How to Validate Request Data in Gin

Use the binding package to automatically validate request data against a struct by defining validation tags on your fields. Define a struct with tags like required, min, or email, then pass it to c.ShouldBindJSON() to trigger validation and return errors if the data is invalid.

type LoginRequest struct {
    Email    string `json:"email" binding:"required,email"`
    Password string `json:"password" binding:"required,min=6"`
}

func loginHandler(c *gin.Context) {
    var req LoginRequest
    if err := c.ShouldBindJSON(&req); err != nil {
        c.JSON(400, gin.H{"error": err.Error()})
        return
    }
    // Process valid request
}

Validation ensures the data sent to your server matches the rules you expect, like checking if an email is real or a password is long enough. It works like a bouncer at a club checking IDs; if the data doesn't meet the requirements, the server rejects it immediately before processing. This prevents your application from crashing or behaving unexpectedly due to bad input.