Spring TwitterCLI项目运行报错：NoClassDefFoundError与类找不到问题

报错信息1：直接运行Java命令时的NoClassDefFoundError #

Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.NoClassDefFoundError: com/fasterxml/jackson/core/JsonProcessingException
        at java.lang.Class.getDeclaredMethods0(Native Method)
        at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
        at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
        at java.lang.Class.getMethod0(Class.java:3018)
        at java.lang.Class.getMethod(Class.java:1784)
        at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:650)
        at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:632)
Caused by: java.lang.ClassNotFoundException: com.fasterxml.jackson.core.JsonProcessingException
        at java.net.URLClassLoader.findClass(URLClassLoader.java:387)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
        ... 7 more

报错信息2：使用mvn spring-boot:run时的主类找不到 #

java.lang.ClassNotFoundException: ca.jrvs.apps.twitter.TwitterCLIApp
    at java.net.URLClassLoader.findClass (URLClassLoader.java:387)
    at java.lang.ClassLoader.loadClass (ClassLoader.java:418)
    at java.lang.ClassLoader.loadClass (ClassLoader.java:351)
    at org.springframework.boot.maven.AbstractRunMojo$LaunchRunner.run (AbstractRunMojo.java:553)
    at java.lang.Thread.run (Thread.java:750)

POM文件依赖配置 #

<dependencies>

    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>1.7.28</version>
    </dependency>

    <!--oauth 1.0 and httpclient4-->
    <dependency>
      <groupId>oauth.signpost</groupId>
      <artifactId>signpost-commonshttp4</artifactId>
      <version>1.2.1.2</version>
    </dependency>
    <!--Jackson JSON-->
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-core</artifactId>
      <version>${jackson.version}</version>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>${jackson.version}</version>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-annotations</artifactId>
      <version>${jackson.version}</version>
    </dependency>
    <!--testing-->
    <dependency>
      <groupId>org.mockito</groupId>
      <artifactId>mockito-core</artifactId>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <scope>test</scope>
    </dependency>

    <!--spring-->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
    </dependency>
  </dependencies>

操作步骤 #

• 执行mvn clean compile package，构建成功。
• 运行命令：java -classpath target/test-classes ca.jrvs.apps.twitter.TwitterCLIApp post "hahaha" "42.98693964646016:-81.31011004242582"，触发第一个错误。
• 尝试过jackson.version为2.7.3、2.12.0、2.14.0版本，均无效。
• 改用mvn spring-boot:run运行，触发第二个错误。

解决方案 #

针对第一个错误：NoClassDefFoundError #

1. 修正classpath路径：target/test-classes仅包含测试代码和测试依赖，Jackson属于主代码依赖，不在该路径。推荐使用Maven exec:java插件自动处理依赖classpath：

   mvn exec:java -Dexec.mainClass="ca.jrvs.apps.twitter.TwitterCLIApp" -Dexec.args='post "hahaha" "42.98693964646016:-81.31011004242582"'
   

2. 确认jackson.version变量定义：检查POM是否在<properties>中定义该变量，未定义则添加：

   <properties>
       <jackson.version>2.14.0</jackson.version>
   </properties>
   

   否则Maven无法解析变量，导致依赖无法正确引入。

针对第二个错误：mvn spring-boot:run找不到主类 #

1. 明确配置主类：在Spring Boot POM中添加插件配置指定主类：

   <build>
       <plugins>
           <plugin>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-maven-plugin</artifactId>
               <configuration>
                   <mainClass>ca.jrvs.apps.twitter.TwitterCLIApp</mainClass>
               </configuration>
           </plugin>
       </plugins>
   </build>
   

2. 检查主类位置与注解：确保TwitterCLIApp在src/main/java/ca/jrvs/apps/twitter/目录下，且类上添加@SpringBootApplication注解，让Spring Boot能自动扫描到。

额外建议 #

若需打包为可执行JAR，确保Spring Boot插件配置正确，执行mvn clean package后，直接运行：

java -jar target/your-project-name.jar

无需手动配置classpath。

内容的提问来源于stack exchange，提问作者Alice Huang