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为什么 Kotlin 会收到这样的 UndeclaredThrowableException 而不是 ParseException

我有一个extension方法，可以将字符串转换为kotlin中的日期. 

fun String.convertToDate() : Date {
  var pattern: String = "dd-mm-yyyy"
  val dateFormatter = SimpleDateFormat(pattern)
  return dateFormatter.parse(this) // parse method throw ParseException
}

And this is the code where I am trying to catch possible exception.

    try {
        "22---2017".convertToDate()
    } catch (ex: ParseException) {
        // ParseException supposed to be caught in this block

        logger.error("Parse exception occur")      
    } catch (ex: Exception) {

        // ParseException caught in this block

        logger.error("Exception occur")            
    }

最后一个街区抓到的ParseException个，也就是抓到Exception个的地方.但它应该被捕获到ParseException块中吗？我错过了什么？

===UPDATE===

我正在开发一个Spring MVC项目.我已经在简单的独立kotlin程序中运行了这些代码，它会相应地运行.但在我的spring项目中，它的表现有所不同.我给出了完整的代码，Controller和Service层.

Controller

@PostMapping
@PreAuthorize("hasAnyRole('USER','ROLE_USER','ROLE_ADMIN','ADMIN')")
fun postAttendance(@RequestBody attendanceJson: AttendanceJsonWrapper,
                   request: HttpServletRequest): ResponseEntity<*> {
    val organization = getOrganizationFromSession(request)
    try {
        val attendanceBook: AttendanceBook = attendanceService.post(attendanceJson, organization.id!!)
        logger.info("Post successfully attendance book {}", attendanceBook)
    } catch (ex: SameDateAttendanceException) {
        logger.error("Duplicate attendance entry found at date [{}]", attendanceJson.date, attendanceJson.classId)
        return responseConflict(attendanceJson)
    } catch (ex: java.text.ParseException) {
        ex.printStackTrace()
        logger.error("Parse exception occur")
        return responseError(ErrorObject(
                attendanceJson,
                "date",
                Constants.INVALID_DATE_FORMAT,
                Constants.EXPECTED_DATE_FORMAT))
    } catch (ex: Exception) {
        ex.printStackTrace()
        logger.error("Exception occur")
        if (ex.cause is ParseException) {
            logger.info("What the hell is happening")
        }
    return responseOK(attendanceJson)
}

Service个

@Service
open class AttendanceService constructor(val attendanceRepository: AttendanceRepository) {
@Transactional
open fun post(attendanceJsonWrapper: AttendanceJsonWrapper, orgId: Long): AttendanceBook {
    // ParseException should thrown from this line.
    val _attendanceDate = attendanceJsonWrapper.date.convertToDate()
    // Other logic goes here
    return attendanceRepository.save(attendanceBook)
}
}

Log

对于给定输入，从前端输入28--2017，然后生成日志(log).

2017-06-28 02:36:52.942 ERROR 4632 --- [nio-8080-exec-1] c.l.c.rest.AttendanceRestController      : Exception occur
2017-06-28 02:52:32.485  INFO 2796 --- [io-8080-exec-10] c.l.c.rest.AttendanceRestController      : What the hell is happening

Exception

java.lang.reflect.UndeclaredThrowableException
at com.lynas.service.AttendanceService$$EnhancerBySpringCGLIB$$7b42c004.post(<generated>)
at com.lynas.controller.rest.AttendanceRestController.postAttendance(AttendanceRestController.kt:34)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.boot.web.filter.ApplicationContextHeaderFilter.doFilterInternal(ApplicationContextHeaderFilter.java:55)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:110)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:317)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:114)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:137)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:170)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:200)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:124)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:64)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:214)
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:177)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:106)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:861)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.text.ParseException: Unparseable date: "28--2017"
at java.text.DateFormat.parse(DateFormat.java:366)
at com.lynas.util.UtilKt.convertToDate(Util.kt:56)
at com.lynas.service.AttendanceService.post(AttendanceService.kt:23)
at com.lynas.service.AttendanceService$$FastClassBySpringCGLIB$$2b941a4b.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:738)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:673)
... 103 more

推荐答案

The UndeclaredThrowableException is caused by kotlin. why? we know kotlin does not have checked exceptions.

UndeclaredThrowableException的文件说:

如果其调用处理程序的Invoke方法引发判断的异常，则在proxy instance上由a method invocation引发

On the other hand, Kotlin can throw any exceptions but in java them will are: unchecked/checked exception and error. we know almost all of the popular frameworks is created base on java.reflect package includes java.reflect.Proxy.

In short, when the kotlin function throw a java checked exception and don't declare the exception that it will maybe throwing. then call a java Proxy you maybe receive such a UndeclaredThrowableException.

In java you can declare a checked-exception will be throwing as below:

//                v--- it is a checked exception in java
int read() throws IOException{/**/}

感谢@glee8e指出我的错误.

@Throws(IOException::class)
fun read():Int{/**/}

let's reproduce the UndeclaredThrowableException in kotlin:

//throws a UndeclaredThrowableException takes the original IOException as its cause
// because java.lang.Runnable don't declare any checked exception at all
//                                                      |
//                                                      v
Runnable::class.proxying(::throwsAJavaCheckedException).run()


// throws the original IOException directly because java.util.concurrent.Callable
// has declared that it will be throwing a checked Exception
//                                                      |
//                                                      v
Callable::class.proxying(::throwsAJavaCheckedException).call()

fun throwsAJavaCheckedException(proxy:Any, method:Method, args:Array<Any>?): Any? {
    throw IOException();
}

typealias Invocation = (Any, Method, Array<Any>?) -> Any?;

fun <T:Any> KClass<T>.proxying(handler:Invocation) = cast(Proxy.newProxyInstance(
        ClassLoader.getSystemClassLoader(),
        arrayOf(java),
        handler
));

如何避免这个问题？

如果函数是您自己编写的，那么解决方案就简单多了. 是的，声明函数将抛出判断异常.例如:

@Throws(ParseException::class)
fun convertToDate(){/**/}

OR write some gradle-plugin like as allopen, I named it allthrows here.

But you also can make some compromises. If you are not sure what will be happens in the frameworks like as spring, you should wrap your invocation into a helper method. for example:

val task = Runnable::class.proxying(::throwsAJavaCheckedException)

//  v-- the result return by catch-block immediately if no exception occurs
val result : Unit = catch(task::run).by { actual: Throwable ->
    val exceptional: Unit = Unit;
    //    v--- you can choose return an exceptional value or rethrow the exception
    when (actual) {
        is RuntimeException -> exceptional
        is ParseException -> logger.info(acutal)
        else -> throw actual
    }
}


val result : Unit? = catch(task::run).only { actual:Throwable ->
// only handle the exception don't return the exceptional value
    logger.info(actual);
}

inline fun <T> catch(crossinline block: () -> T): () -> T {
    return { block(); };
}

inline fun <T> (() -> T).by(exceptionally: (Throwable) -> T): T {
    return only { exceptionally(it) }!!
}

inline fun <T : R, R> (() -> T).only(exceptionally: (Throwable) -> R): R? {
    try {
        return invoke();
    } catch(e: UndeclaredThrowableException) {
        return exceptionally(e.cause ?: e);
    } catch(e: Exception) {
        return exceptionally(e);
    }
}

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