如何使用resttemplate发送和接收列表？

Question

我想使用RestTemplate发送和接收对象列表。

我一直得到Cannot deserialize instance of java.util.ArrayList out of START_OBJECT token的错误。已经有几天了，我需要继续前进。我试图使用restTemplate发送一批对象由REST api处理。

异常跟踪：

java.util.concurrent.ExecutionException:
org.springframework.web.client.RestClientException: Error while extracting 
response for type 
[java.util.List<com.rfidreader.async.model.Maybevehicle>] and content type 
[application/json;charset=UTF-8]; nested exception is 
org.springframework.http.converter.HttpMessageNotReadableException: JSON 
parse error: Cannot deserialize instance of `java.util.ArrayList` out of 
START_OBJECT token; nested exception is 
com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot 
deserialize instance of `java.util.ArrayList` out of START_OBJECT token
 at [Source: (PushbackInputStream); line: 1, column: 1]
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:192)
at com.rfidreader.async.AsyncRfidpringApplication.getTagsCheckVehicle(AsyncRfidpringApplication.java:432)
at com.rfidreader.async.AsyncRfidpringApplication.lambda$0(AsyncRfidpringApplication.java:105)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.web.client.RestClientException: Error while extracting response for type [java.util.List<com.rfidreader.async.model.Maybevehicle>] and content type [application/json;charset=UTF-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token
 at [Source: (PushbackInputStream); line: 1, column: 1]
    at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:115)
    at org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:991)
    at org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:974)
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:725)
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:680)
    at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:629)
    at com.rfidreader.async.model.SimpleTaskBatch2.call(SimpleTaskBatch2.java:57)
    at com.rfidreader.async.model.SimpleTaskBatch2.call(SimpleTaskBatch2.java:1)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    ... 3 more
Caused by: org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token
 at [Source: (PushbackInputStream); line: 1, column: 1]
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:243)
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:225)
    at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:100)
    ... 11 more
Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token
 at [Source: (PushbackInputStream); line: 1, column: 1]
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)
    at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1342)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1138)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1092)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.handleNonArray(CollectionDeserializer.java:332)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:265)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:245)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:27)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4013)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3084)
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:237)
    ... 13 more

我尝试过创建一个对象映射器，但它不起作用。

@Override
public List<Maybevehicle> call() throws Exception {

    String url="url";
    String authString= "user"+":"+"password";
    byte[] encodedAuth= 
    Base64.encodeBase64(authString.getBytes(Charset.forName("US-ASCII")));
    String authHeader="Basic "+new String(encodedAuth);
    HttpHeaders headers = new HttpHeaders();

   headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON_UTF8));
    headers.setContentType(MediaType.APPLICATION_JSON_UTF8);
    headers.set("Authorization", authHeader);
    HttpEntity<List<Maybevehicle>> requestEntity=new 
 HttpEntity<List<Maybevehicle>>(list,headers);
    ResponseEntity<List<Maybevehicle>> 
  results=appRestTemplate2.exchange(url, HttpMethod.GET, requestEntity, 
new ParameterizedTypeReference<List<Maybevehicle>>(){});


    if(results.getStatusCode().is2xxSuccessful()){
        List<Maybevehicle> vehlist=results.getBody();
        return vehlist;
    }else{
        List<Maybevehicle> vehlist=null;
        return vehlist;
    }

}

REST api：

@GetMapping(path="", consumes="application/json", 
produces="application/json")
public List<Maybevehicle> getBmwvehicle2(@RequestBody List<Maybevehicle> vehList){

     List<Maybevehicle> results=bmwService.findMaybeVehicles(vehList);

     return results; 

我希望能够接受来自list的json array或rest api的回应。提前致谢！

这是我的Maybevehicle class：

public class Maybevehicle {

private Bmwvehiclemain b;
private String newtaglocation;
private Future<Bmwvehiclemain> e;
private Integer i;
private Integer vehid;
private Maybevehicle veh;

public Maybevehicle(Bmwvehiclemain b, String newtaglocation){
    this.b=b;
    this.newtaglocation=newtaglocation;
}


public Maybevehicle(Integer i, Future<Bmwvehiclemain> e, String 
newtaglocation) {
    // TODO Auto-generated constructor stub
    this.i=i;
    this.e=e;
    this.newtaglocation=newtaglocation;
} 
//getters and setters

Answer 1

虽然我看不到您的MaybeVehicle.class，但我遇到了类似的问题并通过添加来解决它

@JsonDeserialize(as = MaybeVehicle.class)
public class MaybeVehicle {
....
}

由于JSON - 默认情况下无法反序列化为Collection，因为它实际上不是JSON Array.So您需要控制反序列化的过程。如果您发布MaybeVehicle对象会很有帮助。