Feign 动态设定服务器名称 与 调用接口
1. 新增编码器（由于使用了动态的Feign，所以不能像正常使用Feign一样指定configuration配置编码器）
import feign.RequestTemplate;
import feign.codec.EncodeException;
import feign.codec.Encoder;
import org.springframework.core.io.InputStreamResource;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.multipart.MultipartFile;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.Type;
import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
/**
* A custom {@link Encoder} that supports Multipart requests. It uses
* {@link HttpMessageConverter}s like {@link RestTemplate} does.
*
* @author Pierantonio Cangianiello
*/
public class FeignSpringFormEncoder implements Encoder {
private final List<HttpMessageConverter<?>> converters = new RestTemplate().getMessageConverters();
public static final Charset UTF_8 = Charset.forName("UTF-8");
public FeignSpringFormEncoder() {
}
/**
* {@inheritDoc }
*/
@Override
public void encode(Object object, Type bodyType, RequestTemplate template) throws EncodeException {
if (isFormRequest(bodyType)) {
final HttpHeaders multipartHeaders = new HttpHeaders();
multipartHeaders.setContentType(MediaType.MULTIPART_FORM_DATA);
encodeMultipartFormRequest((Map<String, ?>) object, multipartHeaders, template);
} else {
final HttpHeaders jsonHeaders = new HttpHeaders();
jsonHeaders.setContentType(MediaType.APPLICATION_JSON);
encodeRequest(object, jsonHeaders, template);
}
}
/**
* Encodes the request as a multipart form. It can detect a single {@link MultipartFile}, an
* array of {@link MultipartFile}s, or POJOs (that are converted to JSON).
*
* @param formMap
* @param template
* @throws EncodeException
*/
private void encodeMultipartFormRequest(Map<String, ?> formMap, HttpHeaders multipartHeaders, RequestTemplate template) throws EncodeException {
if (formMap == null) {
throw new EncodeException("Cannot encode request with null form.");
}
LinkedMultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
for (Entry<String, ?> entry : formMap.entrySet()) {
Object value = entry.getValue();
if (isMultipartFile(value)) {
map.add(entry.getKey(), encodeMultipartFile((MultipartFile) value));
} else if (isMultipartFileArray(value)) {
encodeMultipartFiles(map, entry.getKey(), Arrays.asList((MultipartFile[]) value));
} else {
map.add(entry.getKey(), encodeJsonObject(value));
}
}
encodeRequest(map, multipartHeaders, template);
}
private boolean isMultipartFile(Object object) {
return object instanceof MultipartFile;
}
private boolean isMultipartFileArray(Object o) {
return o != null && o.getClass().isArray() && MultipartFile.class.isAssignableFrom(o.getClass().getComponentType());
}
/**
* Wraps a single {@link MultipartFile} into a {@link HttpEntity} and sets the
* {@code Content-type} header to {@code application/octet-stream}
*
* @param file
* @return
*/
private HttpEntity<?> encodeMultipartFile(MultipartFile file) {
HttpHeaders filePartHeaders = new HttpHeaders();
filePartHeaders.setContentType(MediaType.APPLICATION_OCTET_STREAM);
try {
Resource multipartFileResource = new MultipartFileResource(file.getOriginalFilename(), file.getSize(), file.getInputStream());
return new HttpEntity<>(multipartFileResource, filePartHeaders);
} catch (IOException ex) {
throw new EncodeException("Cannot encode request.", ex);
}
}
/**
* Fills the request map with {@link HttpEntity}s containing the given {@link MultipartFile}s.
* Sets the {@code Content-type} header to {@code application/octet-stream} for each file.
*
* @param map current request map.
* @param name the name of the array field in the multipart form.
* @param files
*/
private void encodeMultipartFiles(LinkedMultiValueMap<String, Object> map, String name, List<? extends MultipartFile> files) {
HttpHeaders filePartHeaders = new HttpHeaders();
filePartHeaders.setContentType(MediaType.APPLICATION_OCTET_STREAM);
try {
for (MultipartFile file : files) {
Resource multipartFileResource = new MultipartFileResource(file.getOriginalFilename(), file.getSize(), file.getInputStream());
map.add(name, new HttpEntity<>(multipartFileResource, filePartHeaders));
}
} catch (IOException ex) {
throw new EncodeException("Cannot encode request.", ex);
}
}
/**
* Wraps an object into a {@link HttpEntity} and sets the {@code Content-type} header to
* {@code application/json}
*
* @param o
* @return
*/
private HttpEntity<?> encodeJsonObject(Object o) {
HttpHeaders jsonPartHeaders = new HttpHeaders();
jsonPartHeaders.setContentType(MediaType.APPLICATION_JSON);
return new HttpEntity<>(o, jsonPartHeaders);
}
/**
* Calls the conversion chain actually used by
* {@link RestTemplate}, filling the body of the request
* template.
*
* @param value
* @param requestHeaders
* @param template
* @throws EncodeException
*/
private void encodeRequest(Object value, HttpHeaders requestHeaders, RequestTemplate template) throws EncodeException {
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
HttpOutputMessage dummyRequest = new HttpOutputMessageImpl(outputStream, requestHeaders);
try {
Class<?> requestType = value.getClass();
MediaType requestContentType = requestHeaders.getContentType();
for (HttpMessageConverter<?> messageConverter : converters) {
if (messageConverter.canWrite(requestType, requestContentType)) {
((HttpMessageConverter<Object>) messageConverter).write(
value, requestContentType, dummyRequest);
break;
}
}
} catch (IOException ex) {
throw new EncodeException("Cannot encode request.", ex);
}
HttpHeaders headers = dummyRequest.getHeaders();
if (headers != null) {
for (Entry<String, List<String>> entry : headers.entrySet()) {
template.header(entry.getKey(), entry.getValue());
}
}
/*
we should use a template output stream... this will cause issues if files are too big,
since the whole request will be in memory.
*/
template.body(outputStream.toByteArray(), UTF_8);
}
/**
* Minimal implementation of {@link HttpOutputMessage}. It's needed to
* provide the request body output stream to
* {@link HttpMessageConverter}s
*/
private class HttpOutputMessageImpl implements HttpOutputMessage {
private final OutputStream body;
private final HttpHeaders headers;
public HttpOutputMessageImpl(OutputStream body, HttpHeaders headers) {
this.body = body;
this.headers = headers;
}
@Override
public OutputStream getBody() throws IOException {
return body;
}
@Override
public HttpHeaders getHeaders() {
return headers;
}
}
/**
* Heuristic check for multipart requests.
*
* @param type
* @return
* @see feign.Types
*/
static boolean isFormRequest(Type type) {
return MAP_STRING_WILDCARD.equals(type);
}
/**
* Dummy resource class. Wraps file content and its original name.
*/
static class MultipartFileResource extends InputStreamResource {
private final String filename;
private final long size;
public MultipartFileResource(String filename, long size, InputStream inputStream) {
super(inputStream);
this.size = size;
this.filename = filename;
}
@Override
public String getFilename() {
return this.filename;
}
@Override
public InputStream getInputStream() throws IOException, IllegalStateException {
return super.getInputStream(); //To change body of generated methods, choose Tools | Templates.
}
@Override
public long contentLength() throws IOException {
return size;
}
}
}
2. 配置文件中配置编码器
feign.client.config.default.encoder=完整包名.FeignSpringFormEncoder
3. 新增FeignClientUtil类
import org.springframework.beans.BeansException;
import org.springframework.cloud.openfeign.FeignClientBuilder;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;
@Component
public class FeignClientUtils implements ApplicationContextAware {
private static ApplicationContext applicationContext = null;
private static final Map<String, Object> BEAN_CACHE = new ConcurrentHashMap<>();
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
if (FeignClientUtils.applicationContext == null) {
FeignClientUtils.applicationContext = applicationContext;
}
}
public static <T> T build(String serverName, Class<T> targetClass) {
return buildClient(serverName, targetClass);
}
@SuppressWarnings("unchecked")
private static <T> T buildClient(String serverName, Class<T> targetClass) {
T t = (T) BEAN_CACHE.get(serverName);
if (Objects.isNull(t)) {
FeignClientBuilder.Builder<T> builder = new FeignClientBuilder(applicationContext).forType(targetClass, serverName);
t = builder.build();
BEAN_CACHE.put(serverName, t);
}
return t;
}
}
4. 新增interface
import xxx.ApiResult;
import org.springframework.web.bind.annotation.*;
import java.util.Map;
public interface IFeignClientTemplate {
@GetMapping(value = "/{url}", headers = {"Content-Type: application/json"})
ApiResult get(@PathVariable("url") String url, @RequestParam Map<String, Object> params);
@PostMapping(value = "/{url}", headers = {"Content-Type: application/json"}, consumes = "application/json")
ApiResult post(@PathVariable("url") String url, Map<String, Object> params);
@PostMapping(value = "/{url}")
ApiResult postFile(@PathVariable("url") String url, Map<String, ?> params);
}
5. 使用实例
String serviceName = "xxx"; // 注册在nacos的服务名称
String url = "xxx"; // 请求的url的接口
DynamicFeignClient client = FeignClientUtils.build(serviceName, DynamicFeignClient.class);
ApiResult result = client.get(url,new HashMap<>());
PS：过程中遇到了一些问题，也使用了RequestLine注解，最后都调整与解决了，编码器是必要的，不然无法转换为指定的DTO
如果有人知道怎么在这种情况下使用Configuration配置编码解码注解，也请不吝赐教（试了几个都不行，在build client中指定也不行，没有对应方法）
target values must be absolute.
java.lang.IllegalStateException: Method has too many Body parameters: public abstract java.lang.String xxx.IFeignClientTemplate.get(java.lang.String,java.lang.Object)
feign.FeignException$NotFound: status 404 reading IFeignClientTemplate#get(String)
status 405 reading IFeignClientTemplate#get(String,HashMap)
No serializer found for class java.io.FileDescriptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)
等报错
