Spring Data Jpa原生SQL返回自定义对象最简洁方式是什么
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Spring Data Jpa 原生SQL返回自定义对象最简洁方式
此文章只讨论两种方式查询, 使用jpa关键字查询和自定义sql
// 方式1 1. List<UserName> findByName(String name); // 方式2 2. @Query(value = "select name from t_users where name = ?", nativeQuery = true) List<UserName> findByName2(String name);
使用接口接收
即通过定义一个接口接口 UserName,两种方式都支持通过定义接口接受返回,JPA原生支持
public interface UserName { String getNname(); }
自定义对象接收
方式一 JAP原生支持自定义对象,但条件是而且只有一个构造函数,有些工具类需要用到默认构造函数,不方便
方式二 JAP不支持自定义对象,会返回Object[] 对象数组
解决方案
例子只是解决方式二, 如果需要解决方式一构造函数问题,可以借鉴,下面例子自己实现 我们定义一个接口ReabamDTO
public interface ReabamDTO { }
GenericConverter实现类
内容是map 转 ReabamDTO
public final class JpaConvert implements GenericConverter { @Override public Set<ConvertiblePair> getConvertibleTypes() { return Collections.singleton(new ConvertiblePair(Map.class, ReabamDTO.class)); } @Override public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) { return map2Pojo(source, targetType.getObjectType()); } 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); } }
将自定义convert加入到GenericConversionService
@Configuration public class JpaConfig { @PostConstruct public void init() { GenericConversionService genericConversionService = ((GenericConversionService) DefaultConversionService.getSharedInstance()); genericConversionService.addConverter(new JpaConvert()); } }
测试
public interface UsersRepository extends JpaRepository<Users, Integer> { List<UserName> findByName(String name); @Query(value = "select name from t_users where name = ?", nativeQuery = true) List<UserName> findByName2(String name); }
@Data @ToString @NoArgsConstructor public class UserName implements ReabamDTO { private String name; }
@RunWith(SpringJUnit4ClassRunner.class) @SpringBootTest(classes = DemoApplication.class, properties = {"spring.profiles.active=local"}) class DemoApplicationTests { @Autowired private UsersRepository usersRepository; @Test void contextLoads() { Users users = new Users(); users.setName("A"); users.setAge(1); users.setAddress("AA"); usersRepository.save(users); } /** * 非自定义sql可以返回自定义对象 */ @Test void t2() { List<UserName> a = usersRepository.findByName("A"); System.out.println(a); } /** * 自定义sql 自定义对象 */ @Test void t3() { List<UserName> a = usersRepository.findByName2("A"); System.out.println(a); } }
原理可选择观看
查看报错信息,找不到转换器异常, 那么只需要加入对应的装换器就可以了,
org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [org.springframework.data.jpa.repository.query.AbstractJpaQuery$TupleConverter$TupleBackedMap] to type [com.architeture.demo.UserName] at org.springframework.core.convert.support.GenericConversionService.handleConverterNotFound(GenericConversionService.java:322) at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:195) at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:175) at org.springframework.data.repository.query.ResultProcessor$ProjectingConverter.convert(ResultProcessor.java:309) at org.springframework.data.repository.query.ResultProcessor$ChainingConverter.lambda$and$0(ResultProcessor.java:225) at org.springframework.data.repository.query.ResultProcessor$ChainingConverter.convert(ResultProcessor.java:236) at org.springframework.data.repository.query.ResultProcessor.processResult(ResultProcessor.java:156) at org.springframework.data.jpa.repository.query.AbstractJpaQuery.doExecute(AbstractJpaQuery.java:158) at org.springframework.data.jpa.repository.query.AbstractJpaQuery.execute(AbstractJpaQuery.java:143)
通过查看源码, 获取转换器的位置 org.springframework.core.convert.support.GenericConversionService#getConverter
@Nullable protected GenericConverter getConverter(TypeDescriptor sourceType, TypeDescriptor targetType) { ConverterCacheKey key = new ConverterCacheKey(sourceType, targetType); GenericConverter converter = this.converterCache.get(key); if (converter != null) { return (converter != NO_MATCH ? converter : null); } converter = this.converters.find(sourceType, targetType); if (converter == null) { converter = getDefaultConverter(sourceType, targetType); } if (converter != null) { this.converterCache.put(key, converter); return converter; } this.converterCache.put(key, NO_MATCH); return null; }
继续看源码, 查找能加入转换器位置 converter = this.converters.find(sourceType, targetType);
@Nullable public GenericConverter find(TypeDescriptor sourceType, TypeDescriptor targetType) { // Search the full type hierarchy // 获取 List<Class<?>> sourceCandidates = getClassHierarchy(sourceType.getType()); List<Class<?>> targetCandidates = getClassHierarchy(targetType.getType()); for (Class<?> sourceCandidate : sourceCandidates) { for (Class<?> targetCandidate : targetCandidates) { ConvertiblePair convertiblePair = new ConvertiblePair(sourceCandidate, targetCandidate); GenericConverter converter = getRegisteredConverter(sourceType, targetType, convertiblePair); if (converter != null) { return converter; } } } return null; }
此方法 源对象TupBackedMap父类或接口和UserName父类或接口进行组合,获取到对应的转换器
TupBackedMap的父类或接口
org.springframework.core.convert.support.GenericConversionService#addConverter(org.springframework.core.convert.converter.GenericConverter)
@Nullable private GenericConverter getRegisteredConverter(TypeDescriptor sourceType, TypeDescriptor targetType, ConvertiblePair convertiblePair) { // Check specifically registered converters ConvertersForPair convertersForPair = this.converters.get(convertiblePair); if (convertersForPair != null) { GenericConverter converter = convertersForPair.getConverter(sourceType, targetType); if (converter != null) { return converter; } } // Check ConditionalConverters for a dynamic match for (GenericConverter globalConverter : this.globalConverters) { if (((ConditionalConverter) globalConverter).matches(sourceType, targetType)) { return globalConverter; } } return null; }
可以看到在 ConvertersForPair convertersForPair = this.converters.get(convertiblePair); 在convertes中加入转换器
org.springframework.core.convert.support.GenericConversionService.Converters
private static class Converters { private final Map<ConvertiblePair, ConvertersForPair> converters = new LinkedHashMap<>(36); public void add(GenericConverter converter) { } }
查看调用 add 方法位置, org.springframework.core.convert.support.GenericConversionService#addConverter(org.springframework.core.convert.converter.GenericConverter) 最终定位到这里
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