feign远程调用时，get请求时，如果有特殊的字段类型，用@SpringQueryMap接收参数时，会出现异常，需要自定义QueryMapEncoder
本文例举OffsetDateTime字段类型处理：
1.OffsetDateTimeQueryMapEncoder文件：
import feign.Param;
import feign.QueryMapEncoder;
import feign.codec.EncodeException;
import org.apache.commons.lang3.ObjectUtils;
import java.lang.reflect.Field;
import java.time.OffsetDateTime;
import java.time.format.DateTimeFormatter;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.stream.Collectors;
public class OffsetDateTimeQueryMapEncoder implements QueryMapEncoder {
private final Map<Class<?>, ObjectParamMetadata> classToMetadata = new ConcurrentHashMap<>();
@Override
public Map<String, Object> encode(Object object) throws EncodeException {
ObjectParamMetadata metadata = classToMetadata.computeIfAbsent(object.getClass(),
ObjectParamMetadata::parseObjectType);
return metadata.objectFields.stream()
.map(field -> this.FieldValuePair(object, field))
.filter(fieldObjectPair -> fieldObjectPair.right.isPresent())
.collect(Collectors.toMap(this::fieldName, this::fieldObject));
}
private String fieldName(Pair<Field, Optional<Object>> pair) {
Param alias = pair.left.getAnnotation(Param.class);
return alias != null ? alias.value() : pair.left.getName();
}
// 可扩展为策略模式，支持更多的格式转换
private Object fieldObject(Pair<Field, Optional<Object>> pair) {
Object fieldObject = pair.right.get();
if (ObjectUtils.isNotEmpty(fieldObject) && fieldObject instanceof OffsetDateTime) {
fieldObject = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss xxx").format((OffsetDateTime) fieldObject);
}
return fieldObject;
}
private Pair<Field, Optional<Object>> FieldValuePair(Object object, Field field) {
try {
return Pair.pair(field, Optional.ofNullable(field.get(object)));
} catch (IllegalAccessException e) {
throw new EncodeException("Failure encoding object into query map", e);
}
}
private static class ObjectParamMetadata {
private final List<Field> objectFields;
private ObjectParamMetadata(List<Field> objectFields) {
this.objectFields = Collections.unmodifiableList(objectFields);
}
private static ObjectParamMetadata parseObjectType(Class<?> type) {
List<Field> allFields = new ArrayList<Field>();
for (Class<?> currentClass = type; currentClass != null; currentClass = currentClass.getSuperclass()) {
Collections.addAll(allFields, currentClass.getDeclaredFields());
}
return new ObjectParamMetadata(allFields.stream()
.filter(field -> !field.isSynthetic())
.peek(field -> field.setAccessible(true))
.collect(Collectors.toList()));
}
}
private static class Pair<T, U> {
private Pair(T left, U right) {
this.right = right;
this.left = left;
}
public final T left;
public final U right;
public static <T, U> Pair<T, U> pair(T left, U right) {
return new Pair<>(left, right);
}
}
}
2.在FeignConfig中，配置自定义的OffsetDateTimeQueryMapEncoder：
@Configuration
public class FeignConfig {
@Bean
public QueryMapEncoder queryMapEncoder() {
return new OffsetDateTimeQueryMapEncoder();
}
}
3.在远程需要使用feign的api接口，引用configuration：
@FeignClient(contextId = "xxxx",name = "xxxx",configuration = FeignConfig.class)
配置完成后，使用OffesetDateTime作为参数，get传参就不会报错。
