尝试使用Jackson Mapper将JSON数据（请参阅下面的data.json）映射到Java POJO类。在反序列化期间出现以下错误。我不确定这意味着什么。请指教。
org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Can not deserialize instance of org.springframework.social.test.api.impl.AccountList out of START_OBJECT token
at [Source: java.io.BufferedInputStream@c3020c; line: 2, column: 3]; nested exception is org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of org.springframework.social.test.api.impl.AccountList out of START_OBJECT token
at [Source: java.io.BufferedInputStream@c3020c; line: 2, column: 3]
at org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.readJavaType(MappingJacksonHttpMessageConverter.java:169)
at org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.read(MappingJacksonHttpMessageConverter.java:161)
at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:94)
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:491)
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:460)
at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:228)
at org.springframework.social.test.api.impl.AccountTemplate.getAccounts(AccountTemplate.java:44)
at org.springframework.social.test.api.impl.AccountTemplateTest.getAccounts_current_user(AccountTemplateTest.java:24)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of org.springframework.social.test.api.impl.AccountList out of START_OBJECT token
at [Source: java.io.BufferedInputStream@c3020c; line: 2, column: 3]
at org.codehaus.jackson.map.JsonMappingException.from(JsonMappingException.java:163)
at org.codehaus.jackson.map.deser.StdDeserializationContext.mappingException(StdDeserializationContext.java:219)
at org.codehaus.jackson.map.deser.StdDeserializationContext.mappingException(StdDeserializationContext.java:212)
at org.codehaus.jackson.map.deser.std.CollectionDeserializer.handleNonArray(CollectionDeserializer.java:246)
at org.codehaus.jackson.map.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:204)
at org.codehaus.jackson.map.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:194)
at org.codehaus.jackson.map.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:30)
at org.codehaus.jackson.map.ObjectMapper._unwrapAndDeserialize(ObjectMapper.java:2802)
at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2730)
at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1923)
at org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.readJavaType(MappingJacksonHttpMessageConverter.java:166)
... 31 more
JUnit Test Class
@Test
public void getAccounts() {
mockServer.expect(requestTo("api"))
.andExpect(method(GET))
.andExpect(header("Authorization", "Bearer someAccessToken"))
.andRespond(withSuccess(jsonResource("data.json"), MediaType.APPLICATION_JSON));
List<Account> accounts = tester.operations().getAccounts();
assertEquals(4, accounts.size());
Account account = accounts.get(0);
assertEquals(new Long(9880), account.getId());
assertEquals("My Account", account.getAlias());
assertEquals("FULL", account.getPermissions());
assertEquals("USER", account.getType());
assertEquals(new Character('U'),account.getStatus());
Account account1 = accounts.get(1);
assertEquals(new Long(9887),account1.getId());
assertEquals("Account",account1.getAlias());
assertEquals("FULL",account1.getPermissions());
assertEquals("USER",account1.getType());
assertEquals(new Character('U'),account1.getStatus());
Account account2 = accounts.get(2);
assertEquals(new Long(00008),account2.getId());
assertEquals("Mom's Account",account2.getAlias());
assertEquals("FULL",account2.getPermissions());
assertEquals("USER",account2.getType());
assertEquals(new Character('U'),account2.getStatus());
Account account3 = accounts.get(3);
assertEquals(new Long(00009),account3.getId());
assertEquals("Steph's Account",account3.getAlias());
assertEquals("FULL",account3.getPermissions());
assertEquals("USER",account3.getType());
assertEquals(new Character('U'),account3.getStatus());
//The method used to configure ObjectMapper
@Override
protected MappingJacksonHttpMessageConverter getJsonMessageConverter() {
MappingJacksonHttpMessageConverter converter = super.getJsonMessageConverter();
objectMapper = new ObjectMapper();
//UnComment if root element is not required
objectMapper.enable(DeserializationConfig.Feature.UNWRAP_ROOT_VALUE);
objectMapper.registerModule(new TestModule());
converter.setObjectMapper(objectMapper);
return converter;
}
如果从data.json
中删除了以下3行，则上述错误消失了The lines causing problem.
{
"accounts": {
"account":
Entire data json File
{
"accounts": {
"account": [
{
"id": "9880,
"alias": "My Account",
"permissions": "FULL",
"type": "USER",
"status": "U"
},
{
"id": "9887",
"alias": "Account",
"permissions": "FULL",
"type": "USER",
"status": "U"
},
{
"id": "00008",
"alias": "Mom's Account",
"permissions": "FULL",
"type": "USER",
"status": "U"
},
{
"id": "00009",
"alias": "Steph's Account",
"permissions": "FULL",
"type": "USER",
"status": "U"
}
]
}
}
答案 0 :(得分：1)
杰克逊正试图将JSON反序列化为AccountList类型。我猜这种类型映射到JSON中的数组，所以Jackson期待流中的'['下一个，但是你的JSON以'{'开头（又叫START_OBJECT标记）。
基本上，您的JSON与您尝试反序列化的类型不匹配。为了匹配我希望目标类型是这样的：
class SomeClassName {
AccountList accounts;
[...]
}
答案 1 :(得分：0)
解决方案是：
@JsonRootName(value="accounts")
public class AccountList implements Serializable{
private static final long serialVersionUID = 1L;
private ArrayList<Account> account;
public AccountList(ArrayList<Account> account){
this.account = account;
}
public ArrayList<Account> getAccount() {
return account;
}
public void setAccount(ArrayList<Account> account) {
this.account = account;
}