投稿
  1. 极客之音首页
  2. 后端开发

Spring Mvc使用Jackson进行json转对象时，遇到的字符串转日期的异常处理（Can not deserialize value of type Date from String）

小半 • • 后端开发 • 阅读 321

导读：本篇文章讲解 Spring Mvc使用Jackson进行json转对象时，遇到的字符串转日期的异常处理（Can not deserialize value of type Date from String），希望对大家有帮助，欢迎收藏，转发！站点地址：www.bmabk.com

1、问题排查

出现的场景：

  • 服务端通过 springmvc 写了一个对外的接口，返回一个 json 字符串，其中该 json 带有日期，格式为 yyyy-MM-dd HH:mm:ss。
  • 客户端通过 feign 调用该 http 接口，指定返回值为一个 Dto，Dto 中日期的字段为 Date 类型。
  • 客户端调用该接口后抛异常了。

报错异常如下：

feign.codec.DecodeException: JSON parse error: Can not deserialize value of type java.util.Date from String "2018-03-07 16:18:35": not a valid representation (error: Failed to parse Date value '2018-03-07 16:18:35': Can not parse date "2018-03-07 16:18:35Z": while it seems to fit format 'yyyy-MM-dd'T'HH:mm:ss.SSS'Z'', parsing fails (leniency? null)); nested exception is com.fasterxml.jackson.databind.exc.InvalidFormatException: Can not deserialize value of type java.util.Date from String "2018-03-07 16:18:35": not a valid representation (error: Failed to parse Date value '2018-03-07 16:18:35': Can not parse date "2018-03-07 16:18:35Z": while it seems to fit format 'yyyy-MM-dd'T'HH:mm:ss.SSS'Z'', parsing fails (leniency? null))
 at [Source: java.io.PushbackInputStream@4615bc00; line: 1, column: 696] (through reference chain: com.RestfulDataBean["data"]->java.util.ArrayList[0]->com.entity.XxxDto["createTime"])
	at feign.SynchronousMethodHandler.decode(SynchronousMethodHandler.java:169)
	at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:133)
	at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:76)
	at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103)
	at com.sun.proxy.$Proxy138.queryMonitorByTime(Unknown Source)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:738)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
	at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282)
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:673)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
	at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
	at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
	at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Can not deserialize value of type java.util.Date from String "2018-03-07 16:18:35": not a valid representation (error: Failed to parse Date value '2018-03-07 16:18:35': Can not parse date "2018-03-07 16:18:35Z": while it seems to fit format 'yyyy-MM-dd'T'HH:mm:ss.SSS'Z'', parsing fails (leniency? null)); nested exception is com.fasterxml.jackson.databind.exc.InvalidFormatException: Can not deserialize value of type java.util.Date from String "2018-03-07 16:18:35": not a valid representation (error: Failed to parse Date value '2018-03-07 16:18:35': Can not parse date "2018-03-07 16:18:35Z": while it seems to fit format 'yyyy-MM-dd'T'HH:mm:ss.SSS'Z'', parsing fails (leniency? null))
 at [Source: java.io.PushbackInputStream@4615bc00; line: 1, column: 696] (through reference chain: com.RestfulDataBean["data"]->java.util.ArrayList[0]->com.XxxDto["createTime"])
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:238)
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:223)
	at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:96)
	at org.springframework.cloud.netflix.feign.support.SpringDecoder.decode(SpringDecoder.java:59)
	at org.springframework.cloud.netflix.feign.support.ResponseEntityDecoder.decode(ResponseEntityDecoder.java:47)
	at feign.SynchronousMethodHandler.decode(SynchronousMethodHandler.java:165)
	... 45 more
Caused by: com.fasterxml.jackson.databind.exc.InvalidFormatException: Can not deserialize value of type java.util.Date from String "2018-03-07 16:18:35": not a valid representation (error: Failed to parse Date value '2018-03-07 16:18:35': Can not parse date "2018-03-07 16:18:35Z": while it seems to fit format 'yyyy-MM-dd'T'HH:mm:ss.SSS'Z'', parsing fails (leniency? null))
 at [Source: java.io.PushbackInputStream@4615bc00; line: 1, column: 696] (through reference chain: com.RestfulDataBean["data"]->java.util.ArrayList[0]->com.XxxDto["createTime"])
	at com.fasterxml.jackson.databind.exc.InvalidFormatException.from(InvalidFormatException.java:74)
	at com.fasterxml.jackson.databind.DeserializationContext.weirdStringException(DeserializationContext.java:1410)
	at com.fasterxml.jackson.databind.DeserializationContext.handleWeirdStringValue(DeserializationContext.java:926)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer._parseDate(StdDeserializer.java:819)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer._parseDate(StdDeserializer.java:788)
	at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateBasedDeserializer._parseDate(DateDeserializers.java:172)
	at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateDeserializer.deserialize(DateDeserializers.java:259)
	at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateDeserializer.deserialize(DateDeserializers.java:242)
	at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:504)
	at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:104)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:357)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
	at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:287)
	at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:259)
	at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:26)
	at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:504)
	at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:104)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:357)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3814)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2938)
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:235)
	... 50 more

       从异常信息中我们可以看出，是在 AbstractJackson2HttpMessageConverter 类中调用了 readJavaType 方法之后抛的异常，一步一步往下深入，我们找到了最关键的地方，在 DeserializationContext 类的 _parseDate 方法中，执行了 df.parse(dateStr) 之后抛异常了。

public Date parseDate(String dateStr) throws IllegalArgumentException {
    try {
        DateFormat df = getDateFormat();
        // 这行代码报错了
        return df.parse(dateStr);
    } catch (ParseException e) {
        throw new IllegalArgumentException(String.format(
                "Failed to parse Date value '%s': %s", dateStr, e.getMessage()));
    }
}

       DeserializationContext 是 jackson 的一个反序列化的一个上下文，那么它的 DateFormat 是从哪来的呢?我们再来看下getDateFormat 的源码：

protected DateFormat getDateFormat() {
    if (_dateFormat != null) {
        return _dateFormat;
    }
    DateFormat df = _config.getDateFormat();
    _dateFormat = df = (DateFormat) df.clone();
    return df;
}

       DateFormat 又是从 MapperConfig 而来，我们再看下 config.getDateFormat() 的源码。

public final DateFormat getDateFormat() { return _base.getDateFormat(); }

       我们知道，SpringMvc 就是通过 AbstractJackson2HttpMessageConverter 类来整合 jackson 的，该类维护 jackson 的ObjectMapper，而 ObjectMapper 又是通过 MapperConfig 来进行配置的。

       由此可见，本异常就是因为 ObjectMapper 中的 DateFormat 无法对 yyyy-MM-dd HH:mm:ss 格式的字符串进行转换所导致的。

2、问题处理

       异常说的值服务器返回了一个带有日期的 json，日期的形式是字符串 2018-03-07 16:18:35，jackson 无法将该字符串转成一个Date 对象，网上查资料，上面说的是 jackson 只支持以下几种日期格式：

  • “yyyy-MM-dd’T’HH:mm:ss.SSSZ”；
  • “yyyy-MM-dd’T’HH:mm:ss.SSS’Z'”；
  • “yyyy-MM-dd”;
  • “EEE, dd MMM yyyy HH:mm:ss zzz”;
  •  long类型的时间戳

       去掉服务端的以下两个配置，让日期返回时间戳，结果就没报错了

#spring.jackson.date-format=yyyy-MM-dd HH:mm:ss
#spring.jackson.time-zone=Asia/Chongqing

       由于服务端在其他的地方有可能和这里的配置耦合了，也就是说其他地方有可能要用到的是 yyyy-MM-dd HH:mm:ss 这一日期格式而不是时间戳的格式，所以这个配置肯定是不能修改的。

       jackson 竟然不支持 yyyy-MM-dd HH:mm:ss 的这种格式，肯定很不爽啦，所以下面就要开始来研究怎么让 jackson 支持这种格式了。

       要让 jackson 支持这种格式，那么就必须修改 ObjectMapper 中的 DateFormat，因为在 ObjectMapper 中，DateFormat 的默认实现类是 StdDateFormat，StdDateFormat 也就只兼容了我们上述所说的几种格式。

       首先我们先使用装饰模式来创建一个支持 yyyy-MM-dd HH:mm:ss 格式的 DateFormat 如下：

 
import java.text.DateFormat;
import java.text.FieldPosition;
import java.text.ParseException;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.Date;
 
public class MyDateFormat extends DateFormat {
 
	private DateFormat dateFormat;
 
	private SimpleDateFormat format1 = new SimpleDateFormat("yyy-MM-dd HH:mm:ss");
 
	public MyDateFormat(DateFormat dateFormat) {
		this.dateFormat = dateFormat;
	}
 
	@Override
	public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition) {
		return dateFormat.format(date, toAppendTo, fieldPosition);
	}
 
	@Override
	public Date parse(String source, ParsePosition pos) {
 
		Date date = null;
 
		try {
 
			date = format1.parse(source, pos);
		} catch (Exception e) {
 
			date = dateFormat.parse(source, pos);
		}
 
		return date;
	}
 
	// 主要还是装饰这个方法
	@Override
	public Date parse(String source) throws ParseException {
 
		Date date = null;
 
		try {
			
			// 先按我的规则来
			date = format1.parse(source);
		} catch (Exception e) {
 
			// 不行，那就按原先的规则吧
			date = dateFormat.parse(source);
		}
 
		return date;
	}
 
	// 这里装饰clone方法的原因是因为clone方法在jackson中也有用到
	@Override
	public Object clone() {
		Object format = dateFormat.clone();
		return new MyDateFormat((DateFormat) format);
	}
}

       DateFormat 有了，接下来的任务就是让 ObjectMapper 使用我的这个 DateFormat 了，在 config 类中定义如下（本案例基于springboot）:

@Configuration
public class WebConfig {
 
	@Autowired
	private Jackson2ObjectMapperBuilder jackson2ObjectMapperBuilder;
	
	@Bean
	public MappingJackson2HttpMessageConverter MappingJsonpHttpMessageConverter() {
 
		ObjectMapper mapper = jackson2ObjectMapperBuilder.build();
 
		// ObjectMapper为了保障线程安全性，里面的配置类都是一个不可变的对象
		// 所以这里的setDateFormat的内部原理其实是创建了一个新的配置类
		DateFormat dateFormat = mapper.getDateFormat();
		mapper.setDateFormat(new MyDateFormat(dateFormat));
 
		MappingJackson2HttpMessageConverter mappingJsonpHttpMessageConverter = new MappingJackson2HttpMessageConverter(
				mapper);
		return mappingJsonpHttpMessageConverter;
	}
}

       配置了上述代码之后，问题成功解决。

3 为什么往spring容器中注入MappingJackson2HttpMessageConverter，springMvc就会用这个Converter呢？

  查看springboot的源代码如下：

@Configuration
class JacksonHttpMessageConvertersConfiguration {
 
	@Configuration
	@ConditionalOnClass(ObjectMapper.class)
	@ConditionalOnBean(ObjectMapper.class)
	@ConditionalOnProperty(name = HttpMessageConvertersAutoConfiguration.PREFERRED_MAPPER_PROPERTY, havingValue = "jackson", matchIfMissing = true)
	protected static class MappingJackson2HttpMessageConverterConfiguration {
 
		@Bean
		@ConditionalOnMissingBean(value = MappingJackson2HttpMessageConverter.class, ignoredType = {
				"org.springframework.hateoas.mvc.TypeConstrainedMappingJackson2HttpMessageConverter",
				"org.springframework.data.rest.webmvc.alps.AlpsJsonHttpMessageConverter" })
		public MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter(
				ObjectMapper objectMapper) {
			return new MappingJackson2HttpMessageConverter(objectMapper);
		}
 
}

        默认配置为，当 spring 容器中没有 MappingJackson2HttpMessageConverter 这个实例的时候才会被创建，springboot 的思想是约定优于配置，也就是说，springboot 默认帮我们配好了spring mvc 的 Converter，如果我们没有自定义 Converter 的话，那么框架就会帮我们创建一个，如果我们有自定义的话，那么springboot就直接使用我们所注册的bean进行绑定。
 

版权声明：本文内容由互联网用户自发贡献，该文观点仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 举报，一经查实，本站将立刻删除。

文章由极客之音整理，本文链接：https://www.bmabk.com/index.php/post/9547.html

赞 (0)
小半的头像小半
0 0

相关推荐

极客之音——专业性很强的中文编程技术网站，欢迎收藏到浏览器，订阅我们！