中文开发者报错 / 踩坑经验知识库https://devfix.example.com/https://devfix.example.com/cases/java/java-concurrentmodificationexception/https://devfix.example.com/cases/java/java-concurrentmodificationexception/ConcurrentModificationException 不是多线程专属，单线程遍历集合时直接增删元素一样触发。根因是 iterator 的 expectedModCount 与集合 modCount 不一致。用 removeIf 或 Iterator.remove 即可解决。Sun, 23 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/java/java-deadlock-troubleshooting/https://devfix.example.com/cases/java/java-deadlock-troubleshooting/应用突然假死，没有异常、没有日志，多半是死锁。用 jstack 抓线程快照，JVM 会直接打出 Found one Java-level deadlock 并列出环上线程。从四个必要条件到锁顺序一致、tryLock 超时一次讲清。Sun, 23 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/java/java-outofmemoryerror-heap-space/https://devfix.example.com/cases/java/java-outofmemoryerror-heap-space/堆内存被对象占满，GC 回收不回空间，抛出 OutOfMemoryError: Java heap space。用 -XX:+HeapDumpOnOutOfMemoryError 留堆快照，MAT 看 Dominator Tree 和 GC Roots，揪出泄漏源头。调大 -Xmx 只是缓兵之计。Sun, 23 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/java/java-stackoverflowerror/https://devfix.example.com/cases/java/java-stackoverflowerror/递归写错或调用链太深，栈帧把 JVM 线程栈顶穿，抛出 StackOverflowError。它不是堆内存不够，是调用栈深度超限。先查递归到底有没有出口，能改循环就改循环，必要时用 -Xss 应急。Sun, 23 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/java/java-threadlocal-memory-leak/https://devfix.example.com/cases/java/java-threadlocal-memory-leak/ThreadLocal 在线程池里用完不调用 remove，会慢慢把堆吃满，最终抛出 OutOfMemoryError。根因是 Entry 的 key 是弱引用、value 是强引用，线程复用让无主 value 越积越多。从根因到 try/finally 清理一次讲清。Sun, 23 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/java/java-unable-to-create-new-native-thread/https://devfix.example.com/cases/java/java-unable-to-create-new-native-thread/OutOfMemoryError: unable to create new native thread 不是 Java 堆满了，是操作系统拒绝再创建线程。根因是 ulimit -u、kernel.threads-max 等线程上限，或线程栈吃光 native 内存。调高限制、用有界线程池、减小 -Xss 解决。Sun, 23 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/fastapi/fastapi-async-blocking-event-loop/https://devfix.example.com/cases/fastapi/fastapi-async-blocking-event-loop/async def 端点在事件循环主线程上运行，一旦调了 time.sleep、requests 这类阻塞代码，整个服务连同 /health 一起冻结。本文讲清 def vs async def 的区别和 run_in_threadpool 的正确用法。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/fastapi/fastapi-cors-middleware-config/https://devfix.example.com/cases/fastapi/fastapi-cors-middleware-config/前端一直报 No 'Access-Control-Allow-Origin'，往往是 CORSMiddleware 没加、allow_origins 漏了前端源、或 allow_origins=['*'] 和 allow_credentials=True 撞一起。另外 allow_methods 默认只有 GET、allow_headers 默认空也是高频坑。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/fastapi/fastapi-depends-dependency-injection/https://devfix.example.com/cases/fastapi/fastapi-depends-dependency-injection/参数漏写 Depends() 会被当成 query 参数报 422；yield 依赖的清理要在 finally 里保证、except 后要 raise；默认依赖结果在同一次请求里缓存，副作用依赖要用 use_cache=False。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/fastapi/fastapi-pydantic-422-validation-error/https://devfix.example.com/cases/fastapi/fastapi-pydantic-422-validation-error/接口返回 422 本质是请求体/参数和 Pydantic 模型对不上。本文讲清 detail 里 loc/msg/type 怎么读，以及用 DTO 分离 ORM 模型、处理 camelCase、Optional 字段等常见解法。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/fastapi/fastapi-sqlalchemy-session-lifecycle/https://devfix.example.com/cases/fastapi/fastapi-sqlalchemy-session-lifecycle/每个请求一个 session，用 yield 依赖保证关闭；async 路由里调同步 Session 会阻塞事件循环；session 关闭后再访问懒加载属性会报错。本文讲清这三类坑和对应写法。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/springai/spring-ai-chatmodel-chatclient-config-dependency/https://devfix.example.com/cases/springai/spring-ai-chatmodel-chatclient-config-dependency/ChatModel 注入不到，常见是没引入厂商 starter、api-key 写错、模型名拼错、或版本没走 BOM 管理。本文讲清依赖、配置、自动配置三层排查路径。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/springai/spring-ai-rag-vectorstore-dimension-mismatch/https://devfix.example.com/cases/springai/spring-ai-rag-vectorstore-dimension-mismatch/向量维度是 pgvector 的硬约束，建表后不能 ALTER。报维度冲突，多半是 embedding 模型没固定、或者换了模型，而旧表还留着。改了 dimensions 配置不生效，得 DROP 表重建。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/springai/spring-ai-stream-sse/https://devfix.example.com/cases/springai/spring-ai-stream-sse/用 .stream() 得到 Flux，再通过 SseEmitter（MVC）或直接返回 Flux（WebFlux）推给前端。坑点：某些版本的 OpenAI stream 被内部 collectList 缓冲、SseEmitter 不设超时会挂死、produces 配置漏了连接提前关闭。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/springai/spring-ai-tool-calling-not-working/https://devfix.example.com/cases/springai/spring-ai-tool-calling-not-working/工具调用不触发，常是这些原因：defaultOptions 用了 DefaultChatOptions 而不是 ToolCallingChatOptions、.tools() 的重载只吃 MethodTool 却吞掉 FunctionToolCallback、或者中途换了 options 实例把 callback 丢了。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/springai/spring-ai-version-upgrade-breaking-changes/https://devfix.example.com/cases/springai/spring-ai-version-upgrade-breaking-changes/Spring AI 迭代极快，pre-1.0 到 1.0 有一大批 breaking change：旧的 ChatClient 功能挪进 ChatModel、EmbeddingClient 改成 EmbeddingModel、starter 命名标准化、配置属性去掉了 .options。升级前先读 upgrade notes。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/springboot/spring-boot-3-upgrade-javax-jakarta/https://devfix.example.com/cases/springboot/spring-boot-3-upgrade-javax-jakarta/升级到 Spring Boot 3 不是点个版本号那么简单：最低 Java 17、javax.* 全部变 jakarta.*、Spring Security 配置重写、Hibernate 6。本文梳理最容易踩的几个坑和对应改法。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/springboot/spring-boot-circular-dependency/https://devfix.example.com/cases/springboot/spring-boot-circular-dependency/Spring Boot 2.6 起默认禁止 Bean 循环依赖，升级后启动突然失败怎么办。从根因到重构、@Lazy、setter 注入、allow-circular-references 几种方案一次讲清。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/springboot/spring-boot-cors-config-not-working/https://devfix.example.com/cases/springboot/spring-boot-cors-config-not-working/前端一直报 No 'Access-Control-Allow-Origin'，配置却「没生效」。本文讲清 @CrossOrigin、WebMvcConfigurer、Spring Security 三条路径，以及 OPTIONS 预检和 allowCredentials + * 两个高频坑。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/springboot/spring-boot-jpa-n-plus-1-query/https://devfix.example.com/cases/springboot/spring-boot-jpa-n-plus-1-query/查 N 个父实体再遍历访问关联，会触发 N 条额外查询。本文讲清 FetchType 与 FetchMode 的区别，以及 JOIN FETCH、@EntityGraph、@BatchSize 各自适用场景和坑。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/springboot/spring-boot-port-8080-already-in-use/https://devfix.example.com/cases/springboot/spring-boot-port-8080-already-in-use/内嵌 Web 服务器默认绑 8080，一旦有其他进程占用就会启动失败。本文给出 macOS/Linux/Windows 三步定位并释放端口、改端口、以及预防再次踩坑的做法。Sat, 22 Aug 2026 00:00:00 GMThttps://devfix.example.com/cases/springboot/spring-boot-self-invocation-async-transaction/https://devfix.example.com/cases/springboot/spring-boot-self-invocation-async-transaction/同一个类里用 this 调用带 @Async 或 @Transactional 的方法，注解会静默失效。本文讲清 AOP 代理边界，以及抽 Bean、注入自身代理、AopContext 三种解法。Sat, 22 Aug 2026 00:00:00 GMT