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） - 黄雄杰
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 moreCaused 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）
@Configurationpublic 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：
@Configurationclass 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
Original url: Access
Created at: 2019-12-10 20:36:37
Category: default
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