Spring Data JPA“无法找到 List [重复]

很难弄清楚我是否遇到了错误或做了一些愚蠢的事情......

Spring Boot v2.0.0.M7、spring-data-jpa、spring-data-rest、MySQL

以下@Query

@Query("select DISTINCT item.statusCode from Item item")
public List<String> lookupStatusCodes();

on a PagingAndSortingRepository正在扔一个

java.lang.IllegalArgumentException: Couldn't find PersistentEntity for type class java.lang.String!
at org.springframework.data.mapping.context.PersistentEntities.lambda$getRequiredPersistentEntity$2(PersistentEntities.java:78) ~[spring-data-commons-2.0.2.RELEASE.jar:2.0.2.RELEASE]
at java.util.Optional.orElseThrow(Unknown Source) ~[na:1.8.0_151]
at org.springframework.data.mapping.context.PersistentEntities.getRequiredPersistentEntity(PersistentEntities.java:77) ~[spring-data-commons-2.0.2.RELEASE.jar:2.0.2.RELEASE]
at org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler.wrap(PersistentEntityResourceAssembler.java:72) ~[spring-data-rest-webmvc-3.0.2.RELEASE.jar:3.0.2.RELEASE]

statusCode 是一个 varchar 并且Item本身作为@Entity按预期工作，但尝试投影到字符串列表（或List<Object>）以上失败。

如果重要的话，我故意不想退货Page<String>这里（不需要分页，因为预期结果集很小）。

字符串不能直接映射。您将需要一个映射器对象。创建一个带有字符串字段的模型类 -

package org.xyz.model;

import java.io.Serializable;

public class StringResult implements Serializable {

    private static final long serialVersionUID = 1L;
    private String result;

    public StringResult(
        String result) {
        super();
        this.result = result;
    }

    public String getResult() {
        return result;
    }
}

然后更改查询以使用模型类 -

@Query("select new org.xyz.model.StringResult(DISTINCT item.statusCode as result) from Item item")
public List<StringResult> lookupStatusCodes();