Form repeated submission problem

There are several situations in which forms are submitted repeatedly ：

1. The user repeatedly clicks the submit button （ Asynchronous requests ）
2. The network is not good , Cause the user to think that there is no click , So I clicked submit repeatedly （ Synchronization request , Forwarding causes ）
3. Users submit forms , Forward to another page , Then click refresh to cause repeated submission （ Synchronization request , Forwarding causes ）
4. Users submit forms , Forward to another page , Then click the browser to return to the previous step , Then continue to submit the form （ Synchronization request , Forwarding causes ）

Solution ：

Synchronization request ：
1、JSP The page generates a random value , As the only form id, Place this unique value in Session in , Make a hidden field in the form to store the value , When you submit the form , Submit the form data and the unique value to the background , And then get it in the background session Unique value saved in , Will be backstage session Value and the unique value passed from the front-end form ：

• Front end unique value id == Background unique value id Express ： First form submission , Then put the backstage session Value delete , Forward to a page .
• Front end unique value id != Background unique value id Express ： Resubmitted forms , You can redirect to a page .

Asynchronous requests ：
1、 General idea ： Generate a random value at the front end , Then pass it to the backstage , The background to use Aop To intercept , Take random values as key, Request data as value, Store in redis in , And set expiration time .aop Interception can be used to customize an annotation , load controller On the way . When the user clicks the submit button repeatedly , Methods marked with custom annotations will be intercepted , Get into aop Interception method , Judge in the surround notification , Whether in redis There is the key, If there is a duplicate submission, return or return the original data , If it does not exist, set it in , And set expiration time , The expiration time is controllable , In the user-defined annotation, you can use a user-defined method to obtain the expiration time .
2、 After sending the request , Use js Hide button , Or set the countdown button to click .

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