错误：执行 jar 文件时无法找到或加载主类

Question

我创建了两个 java 文件，我的 maven 项目一个是 POJO 类，另一个是 java 主类文件。我想将我的项目作为一个可执行的 jar 文件，我想使用 java -jar 命令在外部运行。

请找到我的 pom.xml 文件

<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>ElasticSearchUtility</groupId>
    <artifactId>ElasticSearchUtility</artifactId>
    <version>1.0.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.elasticsearch</groupId>
            <artifactId>elasticsearch</artifactId>
            <version>6.1.2</version>
        </dependency>
        <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>elasticsearch-rest-high-level-client</artifactId>
            <version>6.1.2</version>
        </dependency>
        <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>rest</artifactId>
            <version>5.1.2</version>
        </dependency>    
    </dependencies>

    <build>    
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-eclipse-plugin</artifactId>
                <version>2.9</version>
                <configuration>
                    <downloadSources>true</downloadSources>
                    <downloadJavadocs>false</downloadJavadocs>
                </configuration>
            </plugin>

            <!-- Set a compiler level -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>

            <!-- Make this jar executable -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>**/log4j.properties</exclude>
                    </excludes>
                    <archive>
                        <manifest>
                            <addClasspath>true</addClasspath>
                            <mainClass>com.es.utility.DocumentIndex</mainClass>
                            <classpathPrefix>dependency-jars/</classpathPrefix>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
            <!-- Copy project dependency -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <version>2.5.1</version>
                <executions>
                    <execution>
                        <id>copy-dependencies</id>
                        <phase>package</phase>
                        <goals>
                            <goal>copy-dependencies</goal>
                        </goals>
                        <configuration>
                            <!-- exclude junit, we need runtime dependency only -->
                            <includeScope>runtime</includeScope>
                            <outputDirectory>${project.build.directory}/dependency-jars/</outputDirectory>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

在使用java -jar 命令执行我的 jar 文件时。我得到了错误

Error: Could not find or load main class com.es.utility.DocumentIndex

还请找到我的项目结构：

Answer 1

要添加到@kshetline 的评论，请确保com.es.utility.DocumentIndex 是您的主类的正确路径。解压生成的jar包时，DocumentIndex.class应该在com/es/utility文件夹中。

Answer 2

如果 .jar 中没有类，可能是因为 maven 找不到它们。 Maven 中 java 类的默认路径是 src/main/java，尝试将它们移到那里并再次运行 Maven。