SSM报错java.lang.NullPointerException

 今天在运行SSM项目时，报了这个错误。

错误信息：

DEBUG .web.servlet.DispatcherServlet  - Could not complete request
java.lang.NullPointerException
	at com.itheima.ssm.controller.OrdersController.findAll(OrdersController.java:28)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:567)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:871)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:777)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:978)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:870)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:855)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)

Controller部分原代码:

@Controller
@RequestMapping("/orders")
public class OrdersController {

    private IOrdersService ordersService;

    @RequestMapping("/findAll")
    public ModelAndView findAll() throws Exception{
        ModelAndView mv = new ModelAndView();
        List<Orders> ordersList = ordersService.findAll();
        mv.addObject("ordersList",ordersList);
        mv.setViewName("orders-list");
        return mv;
    }
}

发现忘了加注解@Autowried了。下面是修改后的代码：

@Controller
@RequestMapping("/orders")
public class OrdersController {

    @Autowired
    private IOrdersService ordersService;

    @RequestMapping("/findAll")
    public ModelAndView findAll() throws Exception{
        ModelAndView mv = new ModelAndView();
        List<Orders> ordersList = ordersService.findAll();
        mv.addObject("ordersList",ordersList);
        mv.setViewName("orders-list");
        return mv;
    }
}

添加上注解@Autowried后错误就没有了。

总结：记得加注解@Autowried。