How to check if @RequestParam is empty-CodePudding

I am wondering how I could check the RequestParams to see if they are empty so I could forward to another html page, right now I am just working around this by checking if each parameter is empty. The problem is I want to forward to another page if the user tries to submit a compeletly empty form and if they do that my program will crash. It will crash because the program tries to convert the int Price to a string becasue that is what is submitted in the empty form. I know I could just make the Int Price a String but I was wondering if there was another soultion.

@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";
        
        
        
    }
}

CodePudding user response：

Instead of handling too many request params, you can use RequestBody and send those params in that request like below: Define a class representing all your request-params:

public class AllParams{
       @NotNull
       @NotEmpty
       private String productName;
       @NotNull
       @NotEmpty
       private String brandName;
       @NotNull
       @NotEmpty 
       private String frameType;
       @NotNull
       @NotEmpty
       private String color;
       @NotNull
       @NotEmpty
       private String size; 
       @NotNull
       @NotEmpty
       private String lensType;
    
       @Min(1)
       private int price;
    
      //getters and setters
    }

Now, use this in your method and bind the errors:

 @PostMapping("/formPost")public String processForm (@Valid @RequestBody AllParams requestParam, BindingResult bindingResult,
            Model model){

     //check if there is any error[based on your annotations]
     if(bindingResult.hasErrors()) {
        return "displayGlasses";
       
     }

//otherwise, write your usual code here
  ....
...
}

About annotations, please refer here: Difference Between @NotNull, @NotEmpty, and @NotBlank Constraints in Bean Validation