java - Spring boot如何实现错误页面

Question

我正在尝试制作一个 Spring 应用程序，如果客户尝试购买没有库存的产品，该应用程序会出现错误页面。我收到一条错误消息:HTTP Status 500 - 请求处理失败；每当我尝试测试它时，嵌套异常都是 java.lang.NullPointerException 。我尝试了很多方法，我觉得我已经很接近了。

请参阅下面的 Controller ，错误类只有 getter 和 setter 等

任何帮助将不胜感激!!!

package com.sales.controllers;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import javax.validation.Valid;

import org.apache.taglibs.standard.lang.jstl.LessThanOperator;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

import com.sales.exceptions.ErrorController;
import com.sales.models.Customer;
import com.sales.models.Order;
import com.sales.models.Product;
import com.sales.services.CustomerService;
import com.sales.services.OrderService;
import com.sales.services.ProductService;

@Controller                             //implementing the error class here
public class OrderController implements org.springframework.boot.autoconfigure.web.ErrorController {

    @Autowired
    ProductService ps;

    @Autowired
    CustomerService cs;

    @Autowired
    OrderService os;

    private Product prod;
    private Customer cust;

    ErrorController ec;



    @RequestMapping(value = "/showOrders.html")
    public String listOrders(Model model) {

        ArrayList<Order> orders = os.findAll();
        model.addAttribute("allOrders", orders);

        ArrayList<Customer> cust = cs.findAll();
        model.addAttribute("ordrs", cust);
        return "allOrders";
    }

    @RequestMapping(value = "/newOrder.html", method = RequestMethod.GET)
    public String addPerson(Model model) {
        ArrayList<Customer> customer = cs.findAll();
        ArrayList<Product> product = ps.findAll();

        Map<Long, String> customers = new LinkedHashMap<Long, String>();
        for (Customer c : customer) {
            customers.put(c.getcId(), c.getcName());

            model.addAttribute("customers", customers);

            Map<Long, String> products = new LinkedHashMap<Long, String>();
            for (Product p : product) {
                products.put(p.getpId(), p.getpDesc());

                model.addAttribute("products", products);
            }

        }
        Order o = new Order();

        model.addAttribute("orderList", o);

        return "addOrder";

    }

    @RequestMapping(value = "/newOrder.html", method = RequestMethod.POST)
    public String addOrderPost(@Valid @ModelAttribute("orderList") Order o, BindingResult result) {

        boolean qty = false;

        System.out.println("In order add");

        if (result.hasErrors()) {
            return "addOrder";
        }

        prod = ps.findOne(o.getProd().getpId());
        cust = cs.findOne(o.getCust().getcId());

        o.setProd(prod);
        prod.setQtyInStock(prod.getQtyInStock() - (o.getQty()));

        //if this happens the user should be redireccted with the following headings and error
        if (prod.getQtyInStock() < (o.getQty())) {
            ec.setHeader("Error creating the following order");
            ec.setError("Quantity to large: " + "Product stock" + prod.getQtyInStock());

            return "redirect:errorPage";
        }

        os.save(o);

        return "redirect:showOrders.html";

    }

    // Object that holds info related to the errors

        private static final String PATH = "/error";

        // adds ec object to the model and user is moved to the errorPage and error is
        // displayed
        @RequestMapping(value = PATH)
        public String errorPage(Model model) {

            System.out.println(ec.getHeader());
            System.out.println(ec.getError());

            model.addAttribute("exception", ec);

            return "errorPage";
        }
        @Override
        public String getErrorPath() {
            return PATH;
        }

}

错误页面(JSP)

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
 <h1>${exception.header}</h1>
  <h2>${exception.error}</h2>
</body>
</html>

Answer 1

您需要处理您的异常类型的异常处理程序或处理任何类型异常的异常处理程序。

我个人更喜欢全局应用程序异常处理程序。它们是在 @ControllerAdvice 注释的帮助下创建的:

@ControllerAdvice
public class ResponseExceptionHandler {

    @ExceptionHandler(Exception.class)
    public ModelAndView handleAnyException(HttpServletRequest request, Exception e) {

        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("your-error-page");

        return modelAndView;
    }
}

这个异常处理程序将处理应用程序中任何类型的异常，因为它处理 -> @ExceptionHandler(Exception.class) -> Exception.class。

如果您需要处理特定异常并提供不同的页面，则需要将特定异常类放入@ControllerAdvice。

示例:

    @ExceptionHandler(CustomException.class)
    public ModelAndView handleAnyException(HttpServletRequest request, CustomException e) {

        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("your-custom-page");

        return modelAndView;
    }

关于异常处理的好文章:https://www.baeldung.com/exception-handling-for-rest-with-spring