Could not read document: Can not deserialize instance of java.lang.xxx out of START_OBJECT token

Java 项目中遇到的问题：Could not read document: Can not deserialize instance of java.lang.String out of START_OBJECT token

前些日子在项目中遇到这样一个问题，调用一个方法时报错，特意记录下。
下面是控制台输出信息：

org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not deserialize instance of java.lang.String out of START_OBJECT token at [Source: java.io.PushbackInputStream@33b082c5; line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_OBJECT token at [Source: java.io.PushbackInputStream@33b082c5; line: 1, column: 1]    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:240)    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:225)    at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:95)    at org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:917)    at org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:901)    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:655)    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:613)    at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:531)    at com.einwin.jd.utils.JDRequestUtil.postForEntityWithOutToken(JDRequestUtil.java:91)    at com.einwin.jd.utils.JDRequestUtil.postForEntity(JDRequestUtil.java:61)    at com.einwin.jd.utils.JDRequestUtil.postForEntity(JDRequestUtil.java:36)    at com.einwin.jd.client.OrderClient.comfirmReceipt(OrderClient.java:253)    at com.einwin.test.OrderTest.comfirmReceipt(OrderTest.java:223)    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$2.evaluate(ParentRunner.java:268)    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:237)    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)    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 com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_OBJECT token...

由消息日志可以看出，它报了HttpMessageNotReadableException消息不可读异常和JsonMappingException JSON映射异常，由此知是由于JSON映射不一致而导致HttpMessageNotReadableException

一般情况下是由于你请求回来的数据是json类型，而你用来接收的参数类型不是json类型造成的。或者是其他返回参数和接收参数不一致造成的，仔细检查代码，改为一致即可。