How do I parse snake case fields in a FeignClient response json?

user_1766417 0
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I have configured a FeignClient in my spring boot webapp where I'm calling an external api that returns the following object.

public class Issue {

    private Assignee assignee;
    private Date createdAt;
    private Date updatedAt;
    private Date closedAt;
    private String description;
    private Date dueDate;

    public Assignee getAssignee() {
        return assignee;
    }

    public void setAssignee(Assignee assignee) {
        this.assignee = assignee;
    }


    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public Date getDueDate() {
        return dueDate;
    }

    public void setDueDate(Date dueDate) {
    this.dueDate = dueDate;
    }

    public Date getUpdatedAt() {
        return updatedAt;
    }

    public void setUpdatedAt(Date updatedAt) {
        this.updatedAt = updatedAt;
    }

    public Date getClosedAt() {
        return closedAt;
    }

    public void setClosedAt(Date closedAt) {
        this.closedAt = closedAt;
    }


    @Override
    public String toString() {
        return (JacksonJson.toJsonString(this));
    }
}

The fields updatedAt, createdAt and closedAt are all in snake case. All multi-word fields show up as null. Is there any way of configuring the FeignClient's Jackson parser so that it can process snake case characters? Note, that I cannot change the default Jackson Parser for my spring boot webapp because I myself render json in camel case. I just need to configure this parser on the FeignClient that I'm using to connect to an external REST api.

I have verified that the json response returned from the api call contains valid values in each of these json fields.

spring-cloud-feign spring-boot jackson
1 Answers

Here's how I solved it. I created a custom JacksonParser as a Spring Bean.

@Configuration(proxyBeanMethods = false)
public class FeignClientDateFormatConfig {

    @Bean
    public Decoder feignDecoder() {
        HttpMessageConverter jacksonConverter = new MappingJackson2HttpMessageConverter(customObjectMapper());
        ObjectFactory<HttpMessageConverters> objectFactory = () -> new HttpMessageConverters(jacksonConverter);
        return new ResponseEntityDecoder(new SpringDecoder(objectFactory));
    }

    public ObjectMapper customObjectMapper() {
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        return objectMapper;
    }
}

This successfully parses all snake case properties.

Please note that this has a severe limitation. If you have multiple FeignClients and only one of them returns snake-case json, then you're out of luck. This overrides the default FeignClient config. The only workaround possible with this solution is to move your FeignClient calls into a separate microservice so other FeignClient calls are not affected.

user_17664170
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