Java 报了个空指针，请大神看看问题何在？
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2022-04-16 14:48:05
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<a href="javascript:void(0);" onclick="clearCart()" id="clear" class="clear">清空购物车</a>
//cart.jsp页面上点击清空购物车事件
function clearCart(){
if(confirm("您是否要清空购物车？")){
location.href="${pageContext.request.contextPath }/product?method=clearCart";
}
}
public void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {
req.setCharacterEncoding("UTF-8"); try { //1.获得请求对象的method的名称
String methodName = req.getParameter("methodName"); //2.获得当前被访问的对象的字节码对象
Class clazz = this.getClass();//ProductServlet.class 或者
//3.获得当前字节码对象中的指定方法
Method method = clazz.getMethod(methodName, HttpServletRequest.class,HttpServletResponse.class); //4执行相应功能方法
method.invoke(this, req,resp);
} catch (Exception e) {
e.printStackTrace();
}
}
//清空购物车方法
public void clearCart(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
session.removeAttribute("cart"); //跳转回cart.jsp
response.sendRedirect(request.getContextPath()+"/cart.jsp");
}
我点击清空就报异常了
java.lang.NullPointerException
at java.lang.Class.searchMethods(Class.java:2832)
at java.lang.Class.getMethod0(Class.java:2856)
at java.lang.Class.getMethod(Class.java:1668)
at com.itheima.web.servlet.BaseServlet.service(BaseServlet.java:25)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:315)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
<a href="javascript:void(0);" onclick="clearCart()" id="clear" class="clear">清空购物车</a>
//cart.jsp页面上点击清空购物车事件
function clearCart(){
if(confirm("您是否要清空购物车？")){
location.href="${pageContext.request.contextPath }/product?method=clearCart";
}
}
public void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {
req.setCharacterEncoding("UTF-8"); try { //1.获得请求对象的method的名称
String methodName = req.getParameter("methodName"); //2.获得当前被访问的对象的字节码对象
Class clazz = this.getClass();//ProductServlet.class 或者
//3.获得当前字节码对象中的指定方法
Method method = clazz.getMethod(methodName, HttpServletRequest.class,HttpServletResponse.class); //4执行相应功能方法
method.invoke(this, req,resp);
} catch (Exception e) {
e.printStackTrace();
}
}
//清空购物车方法
public void clearCart(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
session.removeAttribute("cart"); //跳转回cart.jsp
response.sendRedirect(request.getContextPath()+"/cart.jsp");
}
我点击清空就报异常了
java.lang.NullPointerException
at java.lang.Class.searchMethods(Class.java:2832)
at java.lang.Class.getMethod0(Class.java:2856)
at java.lang.Class.getMethod(Class.java:1668)
at com.itheima.web.servlet.BaseServlet.service(BaseServlet.java:25)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:315)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
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