hadoop中空值显示0

Posted 2023-05-15

参考技术A 可以尝试以下步骤解决:

1 ,分别删除:主节点从节点的 /usr/local/hadoop-2.6.2/etc/tmp
2: 编辑cd usr/local/hadoop-2.6.2/etc/hadoop/ vi slaves
删除slaves里面的 localhost

3:然后 hadoop namenode -format

4: 重新启动 start-all.sh 参考技术B 答:去到所有从节的/hadoop/tmp/dfs/data/current/目录中,同样将目录中的VERSION文件利用编辑器.
hadoop集群启动成功但进入管理界面显示DataNode为0的问题总结 - 爱...

如何处理枚举中空值的 InvalidFormatException

【中文标题】如何处理枚举中空值的 InvalidFormatException

【英文标题】：How to handle InvalidFormatException for empty values on enumerations

【发布时间】：2021-09-02 00:09:57

【问题描述】：

。当一个空值被传递给底层的杰克逊解析器而不是一个低级错误时，我们想抛出一个验证错误。我们怎样才能避免这种情况？

Exception is com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type `com.company.model.Flower` from String "": not one of the values accepted for Enum class: [Lilly, Jasmine]
 at [Source: (PushbackInputStream); line: 1, column: 64] 
        at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:389)
        at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:342)
        at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:186)
        at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.readWithMessageConverters(RequestResponseBodyMethodProcessor.java:158)
        at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:131)
        at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)
        at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:170)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
        at org.springframework.web.servlet.FrameworkServlet.doPut(FrameworkServlet.java:920)

【参考方案1】：

假设您的 jackson-databind 版本 >= 2.12.0， 参考this article - Jackson 2.12 Most Wanted (4/5): CoercionConfig system

---

你可以在ObjectMapper中添加一个配置bean来添加枚举的强制设置，这样空字符串就会被映射为null，然后在对应的枚举属性中添加@NotNull注解就可以解决问题了。

import com.fasterxml.jackson.databind.cfg.CoercionAction;
import com.fasterxml.jackson.databind.cfg.CoercionInputShape;
import com.fasterxml.jackson.databind.type.LogicalType;
import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class ObjectMapperConfig 
    @Bean
    public Jackson2ObjectMapperBuilderCustomizer jsonCustomizer() 
        return builder -> builder.postConfigurer(objectMapper -> 
            objectMapper.coercionConfigFor(LogicalType.Enum)
                    .setCoercion(CoercionInputShape.EmptyString, CoercionAction.AsNull);
        );