Spring Data返回List <Object[]>

Question

我有這個存儲庫：

@Repository
public interface ProductRepository extends JpaRepository<Product, Long>{

@Query("SELECT p.textToSearch as text, count(*) as counter FROM Product p GROUP BY text_to_search ORDER BY counter DESC")
List<TopProductDTO> findTopProducts();
}

TopProductDTO類的位置是：

public class TopProductDTO {

public TopProductDTO() {}

private String text;
private Integer counter;

// Getters and Setters are omited
}

但是當我執行代碼時

List<TopProductDTO> topProducts = productRepository.findTopProducts();

它返回一個

List<Object[]> insted a List<TopProductDTO>

就像每列都是列表中對象數組的索引一樣...... Spring Data是否應該將查詢中的'text'和'counter'列與TopProductDTO中的字段綁定？

結果我的Thymeleaf模板中出現了這個錯誤：

00:37:22.659 [http-nio-8080-exec-5] ERROR o.a.c.c.C.[.[.[.[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.thymeleaf.exceptions.TemplateProcessingException: Exception evaluating SpringEL expression: "topProductDTO.text" (products/top:46)] with root cause
org.springframework.expression.spel.SpelEvaluationException: EL1008E:(pos 14): Property or field 'text' cannot be found on object of type 'java.lang.Object[]' - maybe not public?

我正在使用Spring Boot 1.3.3和Postgres 9.2

Answer 1

嘗試使用DTO的構造函數。

聲明一個新的構造函數

public TopProductDTO(String text, Integer count) {
    this.text = text;
    this.count = count;
}

在您的查詢中使用新的構造函數

@Query("SELECT new TopProductDTO(p.textToSearch, count(id))FROM Product p GROUP BY text_to_search ORDER BY counter DESC")
List<TopProductDTO> findTopProducts();
}

使用班級的完全限定名稱。