Maven -无法找到或加载主类

Question

我使用Java SDK13在IntelliJ中创建了一个maven项目，其中包含以下项目树：

bot.discord
    package1
    package2
    package3
    package4
    Bot.java

在我的pom.xml文件中，我有以下内容：

<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>org.example</groupId>
    <artifactId>Discord Bot</artifactId>
    <version>1.0-SNAPSHOT</version>
    <build>
        <plugins>
            <!--Maven Compiler-->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>8</source>
                    <target>8</target>
                </configuration>
            </plugin>

            <!--Shade Plugin-->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.2.1</version>
                <configuration>
                    <minimizeJar>true</minimizeJar>
                </configuration>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <!--Discord JDA-->
        <dependency>
            <groupId>net.dv8tion</groupId>
            <artifactId>JDA</artifactId>
            <version>3.8.3_464</version>
            <exclusions>
                <exclusion>
                    <groupId>club.minnced</groupId>
                    <artifactId>opus-java</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <!--Discord JDA Utilities-->
        <dependency>
            <groupId>com.jagrosh</groupId>
            <artifactId>jda-utilities</artifactId>
            <version>3.0.2</version>
        </dependency>

        <!--Lava Player-->
        <dependency>
            <groupId>com.sedmelluq</groupId>
            <artifactId>lavaplayer</artifactId>
            <version>1.3.34</version>
        </dependency>

        <!--SLF4J API-->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>2.0.0-alpha1</version>
        </dependency>

        <!--SLF4J NOP-->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-nop</artifactId>
            <version>2.0.0-alpha1</version>
        </dependency>
    </dependencies>

    <repositories>
        <repository>
            <id>jcenter</id>
            <name>jcenter-bintray</name>
            <url>https://jcenter.bintray.com</url>
        </repository>
    </repositories>
</project>

这在以前对我很有效，直到有一次我试图运行这个项目时，我得到了以下错误：

Error: Could not find or load main class bot.discord.Bot
Caused by: java.lang.ClassNotFoundException: bot.discord.Bot

为什么我会得到这个错误，尽管它在过去是有效的？

我曾尝试添加Maven JAR插件和Maven Assembly插件，它们可以帮助人们解决同样的问题，但对我来说不起作用。

​

Answer 1

首先更改您的artifactId以删除空格：

<artifactId>Discord-Bot</artifactId>

您的着色插件应该将主类指定为文档化的here

             <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.2.2</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <transformers>
                                <transformer
                                        implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>bot.discord.Bot</mainClass>
                                </transformer>
                            </transformers>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

然后从jar中运行

java -jar Discord-Bot-1.0-SNAPSHOT.jar