Spring数据返回列表

  • Z时代
  • 2024-01-10
  • 分类：问答

我有这个存储库：

@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();
}

其中TopProductDTO类为：

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……难道不是Spring

Data会将查询的’text’和’counter’列与TopProductDTO中的字段绑定在一起吗？

结果我在Thymeleaf模板中遇到了这个错误：

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

回答：

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();
}

使用课程的全限定名。

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