ParseHandlersByName
ParseHandlersByName是Feign解析接口定義的方法的實現,在Feign.Builder的build()方法中會初始化一個它的實例傳遞給ReflectiveFeign,以便在生成代理對象時通過ParseHandlersByName類的實例來解析接口方法.
如下代碼片段:
public Feign build() {
SynchronousMethodHandler.Factory synchronousMethodHandlerFactory =
new SynchronousMethodHandler.Factory(client, retryer, requestInterceptors, logger,
logLevel, decode404, closeAfterDecode);
ParseHandlersByName handlersByName =
new ParseHandlersByName(contract, options, encoder, decoder,
errorDecoder, synchronousMethodHandlerFactory);
return new ReflectiveFeign(handlersByName, invocationHandlerFactory);
}
ParseHandlersByName.apply()
這個是解析接口方法的具體實現,如下代碼片段:
public Map<String, MethodHandler> apply(Target key) {
List<MethodMetadata> metadata = contract.parseAndValidatateMetadata(key.type());
Map<String, MethodHandler> result = new LinkedHashMap<String, MethodHandler>();
for (MethodMetadata md : metadata) {
BuildTemplateByResolvingArgs buildTemplate;
if (!md.formParams().isEmpty() && md.template().bodyTemplate() == null) {
buildTemplate = new BuildFormEncodedTemplateFromArgs(md, encoder);
} else if (md.bodyIndex() != null) {
buildTemplate = new BuildEncodedTemplateFromArgs(md, encoder);
} else {
buildTemplate = new BuildTemplateByResolvingArgs(md);
}
result.put(md.configKey(),
factory.create(key, md, buildTemplate, options, decoder, errorDecoder));
}
return result;
}
分析如下:
- 1.通過Contract對象解析方法元數據
- 2.根據方法參數獲取HTTP請求構建模板
- 3.根據方法生成HTTP調用代理類
Contract:方法解析
Contract接口只定義了一個解析元數據的方法:
List<MethodMetadata> parseAndValidatateMetadata(Class<?> targetType);
Contract中的內部類:BaseContract
BaseContract是一個實現了Contract接口的抽象類,抽象了一些具體的解析方法,如下:
@Override
public List<MethodMetadata> parseAndValidatateMetadata(Class<?> targetType) {
checkState(targetType.getTypeParameters().length == 0, "Parameterized types unsupported: %s",
targetType.getSimpleName());
checkState(targetType.getInterfaces().length <= 1, "Only single inheritance supported: %s",
targetType.getSimpleName());
if (targetType.getInterfaces().length == 1) {
checkState(targetType.getInterfaces()[0].getInterfaces().length == 0,
"Only single-level inheritance supported: %s",
targetType.getSimpleName());
}
Map<String, MethodMetadata> result = new LinkedHashMap<String, MethodMetadata>();
for (Method method : targetType.getMethods()) {
if (method.getDeclaringClass() == Object.class ||
(method.getModifiers() & Modifier.STATIC) != 0 ||
Util.isDefault(method)) {
continue;
}
MethodMetadata metadata = parseAndValidateMetadata(targetType, method);
checkState(!result.containsKey(metadata.configKey()), "Overrides unsupported: %s",
metadata.configKey());
result.put(metadata.configKey(), metadata);
}
return new ArrayList<MethodMetadata>(result.values());
}
這裏主要是對Feign接口類做了一些校驗,比如說不支持泛型,只能單一接口繼承等,以及檢驗接口中的方法是否符合代理規則,比如說是否是繼承自Object類的方法、是否是static方法、是否是default方法,如果是的話則不進行解析,如果不是的話則循環解析接口中的各個方法,解析的具體方法是parseAndValidateMetadata(Class<?> targetType, Method method),如下代碼段:
protected MethodMetadata parseAndValidateMetadata(Class<?> targetType, Method method) {
MethodMetadata data = new MethodMetadata();
data.returnType(Types.resolve(targetType, targetType, method.getGenericReturnType()));
data.configKey(Feign.configKey(targetType, method));
if(targetType.getInterfaces().length == 1) {
processAnnotationOnClass(data, targetType.getInterfaces()[0]);
}
processAnnotationOnClass(data, targetType);
for (Annotation methodAnnotation : method.getAnnotations()) {
processAnnotationOnMethod(data, methodAnnotation, method);
}
checkState(data.template().method() != null,
"Method %s not annotated with HTTP method type (ex. GET, POST)",
method.getName());
Class<?>[] parameterTypes = method.getParameterTypes();
Type[] genericParameterTypes = method.getGenericParameterTypes();
Annotation[][] parameterAnnotations = method.getParameterAnnotations();
int count = parameterAnnotations.length;
for (int i = 0; i < count; i++) {
boolean isHttpAnnotation = false;
if (parameterAnnotations[i] != null) {
isHttpAnnotation = processAnnotationsOnParameter(data, parameterAnnotations[i], i);
}
if (parameterTypes[i] == URI.class) {
data.urlIndex(i);
} else if (!isHttpAnnotation) {
checkState(data.formParams().isEmpty(),
"Body parameters cannot be used with form parameters.");
checkState(data.bodyIndex() == null, "Method has too many Body parameters: %s", method);
data.bodyIndex(i);
data.bodyType(Types.resolve(targetType, targetType, genericParameterTypes[i]));
}
}
if (data.headerMapIndex() != null) {
checkMapString("HeaderMap", parameterTypes[data.headerMapIndex()], genericParameterTypes[data.headerMapIndex()]);
}
if (data.queryMapIndex() != null) {
checkMapString("QueryMap", parameterTypes[data.queryMapIndex()], genericParameterTypes[data.queryMapIndex()]);
}
return data;
}
分析如下:
- 1.獲取方法返回類型以及路由key
- 2.處理此接口以及繼承的接口上的註解
- 3.處理接口中各個方法上的註解
- 4.處理方法各個參數上的註解
- 5.校驗HeaderMap與QueryMap
Feign繼承BaseContract的默認子類Default
Feign build的時候如果沒有自定義Contract實現類,那將默認使用Default作爲接口方法解析的Contract,這個類主要實現了接口註解的處理、方法上註解的處理以及方法參數上註解的處理
接口註解的處理:processAnnotationOnClass
@Override
protected void processAnnotationOnClass(MethodMetadata data, Class<?> targetType) {
if (targetType.isAnnotationPresent(Headers.class)) {
String[] headersOnType = targetType.getAnnotation(Headers.class).value();
checkState(headersOnType.length > 0, "Headers annotation was empty on type %s.",
targetType.getName());
Map<String, Collection<String>> headers = toMap(headersOnType);
headers.putAll(data.template().headers());
data.template().headers(null); // to clear
data.template().headers(headers);
}
}
這個方法主要處理Headers這個註解,如果類上存在Headers註解的話,獲取到註解設置的headers,然後將其加入RequestTemplate對象的headers集合中
方法註解的處理:processAnnotationOnMethod
@Override
protected void processAnnotationOnMethod(MethodMetadata data, Annotation methodAnnotation,
Method method) {
Class<? extends Annotation> annotationType = methodAnnotation.annotationType();
if (annotationType == RequestLine.class) {
String requestLine = RequestLine.class.cast(methodAnnotation).value();
checkState(emptyToNull(requestLine) != null,
"RequestLine annotation was empty on method %s.", method.getName());
if (requestLine.indexOf(' ') == -1) {
checkState(requestLine.indexOf('/') == -1,
"RequestLine annotation didn't start with an HTTP verb on method %s.",
method.getName());
data.template().method(requestLine);
return;
}
data.template().method(requestLine.substring(0, requestLine.indexOf(' ')));
if (requestLine.indexOf(' ') == requestLine.lastIndexOf(' ')) {
// no HTTP version is ok
data.template().append(requestLine.substring(requestLine.indexOf(' ') + 1));
} else {
// skip HTTP version
data.template().append(
requestLine.substring(requestLine.indexOf(' ') + 1, requestLine.lastIndexOf(' ')));
}
data.template().decodeSlash(RequestLine.class.cast(methodAnnotation).decodeSlash());
} else if (annotationType == Body.class) {
String body = Body.class.cast(methodAnnotation).value();
checkState(emptyToNull(body) != null, "Body annotation was empty on method %s.",
method.getName());
if (body.indexOf('{') == -1) {
data.template().body(body);
} else {
data.template().bodyTemplate(body);
}
} else if (annotationType == Headers.class) {
String[] headersOnMethod = Headers.class.cast(methodAnnotation).value();
checkState(headersOnMethod.length > 0, "Headers annotation was empty on method %s.",
method.getName());
data.template().headers(toMap(headersOnMethod));
}
}
方法分析如下:
- 1.如果註解是RequestLine類型,則解析註解設置的value,重點在於’ '空格字符串的解析,空格之前的會設置爲RequestTemplate的method,空格之後的會解析成追加到url中並進行query的解析,至於具體的query解析後面講到RequestTemplate的時候再進行贅述
- 2.如果註解是Body類型,解析註解設置的value,判斷是否存在佔位符’{’,如果不存在則直接作爲body,如果存在則需要解析參數
- 3.如果註解是Headers類型,獲取到註解設置的headers,然後將其加入RequestTemplate對象的headers集合中
參數上註解的處理:processAnnotationsOnParameter
@Override
protected boolean processAnnotationsOnParameter(MethodMetadata data, Annotation[] annotations,
int paramIndex) {
boolean isHttpAnnotation = false;
for (Annotation annotation : annotations) {
Class<? extends Annotation> annotationType = annotation.annotationType();
if (annotationType == Param.class) {
Param paramAnnotation = (Param) annotation;
String name = paramAnnotation.value();
checkState(emptyToNull(name) != null, "Param annotation was empty on param %s.", paramIndex);
nameParam(data, name, paramIndex);
Class<? extends Param.Expander> expander = paramAnnotation.expander();
if (expander != Param.ToStringExpander.class) {
data.indexToExpanderClass().put(paramIndex, expander);
}
data.indexToEncoded().put(paramIndex, paramAnnotation.encoded());
isHttpAnnotation = true;
String varName = '{' + name + '}';
if (!data.template().url().contains(varName) &&
!searchMapValuesContainsSubstring(data.template().queries(), varName) &&
!searchMapValuesContainsSubstring(data.template().headers(), varName)) {
data.formParams().add(name);
}
} else if (annotationType == QueryMap.class) {
checkState(data.queryMapIndex() == null, "QueryMap annotation was present on multiple parameters.");
data.queryMapIndex(paramIndex);
data.queryMapEncoded(QueryMap.class.cast(annotation).encoded());
isHttpAnnotation = true;
} else if (annotationType == HeaderMap.class) {
checkState(data.headerMapIndex() == null, "HeaderMap annotation was present on multiple parameters.");
data.headerMapIndex(paramIndex);
isHttpAnnotation = true;
}
}
return isHttpAnnotation;
}
分析如下:
- 1.遍歷參數的各個註解,如果註解是Param類型,將參數索引存入MethodMetadata實例中,並且判斷url中、url後面跟着的queries參數、被@Headers註解聲明的headers這三者是否包含 {參數名} 字符串如果不存在則加入formParams集合中,代表表單數據
- 2.如果註解是QueryMap類型,將QueryMap類型的Map參數索引以及是否encode的標註存入MethodMetadata實例中
- 3.如果註解是HeaderMap類型,將HeaderMap類型的Map參數索引存入MethodMetadata實例中
- 4.處理參數註解的地方有個小細節,這個方法有一個返回值isHttpAnnotation,如果參數是URI類型的話,會設置一個urlIndex記錄以便在創建RequestTemplate的時候更新url,如果參數不是URI類型並且返回值isHttpAnnotation爲false的話這個參數將會被當成body類型的