springboot-请求处理源码分析(二) 解析request参数

WebRequest、ServletRequest、MultipartRequest、 HttpSession、javax.servlet.http.PushBuilder、Principal、InputStream、Reader、HttpMethod、Locale、TimeZone、ZoneId

ServletRequestMethodArgumentResolver 以上的部分参数

传入Servlet api以及内部原理

//真正执行的目标方法
lnvocableHandlerMethod.java
//核心方法
--->getMethodArgumentValues();方法
    --->
        //核心代码片段(判断那个解析器，能解析当前参数HttpServletRequest)
1       //Dbug调试代码
        if(!this.resoulvers.supportsParameter(parameter)){
	    throw new IllegalStateException(formatArgumentError(parameter,"No suitable resolver"))
	    }
//【Dbug调试1】
//进入源码看那个解析器能够解析当前参数HttpServletRequest
@Nullable
private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {
    HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);
    if (result == null) {
        //遍历26个参数解析器，按个确定
        for (HandlerMethodArgumentResolver resolver : this.argumentResolvers) {
            //判断当前26个参数解析器，谁支持当前参数的解析，
2           //Dbug调试
            if (resolver.supportsParameter(parameter)) {
                result = resolver;
                //缓存
                //原理就是：将当前的参数同26个参数解析器进行循环对比，直到找到匹配的那个
                //然后在缓存，这样下次直接在缓存中获取，效率会提高
                this.argumentResolverCache.put(parameter, result);
                break;
            }
        }
    }
    return result;
//【Dbug调试2】
@Override
	public boolean supportsParameter(MethodParameter parameter) {
        //获取当前参数类型，判断
		Class paramType = parameter.getParameterType();
		return (WebRequest.class.isAssignableFrom(paramType) ||
                //判断是否为ServletRequest，我们的参数HttpServletRequest就是ServletRequest
                //所以判断成功
				ServletRequest.class.isAssignableFrom(paramType) ||
				MultipartRequest.class.isAssignableFrom(paramType) ||
				HttpSession.class.isAssignableFrom(paramType) ||
				(pushBuilder != null && pushBuilder.isAssignableFrom(paramType)) ||
				Principal.class.isAssignableFrom(paramType) ||
				InputStream.class.isAssignableFrom(paramType) ||
				Reader.class.isAssignableFrom(paramType) ||
				HttpMethod.class == paramType ||
				Locale.class == paramType ||
				TimeZone.class == paramType ||
				ZoneId.class == paramType);
	}
//--------------------------------------------------------------
//--->第二段核心代码片段    查看是如何解析的（刚刚我们获取到了能解析request参数的解析器，现在要准备开始解析了）
@Override
@Nullable
public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
                                        NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
    HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter);
    if (resolver == null) {
        throw new IllegalArgumentException("Unsupported parameter type [" +
        parameter.getParameterType().getName() + "]. supportsParameter should be called first.");
    }
    //Dug调试
    return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory);
}
//-----------------------------------------------------
//resolveArgument()方法源码分析
@Override
public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
			      NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
    Class paramType = parameter.getParameterType();
    // WebRequest / NativeWebRequest / ServletWebRequest
    //判断当前类型是不是webRequest
    if (WebRequest.class.isAssignableFrom(paramType)) {
        if (!paramType.isInstance(webRequest)) {
            throw new IllegalStateException(
            "Current request is not of type [" + paramType.getName() + "]: " + webRequest);
        }
        return webRequest;
    }
    // ServletRequest / HttpServletRequest / MultipartRequest / MultipartHttpServletRequest
    //判断当前类型是不是ServletRequest
    if (ServletRequest.class.isAssignableFrom(paramType) || MultipartRequest.class.isAssignableFrom(paramType)) {
        //进入源码查看
        return resolveNativeRequest(webRequest, paramType);
    }
    // HttpServletRequest required for all further argument types
    return resolveArgument(paramType, resolveNativeRequest(webRequest, HttpServletRequest.class));
}
//-----------------------------------------------------------------
//resolveNativeRequest源码查看
private  T resolveNativeRequest(NativeWebRequest webRequest, Class requiredType) {
    //获取当前request
    T nativeRequest = webRequest.getNativeRequest(requiredType);
    if (nativeRequest == null) {
        throw new IllegalStateException(
	    "Current request is not of type [" + requiredType.getName() + "]: " + webRequest);
	}
        //把原生的request请求返回即可
        return nativeRequest;
}