从 Spring Boot RestController 返回 Clojure PersistentVector

Posted 2023-02-26

【中文标题】从 Spring Boot RestController 返回 Clojure PersistentVector

【英文标题】：Returning a Clojure PersistentVector from a Spring Boot RestController

【发布时间】：2019-05-14 02:36:02

【问题描述】：

我正在尝试从 Spring Boot RestController 方法返回 Clojure PersistentVector：

@GetMapping("example")
public PersistentVector someVector() 
    return PersistentVector.create(42, "hello");

但是，Spring Boot 似乎将PersistentVector 视为一个函数（它是Runnable 和Callable 的子类型）：

clojure.lang.ArityException: Wrong number of args (0) passed to: PersistentVector

at clojure.lang.AFn.throwArity(AFn.java:429) ~[clojure-1.9.0.jar:na]
at clojure.lang.AFn.invoke(AFn.java:28) ~[clojure-1.9.0.jar:na]
at clojure.lang.AFn.call(AFn.java:18) ~[clojure-1.9.0.jar:na]

at org.springframework.web.context.request.async.WebAsyncManager.lambda$startCallableProcessing$4(WebAsyncManager.java:323) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]

at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[na:1.8.0_181]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_181]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[na:1.8.0_181]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[na:1.8.0_181]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_181]

我如何告诉 Spring Boot 将 PersistentVector 视为 List（它也是 List 的子类型）？

【参考方案1】：

列表和函数的混淆可以通过在向量上显式调用.iterator()来解决：

@GetMapping("example")
public Iterator someVector() 
    // ~~~~~~~~
    return PersistentVector.create(42, "hello").iterator();
                                           // ~~~~~~~~~~~

也许不是最干净的解决方案，但嘿，它完成了工作！