09、SpringCloud Alibaba - feign 接口注解解析规则 Contract
前言
Contract用于标识feign接口和接口方法上那些注解是有效的，并对这些注解进行提取，封装成方法的元数据信息。
一、Contract
public interface Contract {
/**
* Called to parse the methods in the class that are linked to HTTP requests.
*
* @param targetType {@link feign.Target#type() type} of the Feign interface.
*
* 根据接口类型提取出接口里方法的元数据信息，保存在MethodMetadata中
*/
List<MethodMetadata> parseAndValidateMetadata(Class<?> targetType);
}
二、BaseContract
1、抽象基类
abstract class BaseContract implements Contract {
/**
* @param targetType {@link feign.Target#type() type} of the Feign interface.
* @seeparseAndValidateMetadata(Class)
*/
@Override
public List<MethodMetadata> parseAndValidateMetadata(Class<?> targetType) {
//接口上不能有泛型变量
checkState(targetType.getTypeParameters().length == 0, "Parameterized types unsupported: %s",
targetType.getSimpleName());
//接口最多有一个父接口
checkState(targetType.getInterfaces().length <= 1, "Only single inheritance supported: %s",
targetType.getSimpleName());
if (targetType.getInterfaces().length == 1) {
//父接口存在时，父接口的父接口不能存在
checkState(targetType.getInterfaces()[0].getInterfaces().length == 0,
"Only single-level inheritance supported: %s",
targetType.getSimpleName());
}
final Map<String, MethodMetadata> result = new LinkedHashMap<String, MethodMetadata>();
//遍历接口方法
for (final Method method : targetType.getMethods()) {
//过滤掉Object的方法、static方法、default方法
if (method.getDeclaringClass() == Object.class ||
(method.getModifiers() & Modifier.STATIC) != 0 ||
Util.isDefault(method)) {
continue;
}
//解析出每个方法的元数据 MethodMetadata
final MethodMetadata metadata = parseAndValidateMetadata(targetType, method);
checkState(!result.containsKey(metadata.configKey()), "Overrides unsupported: %s",
metadata.configKey());
result.put(metadata.configKey(), metadata);
}
return new ArrayList<>(result.values());
}
2、parseAndValidateMetadata(Class<?> targetType, Method method)
protected MethodMetadata parseAndValidateMetadata(Class<?> targetType, Method method) {
final MethodMetadata data = new MethodMetadata();
data.targetType(targetType);
data.method(method);
data.returnType(Types.resolve(targetType, targetType, method.getGenericReturnType()));
data.configKey(Feign.configKey(targetType, method));
if (targetType.getInterfaces().length == 1) {
//处理父接口上的注解，留给子类实现
processAnnotationOnClass(data, targetType.getInterfaces()[0]);
}
//处理当前接口上的注解，留给子类实现
processAnnotationOnClass(data, targetType);
for (final Annotation methodAnnotation : method.getAnnotations()) {
//处理接口方法上的注解，留给子类实现
processAnnotationOnMethod(data, methodAnnotation, method);
}
if (data.isIgnored()) {
return data;
}
checkState(data.template().method() != null,
"Method %s not annotated with HTTP method type (ex. GET, POST)%s",
data.configKey(), data.warnings());
//方法参数类型
final Class<?>[] parameterTypes = method.getParameterTypes();
final Type[] genericParameterTypes = method.getGenericParameterTypes();
//参数注解
final Annotation[][] parameterAnnotations = method.getParameterAnnotations();
final int count = parameterAnnotations.length;
for (int i = 0; i < count; i++) {
boolean isHttpAnnotation = false;
if (parameterAnnotations[i] != null) {
//http相关的注解，留给子类实现
isHttpAnnotation = processAnnotationsOnParameter(data, parameterAnnotations[i], i);
}
if (isHttpAnnotation) {
data.ignoreParamater(i);
}
//参数类型是否是URI，有了就使用，没有就使用默认的
if (parameterTypes[i] == URI.class) {
data.urlIndex(i);
} else if (!isHttpAnnotation && parameterTypes[i] != Request.Options.class) {
if (data.isAlreadyProcessed(i)) {
checkState(data.formParams().isEmpty() || data.bodyIndex() == null,
"Body parameters cannot be used with form parameters.%s", data.warnings());
} else {
checkState(data.formParams().isEmpty(),
"Body parameters cannot be used with form parameters.%s", data.warnings());
checkState(data.bodyIndex() == null,
"Method has too many Body parameters: %s%s", method, data.warnings());
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) {
if (Map.class.isAssignableFrom(parameterTypes[data.queryMapIndex()])) {
checkMapKeys("QueryMap", genericParameterTypes[data.queryMapIndex()]);
}
}
return data;
}
三、Default
它是feign里 Contract 的默认实现，支持Headers 、RequestLine 、Body、Param、QueryMap 注解
class Default extends DeclarativeContract {
static final Pattern REQUEST_LINE_PATTERN = Pattern.compile("^([A-Z]+)[ ]*(.*)$");
public Default() {
//类上支持 Headers 注解
super.registerClassAnnotation(Headers.class, (header, data) -> {
final String[] headersOnType = header.value();
checkState(headersOnType.length > 0, "Headers annotation was empty on type %s.",
data.configKey());
final Map<String, Collection<String>> headers = toMap(headersOnType);
headers.putAll(data.template().headers());
data.template().headers(null); // to clear
data.template().headers(headers);
});
//方法上支持 RequestLine 注解
super.registerMethodAnnotation(RequestLine.class, (ann, data) -> {
final String requestLine = ann.value();
checkState(emptyToNull(requestLine) != null,
"RequestLine annotation was empty on method %s.", data.configKey());
final Matcher requestLineMatcher = REQUEST_LINE_PATTERN.matcher(requestLine);
if (!requestLineMatcher.find()) {
throw new IllegalStateException(String.format(
"RequestLine annotation didn't start with an HTTP verb on method %s",
data.configKey()));
} else {
data.template().method(HttpMethod.valueOf(requestLineMatcher.group(1)));
data.template().uri(requestLineMatcher.group(2));
}
data.template().decodeSlash(ann.decodeSlash());
data.template()
.collectionFormat(ann.collectionFormat());
});
//方法上支持 Body 注解
super.registerMethodAnnotation(Body.class, (ann, data) -> {
final String body = ann.value();
checkState(emptyToNull(body) != null, "Body annotation was empty on method %s.",
data.configKey());
if (body.indexOf('{') == -1) {
data.template().body(body);
} else {
data.template().bodyTemplate(body);
}
});
//方法上支持 Headers 注解
super.registerMethodAnnotation(Headers.class, (header, data) -> {
final String[] headersOnMethod = header.value();
checkState(headersOnMethod.length > 0, "Headers annotation was empty on method %s.",
data.configKey());
data.template().headers(toMap(headersOnMethod));
});
//参数上支持 Param 注解
super.registerParameterAnnotation(Param.class, (paramAnnotation, data, paramIndex) -> {
final String name = paramAnnotation.value();
checkState(emptyToNull(name) != null, "Param annotation was empty on param %s.",
paramIndex);
nameParam(data, name, paramIndex);
final Class<? extends Param.Expander> expander = paramAnnotation.expander();
if (expander != Param.ToStringExpander.class) {
data.indexToExpanderClass().put(paramIndex, expander);
}
if (!data.template().hasRequestVariable(name)) {
data.formParams().add(name);
}
});
//参数上支持 QueryMap 注解
super.registerParameterAnnotation(QueryMap.class, (queryMap, data, paramIndex) -> {
checkState(data.queryMapIndex() == null,
"QueryMap annotation was present on multiple parameters.");
data.queryMapIndex(paramIndex);
data.queryMapEncoded(queryMap.encoded());
});
super.registerParameterAnnotation(HeaderMap.class, (queryMap, data, paramIndex) -> {
checkState(data.headerMapIndex() == null,
"HeaderMap annotation was present on multiple parameters.");
data.headerMapIndex(paramIndex);
});
}
四、SpringMvcContract
它是openFeign 里 Contract 的默认实现
1、 类上支持注解RequestMapping；
@Override
protected void processAnnotationOnClass(MethodMetadata data, Class<?> clz) {
if (clz.getInterfaces().length == 0) {
RequestMapping classAnnotation = findMergedAnnotation(clz, RequestMapping.class);
if (classAnnotation != null) {
// Prepend path from class annotation if specified
if (classAnnotation.value().length > 0) {
String pathValue = emptyToNull(classAnnotation.value()[0]);
pathValue = resolve(pathValue);
if (!pathValue.startsWith("/")) {
pathValue = "/" + pathValue;
}
data.template().uri(pathValue);
if (data.template().decodeSlash() != decodeSlash) {
data.template().decodeSlash(decodeSlash);
}
}
}
}
}
2、 方法上支持注解CollectionFormat、RequestMapping；
@Override
protected void processAnnotationOnMethod(MethodMetadata data, Annotation methodAnnotation, Method method) {
//CollectionFormat 注解
if (CollectionFormat.class.isInstance(methodAnnotation)) {
CollectionFormat collectionFormat = findMergedAnnotation(method, CollectionFormat.class);
data.template().collectionFormat(collectionFormat.value());
}
//RequestMapping 注解
if (!RequestMapping.class.isInstance(methodAnnotation)
&& !methodAnnotation.annotationType().isAnnotationPresent(RequestMapping.class)) {
return;
}
RequestMapping methodMapping = findMergedAnnotation(method, RequestMapping.class);
// HTTP Method
RequestMethod[] methods = methodMapping.method();
if (methods.length == 0) {
methods = new RequestMethod[] {
RequestMethod.GET };
}
checkOne(method, methods, "method");
data.template().method(Request.HttpMethod.valueOf(methods[0].name()));
// path
checkAtMostOne(method, methodMapping.value(), "value");
if (methodMapping.value().length > 0) {
String pathValue = emptyToNull(methodMapping.value()[0]);
if (pathValue != null) {
pathValue = resolve(pathValue);
// Append path from @RequestMapping if value is present on method
if (!pathValue.startsWith("/") && !data.template().path().endsWith("/")) {
pathValue = "/" + pathValue;
}
data.template().uri(pathValue, true);
if (data.template().decodeSlash() != decodeSlash) {
data.template().decodeSlash(decodeSlash);
}
}
}
//处理 @RequestMapping 注解里的属性
// produces
parseProduces(data, method, methodMapping);
// consumes
parseConsumes(data, method, methodMapping);
// headers
parseHeaders(data, method, methodMapping);
data.indexToExpander(new LinkedHashMap<>());
}
3、 参数上支持注解；
默认的参数注解处理器如下
private List<AnnotatedParameterProcessor> getDefaultAnnotatedArgumentsProcessors() {
List<AnnotatedParameterProcessor> annotatedArgumentResolvers = new ArrayList<>();
//MatrixVariable 注解
annotatedArgumentResolvers.add(new MatrixVariableParameterProcessor());
//PathVariable 注解
annotatedArgumentResolvers.add(new PathVariableParameterProcessor());
//RequestParam 注解
annotatedArgumentResolvers.add(new RequestParamParameterProcessor());
//RequestHeader 注解
annotatedArgumentResolvers.add(new RequestHeaderParameterProcessor());
//SpringQueryMap 注解
annotatedArgumentResolvers.add(new QueryMapParameterProcessor());
//RequestPart 注解
annotatedArgumentResolvers.add(new RequestPartParameterProcessor());
return annotatedArgumentResolvers;
}
@Override
protected boolean processAnnotationsOnParameter(MethodMetadata data, Annotation[] annotations, int paramIndex) {
boolean isHttpAnnotation = false;
AnnotatedParameterProcessor.AnnotatedParameterContext context = new SimpleAnnotatedParameterContext(data,
paramIndex);
Method method = processedMethods.get(data.configKey());
for (Annotation parameterAnnotation : annotations) {
//获取参数处理器 AnnotatedParameterProcessor
AnnotatedParameterProcessor processor = annotatedArgumentProcessors
.get(parameterAnnotation.annotationType());
if (processor != null) {
Annotation processParameterAnnotation;
// synthesize, handling @AliasFor, while falling back to parameter name on
// missing Stringvalue():
processParameterAnnotation = synthesizeWithMethodParameterNameAsFallbackValue(parameterAnnotation,
method, paramIndex);
//处理参数
isHttpAnnotation |= processor.processArgument(context, processParameterAnnotation, method);
}
}
if (!isMultipartFormData(data) && isHttpAnnotation && data.indexToExpander().get(paramIndex) == null) {
TypeDescriptor typeDescriptor = createTypeDescriptor(method, paramIndex);
if (conversionService.canConvert(typeDescriptor, STRING_TYPE_DESCRIPTOR)) {
Param.Expander expander = convertingExpanderFactory.getExpander(typeDescriptor);
if (expander != null) {
data.indexToExpander().put(paramIndex, expander);
}
}
}
return isHttpAnnotation;
}