client.Service not found
        Resolution2Locator r2 = new Resolution2Locator ();

    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:213)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:320)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)
Caused by: org.apache.maven.plugin.CompilationFailureException: Compilation failure
C:\Users\user\Documents\Dev\workspace\project\src\main\java\com\project\jobs\citizen\model\service\CitizenService.java:[38,34] can
not access org.apache.axis.client.Service
class file for org.apache.axis.client.Service not found
        Resolution2Locator r2 = new Resolution2Locator ();

    at org.apache.maven.plugin.AbstractCompilerMojo.execute(AbstractCompilerMojo.java:729)
    at org.apache.maven.plugin.CompilerMojo.execute(CompilerMojo.java:128)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
    ... 19 more
[ERROR] 
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

- Pmt

---

只是确认一下：你是否在使用Eclipse？并且从Eclipse中运行了'mvn clean'和'mvn package'命令吗？你遇到了什么样的错误？ - benzonico

是的，我正在使用Eclipse，并通过“Run as > Maven Build”运行命令{mvn clean}和{mvn package}。 我在其中一个依赖项中遇到了编译错误。 - Pmt

Maven和Eclipse的整合非常有问题。如果你正在学习Maven，我强烈建议使用命令行或任何其他IDE。也就是说，你需要运行更新依赖项这个步骤是因为Eclipse中存在那些bug，当你只用Maven时是不需要做这一步骤的。 - ben75

真的吗？好的，我会在命令行中尝试并告诉你结果。 - Pmt

我认为 Maven 配置或项目的 pom.xml 出了问题。在添加所需类的依赖项后，我已成功使用 Maven 编译项目。但这是一种传递性依赖。即使依赖插件报告它是不必要的。 - Dmitry D

Answer 1

以下是发生的情况：

1. mvn clean 删除了 target 目录。
2. mvn package 执行一些操作，但是由于缺失依赖项而导致编译错误。这就是为什么目标文件夹处于错误状态。
3. 在 Eclipse 中运行 Maven > Update Project 会导致 Eclipse 执行自己的编译，与 Maven 分开。Eclipse 的 classpath 不同于 Maven，因此它的编译成功。现在 target 文件夹具有所有已编译类。
4. 重新运行 mvn package 现在成功，因为它找到了所有已编译的类，并且不需要执行任何编译。

最终，问题在于 pom.xml 中的项目配置。我遇到了同样的问题，在添加缺失的依赖项后，我成功地使用 Maven 编译了项目。

- Dmitry D

---

刚刚添加了这个依赖，一切都运行正常了！非常感谢！ org.apache.axis axis 1.4 - Pmt

讲解得很清楚，非常有帮助！谢谢您 - Hartmut Pfarr

Answer 2

Eclipse的m2e插件（这是一种简化）读取POM文件并将其转换为Eclipse的指令，以便Eclipse可以完成其工作。由于Eclipse一直在控制，因此您的视图会正确更新，事情相当顺利。一些更高级的Maven操作与插件不受m2e支持，因此这些操作将不会发生。一些简单的东西，例如类路径与Maven的做法不同--m2e使用“测试”类路径，因为Eclipse无法预测您要运行什么。

另一方面，“Run as> Maven ...”实际上调用了Maven，这是完全独立于Eclipse的程序，并要求它运行。Eclipse不会自动知道Maven创建或删除文件的时间。

我通常会远离“Run as> Maven”命令。集成很差，Eclipse控制台界面很丑陋，如果需要运行特定的Maven目标，只需从命令行调用mvn即可。

如果您只想开发Maven项目，我认为m2e集成非常好。我使用Jenkins来处理打包和部署，因此我只使用Eclipse来编辑和测试我的代码。

- Nathaniel Waisbrot

---

非常感谢您的解释！我们的想法是使用Jenkins来运行它，但在迁移完成之前，我们需要在本地执行这些命令。不幸的是，当我直接从提示符中执行mvn clean时，出现了相同的错误。您有任何想法应该怎么做吗？再次感谢。 - Pmt

@PimentaDev。当您运行“mvn clean”时，您看到的错误是什么？ - Nathaniel Waisbrot

mvn clean 运行得很好。问题出在 mvn package 命令之后。我的一个库出现了编译错误，但我不知道原因。只有当我打开 Eclipse 并运行 "Maven > Update Project" 命令时，错误才会停止！ - Pmt

这些听起来是远离Eclipse的好理由。IntelliJ没有问题让Maven运行构建。 - Greg Chabala

对于需要在Maven中执行复杂或奇怪操作的项目，我不建议使用Eclipse。但是对于已经熟悉Eclipse并且只需要清理和构建项目的用户来说，m2e非常好用。 - Nathaniel Waisbrot

Answer 3

如果有新的更新可用，它将更新文件。您可以在执行maven clean后使用maven install。

- PSR

---

但是为什么命令mvn package有效呢？ 而且没有任何更新需要进行，只需重新构建项目即可。 - Pmt