本文介绍了Maven项目中的ClassNotFoundException的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
有一个基于Maven的项目，可以由maven install构建，但是在运行out jar时会抛出异常:
There is a maven based project, which can be built by maven install, but throw exception when run the out jar:
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/cli/CommandLineParser
Caused by: java.lang.ClassNotFoundException: org.apache.commons.cli.CommandLineParser
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
我想知道为什么Java找不到maven依赖库?
I want to know why java can not find the maven dependency library ?
<?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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.artofsolving.jodconverter</groupId>
<artifactId>jodconverter-core</artifactId>
<version>3.0-SNAPSHOT</version>
<packaging>jar</packaging>
<name>JODConverter - Core Library</name>
<description>
JODConverter converts office documents using OpenOffice.org
</description>
<url>http://jodconverter.googlecode.com</url>
<licenses>
<license>
<name>GNU Lesser General Public License, Version 3 or later</name>
<url>http://www.gnu.org/licenses/lgpl.html</url>
</license>
</licenses>
<scm>
<url>http://jodconverter.googlecode.com/svn/trunk/jodconverter-core</url>
<connection>scm:svn:https://jodconverter.googlecode.com/svn/trunk/jodconverter-core/</connection>
</scm>
<inceptionYear>2003</inceptionYear>
<developers>
<developer>
<id>mirko.nasato</id>
<name>Mirko Nasato</name>
<email>[email protected]</email>
</developer>
</developers>
<contributors>
<contributor>
<name>Shervin Asgari</name>
<email>[email protected]</email>
</contributor>
</contributors>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<repositories>
<repository>
<!-- required for org.hyperic:sigar -->
<id>jboss-public-repository-group</id>
<url>https://repository.jboss.org/nexus/content/groups/public-jboss/</url>
</repository>
</repositories>
<dependencies>
<!-- Required dependencies -->
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>1.4</version>
</dependency>
<dependency>
<groupId>org.openoffice</groupId>
<artifactId>juh</artifactId>
<version>3.2.1</version>
</dependency>
<dependency>
<groupId>org.openoffice</groupId>
<artifactId>ridl</artifactId>
<version>3.2.1</version>
</dependency>
<dependency>
<groupId>org.openoffice</groupId>
<artifactId>unoil</artifactId>
<version>3.2.1</version>
</dependency>
<dependency>
<!-- for the command line tool -->
<groupId>commons-cli</groupId>
<artifactId>commons-cli</artifactId>
<version>1.2</version>
</dependency>
<!-- Optional dependencies -->
<dependency>
<!-- for more robust process management -->
<groupId>org.hyperic</groupId>
<artifactId>sigar</artifactId>
<version>1.6.5.132</version>
<optional>true</optional>
</dependency>
<dependency>
<!-- for JSON configuration -->
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20090211</version>
<optional>true</optional>
</dependency>
<!-- Test dependencies -->
<dependency>
<groupId>org.testng</groupId>
<artifactId>testng</artifactId>
<version>6.0.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.7.2</version>
<configuration>
<!-- don't run tests in parallel -->
<perCoreThreadCount>false</perCoreThreadCount>
<threadCount>1</threadCount>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.3.1</version>
<configuration>
<archive>
<manifest>
<mainClass>org.artofsolving.jodconverter.cli.Convert</mainClass>
<addClasspath>true</addClasspath>
</manifest>
</archive>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.2-beta-5</version>
<configuration>
<descriptors>
<descriptor>src/main/assembly/dist.xml</descriptor>
</descriptors>
</configuration>
</plugin>
</plugins>
</build>
<reporting>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<version>2.7</version>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>cobertura-maven-plugin</artifactId>
<version>2.4</version>
</plugin>
</plugins>
</reporting>
</project>
推荐答案
使用java -jar运行Jar时，不再使用依赖项的maven解决方案来运行.您必须确保在Jar的MANIFEST.mf文件中指定的相对位置上可以使用所有依赖的jar.通常，您将使用Assembly插件创建可创建此结构的可分发存档.或者，您可以使用uberjar/onejar插件将所有内容包含在Jar中.
When running your Jar with java -jar, you're no longer running with the maven resolving of dependencies. You have to make sure that all the jars you depend on are available at the relative loacation specificied in the MANIFEST.mf file in your Jar. Usually, you would use the assembly plugin to create a distributable archive that creates this structure. Or you could use a uberjar/onejar plugin to included everything inside your Jar.
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