java - SpringBoot RestTemplate交换遇到ResponseEntity的ParameterizedTypeReference转换问题

我正在构建两个应该相互通信的微服务。
我正在使用Eureka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);
    }
}

Microservice1Controller.java

@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);
    }
}

Microservice1ResponseWrapper.java-这是通用包装器

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

applicationProperties.yaml

spring:
  application:
    name: microservice1

server:
  port: 8073

微服务2
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
}

applicationProperties.yaml

spring:
  application:
    name: microservice2

server:
  port: 8074

Customer1（在Microservice1中）和Customer2（在Microservice2中）几乎是相同的对象。

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
}

Microservice2中的Customer2.java

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，它从数据库中获取数据并且运行良好。这是我在屏幕上看到的响应：

<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Microservice 1并获取数据。

但是，我收到如下错误：

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)

我在ParameterizedTypeReference或resttemplate交换呼叫中犯了任何错误吗？

注意：如果我在没有Eureka注册表的情况下运行这两个微服务，它们绝对可以正常工作。但是，当我介绍Eureka并在Eureka中注册这两项服务时，就会遇到上述问题。
为此，我刚刚对Miroservice2控制器进行了更改：
字符串getAllUrl =“ http://localhost:8073/getdata/”;



更新-19/02/22

这是我尝试过的

更新了Microservice1Controller-getAll（）如下：

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

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

更新了Microservice2Controller- getAll（）方法

    @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;
    }

如前面的描述所述，这可以很好地调用Microservice2的Microservice1。
Microservice1将ResponseEntity>返回到Microservice2，而Microservice2将其转换为ResponseEntity>。

然而，
将ResponseEntity<Microservice1ResponseWrapper<List<Customer1>>>返回到Microservice2的Microservice1和Microservice2无法转换为ResponseEntity<Microservice2ResponseWrapper<List<Customer2>>>。



更新06/28/19

如果我在Microservice2 Controller中进行以下更改，则会看到2个问题：


开始收到LinkedHashMap错误。
java.lang.ClassCastException：无法将java.util.LinkedHashMap强制转换为java.util.List
它不会提取所有记录，而只会提取List中的最后一个元素。例如有2个用户，则仅显示最后一个用户，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.

最佳答案

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