Golang Chromedp: pdf file download without saving in server

Question

Golang Chromedp: pdf file download without saving in server

616 Views Asked by Shakhawat Hossain At 03 February 2023 at 17:35

How to chromedp pdf download without saving in server? Below code is working for generating pdf file and saving in server side. But I want to download pdf file without saving in server side.

func PDFInvoice(c *gin.Context) {
session := sessions.Default(c)
id := c.Params.ByName("id")
token := session.Get("login_session").(string)

// create context
ctx, cancel := chromedp.NewContext(context.Background())
defer cancel()

// capture pdf
var buf []byte
url := "http://localhost:8080/invoice/" + id + "/" + token
if err := chromedp.Run(ctx, printToPDF(url, &buf)); err != nil {

    log.Fatal(err)
}
buff := new(bytes.Buffer)
if _, err := buff.WriteTo(c.Writer); err != nil {
    panic(err)
}

 if err := os.WriteFile("sample.pdf", buf, 0o644); err != nil {
    log.Fatal(err)
 }

//ioutil.WriteFile("sample.pdf", buf, 0644)
c.JSON(200, id+" "+token)
}

// print a specific pdf page.
    func printToPDF(urlstr string, res *[]byte) chromedp.Tasks {
      return chromedp.Tasks{
       chromedp.Navigate(urlstr),
       chromedp.ActionFunc(func(ctx context.Context) error {
        buf, _, err := page.PrintToPDF().WithPrintBackground(false).Do(ctx)
        if err != nil {
            return err
        }
        *res = buf
        return nil
      }),
    }
   }

Original Q&A

There are 1 best solutions below

**Zeke Lu** · Answer 1 · 2023-02-04T04:42:43.660000

You can write the bytes to http.ResponseWriter directly. See the demo below:

package main

import (
    "context"
    "log"
    "net/http"
    "sync"

    "github.com/chromedp/cdproto/page"
    "github.com/chromedp/chromedp"
)

func main() {
    http.Handle("/pdf", http.HandlerFunc(servePDF))

    log.Fatal(http.ListenAndServe(":8080", http.DefaultServeMux))
}

func servePDF(w http.ResponseWriter, r *http.Request) {
    buf, err := createPDF()

    if err != nil {
        log.Fatalln(err)
        w.WriteHeader(http.StatusInternalServerError)
        return
    }

    w.Header().Set("Content-Type", "application/pdf")
    w.Write(buf)
}

func createPDF() ([]byte, error) {
    ctx, cancel := newTabContext()
    defer cancel()

    html := `<html>
<body>
<div>text</div>
<img src="https://pkg.go.dev/static/shared/gopher/package-search-700x300.jpeg"/>
<img src="https://go.dev/images/gophers/motorcycle.svg"/>
<img src="https://go.dev/images/go_google_case_study_carousel.png" />
</body>
</html>`

    var buf []byte
    if err := chromedp.Run(ctx,
        chromedp.Navigate("about:blank"),
        // set the page content and wait until the page is loaded (including its resources).
        chromedp.ActionFunc(func(ctx context.Context) error {
            lctx, cancel := context.WithCancel(ctx)
            defer cancel()
            var wg sync.WaitGroup
            wg.Add(1)
            chromedp.ListenTarget(lctx, func(ev interface{}) {
                if _, ok := ev.(*page.EventLoadEventFired); ok {
                    // It's a good habit to remove the event listener if we don't need it anymore.
                    cancel()
                    wg.Done()
                }
            })

            frameTree, err := page.GetFrameTree().Do(ctx)
            if err != nil {
                return err
            }

            if err := page.SetDocumentContent(frameTree.Frame.ID, html).Do(ctx); err != nil {
                return err
            }
            wg.Wait()
            return nil
        }),
        chromedp.ActionFunc(func(ctx context.Context) error {
            var err error
            buf, _, err = page.PrintToPDF().WithPrintBackground(false).Do(ctx)
            if err != nil {
                return err
            }
            return nil
        }),
    ); err != nil {
        return nil, err
    }

    return buf, nil
}

var (
    browserCtx context.Context
    once       sync.Once
)

// newTabContext creates a tab context with the global browser context as its parent context.
//
// When tasks is run with the returned context, a new tab will be created in the browser.
func newTabContext() (context.Context, context.CancelFunc) {
    once.Do(func() { initBrowser() })

    if browserCtx == nil || browserCtx.Err() != nil {
        log.Fatalf("browser is not available: %v", browserCtx.Err())
    }

    return chromedp.NewContext(browserCtx)
}

// initBrowser starts a browser in which to create new tab for running tasks.
func initBrowser() {
    browserCtx, _ = chromedp.NewContext(context.Background())

    // to start the browser
    if err := chromedp.Run(browserCtx); err != nil {
        log.Fatal(err)
    }
}

Usage:

go run main.go
curl http://localhost:8080/pdf > sample.pdf

References:

Golang Chromedp: pdf file download without saving in server

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