Maven构建后Jar无.class文件，Target/Classes为空求助

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2026-8-21

Maven打包后target/classes为空，Jar无.class文件排查与修复

问题描述

执行mvn clean install后，target目录下的classes文件夹是空的，生成的Jar中没有包含编译后的.class文件。项目使用Groovy编写（1个Groovy脚本+1个AWS Lambda Handler Groovy类），代码存放于/src/main/java/路径下，已配置maven-assembly-plugin生成AWS Lambda所需的Zip包，相关配置如下：

pom.xml配置

<?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.example</groupId>
    <artifactId>dvalidator</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
        <maven-assembly-plugin.version>2.2.2</maven-assembly-plugin.version>
        <maven-resources-plugin.version>2.5</maven-resources-plugin.version>
        <maven-surefire-plugin.version>2.22.2</maven-surefire-plugin.version>
    </properties>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.codehaus.gmaven/groovy-maven-plugin -->
        <dependency>
            <groupId>org.codehaus.gmaven</groupId>
            <artifactId>groovy-maven-plugin</artifactId>
            <version>2.0</version>
        </dependency>
        <dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-lambda-java-core</artifactId>
            <version>1.2.1</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <executions>
                    <execution>
                        <id>assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                        <configuration>
                            <appendAssemblyId>false</appendAssemblyId>
                            <descriptors>
                                <descriptor>src/main/java/assembly/assembly.xml</descriptor>
                            </descriptors>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>${maven-assembly-plugin.version}</version>
                <executions>
                    <execution>
                        <id>assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                        <configuration>
                            <descriptorRefs>
                                <descriptorRef>jar-with-dependencies</descriptorRef>
                            </descriptorRefs>
                            <archive>
                            </archive>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>${maven-surefire-plugin.version}</version>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.0</version>
            </plugin>

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-resources-plugin</artifactId>
                <version>${maven-resources-plugin.version}</version>
                <configuration>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

assembly.xml配置

<assembly
        xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0 http://maven.apache.org/xsd/assembly-1.1.0.xsd">
    <id>bin</id>
    <formats>
        <format>zip</format>
    </formats>
    <fileSets>
        <fileSet>
            <directory>${project.build.directory}</directory>
            <outputDirectory>/</outputDirectory>
            <includes>
                <include>*.jar</include>
            </includes>
        </fileSet>
    </fileSets>
    <dependencySets>
        <dependencySet>
            <outputDirectory>lib/</outputDirectory>
            <useProjectArtifact>false</useProjectArtifact>
            <scope>runtime</scope>
            <excludes>
            </excludes>
        </dependencySet>
    </dependencySets>
</assembly>

核心错误原因

未配置Groovy编译插件：默认的maven-compiler-plugin仅处理.java文件，不会编译Groovy代码，导致Groovy文件未被转换成.class文件，target/classes自然为空。
Groovy依赖错误：当前依赖的groovy-maven-plugin是Maven插件，不是Groovy语言的核心库，项目编译时缺少Groovy运行时支持。
重复配置maven-assembly-plugin：pom中两次配置了maven-assembly-plugin，且执行ID相同，会导致打包逻辑冲突，可能覆盖正确的打包结果。

修复步骤

1. 添加Groovy核心依赖与编译插件

在<dependencies>中添加Groovy核心库，在<build><plugins>中添加Groovy编译插件，确保Groovy代码被正确编译：

<!-- Groovy核心依赖 -->
<dependency>
    <groupId>org.codehaus.groovy</groupId>
    <artifactId>groovy-all</artifactId>
    <version>3.0.9</version> <!-- 选择与JDK11兼容的版本 -->
    <scope>compile</scope>
</dependency>

<!-- Groovy编译插件，负责编译Groovy代码 -->
<plugin>
    <groupId>org.codehaus.gmaven</groupId>
    <artifactId>groovy-maven-plugin</artifactId>
    <version>2.0</version>
    <executions>
        <execution>
            <goals>
                <goal>compile</goal>
                <goal>testCompile</goal>
            </goals>
        </execution>
    </executions>
</plugin>

2. 移除重复的maven-assembly-plugin配置

保留自定义的Zip打包配置（适配AWS Lambda需求），删除重复的jar-with-dependencies配置，修改后的plugins部分如下：

<plugins>
    <!-- 自定义AWS Lambda Zip打包配置 -->
    <plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <version>${maven-assembly-plugin.version}</version>
        <executions>
            <execution>
                <id>assembly-zip</id> <!-- 修改ID避免冲突 -->
                <phase>package</phase>
                <goals>
                    <goal>single</goal>
                </goals>
                <configuration>
                    <appendAssemblyId>false</appendAssemblyId>
                    <descriptors>
                        <descriptor>src/main/java/assembly/assembly.xml</descriptor>
                    </descriptors>
                </configuration>
            </execution>
        </executions>
    </plugin>
    <!-- 保留其他必要插件 -->
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>${maven-surefire-plugin.version}</version>
    </plugin>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.8.0</version>
    </plugin>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-resources-plugin</artifactId>
        <version>${maven-resources-plugin.version}</version>
        <configuration>
            <encoding>UTF-8</encoding>
        </configuration>
    </plugin>
    <!-- 添加Groovy编译插件 -->
    <plugin>
        <groupId>org.codehaus.gmaven</groupId>
        <artifactId>groovy-maven-plugin</artifactId>
        <version>2.0</version>
        <executions>
            <execution>
                <goals>
                    <goal>compile</goal>
                    <goal>testCompile</goal>
                </goals>
            </execution>
        </executions>
    </plugin>
</plugins>

3. 优化assembly.xml（可选）

如果希望将项目自身的.class文件直接打包到Zip根目录（而非依赖Jar），可以修改assembly.xml的<fileSets>，添加对编译输出目录的引用：

<fileSets>
    <fileSet>
        <directory>${project.build.directory}</directory>
        <outputDirectory>/</outputDirectory>
        <includes>
            <include>*.jar</include>
        </includes>
    </fileSet>
    <!-- 加入项目编译后的class文件 -->
    <fileSet>
        <directory>${project.build.outputDirectory}</directory>
        <outputDirectory>/</outputDirectory>
    </fileSet>
</fileSets>

完成以上修改后，重新执行mvn clean install，target/classes会生成Groovy编译后的.class文件，最终生成的Zip包也会包含必要的代码与依赖。

内容的提问来源于stack exchange，提问作者deewreck

Maven构建后Jar无.class文件，Target/Classes为空求助

问题描述 #

pom.xml配置 #

assembly.xml配置 #

核心错误原因 #

修复步骤 #

1. 添加Groovy核心依赖与编译插件 #

2. 移除重复的maven-assembly-plugin配置 #

3. 优化assembly.xml（可选） #