Java前台input如果什么都不输入的话，后台获取到的是空字符串，如何让让变成null呀？

Question

前台不输入，如何让后台获取到的是null？我想获取null

Answer 1

Use js to determine whether the value is empty before submitting. If it is empty, assign null

Answer 2

When submitting, wouldn’t it be enough to remove the name of the empty input?

Answer 3

When you pass the value from the front-end drop-down box to the back-end, if you don't select it, the attribute will be assigned a value of "". You can just judge this on the backend. Normally, the frontend will pass "" for processing

Answer 4

Why must it be null? The default is ""
if(x!=null && x!equals("")){

//daima

}

Answer 5

if(x.length>0){
    //TODO
}

Answer 6

It is recommended to use Google’s guava library which has the emptyToNull method under strings

Answer 7

Check if it is empty and assign null