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Today, the editor will share with you the relevant knowledge about the method of SpringCloud Feign Jackson custom configuration. The content is detailed and the logic is clear. I believe most people still know too much about this, so share this article for your reference. I hope you can get something after reading this article. Let's take a look at it.

Feign Jackson Custom configuration

Spring Cloud Feign supports Spring MVC annotations using the same HttpMessageConverters class transformation by default

The official document states:

Spring Cloud adds support for Spring MVC annotations and for using the same HttpMessageConverters used by default in Spring Web.

But we usually change the corresponding NULL value to the corresponding "" when returning to the front-end JSON format, which makes Spring Cloud Feign use the same Jackson configuration, such as the configuration of our project.

@ Bean public ObjectMapper jacksonObjectMapper () {ObjectMapper objectMapper = new ObjectMapper (); / / objectMapper.setSerializationInclusion (Include.NON_NULL); objectMapper.getSerializerProvider () .setNullValueSerializer (new JsonSerializer () {@ Override public void serialize (Object value, JsonGenerator jg, SerializerProvider sp) throws IOException, JsonProcessingException {jg.writeString ("); sp.getDefaultNullKeySerializer () Problems with objectMapper.configure (SerializationFeature.FAIL_ON_EMPTY_BEANS, false); return objectMapper;}

When the service makes a request through Feign, a type conversion exception occurs when the NULL value is passed to refer to the type value, because HttpMessageConverters directly converts the NULL to "".

Solution idea

Custom configuration of Spring Cloud Feign Encoder and Decoder

The official document states:

Spring Cloud Netflix provides the following beans by default for feign (BeanType beanName: ClassName): Decoder feignDecoder: ResponseEntityDecoder (which wraps a SpringDecoder) Encoder feignEncoder: SpringEncoderLogger feignLogger: Slf4jLoggerContract feignContract: SpringMvcContractFeign.Builder feignBuilder: HystrixFeign.BuilderClient feignClient: if Ribbon is enabled it is a LoadBalancerFeignClient, otherwise the default feign client is used.

Solution method

Unified configuration of Encoder of Feign and Jackson conversion of Decoder

Import com.fasterxml.jackson.databind.DeserializationFeature;import com.fasterxml.jackson.databind.ObjectMapper;import org.springframework.beans.factory.ObjectFactory;import org.springframework.boot.autoconfigure.http.HttpMessageConverters;import org.springframework.cloud.openfeign.support.ResponseEntityDecoder;import org.springframework.cloud.openfeign.support.SpringDecoder;import org.springframework.cloud.openfeign.support.SpringEncoder;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.http.converter.HttpMessageConverter;import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter Import feign.codec.Decoder;import feign.codec.Encoder;@Configurationpublic class CustomFeignConfig {@ Bean public Decoder feignDecoder () {HttpMessageConverter jacksonConverter = new MappingJackson2HttpMessageConverter (customObjectMapper ()); ObjectFactory objectFactory = ()-> new HttpMessageConverters (jacksonConverter); return new ResponseEntityDecoder (new SpringDecoder (objectFactory));} @ Bean public Encoder feignEncoder () {HttpMessageConverter jacksonConverter = new MappingJackson2HttpMessageConverter (customObjectMapper ()); ObjectFactory objectFactory = ()-> new HttpMessageConverters (jacksonConverter) Return new SpringEncoder (objectFactory);} public ObjectMapper customObjectMapper () {ObjectMapper objectMapper = new ObjectMapper (); / / Customize as much as you want objectMapper.configure (DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT, true); return objectMapper;}}

If configuring DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT doesn't work, you can try this.

Public ObjectMapper customObjectMapper () {ObjectMapper objectMapper = new ObjectMapper (); / / Customize as much as you want objectMapper.registerModule (new StringSanitizerModule ()); return objectMapper;} public class StringSanitizerModule extends SimpleModule {public StringSanitizerModule () {addDeserializer (String.class, new StdScalarDeserializer (String.class) {@ Override public String deserialize (JsonParser jsonParser, DeserializationContext ctx) throws IOException {return StringUtils.trimToNull (jsonParser.getValueAsString ()) }});}} Feign custom configuration application environment

Nacos: 1.3.1

Start nacos

Cd / usr/local/nacos/bin

Sh startup.sh-m standalone

Customize the configuration of Feign

1) add dependencies

Add dependency of nacos-discovery Discovery Service, web, actuator for monitoring check, and add openfeign dependency to use Feign function.

2) modify the configuration file

Configure the nacos registry address, because no services are provided, so there is no need for registry registration, so register-enabled=false

3) add Feign support

Configure FeignConfiguration class files

The default SpringMvcController of Spring Cloud Netflix will be replaced with feign.Contract.Default

Using feign.Contract.Default to change the contract to the native default contract of Feign, you can use the annotations that come with feign.

4) Custom Feign API

The Feign interface file needs to be in the same package directory as the startup class. Use @ FeignClient annotation to configure the required services. Here, nacos-provider needs to provide services in the registry.

Because feign.Contract.Deafault is configured above, the native annotation @ RequestLine of Feign can be used in the interface

Add a HelloController class file

Here we use the interface MyFeignClient to call the hello method to get the services provided by the nacos-provider client

Log in Feign

1) add configuration item

Add logging packages to the configuration file, * and each FeignClient needs to be configured separately, which can only respond to debug-level logs

2) set log level

Configure log levels in the FeignConfiguration class file

Log level:

NONE: do not record (default)

BASIC: only the request method, URL, response status code and execution time are recorded

HEADERS: record basic information, request and response headers

FULL: record request and response headers, body, and row data

Test the configuration customized by Feign

Start the nacos-provider and feign-config clients, and enter nacos to query whether the nacos-provider service is registered

Enter the browser and type the address http://localhost:2334/hello to access the service content provided by nacos-provider.

View the log

The console will output the following information

[MyFeignClient#hello]

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