如何通过Java流收集具有特定功能的现有List元素的新List？

Question

我想通过根据某些条件过滤现有元素来从现有列表中收集新列表，但是下面的代码抛出了强制转换异常（java.lang.object;无法强制转换为PaymentDelayInfo）。这是什么原因呢？

我尝试先将列表元素放入流中，然后尝试过滤和收集，但它也无法正常工作。

public MaxLatencyCounts calculateMaxLatencyCounts(LocalDate reportDate, String loanId) {

    final List<PaymentDelayInfo> maxLatencyDaysInLast12Month = oraclePaymentDelayInformationRepository.getPaymentDelayInfoListInLast12Months(reportDate, loanId);

    if (maxLatencyDaysInLast12Month == null || maxLatencyDaysInLast12Month.isEmpty()) {
        return null;
    }

    List<PaymentDelayInfo> collect = maxLatencyDaysInLast12Month
            .stream()
            .filter(maxLatencyDaysInLast6 -> maxLatencyDaysInLast6.getDate() != null)
            .filter(date -> date.getDate().isAfter(reportDate.minusMonths(6))).collect(Collectors.toList());

    final List<PaymentDelayInfo> maxLatencyDaysInLast3Month = maxLatencyDaysInLast12Month
            .stream()
            .filter(maxLatencyDaysInLast3 -> maxLatencyDaysInLast3.getDate() != null)
            .filter(date -> date.getDate().isAfter(reportDate.minusMonths(3)))
            .collect(Collectors.toList());

    final MaxLatencyCounts maxLatencyCounts = MaxLatencyCounts.builder()
            .maxLatencyDayInLast3Month(calculateMaxLatencyDayCount(maxLatencyDaysInLast3Month))
            .maxLatencyDayInLast6Month(calculateMaxLatencyDayCount(collect))
            .maxLatencyDayInLast12Month(calculateMaxLatencyDayCount(maxLatencyDaysInLast12Month))
            .build();

    return maxLatencyCounts;
}

因此，我想创建两个新列表及其由适合条件的旧列表元素组成的元素。我该怎么办？

更新：在存储库代码下方；

public List<PaymentDelayInfo> getPaymentDelayInfoListInLast12Months(final LocalDate reportDate, final String loanId) {
    final String reportDateParameter = reportDate.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));

    final String query = "SELECT a.* " +
            "FROM FINANCE.LATENCY_DAYS a " +
            "WHERE a.talep_no = :loanId " +
            "AND a.tarih >= add_months(trunc(TO_DATE(:reportDate,'yyyy-mm-dd')),-12)";

    final Query paymentDelayInfoListQuery = entityManager.createNativeQuery(query);
    paymentDelayInfoListQuery.setParameter("reportDate", reportDateParameter);
    paymentDelayInfoListQuery.setParameter("loanId", loanId);

    return paymentDelayInfoListQuery.getResultList();
}

及以下实体；

@Entity
@Table(name = "LATENCY_DAYS", schema = "FINANCE")
@Getter
@Setter
@Builder
@NoArgsConstructor
@AllArgsConstructor
@Cacheable(false)
@IdClass(PaymentDelayInfoId.class)
public class PaymentDelayInfo {
    @Id
    @Column(name = "GECIKME_GUN")
    private Integer delay;
    @Id
    @Column(name = "TALEP_NO")
    private String loanId;
    @Id
    @Column(name = "TARIH")
    private LocalDate date;
}

class PaymentDelayInfoId implements Serializable {
    private Integer delay;
    private String loanId;
    private LocalDate date;
}

下面是我的堆栈跟踪：

{"timestamp":"2019-05-02 10:33:26.438","level":"WARN","thread":"http-nio-4567-exec-2","mdc":{"traceId":"ca59a358bf36528a","spanId":"ca59a358bf36528a","spanExportable":"true","X-Span-Export":"true","X-B3-SpanId":"ca59a358bf36528a","X-B3-TraceId":"ca59a358bf36528a"},"logger":"com.kocfinans.loancontactinfo.application.LoanContactInfoController","message":"Unhandled exception occurred!","context":"default","exception":"…

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.kocfinans.loancontactinfo.infrastructure.entities.PaymentDelayInfo
    at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:174)
    at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1382)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
    at com.kocfinans.loancontactinfo.application.calculation.PaymentDelayCalculationService.calculateMaxLatencyCounts(PaymentDelayCalculationService.java:49)
    at com.kocfinans.loancontactinfo.application.DefaultLoanContactInfoService.generateLoanContactInfoResponse(DefaultLoanContactInfoService.java:57)
    at com.kocfinans.loancontactinfo.application.LoanContactInfoController.getLoanContactInformation(LoanContactInfoController.java:30)
    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:209)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:891)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:981)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:873)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:858)
    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.actuate.web.trace.servlet.HttpTraceFilter.doFilterInternal(HttpTraceFilter.java:90)
    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.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:109)
    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:93)
    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.cloud.sleuth.instrument.web.ExceptionLoggingFilter.doFilter(ExceptionLoggingFilter.java:48)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at brave.servlet.TracingFilter.doFilter(TracingFilter.java:86)
    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.metrics.web.servlet.WebMvcMetricsFilter.filterAndRecordMetrics(WebMvcMetricsFilter.java:117)
    at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.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.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
    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:493)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    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:800)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

…"}

Answer 1

return paymentDelayInfoListQuery.getResultList();会返回一个List<Object[]>，它不能转换为List<PaymentDelayInfo>。

您需要做的是使用entityManager返回TypedQuery<T>的方法之一

entityManager#createQuery(String qlString, Class<T> resultClass)是您在这种情况下要寻找的东西