Maven命令行：依赖项无效

huangapple
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英文:

Maven from command line: dependencies don't work

问题

以下是翻译好的内容：

我使用了以下基本的Maven命令来生成一个项目：

  1. mvn archetype:generate -DgroupId=it.maven.project -DartifactId=MavenExample -DarchetypeArtifactId=maven-archetype-quickstart -DarchetypeVersion=1.4 -DinteractiveMode=false

项目已经正确创建，我可以使用以下指令无问题地测试自动生成的App类：

  1. java -cp target/MavenExample-1.0-SNAPSHOT.jar:lib/* it.maven.project.App

后来，我向POM添加了一些依赖，得到了以下文件：

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  3.   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  4.   <modelVersion>4.0.0</modelVersion>
  6.   <groupId>it.maven.project</groupId>
  7.   <artifactId>MavenExample</artifactId>
  8.   <version>1.0-SNAPSHOT</version>
  10.   <name>MavenExample</name>
  11.   <!-- FIXME change it to the project's website -->
  12.   <url>http://maven.apache.org</url>
  14.   <dependencies>
  15.     <dependency>
  16.       <groupId>junit</groupId>
  17.       <artifactId>junit</artifactId>
  18.       <version>4.11</version>
  19.       <scope>test</scope>
  20.     </dependency>
  22.      <dependency>
  23.       <groupId>org.apache.commons</groupId>
  24.       <artifactId>commons-lang3</artifactId>
  25.       <version>3.10</version>
  26.       <scope>compile</scope>
  27.     </dependency>
  29.     <dependency>
  30.       <groupId>org.apache.commons</groupId>
  31.       <artifactId>commons-collections4</artifactId>
  32.       <version>4.0</version>
  33.       <scope>compile</scope>
  34.     </dependency>
  35.   </dependencies>
  37.   <build>
  38.     <sourceDirectory>src</sourceDirectory>
  39.     <plugins>
  40.       <plugin>
  41.         <artifactId>maven-compiler-plugin</artifactId>
  42.         <version>3.7.0</version>
  43.         <configuration>
  44.           <source>1.8</source>
  45.           <target>1.8</target>
  46.         </configuration>
  47.       </plugin>
  48.     </plugins>
  49.   </build>
  50. </project>

最后，为了测试，我修改了之前由Maven自动生成的App类：

  1. package it.maven.project;
  2. import org.apache.commons.lang3.RandomStringUtils;
  4. /**
  5.  * Hello world!
  6.  *
  7.  */
  8. public class App 
  9. {
  10.     public static void main( String[] args )
  11.     {
  12.         System.out.println( "Hello World!" );
  13.         System.out.println("Stringa generata casualmente: " + RandomStringUtils.random(16, true, true).toUpperCase());
  14.     }
  15. }

出现了一系列奇怪的情况：

  1. 尽管在POM中指定了更近版本的依赖，但在.m2文件夹中下载的版本似乎较旧（例如，我得到了commons-lang3的2.1和2.5版本）
  2. 项目通过指令 mvn clean install -U 正确编译
  3. 当我再次运行执行App的命令时，出现以下异常：
  1. Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/lang3/RandomStringUtils
  2.         at it.maven.project.App.main(App.java:13)
  3.     Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang3.RandomStringUtils
  4.         at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
  5.         at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
  6.         at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
  7.         at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
  8.         ... 1 more

问题：

  • 项目为什么可以编译，但在编译时返回错误？为什么App中的导入语句被接受，但是 System.out.println("Stringa generata casualmente: " + RandomStringUtils.random(16, true, true).toUpperCase()); 这条指令会生成异常？
  • 我应该如何更正/执行，以使我的程序能够正常工作并正确使用依赖？
英文:

I used the following basic Maven command to generate a project:

  1. mvn archetype:generate -DgroupId=it.maven.project -DartifactId=MavenExample -DarchetypeArtifactId=maven-archetype-quickstart -DarchetypeVersion=1.4 -DinteractiveMode=false

The project was correctly created and I could test the automatically generated App class without any problem with this instruction:

  1. java -cp target/MavenExample-1.0-SNAPSHOT.jar:lib/* it.maven.project.App

Later on, I added some dependencies to the POM, obtaining the following file:

  1. &lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;
  3. &lt;project xmlns=&quot;http://maven.apache.org/POM/4.0.0&quot; xmlns:xsi=&quot;http://www.w3.org/2001/XMLSchema-instance&quot;
  4.   xsi:schemaLocation=&quot;http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd&quot;&gt;
  5.   &lt;modelVersion&gt;4.0.0&lt;/modelVersion&gt;
  7.   &lt;groupId&gt;it.maven.project&lt;/groupId&gt;
  8.   &lt;artifactId&gt;MavenExample&lt;/artifactId&gt;
  9.   &lt;version&gt;1.0-SNAPSHOT&lt;/version&gt;
  11.   &lt;name&gt;MavenExample&lt;/name&gt;
  12.   &lt;!-- FIXME change it to the project&#39;s website --&gt;
  13.   &lt;url&gt;http://maven.apache.org&lt;/url&gt;
  15.   &lt;dependencies&gt;
  16.     &lt;dependency&gt;
  17.       &lt;groupId&gt;junit&lt;/groupId&gt;
  18.       &lt;artifactId&gt;junit&lt;/artifactId&gt;
  19.       &lt;version&gt;4.11&lt;/version&gt;
  20.       &lt;scope&gt;test&lt;/scope&gt;
  21.     &lt;/dependency&gt;
  23.      &lt;dependency&gt;
  24.       &lt;groupId&gt;org.apache.commons&lt;/groupId&gt;
  25.       &lt;artifactId&gt;commons-lang3&lt;/artifactId&gt;
  26.       &lt;version&gt;3.10&lt;/version&gt;
  27.       &lt;scope&gt;compile&lt;/scope&gt;
  28.     &lt;/dependency&gt;
  30.     &lt;dependency&gt;
  31.       &lt;groupId&gt;org.apache.commons&lt;/groupId&gt;
  32.       &lt;artifactId&gt;commons-collections4&lt;/artifactId&gt;
  33.       &lt;version&gt;4.0&lt;/version&gt;
  34.       &lt;scope&gt;compile&lt;/scope&gt;
  35.     &lt;/dependency&gt;
  36.   &lt;/dependencies&gt;
  38.   &lt;build&gt;
  39.     &lt;sourceDirectory&gt;src&lt;/sourceDirectory&gt;
  40.     &lt;plugins&gt;
  41.       &lt;plugin&gt;
  42.         &lt;artifactId&gt;maven-compiler-plugin&lt;/artifactId&gt;
  43.         &lt;version&gt;3.7.0&lt;/version&gt;
  44.         &lt;configuration&gt;
  45.           &lt;source&gt;1.8&lt;/source&gt;
  46.           &lt;target&gt;1.8&lt;/target&gt;
  47.         &lt;/configuration&gt;
  48.       &lt;/plugin&gt;
  49.     &lt;/plugins&gt;
  50.   &lt;/build&gt;
  54. &lt;/project&gt;

Finally, for testing sake, I modified the App class previously generated by Maven itself:

  1. package it.maven.project;
  2. import org.apache.commons.lang3.RandomStringUtils;
  4. /**
  5.  * Hello world!
  6.  *
  7.  */
  8. public class App 
  9. {
  10.     public static void main( String[] args )
  11.     {
  12.         System.out.println( &quot;Hello World!&quot; );
  13.         System.out.println(&quot;Stringa generata casualmente: &quot; + RandomStringUtils.random(16, true, true).toUpperCase());
  14.     }
  15. }

A series of strange things happen:

  1. even though more recent versions of dependencies are specified in POM, in .m2 folder the downloaded versions seem to be older (for instance I get 2.1 and 2.5 for commons-lang3)

  2. the project is correctly compiled by instruction

    mvn clean install -U

  3. when I run again command to execute App, I get the following exception:

> Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/lang3/RandomStringUtils
at it.maven.project.App.main(App.java:13)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang3.RandomStringUtils
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 1 more

Questions:

  • how is it possible that project compiles but then errors are returned at compiling time? Why the import in App is accepted but instruction:

    System.out.println(&quot;Stringa generata casualmente: &quot; + RandomStringUtils.random(16, true, true).toUpperCase());

    generates an exception?

  • what should I correct/execute to allow my program to work and use correctly dependencies?

答案1

得分: 0

以下是您要翻译的内容：

当您创建一个简单的Java项目时，您会在pom中定义一组依赖关系，但是如果您不创建Java存档文件（ejb-jar或war），则在运行目标目录中编译的jar时，所有依赖关系在运行时不可用。
有两种解决方案：

  1. 创建一个超级jar，将所有依赖项包含在您的jar中：使用stackoverflow的解决方案。

  2. 当您从命令行运行jar时，您必须将依赖项添加到类路径中：

    java -cp "/path/dependencies/dep1.jar;/path/dependencies/dep2.jar" -jar myApp.jar

英文:

when you create a simple java project you define a set of dependencies in the pom but if you don't create a java archive file (ejb-jar or war) all the dependencies are not available at runtime if you run the jar compiled in the target directory.
There are two solutions:

  1. Create a uber jar that include all your depenencies in your jar: use stackoverflow solution

  2. when you run the jar from command line you have to add the dependencies to the classpath:

    java -cp "/path/dependencies/dep1.jar;/path/dependencies/dep2.jar" -jar myApp.jar

huangapple
  • 本文由 发表于 2020年10月13日 04:25:50
  • 转载请务必保留本文链接：https://go.coder-hub.com/64324904.html
  • java
  • maven
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