【SpringMVC】DispatcherServlet重要组件之一HandlerAdapter

- 日理万妓 2022-02-26 10:33 192阅读 0赞

作用使用处理器干活的。共三个方法：

package org.springframework.web.servlet;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public interface HandlerAdapter {
    	
    	boolean supports(Object handler);
    	ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;
    
    	long getLastModified(HttpServletRequest request, Object handler);
    
    }

![20190329154847918.png][]

例子：

public class SimpleControllerHandlerAdapter implements HandlerAdapter {
    
    	public boolean supports(Object handler) {
    		return (handler instanceof Controller);
    	}
    
    	public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
    			throws Exception {
    
    		return ((Controller) handler).handleRequest(request, response);
    	}
    
    	public long getLastModified(HttpServletRequest request, Object handler) {
    		if (handler instanceof LastModified) {
    			return ((LastModified) handler).getLastModified(request);
    		}
    		return -1L;
    	}
    
    }

getHandlerAdapter方法也是按顺序遍历：

protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
    		for (HandlerMapping hm : this.handlerMappings) {
    			if (logger.isTraceEnabled()) {
    				logger.trace(
    						"Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
    			}
    			HandlerExecutionChain handler = hm.getHandler(request);
    			if (handler != null) {
    				return handler;
    			}
    		}
    		return null;
    	}

[20190329154847918.png]: /images/20220226/838cf750b9a048f793fb686cb0cebe36.png