如何從Spring Data JPA NativeQuery接收集合？ [導致NotReadablePropertyException]

Question

首先：我在Java 8中使用Spring-Boot Data JPA 。

我的數據庫中有一個表，我的實體定義如下：

@Entity
@Table(name="ITEMHOURS")
public class ItemHoursEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "ID")
    private int id;

    @Column(name = "YEAR", nullable = false)
    private String year;

    @Enumerated(EnumType.STRING)
    @Column(name = "STATE", nullable = false)
    private TypeEnum type;

    @Column(name = "HOURVALUE", nullable = false)
    private int hourValue = 0;

    @ManyToOne(cascade = CascadeType.MERGE)
    @JoinColumn(name = "ITEM_ID")
    private MyItem item;
//.. some more columns, getters, setters...
}

現在我得到以下選擇返回此結構：

-----------------------
| YEAR | Value | Type |
-----------------------

@Query(value = "Select year as year, sum(hourvalue) as value, state as type from ITEMHOURS h where item_id = :item_id group by h.year, h.state", nativeQuery = true)
    public Optional<Collection<TotalValuesProjection>> getYearTotalsForStateByItem(@Param("item_id") int item_id);

它在MySQL Workbench運行良好。 結果，我聽說我應該通過使用投影來獲取與默認ItemHoursEntity不同的結果，所以我嘗試創建以下內容：

@Projection(types = { ItemHoursEntity.class })
public interface TotalValuesProjection {
    public String getYear();
    public int getValue();
    public HourTypeEnum getType();
}

現在在我的service類中，我嘗試以下方法：

@Override
public List<ExtendedDataPasser<String, Integer, String>> getTotalAndYearHourValuesForItem(int itemId) {

    Optional<Collection<TotalValuesProjection>> projectionOptional = this.hoursRepository.getYearTotalsForStateByItem(itemId);
    List<ExtendedDataPasser<String, Integer, String>> entityList = new ArrayList<ExtendedDataPasser<String, Integer, String>>();
    projectionOptional.orElseGet(() -> new ArrayList<TotalValuesProjection>()).forEach(entity -> {
        entityList.add(new ExtendedDataPasser<String, Integer, String>(entity.getYear(), entity.getValue(), entity.getType().toString()));
    });
    return entityList;
}

遺憾的是，這會導致以下錯誤：

org.springframework.beans.NotReadablePropertyException: Invalid property 'year' of bean class [java.util.ArrayList]: Could not find field for property during fallback access!
        at org.springframework.data.util.DirectFieldAccessFallbackBeanWrapper.getPropertyValue(DirectFieldAccessFallbackBeanWrapper.java:58) ~[spring-data-commons-2.1.3.RELEASE.jar!/:2.1.3.RELEASE]
        at org.springframework.data.projection.PropertyAccessingMethodInterceptor.invoke(PropertyAccessingMethodInterceptor.java:73) ~[spring-data-commons-2.1.3.RELEASE.jar!/:2.1.3.RELEASE]
        at org.springframework.data.projection.ProjectingMethodInterceptor.invoke(ProjectingMethodInterceptor.java:64) ~[spring-data-commons-2.1.3.RELEASE.jar!/:2.1.3.RELEASE]
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.3.RELEASE.jar!/:5.1.3.RELEASE]
        at org.springframework.data.projection.ProxyProjectionFactory$TargetAwareMethodInterceptor.invoke(ProxyProjectionFactory.java:245) ~[spring-data-commons-2.1.3.RELEASE.jar!/:2.1.3.RELEASE]
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.3.RELEASE.jar!/:5.1.3.RELEASE]
        at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:59) ~[spring-data-commons-2.1.3.RELEASE.jar!/:2.1.3.RELEASE]
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.3.RELEASE.jar!/:5.1.3.RELEASE]
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.1.3.RELEASE.jar!/:5.1.3.RELEASE]
        at com.sun.proxy.$Proxy133.getYear(Unknown Source) ~[na:na]

也許錯誤的完整屏幕截圖有助於：

當我嘗試訪問year -attribute時，這是一個例外，這是錯誤:(幾乎相同，只是year而不是hourValue ）

我是否因為從投影到實體的映射而弄亂了什么？

Answer 1

試試這段代碼，

@Query(value = "Select year, sum(hourvalue) as value, state as type from ITEMHOURS h where item_id = :item_id group by h.year, h.state", nativeQuery = true)
    public Optional<Collection<TotalValuesProjection>> getYearTotalsForStateByItem(@Param("item_id") int item_id);

如果有任何問題通知!!

Answer 2

這不是一個可靠的解決方案，而只是大聲思考。 它主要取決於DBMS和Hibernate版本，但在某些情況下，由於大小寫緊急情況可能會發生此類異常，因此請嘗試在本機查詢中添加別名，並將表別名添加到列名稱中，如下所示：

@Query(value = "Select h.year as \"year\", sum(h.hourValue) as \"value\", h.state as \"type\" from ITEMHOURS h where h.item_id = :item_id group by h.year, h.state", nativeQuery = true)
    public Optional<Collection<TotalValuesProjection>> getYearTotalsForStateByItem(@Param("item_id") int item_id);

UPD根據Java約定更改hourValue屬性 - 'h'必須為大寫