JPA 添加 converter

1. 问题描述

No converter found capable of converting from type [org.springframework.data.jpa.repository.query.AbstractJpaQuery$TupleConverter$TupleBackedMap] to type xxx

DTO, JPA 查询返回的结果是 List<Map<String, Object>>, 需要添加自定义的 Converter 进行类型转换。

2. 解决方案

通过添加注解，在程序启动时自动添加相关类的的 Converter

@Documented
@Component
@Target(value = {ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface JpaDtoConverter{

}

@Slf4j
@Configuration
public class DtoJpaConfiguration {
    @Autowired
    private ApplicationContext applicationContext;

    /**
     * 初始化注入@JpaDto对应的Converter
     */
    @PostConstruct
    public void init() {
        Map<String, Object> map = applicationContext.getBeansWithAnnotation(JpaDtoConverter.class);
        for (Object o : map.values()) {
            Class c = o.getClass();
            log.info("Jpa添加Converter,class={}", c.getName());
            GenericConversionService genericConversionService = ((GenericConversionService) DefaultConversionService.getSharedInstance());
            genericConversionService.addConverter(Map.class, c, m -> {
                try {
                    Object obj = c.newInstance();
                    return map2Pojo(m, obj.getClass());
                } catch (Exception e) {
                    throw new FatalBeanException("Jpa结果转换出错,class=" + c.getName(), e);
                }
            });
        }
    }

    public static <T> T map2Pojo(Object entity, Class<T> tClass) {
        CopyOptions copyOptions = CopyOptions.create()
                .setIgnoreCase(true)
                .setIgnoreError(true)
                .setIgnoreNullValue(true)
                .setFieldNameEditor(StrUtil::toUnderlineCase);
        return BeanUtil.toBean(entity, tClass, copyOptions);
    }
}

3. 使用注解

@JpaDtoConverter
@Data
public class Xxx {
    @ApiModelProperty(value = "xxx")
    private int xxx;
}

注： 需要引入 hutool 包

<dependency>
    <groupId>cn.hutool</groupId>
    <artifactId>hutool-all</artifactId>
    <version>5.5.5</version>
</dependency>