我想知道如何检查RequestParams以查看它们是否为空，以便我可以转发到另一个html页面，现在我只是通过检查每个参数是否为空来解决这个问题。问题是我想转发到另一个页面，如果用户试图提交一个令人信服的空表单，如果他们这样做，我的程序将崩溃。它将崩溃，因为程序试图将int Price转换为字符串，即以空形式提交的字符串。我知道我可以让Int Price成为一个字符串，但我想知道是否还有另一个灵魂。

@Controller
public class HomeController {
    
    @Autowired
    private GlassesList glassesList;

    
    @GetMapping("/")
    public String goHome(Model model) {
        return "index";
    }
    
    @GetMapping("/addGlasses")
    public String addSunglasses(Model model) {
        return "addGlasses";
    }
    
    
    @GetMapping("/searchGlasses")
    public String searchSunglasses() {
        return "searchGlasses";
    }
    
    @GetMapping("/displayGlasses")
    public String displaySunglasses() {
        return "displayGlasses";
    }
    @PostMapping("/formPost")public String processForm (
            Model model,
            @RequestParam String productName,
            @RequestParam String brandName,
            @RequestParam String frameType,
            @RequestParam String color,
            @RequestParam String size,
            @RequestParam String lensType,
            @RequestParam int price
            ) {
if (productName.equals("") && brandName.equals("") && frameType.equals("") && color.equals("") && size.equals("") && lensType.equals("") && price == 0) {
            
            return "displayGlasses";
        }
        else {
        Glasses glasses = new Glasses(productName, brandName,frameType,
       color, size, lensType, price);
        glassesList.getGlassesList().add(glasses); 
        model.addAttribute("glassesList", glassesList);
        System.out.println(model.getAttribute(lensType));
        System.out.print(glassesList.getGlassesList());
        
        
        return "addGlasses";
        
        
        
    }
}

顺晟科技：

不必处理太多请求参数，您可以使用RequestBody并在该请求中发送这些参数，如下所示： 定义一个表示所有请求参数的类:

@Controller
public class HomeController {
    
    @Autowired
    private GlassesList glassesList;

    
    @GetMapping("/")
    public String goHome(Model model) {
        return "index";
    }
    
    @GetMapping("/addGlasses")
    public String addSunglasses(Model model) {
        return "addGlasses";
    }
    
    
    @GetMapping("/searchGlasses")
    public String searchSunglasses() {
        return "searchGlasses";
    }
    
    @GetMapping("/displayGlasses")
    public String displaySunglasses() {
        return "displayGlasses";
    }
    @PostMapping("/formPost")public String processForm (
            Model model,
            @RequestParam String productName,
            @RequestParam String brandName,
            @RequestParam String frameType,
            @RequestParam String color,
            @RequestParam String size,
            @RequestParam String lensType,
            @RequestParam int price
            ) {
if (productName.equals("") && brandName.equals("") && frameType.equals("") && color.equals("") && size.equals("") && lensType.equals("") && price == 0) {
            
            return "displayGlasses";
        }
        else {
        Glasses glasses = new Glasses(productName, brandName,frameType,
       color, size, lensType, price);
        glassesList.getGlassesList().add(glasses); 
        model.addAttribute("glassesList", glassesList);
        System.out.println(model.getAttribute(lensType));
        System.out.print(glassesList.getGlassesList());
        
        
        return "addGlasses";
        
        
        
    }
}

现在，在您的方法中使用它并绑定错误:

@Controller
public class HomeController {
    
    @Autowired
    private GlassesList glassesList;

    
    @GetMapping("/")
    public String goHome(Model model) {
        return "index";
    }
    
    @GetMapping("/addGlasses")
    public String addSunglasses(Model model) {
        return "addGlasses";
    }
    
    
    @GetMapping("/searchGlasses")
    public String searchSunglasses() {
        return "searchGlasses";
    }
    
    @GetMapping("/displayGlasses")
    public String displaySunglasses() {
        return "displayGlasses";
    }
    @PostMapping("/formPost")public String processForm (
            Model model,
            @RequestParam String productName,
            @RequestParam String brandName,
            @RequestParam String frameType,
            @RequestParam String color,
            @RequestParam String size,
            @RequestParam String lensType,
            @RequestParam int price
            ) {
if (productName.equals("") && brandName.equals("") && frameType.equals("") && color.equals("") && size.equals("") && lensType.equals("") && price == 0) {
            
            return "displayGlasses";
        }
        else {
        Glasses glasses = new Glasses(productName, brandName,frameType,
       color, size, lensType, price);
        glassesList.getGlassesList().add(glasses); 
        model.addAttribute("glassesList", glassesList);
        System.out.println(model.getAttribute(lensType));
        System.out.print(glassesList.getGlassesList());
        
        
        return "addGlasses";
        
        
        
    }
}

关于注释，请参阅此处：Bean验证中@Notnull、@Notempty和@Notblank约束的区别