log4j 没有主类的问题

你的 my-app-1.0-SNAPSHOT.jar 包里面没有 log4j 的依赖 贴你的 pom

pom 给你们看下。。

<?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.mycompany.app</groupId>
<artifactId>my-app</artifactId>
<version>1.0-SNAPSHOT</version>

<name>my-app</name>
<!-- FIXME change it to the project's website -->
<url>http://www.example.com</url>

<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>
</properties>

<dependencies>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.4.29.Final</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.6.1</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.5</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-nop</artifactId>
<version>1.6.4</version>
</dependency>

<dependency>
<groupId>javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.11.0.GA</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.16</version>
<!--<scope>system</scope>
<systemPath>${project.basedir}/target/dependency/log4j-1.2.16.jar</systemPath>-->
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
</dependencies>

<build>
<pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
<plugins>
<!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->

<!--add-->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.4</version>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>package</phase>
<goals><goal>copy-dependencies</goal></goals>
</execution>
</executions>
</plugin>

<!--add end-->

<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>3.1.0</version>
</plugin>
<!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
<plugin>
<artifactId>maven-resources-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
<configuration>
<skip>true</skip>
</configuration>
</plugin>
<plugin>
<artifactId>maven-jar-plugin</artifactId>
<version>3.0.2</version>
<!--add start-->

<!--add end-->
</plugin>
<plugin>
<artifactId>maven-install-plugin</artifactId>
<version>2.5.2</version>
</plugin>
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.8.2</version>
</plugin>
<!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
<plugin>
<artifactId>maven-site-plugin</artifactId>
<version>3.7.1</version>
</plugin>
<plugin>
<artifactId>maven-project-info-reports-plugin</artifactId>
<version>3.0.0</version>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>

target 下面 clean 过后就没有了阿。 你这个路径有问题

@2020beBetter 大佬看下

@2020beBetter 有的，我 build 出来的东西都在 target 目录。包括 depdency 都有。

├─classes
│ ├─com
│ │ ├─HibernateUtil
│ │ └─mycompany
│ │ └─app
│ └─hibernate
│ └─mappings
├─dependency
├─generated-sources
│ └─annotations
├─generated-test-sources
│ └─test-annotations
├─maven-archiver
├─maven-status
│ └─maven-compiler-plugin
│ ├─compile
│ │ └─default-compile
│ └─testCompile
│ └─default-testCompile
├─surefire-reports
└─test-classes
└─com
└─mycompany
└─app

@2020beBetter 不加 log4j 就没问题，可以打出 hello world 。但是加了 log4j 就会出现没有主类的问题。

哪里写的没有主类了。。。NoClassDefFound 十有八九是包冲突

@lululau 不知怎么解决。。

因为你没有使用把所有依赖打包到你的 jar 里的 Maven 插件，而只是把依赖复制到了 target 里，所以打包出来的 jar 应该只包含你自己写的 class 。
所以要运行的时候，应该需要将依赖的 jar 加入到 classpath 里：
java -cp my-app-version.jar:path/to/log4j.jar:path/to/other-dependency.jar com.mycompany.app.App

@coolcfan 在 windows 应该怎么写？