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）

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