Spring Data 返回 List<Object[]>

Question

我有这个仓库：

@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 类在哪里：

public class TopProductDTO {

public TopProductDTO() {}

private String text;
private Integer counter;

// Getters and Setters are omited
}

但是当我执行代码时

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

它返回一个

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

就像每一列都是列表中对象数组的索引一样... 不是应该 Spring Data 将查询中的“文本”和“计数器”列与 TopProductDTO 中的字段绑定吗？

结果我的 Thymeleaf 模板中出现此错误：

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

尝试使用 DTO 的构造函数。

声明一个新的构造函数

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

在您的查询中使用新的构造函数

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

使用您的班级的完全限定名称。