SpringBoot RestTemplate交换存在ResponseEntity的ParameterizedTypeReference转换问题

Question

我正在构建两个微服务，它们应该互相对话。我正在使用尤里卡作为服务注册表。

微服务1-microservice1.java

@SpringBootApplication
public class Microservice1Application {
    public static void main(String[] args) {
        SpringApplication.run(Microservice1Application.class, args);
    }
}

@RestController
@RequestMapping("/getdata")
public class Microservice1Controller {  
    @GetMapping(value = "/") 
public ResponseEntity<Microservice1ResponseWrapper<List<Customer1>>> getAll() {
        List<Customer1> list = //get data from repository

        return new ResponseEntity<Microservice1ResponseWrapper<List<Customer1>>>(new Microservice1ResponseWrapper<List<Customer1>>(Microservice1ResponseStatus.SUCCESS,list);
    }
}

public class Microservice1ResponseWrapper<T> {
private Microservice1ResponseStatus status;
private T data;
//constructor, getter and setters
}

spring:
  application:
    name: microservice1

server:
  port: 8073

Microservice2将从Microservice1获取数据的Microservice2

@SpringBootApplication
public class Microservice2Application {
    public static void main(String[] args) {
        SpringApplication.run(Microservice2Application.class, args);
    }
}

@Configuration
class Config {

    @LoadBalanced
    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

MicroService2Controller.java

@RestController
@RequestMapping("/fetchdata")
public class Microservice2Controller {  
@Autowired
    private RestTemplate restTemplate;


    @GetMapping(value = "/")
public ResponseEntity<Microservice2ResponseWrapper<List<Customer2>>> getAll() {     
            String getAllUrl = "http://microservice1/getdata/";
            ParameterizedTypeReference<Microservice2ResponseWrapper<List<Customer2>>>  parameterizedTypeReference = 
                    new ParameterizedTypeReference<Microservice2ResponseWrapper<List<Customer2>>>(){};

            ResponseEntity<Microservice2ResponseWrapper<List<Customer2>>> listData =
                    restTemplate.exchange(getAllUrl, HttpMethod.GET, null,parameterizedTypeReference);          
            return listData;
    }   
}

microService2ResponseWrapper.java-这是通用包装器

public class Microservice2ResponseWrapper<T> {
private Microservice2ResponseStatus status;
private T data;
//constructor, getter and setters
}

spring:
  application:
    name: microservice2

server:
  port: 8074

public class Customer1 implements Serializable {

    private static final long serialVersionUID = 1L;

    private Long custId;

    private String custName;

    private String firstName;

    private String lastName;

    private Long age;

    public Customer1() {
    }

    public Customer1(String custName, String firstName, String lastName, Long age) {
        this.custName = custName;
        this.firstName = firstName;
        this.lastName = lastName;
        this.age = age;
    }

    public Customer1(Long custId, String custName, String firstName, String lastName, Long age) {
        this.custId = custId;
        this.custName = custName;
        this.firstName = firstName;
        this.lastName = lastName;
        this.age = age;
    }

//getter, setter and toString
}

public class Customer2 implements Serializable {

    private static final long serialVersionUID = 1L;

    private Long custId;

    private String custName;

    private String firstName;

    private String lastName;

    private Long age;

    public Customer2() {
    }

//getter, setter and toString
}

当我运行Microservice1:http://localhost:8073/getdata时，它可以从数据库中获取数据并正常工作。下面是我在屏幕上看到的反应：

<Microservice1ResponseWrapper>
<status>SUCCESS</status>
<data>
<custId>1</custId>
<custName>string1</custName>
<firstName>string1</firstName>
<lastName>string1</lastName>
<age>30</age>
</data>
</Microservice1ResponseWrapper>

当我运行Microservice2:http://localhost:8074/fetchdata时，它应该转到microservice1并获取数据。

然而，我得到了这样的错误：

org.springframework.web.client.RestClientException: Error while extracting response for type
at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:117)
    at org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:994)
    at org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:977)

Caused by: org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot construct instance of `com.rest.Customer2` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('1'); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `com.rest.Customer2` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('1')
 at [Source: (PushbackInputStream); line: 1, column: 61] (through reference chain: com.rest.wrapper.Microservice2ResponseWrapper["data"]->java.util.ArrayList[0])
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:245)
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:227)
    at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:102)
    ... 77 more

Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `com.rest.Customer2` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('1')
 at [Source: (PushbackInputStream); line: 1, column: 61] (through reference chain: com.rest.wrapper.Microservice2ResponseWrapper["data"]->java.util.ArrayList[0])
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)
    at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1343)
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1032)
    at com.fasterxml.jackson.databind.deser.ValueInstantiator._createFromStringFallbacks(ValueInstantiator.java:371)
    at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.createFromString(StdValueInstantiator.java:323)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromString(BeanDeserializerBase.java:1373)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:171)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:161)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:286)
    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.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:127)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:369)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:159)
    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:239) 

我是否在ParameterizedTypeReference或resttemplate交换调用中犯了任何错误？

注意：如果我在没有Eureka注册表的情况下运行这两个微服务，它们工作起来绝对很好。但是当我引入Eureka并在Eureka注册这两个服务时，我得到了上面所述的问题。为此，我只对Miroservice2控制器进行了更改：字符串getAllUrl=“http：//localhost:8073/getData/”；

更新-02/22/19

    @GetMapping(value = "/") 
public ResponseEntity<List<Customer1>> getAll() {
        List<Customer1> list = //get data from repository

        return new ResponseEntity<List<Customer1>>(list);
    }

    @GetMapping(value = "/")
public ResponseEntity<List<Customer2>> getAll() {     
            String getAllUrl = "http://microservice1/getdata/";
            ParameterizedTypeReference<List<Customer2>>  parameterizedTypeReference = 
                    new ParameterizedTypeReference<List<Customer2>>(){};

            ResponseEntity<List<Customer2>> listData =
                    restTemplate.exchange(getAllUrl, HttpMethod.GET, null,parameterizedTypeReference);          
            return listData;
    }   

这很好地工作--如前面的描述所述，从Microservice2调用Microservice1。Microservice1将ResponseEntity>返回到Microservice2,Microservice2将其转换为ResponseEntity>。

但是，将responseEntity > 返回到Microservice2和Microservice2的Microservice1无法转换为responseEntity > 。

更新06/28/19

如果我在Microservice2控制器中做了以下更改，那么我会看到2个问题：

1. 开始获取LinkedHashMap错误。java.lang.ClassCastException：java.util.LinkedHashMap不能强制转换为java.util.List
2. 它不拉出所有记录，它只是从列表中拉出最后一个元素。例如，有2个用户，则只显示最后一个用户，而不是全部。

ParameterizedTypeReference<Microservice2ResponseWrapper>  parameterizedTypeReference = 
                      new ParameterizedTypeReference<Microservice2ResponseWrapper>(){};

ResponseEntity<Microservice2ResponseWrapper> listData =
                      restTemplate.exchange(getAllUrl, HttpMethod.GET, null,parameterizedTypeReference);
List ls = (List) listData.getBody().getData();

//if I print listData.getBody().getData() then it just shows only one record of users.

Answer 1

您需要为Customer2类创建一个默认构造函数。Customer2(){}