楔子

使用ssm，HandlerInterceptorAdapter 時，獲取執行的方法，出現如下錯誤

java.lang.ClassCastException: org.springframework.web.servlet.resource.DefaultServletHttpRequestHandler cannot be cast to org.springframework.web.method.HandlerMethod
    at cn.zhuzi.kindle.interceptor.PrivilegeInterceptorAdapter.preHandle(PrivilegeInterceptorAdapter.java
 
:38)
    at org.springframework.web.servlet.HandlerExecutionChain.applyPreHandle(HandlerExecutionChain.java:133)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:962)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901
 
)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)

出錯事例

public class PrivilegeInterceptorAdapter extends HandlerInterceptorAdapter {
    @Resource
    JdbcTemplate jdbcTemplate;


    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object preHandle) throws
 
 Exception {

        System.out.println(request.getRequestURI());
        /* if (preHandle instanceof HandlerMethod) { */
        //此處出現上述錯誤。使用了
        HandlerMethod method = (HandlerMethod) preHandle;
        Prev pre = method.getMethod().getAnnotation(Prev.class);
        if (pre == null) {
            return true;
        } else {
            String oprator = pre.oprator();
            String decription = pre.decription();
            System.out.println("操作許可權-->" + decription);

            // TODO模擬 從session獲取許可權
            @SuppressWarnings("unchecked")
            List<String> privilegeList = (List<String>) request.getSession().getAttribute("privilege");

            if (privilegeList.contains(oprator)) {
                return true;
            } else {
                if (request.getHeader("X-Requested-With") != null && request.getHeader("X-Requested-With").equalsIgnoreCase("XMLHttpRequest")) {// 是ajax請求
                    response.setCharacterEncoding("text/html;charset=UTF-8");
                    response.setContentType("text/html;charset=UTF-8");
                    PrintWriter writer = response.getWriter();
                    StringBuffer jsonTip = new StringBuffer("{\"result\":");
                    jsonTip.append(false).append(",\"tip\":\"您無權操作\"}");
                    writer.print(jsonTip.toString());
                    return false;
                } else {// 非ajax請求
                    String content = request.getSession().getServletContext().getContextPath();
                    // response.sendRedirect(content +
                    // "/refuse.html");//轉發到頁面
                    response.setContentType("text/html;charset=utf-8");
                    response.getWriter().write("您無權操作");
                    return false;
                }
            }

        }
    }

-- 使用   System.out.println(request.getRequestURI()); 列印請求地址時 
發現，只有在請求資源找不到的情況下才會出現上述轉換錯誤。

解決
1 加上  if (preHandle instanceof HandlerMethod) { 做判斷
2 不處理，因為請求的資源不存在