java - 我正在尝试使用 Spring data JPA 中的 MIN 聚合函数获取日期，它抛出空指针异常答案

【问题标题】：java - I am trying to fetch a date using MIN aggregate function in Spring data JPA , it is throwing null pointer exceptionjava - 我正在尝试使用 Spring data JPA 中的 MIN 聚合函数获取日期，它抛出空指针异常
【发布时间】：2021-11-04 04:09:29
【问题描述】：

我正在尝试使用 Spring data JPA 中的 MIN 聚合函数获取最早的日期，它在我的 IDE 控制台上引发空指针异常，但是当我尝试从数据库中获取它时，我能够成功获取日期在数据库上。

我的POJO课是这样的， `@实体 @ConfigurationProperties("动作日志") @Table(name = "action_log") 公共类 ActionLog {

    @Id
    @NotBlank
    private String id;

    @NotNull
    @Column(name = "job_no")
    private int jobNo;

    @NotNull
    private Date date;

    @NotNull
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_id")
    private Staff staff;

    @NotNull
    @Column(name = "previous_status")
    private JobStatus previousStatus;

    @NotNull
    @Column(name = "new_status")
    private JobStatus newStatus; `

我的仓库界面是这样的，

 public interface ActionLogRepository extends JpaRepository<ActionLog, String> {

@Query(value = "SELECT MIN(a.date) FROM action_log a where (a.previous_status = 4) AND (a.job_no = ?1) AND (a.user_id = ?1)", nativeQuery = true)
    public Date getMinDateByJobNoAndUserId(int jobNo, String id);
}`

我的Service类是这样的，

 @Service
 @EnableConfigurationProperties(ActionLog.class)
public class ActionLogService {
    
    @Autowired
    ActionLogRepository actionLogRepository;
    
    
    public void add(ActionLog actionLog) {
        actionLogRepository.save(actionLog);
    }
    
    
    public void update(ActionLog actionLog) {
        actionLogRepository.saveAndFlush(actionLog);
    }
    
    
    public ActionLog get(String id) throws PaperTrueActionLogNotFoundException {
        Optional<ActionLog> actionLog = actionLogRepository.findById(id);
        if (!actionLog.isPresent()) {
            throw new PaperTrueActionLogNotFoundException("No Action Log found for this id");
        }
        return actionLog.get();
    }

    
    public ActionLog get(int jobNo, String userId) throws PaperTrueJobNotFoundException {
        ActionLog actionLog = actionLogRepository.findByJobNoAndStaffId(jobNo, userId);
        if(actionLog == null){
            throw new PaperTrueJobNotFoundException("No Action log found for this jobNo");
        }
        return actionLog;
    }
    
    
    public void delete(ActionLog actionLog) {
        actionLogRepository.delete(actionLog);
    }

    
    public Date getMinDateByJobNoAndUserId(int jobNo, String id) throws PaperTrueJavaException {
        return actionLogRepository.getMinDateByJobNoAndUserId(jobNo, id);
    }
} `

这是堆栈跟踪，

 ----------------------Get min date from action log by job No-----------------------
Hibernate: 
    SELECT
        MIN(a.date) 
    FROM
        action_log a 
    where
        (
            a.previous_status = 4
        ) 
        AND (
            a.job_no = ?
        ) 
        AND (
            a.user_id = ?
        )
2021-09-08 11:21:48.801 TRACE 11897 --- [           main] o.h.type.descriptor.sql.BasicBinder      : binding parameter [1] as [INTEGER] - [87207]
2021-09-08 11:21:48.801 TRACE 11897 --- [           main] o.h.type.descriptor.sql.BasicBinder      : binding parameter [2] as [INTEGER] - [87207]
2021-09-08 11:21:49.082 TRACE 11897 --- [           main] o.h.type.descriptor.sql.BasicExtractor   : extracted value ([MIN(a.date)] : [TIMESTAMP]) - [null]
2021-09-08 11:21:49.087 DEBUG 11897 --- [           main] o.h.stat.internal.StatisticsImpl         : HHH000117: HQL: SELECT MIN(a.date) FROM action_log a where (a.previous_status = 4) AND (a.job_no = ?) AND (a.user_id = ?), time: 580ms, rows: 1
2021-09-08 11:21:49.091  INFO 11897 --- [           main] i.StatisticalLoggingSessionEventListener : Session Metrics {
    259636242 nanoseconds spent acquiring 1 JDBC connections;
    0 nanoseconds spent releasing 0 JDBC connections;
    287693891 nanoseconds spent preparing 1 JDBC statements;
    268222720 nanoseconds spent executing 1 JDBC statements;
    0 nanoseconds spent executing 0 JDBC batches;
    0 nanoseconds spent performing 0 L2C puts;
    0 nanoseconds spent performing 0 L2C hits;
    0 nanoseconds spent performing 0 L2C misses;
    0 nanoseconds spent executing 0 flushes (flushing a total of 0 entities and 0 collections);
    0 nanoseconds spent executing 0 partial-flushes (flushing a total of 0 entities and 0 collections)
}

java.lang.NullPointerException
    at com.papertrue.ActionLogServiceTest.contextLoads(ActionLogServiceTest.java:86)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:686)
    at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
    at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
    at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:212)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:208)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:137)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:71)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:135)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:248)
    at org.junit.platform.launcher.core.DefaultLauncher.lambda$execute$5(DefaultLauncher.java:211)
    at org.junit.platform.launcher.core.DefaultLauncher.withInterceptedStreams(DefaultLauncher.java:226)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:199)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:132)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)

ActionLogServiceTest 类是这样的，

@SpringBootTest
public class ActionLogServiceTest {
    
    @Autowired
    ActionLogService actionLogService;
    
    @Autowired
    StaffService staffService;
    
    
    @Test
    public void contextLoads() throws PaperTrueJobNotFoundException, PaperTrueJavaException, PaperTrueStaffNotFoundException {
        System.out.println("----------------------Get min date from action log by job No-----------------------");
        java.util.Date minDateByJobNoAndUserId = actionLogService.getMinDateByJobNoAndUserId(87207, "e734edc0-d47e-4d1a-baa0-a20f935f7d70");
        System.out.println("Min date" + minDateByJobNoAndUserId.toString());
        System.out.println("----------------------Get min date from action log by job No-----------------------");

    }
}

【问题讨论】：

您能发布 StackTrace 吗？日期列中有空值吗？
不，我在日期列中没有任何空值，当我尝试使用 mysql 数据库中的查询获取（最小）日期时，我能够获取日期，但是当我正在使用 JPA，然后它在控制台中显示空值
所以请发布 NullPointerException 的完整堆栈跟踪
嗨西蒙，我在问题中添加了堆栈跟踪
这不是堆栈跟踪。堆栈跟踪是包含所有信息的异常

标签： java mysql spring-boot jpa spring-data-jpa

【解决方案1】：

以防万一，如果将来有人遇到类似的问题；我在这里发布答案，

所以基本上，问题在于我在 WHERE 条件中使用的括号“()”。当我删除 WHERE 条件中的括号时，我成功获取了我试图获取的日期。

注意：聚合函数中的括号应该有，否则查询将不起作用。

【讨论】：