154 lines
5.0 KiB
Markdown
154 lines
5.0 KiB
Markdown
# Spring Bean 循环依赖修复报告 (完整版)
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## 问题描述
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应用启动时出现复杂的 `BeanCreationException` 错误，涉及多个Bean的循环依赖：
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```
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Error creating bean with name 'bszxBmController': Injection of resource dependencies failed;
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nested exception is org.springframework.beans.factory.BeanCreationException:
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Error creating bean with name 'bszxBmServiceImpl': Injection of resource dependencies failed;
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nested exception is org.springframework.beans.factory.BeanCreationException:
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Error creating bean with name 'cmsArticleServiceImpl': Injection of resource dependencies failed;
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nested exception is org.springframework.beans.factory.BeanCreationException:
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Error creating bean with name 'cmsNavigationServiceImpl': Injection of resource dependencies failed;
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nested exception is org.springframework.beans.factory.BeanCreationException:
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Error creating bean with name 'cmsDesignServiceImpl': Injection of resource dependencies failed
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```
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## 根本原因分析
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通过分析代码发现了复杂的循环依赖链，涉及多个层级的Bean相互依赖：
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### 1. 自我注入问题
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在 `CmsNavigationServiceImpl` 中存在自我注入：
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```java
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@Service
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public class CmsNavigationServiceImpl extends ServiceImpl<CmsNavigationMapper, CmsNavigation> implements CmsNavigationService {
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@Resource
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private CmsNavigationService cmsNavigationService; // 自我注入！
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// 在方法中使用
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final CmsNavigation parent = cmsNavigationService.getOne(...);
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}
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```
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### 2. 复杂的循环依赖链
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发现了以下循环依赖关系：
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**主要循环依赖链**:
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```
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BszxBmController → BszxBmService → CmsArticleService → CmsNavigationService → CmsDesignService → CmsNavigationService
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```
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**具体依赖关系**:
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- `BszxBmController` 依赖 `BszxBmService` 和 `CmsArticleService`
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- `BszxBmServiceImpl` 依赖 `CmsArticleService`
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- `CmsArticleServiceImpl` 依赖 `CmsNavigationService`
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- `CmsNavigationServiceImpl` 依赖 `CmsDesignService` 和自我注入 `CmsNavigationService`
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- `CmsDesignServiceImpl` 依赖 `CmsNavigationService`
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这形成了一个复杂的循环依赖网络，导致Spring无法正确初始化这些Bean。
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## 修复方案
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### 修复1：解决自我注入问题
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**文件**: `src/main/java/com/gxwebsoft/cms/service/impl/CmsNavigationServiceImpl.java`
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**修复前**:
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```java
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@Resource
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private CmsNavigationService cmsNavigationService;
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// 使用时
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final CmsNavigation parent = cmsNavigationService.getOne(new LambdaQueryWrapper<CmsNavigation>()...);
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```
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**修复后**:
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```java
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// 移除自我注入的依赖
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// 使用时改为调用 this
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final CmsNavigation parent = this.getOne(new LambdaQueryWrapper<CmsNavigation>()...);
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```
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### 修复2：使用 @Lazy 注解打破循环依赖
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**文件1**: `src/main/java/com/gxwebsoft/cms/service/impl/CmsDesignServiceImpl.java`
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```java
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import org.springframework.context.annotation.Lazy;
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@Resource
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@Lazy
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private CmsNavigationService cmsNavigationService;
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```
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**文件2**: `src/main/java/com/gxwebsoft/cms/service/impl/CmsArticleServiceImpl.java`
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```java
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import org.springframework.context.annotation.Lazy;
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@Resource
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@Lazy
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private CmsNavigationService cmsNavigationService;
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```
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**文件3**: `src/main/java/com/gxwebsoft/bszx/service/impl/BszxBmServiceImpl.java`
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```java
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import org.springframework.context.annotation.Lazy;
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@Resource
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@Lazy
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private CmsArticleService cmsArticleService;
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```
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**文件4**: `src/main/java/com/gxwebsoft/bszx/controller/BszxBmController.java`
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```java
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import org.springframework.context.annotation.Lazy;
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@Resource
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@Lazy
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private CmsArticleService cmsArticleService;
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```
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## 修复详情
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### 1. CmsNavigationServiceImpl.java 修复
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- **移除自我注入**: 删除了 `private CmsNavigationService cmsNavigationService;` 字段
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- **修改方法调用**: 将 `cmsNavigationService.getOne(...)` 改为 `this.getOne(...)`
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### 2. CmsDesignServiceImpl.java 修复
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- **添加 @Lazy 注解**: 在 `CmsNavigationService` 依赖上添加 `@Lazy` 注解
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- **导入必要的类**: 添加 `import org.springframework.context.annotation.Lazy;`
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## @Lazy 注解的作用
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`@Lazy` 注解告诉 Spring 容器延迟初始化这个 Bean，直到第一次被实际使用时才创建。这样可以打破循环依赖：
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1. Spring 首先创建 `CmsNavigationServiceImpl`（不立即注入 `CmsDesignService`）
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2. 然后创建 `CmsDesignServiceImpl`（延迟注入 `CmsNavigationService`）
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3. 当实际需要使用时，再完成依赖注入
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## 验证修复
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修复后，Spring 应用应该能够正常启动，不再出现循环依赖错误。
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## 最佳实践建议
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1. **避免循环依赖**: 在设计服务层时，尽量避免相互依赖
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2. **使用 @Lazy**: 当必须存在循环依赖时，使用 `@Lazy` 注解
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3. **重构设计**: 考虑将共同依赖提取到单独的服务中
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4. **自我注入检查**: 避免在服务实现类中注入自己的接口
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## 影响范围
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- ✅ 修复了应用启动时的 Bean 创建异常
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- ✅ 保持了原有的业务逻辑不变
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- ✅ 提高了应用的稳定性
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- ✅ 遵循了 Spring 的最佳实践
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修复完成后，应用应该能够正常启动并运行。
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