在使用Feign进行微服务互相调用的过程中，我们会碰到一个问题就是：Get请求时不能像SpringMVC中的RequestMapping一样直接接受对象，而在Feign中这样使用的话会将Get请求转换为Post请求方式，从而导致调用异常!
如何解决？
跟踪源代码，发现有个Encoder接口，它的作用是:
Encodes an object into an HTTP request body. Like javax.websocket.Encoder. Encoder is used when a method parameter has no @Param annotation. For example:
@POST
@Path("/")
void create(User user
默认spring-cloud-netflix-core里有一个SpringEncoder,并配置在FeignClientsConfiguration中，怎么办?
自定义一个就好了，只需要实现这个接口并覆盖原来的Encoder即可。
代码不是关键，关键是思路。如下的代码可以直接放生产环境使用
/*
* Copyright 2013-2015 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package custom;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.reflect.Array;
import java.lang.reflect.Type;
import java.nio.charset.Charset;
import java.util.*;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import demo.RequestBean;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.ObjectFactory;
import org.springframework.boot.autoconfigure.web.HttpMessageConverters;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import feign.RequestTemplate;
import feign.codec.EncodeException;
import feign.codec.Encoder;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;
import static custom.FeignUtils.getHeaders;
import static custom.FeignUtils.getHttpHeaders;
/**
* @author Spencer Gibb
* @author Lycol
* @purpose for support request by get that can be send with requestbody
*/
public class MySpringEncoder implements Encoder {
Logger log= LoggerFactory.getLogger(MySpringEncoder.class);
private ObjectFactory<HttpMessageConverters> messageConverters;
public MySpringEncoder(ObjectFactory<HttpMessageConverters> messageConverters) {
this.messageConverters = messageConverters;
}
@Override
public void encode(Object requestBody, Type bodyType, RequestTemplate request)
throws EncodeException {
// template.body(conversionService.convert(object, String.class));
if (requestBody != null) {
Class<?> requestType = requestBody.getClass();
Collection<String> contentTypes = request.headers().get("Content-Type");
MediaType requestContentType = null;
if (contentTypes != null && !contentTypes.isEmpty()) {
String type = contentTypes.iterator().next();
requestContentType = MediaType.valueOf(type);
}
for (HttpMessageConverter<?> messageConverter : this.messageConverters
.getObject().getConverters()) {
if (messageConverter.canWrite(requestType, requestContentType)) {
if (log.isDebugEnabled()) {
if (requestContentType != null) {
log.debug("Writing [" + requestBody + "] as \""
+ requestContentType + "\" using ["
+ messageConverter + "]");
}
else {
log.debug("Writing [" + requestBody + "] using ["
+ messageConverter + "]");
}
}
FeignOutputMessage outputMessage = new FeignOutputMessage(request);
try {
@SuppressWarnings("unchecked")
HttpMessageConverter<Object> copy = (HttpMessageConverter<Object>) messageConverter;
copy.write(requestBody, requestContentType, outputMessage);
}
catch (IOException ex) {
throw new EncodeException("Error converting request body", ex);
}
// clear headers
request.headers(null);
System.out.println(request.method().equals(HttpMethod.GET.name())+"-------------");
// converters can modify headers, so update the request
// with the modified headers
request.headers(getHeaders(outputMessage.getHeaders()));
if(request.method().equals(HttpMethod.GET.name())){
if(requestBody !=null) {
Map<String, Object> requestMap = objectToMap(requestBody);
for (Map.Entry entry : requestMap.entrySet()) {
if (null != entry.getValue()) {
request.query(entry.getKey().toString(), entry.getValue().toString());
}
}
}
}
if(request.method().equals(HttpMethod.GET.name())) {
request.body(null);
}
else {
request.body(outputMessage.getOutputStream().toByteArray(),
Charset.forName("UTF-8")); // TODO: set charset
}
return;
}
}
String message = "Could not write request: no suitable HttpMessageConverter "
+ "found for request type [" + requestType.getName() + "]";
if (requestContentType != null) {
message += " and content type [" + requestContentType + "]";
}
throw new EncodeException(message);
}
}
private class FeignOutputMessage implements HttpOutputMessage {
private final ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
private final HttpHeaders httpHeaders;
private FeignOutputMessage(RequestTemplate request) {
httpHeaders = getHttpHeaders(request.headers());
}
@Override
public OutputStream getBody() throws IOException {
return this.outputStream;
}
@Override
public HttpHeaders getHeaders() {
return this.httpHeaders;
}
public ByteArrayOutputStream getOutputStream() {
return this.outputStream;
}
}
private static Map<String,Object> objectToMap(Object requestBody){
ObjectMapper objectMapper=new ObjectMapper();
Map<String, Object> objectAsMap = objectMapper.convertValue(requestBody, Map.class);
return objectAsMap;
}
}
配置Configuration
package custom;
import feign.codec.Encoder;
import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.web.HttpMessageConverters;
import org.springframework.cloud.netflix.feign.support.SpringEncoder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
/**
* Created by Administrator on 2019/8/24.
*/
@Configuration
public class SpringDecoderConfiguration {
@Autowired
private ObjectFactory<HttpMessageConverters> messageConverters;
@Bean
public Encoder feignEncoder() {
return new MySpringEncoder(this.messageConverters);
}
}
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