How to optimize a large number of if else [email protected] Detailed explanation of valib

1、 Business scenario

@RequestMapping("/insert")
    public String insert(Student student){
        if(Objects.equals(student.getName(),"")){
            return " Name cannot be empty ";
        }
        if(null == student.getAge()){
            return " Age cannot be empty ";
        }
        return "success";
    }

Copy

As shown in the figure , When the current end accesses the interface , Now it is required that the parameter cannot be empty , Then we can only write two if Judge whether it is null. if name When the access is empty , It will return as shown in the figure

At present, there are only two fields , What if there are a lot of fields to judge , Write a lot of if？ When there is too much invalid business code in an interface , Design is problematic , And as a good programmer , This is not what we want to see .

How to solve it ？ The answer is @Valid annotation

You can see from the code , First received bean Objects need to use @valid Verify the annotation , After that, we need to pay attention to ,bean Inside

The number type is @NotNull annotation , String type uses @NotBlank annotation , The set type is @NotEmpty Judge whether it exists . They judge the length of the annotation is also different , Namely @Length,@Range,@Size.

Be careful ： When this is done , At the moment 【 It's not 】 Return to the front end and prompt what field is empty , You also need to add BindingResult Parameters , Receive abnormal data , Return an empty field to the front end .