java - Spring mongodb : No enum constant Error

Question

Java初学者在这里，

我正在尝试定义我的模型以使用 Spring 从我的 Mongodb 数据库访问数据。

我想将 Gender 定义为 Enum，其中在数据库中的值存储为字符串:male或 female
但我收到以下错误:No enum constant com.nemeantalestudios.mythology.models.Gender.male
这是我的图 POJO:

@Getter
@Setter
@Document(collection = "figures")
public class Figure {

    @Id
    public String id;
    public String name;
    public String greekName;
    public String romanName;
    public String description;
    public String category;
    public String immortal;
    public Gender gender;
}

这是我的性别枚举:

public enum Gender {
    MALE("male"),
    FEMALE("female");

    private final String text;

    Gender(final String text) {
        this.text = text;
    }

    @Override
    public String toString() {
        return text;
    }
}

这就是我尝试访问它的方式:

@覆盖
public void run(String... args) 抛出异常 {
可选 chronos = figureRepository.findById("5893a17a88dcfdf6dfa73429");
列表 figureSet = figureRepository.findAll();
System.out.println(figureSet.size());

chronos.ifPresent(figure -> {
    System.out.println(figure.name);
    System.out.println(figure.category);
    System.out.println(figure.description);
    System.out.println(figure.immortal);
    System.out.println(figure.romanName);
    System.out.println(figure.greekName);
    System.out.println(figure.gender.toString());
});

}

如果这里是堆栈跟踪:

Caused by: java.lang.IllegalArgumentException: No enum constant com.nemeantalestudios.mythology.models.Gender.male
    at java.lang.Enum.valueOf(Enum.java:238) ~[na:1.8.0_171]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.getPotentiallyConvertedSimpleRead(MappingMongoConverter.java:884) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readValue(MappingMongoConverter.java:1392) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$MongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1335) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readProperties(MappingMongoConverter.java:335) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:297) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:253) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:202) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:198) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:86) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.MongoTemplate$ReadDocumentCallback.doWith(MongoTemplate.java:2785) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.MongoTemplate.executeFindOneInternal(MongoTemplate.java:2401) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.MongoTemplate.doFindOne(MongoTemplate.java:2193) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.core.MongoTemplate.findById(MongoTemplate.java:797) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.mongodb.repository.support.SimpleMongoRepository.findById(SimpleMongoRepository.java:121) ~[spring-data-mongodb-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_171]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_171]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_171]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_171]
    at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:377) ~[spring-data-commons-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:200) ~[spring-data-commons-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:629) ~[spring-data-commons-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:593) ~[spring-data-commons-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:578) ~[spring-data-commons-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:59) ~[spring-data-commons-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) ~[spring-aop-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61) ~[spring-data-commons-2.0.8.RELEASE.jar:2.0.8.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at com.sun.proxy.$Proxy50.findById(Unknown Source) ~[na:na]
    at com.nemeantalestudios.mythology.MythologyApplication.run(MythologyApplication.java:31) [classes/:na]
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:797) [spring-boot-2.0.3.RELEASE.jar:2.0.3.RELEASE]

我究竟做错了什么？

Answer 1

您需要为 spring 数据创建自定义转换器，以了解如何处理枚举中的字符串。

public class FigureConverter {

    @ReadingConverter
    public static class GenderConverter implements Converter<String, Gender> {

        @Override
        public Gender convert(final String source) {
            return Gender.fromString(source);
        }
    }

}

以及启用转换器的配置:

@Configuration
public class MongoDBConfig {

    @Autowired
    private MongoProperties mongoProperties;

    @Autowired
    private MongoClient mongoClient;


    @Bean
    public MongoTemplate mongoTemplate() {

        MongoTemplate mongoTemplate = new MongoTemplate(mongoClient, mongoProperties.getDatabase());
        MappingMongoConverter mongoMapping = (MappingMongoConverter) mongoTemplate.getConverter();
        mongoMapping.setCustomConversions(customConversions()); // tell mongodb to use the custom converters
        mongoMapping.afterPropertiesSet();
        return mongoTemplate;

    }


    public MongoCustomConversions customConversions() {
        return new MongoCustomConversions(Collections.singletonList(new GenderConverter()));
    }
}

您可能还想使用相同的转换器保存数据。您只需添加一个 @WritingConverter实现这一目标。

我建议您使用枚举本身，而不是字符串，因为在这种情况下，您可以利用 spring 数据来处理转换。因此，如果您将其保存为普通枚举，您将在 mongo 中将枚举保存为“MALE”或“FEMALE”，并且 spring 数据将知道如何自动转换。