根据@RequestMapping原理实现自定义注解
基于最近的一个需求：客户端与服务端通过socket连接，在socket通道里传输信息，在信息里定义一个type区分客户端的请求类型，根据这个类型找到对应的业务处理逻辑。这不就是根据url解析对应路径找到Controller吗！于是直接开始撸@RequestMapping源码。
@RequestMapping源码分析
直接看到 AbstractHandlerMethodMapping中afterPropertiesSet()
/**
* 在初始化时检测处理程序方法
* @see #initHandlerMethods
*/
@Override
public void afterPropertiesSet() {
initHandlerMethods();
}
/**
* 在ApplicationContext中扫描bean，检测并注册处理程序方法
* SCOPED_TARGET_NAME_PREFIX表示域代理bean的前缀
* @see #getCandidateBeanNames()
* @see #processCandidateBean
* @see #handlerMethodsInitialized
*/
protected void initHandlerMethods() {
for (String beanName : getCandidateBeanNames()) {
if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
processCandidateBean(beanName);
}
}
handlerMethodsInitialized(getHandlerMethods());
}在properties属性加载好之后就会初始化程序处理方法initHandlerMethods()，getCandidateBeanNames() 获取上下文中beanName，processCandidateBean(beanName)只处理不是域代理bean的bean，然后我们看看processCandidateBean()
protected void processCandidateBean(String beanName) {
Class beanType = null;
try {
beanType = obtainApplicationContext().getType(beanName);
}
catch (Throwable ex) {
// An unresolvable bean type, probably from a lazy bean - let's ignore it.
if (logger.isTraceEnabled()) {
logger.trace("Could not resolve type for bean '" + beanName + "'", ex);
}
}
// beanType != null 表示确定具有给定名称bean的类型
// isHandler(beanType)表示是否被@Controller和@RequestMapping标注
if (beanType != null && isHandler(beanType)) {
detectHandlerMethods(beanName);
}
}
/**
* org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping#isHandler
* 提供实现
*/
@Override
protected boolean isHandler(Class beanType) {
return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
}然后再看看detectHandlerMethods() 就是在指定的bean里面查找当前对应的method
/**
* 在指定的处理程序bean中查找处理程序方法
* @param handler either a bean name or an actual handler instance
* @see #getMappingForMethod
*/
protected void detectHandlerMethods(Object handler) {
//找出当前的类型，为了兼容可以传入beanName再在ApplicationContext里查找初对应的类型
Class handlerType = (handler instanceof String ?
obtainApplicationContext().getType((String) handler) : handler.getClass());
if (handlerType != null) {
//返回给定类的用户定义类：通常只是给定的类，但对于CGLIB生成的子类，则返回原始类
Class userType = ClassUtils.getUserClass(handlerType);
//根据相关联的元数据查找选择给定目标类型上的方法
Map methods = MethodIntrospector.selectMethods(userType,
(MethodIntrospector.MetadataLookup) method -> {
try {
return getMappingForMethod(method, userType);
}
catch (Throwable ex) {
throw new IllegalStateException("Invalid mapping on handler class [" +
userType.getName() + "]: " + method, ex);
}
});
if (logger.isTraceEnabled()) {
logger.trace(formatMappings(userType, methods));
}
//将当前得到信息便利存放到Map中，key是RequestMappingInfo，value包装成HandlerMethod
methods.forEach((method, mapping) -> {
Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
registerHandlerMethod(handler, invocableMethod, mapping);
});
}
} /**
* 使用方法和类型级别的@ {@ link RequestMapping}注解 RequestMappingInfo
* @return the created RequestMappingInfo, or {@code null} if the method
* does not have a {@code @RequestMapping} annotation.
* @see #getCustomMethodCondition(Method)
* @see #getCustomTypeCondition(Class)
*/
@Override
@Nullable
protected RequestMappingInfo getMappingForMethod(Method method, Class handlerType) {
//根据method创建RequestMappingInfo->包含路径信息，参数信息等
RequestMappingInfo info = createRequestMappingInfo(method);
if (info != null) {
//根据类型创建根据method创建RequestMappingInfo
RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
if (typeInfo != null) {
//将类和method的RequestMappingInfo整合
info = typeInfo.combine(info);
}
//解析类的路径信息
String prefix = getPathPrefix(handlerType);
if (prefix != null) {
info = RequestMappingInfo.paths(prefix).options(this.config).build().combine(info);
}
}
return info;
}@Nullable
private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) {
RequestMapping requestMapping = AnnotatedElementUtils.findMergedAnnotation(element, RequestMapping.class);
RequestCondition condition = (element instanceof Class ?
getCustomTypeCondition((Class) element) : getCustomMethodCondition((Method) element));
return (requestMapping != null ? createRequestMappingInfo(requestMapping, condition) : null);
}
protected RequestMappingInfo createRequestMappingInfo(
RequestMapping requestMapping, @Nullable RequestCondition customCondition) {
RequestMappingInfo.Builder builder = RequestMappingInfo
.paths(resolveEmbeddedValuesInPatterns(requestMapping.path()))
.methods(requestMapping.method())
.params(requestMapping.params())
.headers(requestMapping.headers())
.consumes(requestMapping.consumes())
.produces(requestMapping.produces())
.mappingName(requestMapping.name());
if (customCondition != null) {
builder.customCondition(customCondition);
}
return builder.options(this.config).build();
}再回到initHandlerMethods()中的handlerMethodsInitialized()，这个方法就是获取Map中的HandlerMethod数量并打印出来。到这里我们再来缕一缕流程：
- 获取ApplicationContext中所有被@Controller或@RequestMapping标识的bean
- 遍历bean中的method，获取bean和method的RequestMappingInfo，将两个RequestMappingInfo整合，
- 将得到RequestMappingInfo和对应的HandlerMethod存入Map中
- 得到了对应的可执行method，那么什么时候调用呢，接下来看看下面的org.springframework.web.servlet.DispatcherServlet#doDispatch 当请求过来了做的分发
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try {
ModelAndView mv = null;
Exception dispatchException = null;
try {
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
// Determine handler for the current request.
//重点看这个方法，层层递进找怎么获取到handler的，就会看到下面的方法
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
// Process last-modified header, if supported by the handler.
String method = request.getMethod();
boolean isGet = "GET".equals(method);
if (isGet || "HEAD".equals(method)) {
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
// Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
applyDefaultViewName(processedRequest, mv);
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch (Exception ex) {
dispatchException = ex;
}
catch (Throwable err) {
// As of 4.3, we're processing Errors thrown from handler methods as well,
// making them available for @ExceptionHandler methods and other scenarios.
dispatchException = new NestedServletException("Handler dispatch failed", err);
}
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception ex) {
triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
}
catch (Throwable err) {
triggerAfterCompletion(processedRequest, response, mappedHandler,
new NestedServletException("Handler processing failed", err));
}
finally {
if (asyncManager.isConcurrentHandlingStarted()) {
// Instead of postHandle and afterCompletion
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
}
else {
// Clean up any resources used by a multipart request.
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
}org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#lookupHandlerMethod
protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
List matches = new ArrayList<>();
//当前这个this.mappingRegistry就是我们之前把信息存进去的Map
List directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
if (directPathMatches != null) {
addMatchingMappings(directPathMatches, matches, request);
}
if (matches.isEmpty()) {
// No choice but to go through all mappings...
addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
}
if (!matches.isEmpty()) {
Match bestMatch = matches.get(0);
if (matches.size() > 1) {
Comparator comparator = new MatchComparator(getMappingComparator(request));
matches.sort(comparator);
bestMatch = matches.get(0);
if (logger.isTraceEnabled()) {
logger.trace(matches.size() + " matching mappings: " + matches);
}
if (CorsUtils.isPreFlightRequest(request)) {
return PREFLIGHT_AMBIGUOUS_MATCH;
}
Match secondBestMatch = matches.get(1);
if (comparator.compare(bestMatch, secondBestMatch) == 0) {
Method m1 = bestMatch.handlerMethod.getMethod();
Method m2 = secondBestMatch.handlerMethod.getMethod();
String uri = request.getRequestURI();
throw new IllegalStateException(
"Ambiguous handler methods mapped for '" + uri + "': {" + m1 + ", " + m2 + "}");
}
}
request.setAttribute(BEST_MATCHING_HANDLER_ATTRIBUTE, bestMatch.handlerMethod);
handleMatch(bestMatch.mapping, lookupPath, request);
return bestMatch.handlerMethod;
}
else {
return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
}
} 到这里源码就全部阅读完了
尝试实现@SocketMapping
直接上代码
package com.cmge.handler;
import com.alibaba.fastjson.JSONObject;
import com.cmge.annotation.SocketMapping;
import com.cmge.controller.BaseController;
import com.cmge.info.SocketMappingInfo;
import lombok.extern.slf4j.Slf4j;
import org.springframework.aop.support.AopUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.core.MethodIntrospector;
import org.springframework.core.annotation.AnnotatedElementUtils;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Component;
import org.springframework.util.ClassUtils;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.LinkedHashMap;
import java.util.Map;
/**
* @author jasongaoj
* @version 1.0.0
* @Description 请求业务处理类
* @createTime 2020年11月26日 17:49:00
*/
@Slf4j
@Component
public class RequestMappingHandler {
private final Map mappingLookup = new LinkedHashMap<>();
@Autowired
private ApplicationContext applicationContext;
/**
* 解析消息，分发请求
* @param msg
* @return
*/
public String doDispatchMessage(String msg) throws InvocationTargetException, IllegalAccessException {
JSONObject msgJSON=JSONObject.parseObject(msg);
String mapping=msgJSON.getString("type");
SocketMappingInfo socketMappingInfo=mappingLookup.get(mapping);
if(socketMappingInfo!=null){
return (String) socketMappingInfo.getMethod().invoke(applicationContext.getBean(socketMappingInfo.getBeanName()),msg);
}
return null;
}
public boolean parseParam(JSONObject jsonObject){
String mapping=jsonObject.getString("type");
if(mapping.equals("SYS")){
log.trace("过滤网关心跳检测。。。");
}
return true;
}
/**
* 注册所有的mapping
*/
public void registerSocketHandlerMapping(){
String[] beanNames=applicationContext.getBeanNamesForType(BaseController.class);
for (String beanName:beanNames) {
processCandidateBean(beanName);
}
}
/**
* 确定指定候选bean的类型并调用
* @param beanName
*/
private void processCandidateBean(String beanName){
Class beanType = null;
try {
beanType = applicationContext.getType(beanName);
} catch (Throwable ex) {
// An unresolvable bean type, probably from a lazy bean - let's ignore it.
log.trace("Could not resolve type for bean '" + beanName + "'", ex);
}
//如果当前bean存在实例，则检测当前可执行的method
if (beanType != null ) {
detectHandlerMethods(beanType,beanName);
}
}
/**
* 获取当前mapping对应的method，将解析的method注册到mappingLookup
* （key,value）->（@SocketMapping.value(),invokeMethod()）
* @param beanType
* @param beanName
*/
private void detectHandlerMethods(Class beanType,String beanName){
Class userType = ClassUtils.getUserClass(beanType);
Map methods = MethodIntrospector.selectMethods(userType,
(MethodIntrospector.MetadataLookup) method -> {
try {
return createRequestMappingInfo(method);
}
catch (Throwable ex) {
throw new IllegalStateException("Invalid mapping on handler class [" +
userType.getName() + "]: " + method, ex);
}
});
methods.forEach(((method, socketMappingInfo) -> {
Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
socketMappingInfo.setMethod(invocableMethod);
socketMappingInfo.setBeanName(beanName);
mappingLookup.put(socketMappingInfo.getName(),socketMappingInfo);
}));
}
/**
* 创建mapping信息
* @param element
* @return
*/
@Nullable
private SocketMappingInfo createRequestMappingInfo(AnnotatedElement element) {
SocketMapping socketMapping = AnnotatedElementUtils.findMergedAnnotation(element, SocketMapping.class);
SocketMappingInfo socketMappingInfo=SocketMappingInfo.builder()
.name(socketMapping.value())
.build();
return socketMappingInfo;
}
}
package com.cmge.annotation;
import org.springframework.stereotype.Component;
import java.lang.annotation.*;
/**
* @author jasongaoj
* @version 1.0.0
* @Description socket消息中的type实现请求分发
* @createTime 2020年11月27日 10:03:00
*/
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface SocketMapping {
String value() default "";
}
package com.cmge.info;
import lombok.*;
import java.lang.reflect.Method;
/**
* @author jasongaoj
* @version 1.0.0
* @Description SocketMapping信息
* @createTime 2020年11月27日 11:20:00
*/
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
public class SocketMappingInfo {
private String name;
private Method method;
private String beanName;
}
我这里简单实现了根据type查找对应method，@SocketMapping很多地方有待优化。后续可能继续扩展将注解添加到类上、路径解析等功能，希望对大家有所帮助。