项目场景：

提示：halo 插件开发过程中 版本2.21

在halo插件开发中运行main方法直接报错

---

问题描述

例如：运行一个main方法时

    public static void main(String[] args) {
        System.out.println("1111");
    }

报错如下

> Task :WeReadApiClient.main() FAILED
错误: 无法初始化主类 run.halo.weread.util.WeReadApiClient
原因: java.lang.NoClassDefFoundError: com/fasterxml/jackson/databind/JsonNode

Execution failed for task ':WeReadApiClient.main()'.
> Process 'command '/Library/Java/JavaVirtualMachines/jdk-17.jdk/Contents/Home/bin/java'' finished with non-zero exit value 1

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.
> Get more help at https://help.gradle.org.
Deprecated Gradle features were used in this build, making it incompatible with Gradle 9.0.
You can use '--warning-mode all' to show the individual deprecation warnings and determine if they come from your own scripts or plugins.
For more on this, please refer to https://docs.gradle.org/8.9/userguide/command_line_interface.html#sec:command_line_warnings in the Gradle documentation.
BUILD FAILED in 6s
7 actionable tasks: 4 executed, 3 up-to-date

Execution failed for task ':WeReadApiClient.main()'.
> Process 'command '/Library/Java/JavaVirtualMachines/jdk-17.jdk/Contents/Home/bin/java'' finished with non-zero exit value 1

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.
> Get more help at https://help.gradle.org.
Deprecated Gradle features were used in this build, making it incompatible with Gradle 9.0.
You can use '--warning-mode all' to show the individual deprecation warnings and determine if they come from your own scripts or plugins.
For more on this, please refer to https://docs.gradle.org/8.9/userguide/command_line_interface.html#sec:command_line_warnings in the Gradle documentation.
BUILD FAILED in 4s
7 actionable tasks: 3 executed, 4 up-to-date

---

原因分析：

❓ 为什么添加这个依赖就能解决问题？
你在代码中使用了 Jackson 的核心类，例如：
com.fasterxml.jackson.databind.JsonNode
ObjectMapper
或者涉及 JSON 序列化/反序列化的操作
这些功能都属于 Jackson Databind 模块。
但你在最初没有显式声明该依赖，导致运行时抛出异常：

java.lang.NoClassDefFoundError: com/fasterxml/jackson/databind/JsonNode

这表示 JVM 在运行时找不到 JsonNode 这个类，不是编译期找不到（否则 Gradle 编译就会失败），而是 运行时 classpath 中缺少该类所在的 JAR 包。

🧩 Jackson 核心模块说明

模块	功能	是否需要｜
jackson-core	核心流处理 API（如 JsonParser, JsonGenerator）	✅ 自动被 databind 引入
jackson-annotations	注解支持（如 @JsonProperty）	✅ 自动被 databind 引入
jackson-databind	数据绑定，提供 ObjectMapper 和 JsonNode 等高级 API	⚠️ 必须手动引入

⚠️ jackson-databind 不会自动通过平台依赖或 Halo 插件引入，必须在你的项目中显式声明。

---

解决方案：

提示：在build.gradle 中添加 Jackson 的运行时依赖

在 build.gradle 中添加 Jackson 的运行时依赖。
添加 Jackson 依赖
在 dependencies 块中添加以下内容：

implementation 'com.fasterxml.jackson.core:jackson-databind:2.16.1'

完整示例如下：

dependencies {
    implementation 'org.apache.httpcomponents:httpclient:4.5.13'
    implementation 'com.fasterxml.jackson.core:jackson-databind:2.16.1'

    implementation platform('run.halo.tools.platform:plugin:2.20.0-SNAPSHOT')
    compileOnly 'run.halo.app:api'

    testImplementation 'run.halo.app:api'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
}