解決feign接口返回泛型設(shè)置屬性為null的問題
簡介
feign是一種聲明式http請求調(diào)用方式,工作原理就是根據(jù)FeignClient注解生成新的接口(也就是傳說中的動態(tài)代理),常見使用方式如下所示:
@FeignClient(name="UserFeignService",url="${auth.url}",
fallbackFactory = OrgFeignServiceFallback.class,
configuration = FeignErrorDecoderConfiguration.class)
public interface OrgFeignService {
/**
*
* @param org
* @return
*/
@PostMapping(value="Tenant/AddTenantOrg", consumes="application/json; charset=UTF-8")
APIResultTO<TenantOrg> addOrg(OrgDto org, @RequestHeader("token")String token);
}
應用場景
1、序列化以及反序列化采用jackson
2、調(diào)用第三方采用feign注解式接口
問題分析
APIResultTO是一個api通用接口返回泛型類,TenantOrg為傳入的具體泛型類,咱們來看下出問題的類:
@Getter
@Setter
@NoArgsConstructor
public class TenantOrg {
/**
*/
@JsonProperty("Id")
private String Id;
/**
* 父級Id
*/
@JsonProperty("PId")
private String PId;
/**
* 租戶代碼
*/
@JsonProperty("Tenant")
private String tenant;
/**
* 組織架構(gòu)名字
*/
@JsonProperty("Name")
private String name;
}
必須要用@JsonProperty("Id")或者@JsonSetter("Id")注解來顯示聲明屬性名字,尤其是首字母為大寫的情況,否則反序列化后的數(shù)據(jù)就為空值。
為什么TenantOrg類中的Id等其他屬性跟第三方服務(wù)返回的json數(shù)據(jù)字段完全一致,卻沒有成功設(shè)置對應的屬性呢,這個就要看下BeanDeserializer類的deserializeFromObject方法,從其名字上我們可以看出這是將請求返回的數(shù)據(jù)反序列化成對應的類對象:
public Object deserializeFromObject(JsonParser p, DeserializationContext ctxt) throws IOException
{
/* 09-Dec-2014, tatu: As per [databind#622], we need to allow Object Id references
* to come in as JSON Objects as well; but for now assume they will
* be simple, single-property references, which means that we can
* recognize them without having to buffer anything.
* Once again, if we must, we can do more complex handling with buffering,
* but let's only do that if and when that becomes necessary.
*/
if ((_objectIdReader != null) && _objectIdReader.maySerializeAsObject()) {
if (p.hasTokenId(JsonTokenId.ID_FIELD_NAME)
&& _objectIdReader.isValidReferencePropertyName(p.getCurrentName(), p)) {
return deserializeFromObjectId(p, ctxt);
}
}
if (_nonStandardCreation) {
if (_unwrappedPropertyHandler != null) {
return deserializeWithUnwrapped(p, ctxt);
}
if (_externalTypeIdHandler != null) {
return deserializeWithExternalTypeId(p, ctxt);
}
Object bean = deserializeFromObjectUsingNonDefault(p, ctxt);
if (_injectables != null) {
injectValues(ctxt, bean);
}
/* 27-May-2014, tatu: I don't think view processing would work
* at this point, so commenting it out; but leaving in place
* just in case I forgot something fundamental...
*/
/*
if (_needViewProcesing) {
Class<?> view = ctxt.getActiveView();
if (view != null) {
return deserializeWithView(p, ctxt, bean, view);
}
}
*/
return bean;
}
final Object bean = _valueInstantiator.createUsingDefault(ctxt);
// [databind#631]: Assign current value, to be accessible by custom deserializers
p.setCurrentValue(bean);
if (p.canReadObjectId()) {
Object id = p.getObjectId();
if (id != null) {
_handleTypedObjectId(p, ctxt, bean, id);
}
}
if (_injectables != null) {
injectValues(ctxt, bean);
}
if (_needViewProcesing) {
Class<?> view = ctxt.getActiveView();
if (view != null) {
return deserializeWithView(p, ctxt, bean, view);
}
}
if (p.hasTokenId(JsonTokenId.ID_FIELD_NAME)) {
String propName = p.getCurrentName();
do {
p.nextToken();
//如果要跟蹤測試的話,直接定位到該位置就可以,你就會發(fā)現(xiàn)如果沒有
//JSONProperty之類的注解定義屬性名字的話,Id、PId屬性在_beanProperties都成了小寫的屬性
SettableBeanProperty prop = _beanProperties.find(propName);
if (prop != null) { // normal case
try {
prop.deserializeAndSet(p, ctxt, bean);
} catch (Exception e) {
wrapAndThrow(e, bean, propName, ctxt);
}
continue;
}
handleUnknownVanilla(p, ctxt, bean, propName);
} while ((propName = p.nextFieldName()) != null);
}
return bean;
}
具體如下圖所示:

正如上面所示,用@JsonProperty注解配置的屬性,在反序列化時就按照@JsonProperty注解定義的屬性名相同,至于為什么在TenantOrg中定義的PId屬性在使用時怎么變成了pid,
具體可以看下POJOPropertiesCollector類的_removeUnwantedProperties方法以及_renameProperties方法:
protected void _removeUnwantedProperties(Map<String, POJOPropertyBuilder> props)
{
Iterator<POJOPropertyBuilder> it = props.values().iterator();
while (it.hasNext()) {
POJOPropertyBuilder prop = it.next();
// 去除private屬性,PId屬性會在這里移除
if (!prop.anyVisible()) {
it.remove();
continue;
}
// Otherwise, check ignorals
if (prop.anyIgnorals()) {
// first: if one or more ignorals, and no explicit markers, remove the whole thing
if (!prop.isExplicitlyIncluded()) {
it.remove();
_collectIgnorals(prop.getName());
continue;
}
// otherwise just remove ones marked to be ignored
prop.removeIgnored();
if (!prop.couldDeserialize()) {
_collectIgnorals(prop.getName());
}
}
}
}
protected void _renameProperties(Map<String, POJOPropertyBuilder> props)
{
// With renaming need to do in phases: first, find properties to rename
Iterator<Map.Entry<String,POJOPropertyBuilder>> it = props.entrySet().iterator();
LinkedList<POJOPropertyBuilder> renamed = null;
while (it.hasNext()) {
Map.Entry<String, POJOPropertyBuilder> entry = it.next();
POJOPropertyBuilder prop = entry.getValue();
//被@JsonProperty注解的屬性會找到對應的屬性名
Collection<PropertyName> l = prop.findExplicitNames();
// no explicit names? Implicit one is fine as is
if (l.isEmpty()) {
continue;
}
it.remove(); // need to replace with one or more renamed
if (renamed == null) {
renamed = new LinkedList<POJOPropertyBuilder>();
}
// simple renaming? Just do it
//在這里使用@JsonProperty注解里面定義的屬性名,比如PId、Id等
//所以使用了@JsonProperty注解后,我們就無需關(guān)注類里面屬性的大小寫,設(shè)置不用關(guān)注屬性名
if (l.size() == 1) {
PropertyName n = l.iterator().next();
renamed.add(prop.withName(n));
continue;
}
// but this may be problematic...
renamed.addAll(prop.explode(l));
/*
String newName = prop.findNewName();
if (newName != null) {
if (renamed == null) {
renamed = new LinkedList<POJOPropertyBuilder>();
}
prop = prop.withSimpleName(newName);
renamed.add(prop);
it.remove();
}
*/
}
// and if any were renamed, merge back in...
if (renamed != null) {
for (POJOPropertyBuilder prop : renamed) {
String name = prop.getName();
POJOPropertyBuilder old = props.get(name);
if (old == null) {
props.put(name, prop);
} else {
old.addAll(prop);
}
// replace the creatorProperty too, if there is one
_updateCreatorProperty(prop, _creatorProperties);
// [databind#2001]: New name of property was ignored previously? Remove from ignored
// 01-May-2018, tatu: I have a feeling this will need to be revisited at some point,
// to avoid removing some types of removals, possibly. But will do for now.
if (_ignoredPropertyNames != null) {
_ignoredPropertyNames.remove(name);
}
}
}
}
springcloud feign請求:數(shù)據(jù)返回null
問題描述
調(diào)用方調(diào)用服務(wù),DEBUG被調(diào)用方服務(wù)得到正確數(shù)據(jù),但調(diào)用方返回的數(shù)據(jù)對象屬性全為null

原因及解決方法:
在feign調(diào)用接口中與被調(diào)用方接口返回類型不一致。
以上為個人經(jīng)驗,希望能給大家一個參考,也希望大家多多支持腳本之家。
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