Maven 无法找到或加载主类答案

【问题标题】：Maven could not find or load main classMaven 无法找到或加载主类
【发布时间】：2018-02-08 17:34:19
【问题描述】：

我有一个java spring boot 项目dr3你可以在下面找到他的结构。由于某些原因，我最近从 gradle 迁移到 maven。现在我正在尝试使用 maven 运行我的 jar 构建，但由于某种原因，Maven 找不到我的主类，我收到此错误：Error: Could not find or load main class com.mycompany.dr3.admin.Application 即使它在下面声明得很好......你有什么想法这个问题可能来自哪里？

这是我的管理员 pom.xml：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.mycompany.dr3</groupId>
  <artifactId>dr3-admin</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.7.0</version>
        <configuration>
          <source>1.8</source>
          <target>1.8</target>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <version>3.0.2</version>
        <configuration>
          <archive>
            <manifest>
              <addClasspath>true</addClasspath>
              <mainClass>com.mycompany.dr3.admin.Application</mainClass>
            </manifest>
          </archive>
        </configuration>
      </plugin>
    </plugins>
  </build>

  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
      <scope>compile</scope>
      <exclusions>
        <exclusion>
          <artifactId>commons-logging</artifactId>
          <groupId>commons-logging</groupId>
        </exclusion>
      </exclusions>
    </dependency>
    <dependency>
      <groupId>org.apache.httpcomponents</groupId>
      <artifactId>httpcore</artifactId>
      <version>4.4.1</version>
      <scope>compile</scope>
      <exclusions>
        <exclusion>
          <artifactId>commons-logging</artifactId>
          <groupId>commons-logging</groupId>
        </exclusion>
      </exclusions>
    </dependency>
    <dependency>
      <groupId>org.apache.httpcomponents</groupId>
      <artifactId>httpclient</artifactId>
      <version>4.5</version>
      <scope>compile</scope>
      <exclusions>
        <exclusion>
          <artifactId>commons-logging</artifactId>
          <groupId>commons-logging</groupId>
        </exclusion>
      </exclusions>
    </dependency>
    <dependency>
      <groupId>org.apache.httpcomponents</groupId>
      <artifactId>httpmime</artifactId>
      <version>4.4.1</version>
      <scope>compile</scope>
      <exclusions>
        <exclusion>
          <artifactId>commons-logging</artifactId>
          <groupId>commons-logging</groupId>
        </exclusion>
      </exclusions>
    </dependency>
    <dependency>
      <groupId>com.mycompany.dr3</groupId>
      <artifactId>common</artifactId>
      <version>1.0-SNAPSHOT</version>
      <scope>compile</scope>
      <exclusions>
        <exclusion>
          <artifactId>commons-logging</artifactId>
          <groupId>commons-logging</groupId>
        </exclusion>
      </exclusions>
    </dependency>
    <dependency>
      <groupId>commons-io</groupId>
      <artifactId>commons-io</artifactId>
      <version>2.5</version>
      <scope>compile</scope>
      <exclusions>
        <exclusion>
          <artifactId>commons-logging</artifactId>
          <groupId>commons-logging</groupId>
        </exclusion>
      </exclusions>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.7.RELEASE</version>
        <scope>import</scope>
        <type>pom</type>
      </dependency>
    </dependencies>
  </dependencyManagement>
</project>

这是我的 dr3 父 pom.xml：

  <?xml version="1.0" encoding="UTF-8"?>
    <project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

      <modelVersion>4.0.0</modelVersion>
      <groupId>com.mycompany.dr3</groupId>
      <artifactId>dr3</artifactId>
      <version>1.0</version>
      <packaging>pom</packaging>
      <modules>
      <module>batch_engine</module>
      <module>admin</module>
      <module>batch_generic</module>
      <module>common</module>
      </modules>
      <dependencies>
        <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.11</version>
          <scope>test</scope>
        </dependency>
      </dependencies>
    </project>

这是我的 Application.java ：

package com.mycompany.dr3.admin;

import xxx

/**
 */
@SpringBootApplication
public class Application extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Application.class);
    }

    public static void main(String[] args) throws Exception {
        SpringApplication.run(Application.class, args);

    }

    @Bean
    CommandLineRunner init(StorageService storageService) {
        return (args) -> {
            storageService.deleteAll();
            storageService.init();
        };
    }

}

【问题讨论】：

该类是否包含有效的 Java 入口点？（即public static void main (String[] args)）
是的，刚刚上传了关于我的问题的应用程序 java 以便您查看

标签： java maven jar pom.xml maven-plugin

【解决方案1】：

您应该将您的项目组织为multi module project，如下所示

你的父母应该是这样的：

<?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>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.1.RELEASE</version>
    </parent>

    <groupId>com.mycompany.dr3</groupId>
    <artifactId>dr3</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>pom</packaging>

    <modules>
        <module>admin</module>
        <module>batch-engine</module>
    </modules>

</project>

那么你的管理子项目应该是这样的，它包含库作为依赖项，你不应该需要主类，你已经告诉 Spring：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://maven.apache.org/POM/4.0.0"
    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>

    <parent>
        <groupId>com.mycompany.dr3</groupId>
        <artifactId>dr3</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <artifactId>admin</artifactId>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
        </dependency>
        <dependency>
            <groupId>org.dbunit</groupId>
            <artifactId>dbunit</artifactId>
            <version>2.5.3</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.mycompany.dr3</groupId>
            <artifactId>batch-engine</artifactId>
            <version>${project.version}</version>
        </dependency>
    </dependencies>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <artifactId>maven-failsafe-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>integration-test</goal>
                            <goal>verify</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

那么你的每个图书馆项目应该是这样的：

<?xml version="1.0"?>
<project
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
    xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>com.mycompany.dr3</groupId>
        <artifactId>dr3</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <artifactId>batch-engine</artifactId>
    <name>batch-engine</name>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>

当您构建父项目时，它将包含所有子项目，您可以将管理项目作为 Spring Boot 应用程序运行：

java -jar admin/target/admin-1.0-SNAPSHOT.jar

【讨论】：

【解决方案2】：

<configuration>
      <archive>
        <manifest>
          <addClasspath>true</addClasspath>
          <mainClass>com.renault.dr3.admin.Application</mainClass>
        </manifest>
      </archive>
    </configuration>

那应该在 spring-boot 插件配置下。示例：

<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>...</version>
<configuration>
    <mainClass>my.package.MyStartClass</mainClass>
    ...
</configuration>
...

【讨论】：

这个应该在这里吗？
这样做似乎我得到了那个错误：no main manifest attribute, in target/dr3-admin-1.0-SNAPSHOT.jar
@LoganWlv under HERE spring-boot plugin是
就是这样！但不需要添加 ...只需要添加spring boot maven插件然后我也添加了：org.springframework.bootspring-boot-starter -parent1.5.10.RELEASE
如果你调整你的答案，我会验证你的:)