springboot引數解析原理就是引數變數變成對應的固定值。

public class DispatcherServlet{

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {

mappedHandler = this.getHandler(processedRequest);

if (mappedHandler == null) {

this.noHandlerFound(processedRequest, response);

return;

}

//繼續向下

// Determine handler adapter for the current request.

HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

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;

}

//開始真正處理請求的方法

mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

if (asyncManager.isConcurrentHandlingStarted()) {

return;

}

this.applyDefaultViewName(processedRequest, mv);

mappedHandler.applyPostHandle(processedRequest, response, mv);

}

}。這就是HandlerAdapter的作用，在getHandler方法確定好控制器和對應的方法後（執行鏈），getHandlerAdapter就會來幫我們為當前的handler找一個adapter然後我們透過該介面卡，就能夠將請求的連結所帶的引數給適配上。