I am trying to add validation for the go based web application based on GIN framework. On the web page I am selecting a file and submitting and the server is processing it. On the server side I am try to add validation to check if the file has been given or not. If not then redirect back to original page.
func panic(err error) {
if err != nil {
log.Println(err)
}
}
func displayTable (c *gin.Context) {
file, _ , err := c.Request.FormFile("file")
panic(err)
if file == nil {
log.Println("File is nil.")
log.Println(err)
log.Println("*****")
c.HTML(http.StatusInternalServerError, "index.tmpl", gin.H{
"title": "Select the input file","error" : "Please select the input file.",
})
} else {
defer file.Close()
}
filename := strconv.FormatInt(time.Now().Unix(),10)
out, err := os.Create("./tmp/"+filename+".xml")
panic(err)
defer out.Close()
_, err = io.Copy(out, file)
panic(err)
xmlFile, err := os.Open("./tmp/"+filename+".xml")
panic(err)
defer xmlFile.Close()
// Other Implementation Details
}
Even after providing the handling I am getting a panic in the go code. Please let me know what in the implementation am I missing.
Thanks.
http: no such file
File is nil.
http: no such file
*****
2015/08/04 13:19:10 Panic recovery -> runtime error: invalid memory address or nil pointer dereference
c:/go/src/runtime/panic.go:387 (0x414d36)
c:/go/src/runtime/panic.go:42 (0x4142a5)
c:/go/src/runtime/os_windows.go:42 (0x414066)
c:/go/src/io/io.go:362 (0x45268f)
D:/code/src/exmp/serverexmaple.go:45 (0x40168f)
displayTable: _, err = io.Copy(out, file)
D:/code/src/github.com/gin-gonic/gin/context.go:95 (0x49f8ea)
(*Context).Next: c.handlers[c.index](c)
D:/code/src/github.com/gin-gonic/gin/logger.go:56 (0x4ac490)
func.007: c.Next()
D:/code/src/github.com/gin-gonic/gin/context.go:95 (0x49f8ea)
(*Context).Next: c.handlers[c.index](c)
D:/code/src/github.com/gin-gonic/gin/recovery.go:43 (0x4acc80)
func.009: c.Next()
D:/code/src/github.com/gin-gonic/gin/context.go:95 (0x49f8ea)
(*Context).Next: c.handlers[c.index](c)
D:/code/src/github.com/gin-gonic/gin/gin.go:292 (0x4a46d5)
(*Engine).handleHTTPRequest: context.Next()
D:/code/src/github.com/gin-gonic/gin/gin.go:273 (0x4a4459)
(*Engine).ServeHTTP: engine.handleHTTPRequest(c)
c:/go/src/net/http/server.go:1703 (0x468415)
c:/go/src/net/http/server.go:1204 (0x466408)
c:/go/src/runtime/asm_386.s:2287 (0x438ea1)
I understand that I have made mistake with the panic handling. The validation is working if I add the return statement after the c.HTML. This will stop the function from executing the rest of the code. Thanks to @AlexAtNet for his advice and I will keep in mind in future.
if file == nil {
log.Println("File is nil.")
log.Println(err)
log.Println("*****")
c.HTML(http.StatusInternalServerError, "index.tmpl", gin.H{
"title": "Select the input file","error" : "Please select the input file.",
})
return
}
panic. It will confuse everyone who knows how panic works.FormFile returns interface so you have to cast it to underlying structure if you want to check it with nil OR use the second parameter, type of which is available.