The http.ServeContent
function in Golang is part of the net/http
package and is used to serve content directly from a given io.ReadSeeker
, such as a file, with detailed control over the HTTP headers like Content-Type
, Content-Length
, and Last-Modified
. This function is useful when you need to serve content that is dynamically generated or read from a non-file source but still want to provide the appropriate HTTP headers.
Table of Contents
- Introduction
http.ServeContent
Function Syntax- Examples
- Basic Usage
- Serving Dynamic Content with Custom Headers
- Serving a File with Custom HTTP Headers
- Real-World Use Case
- Conclusion
Introduction
The http.ServeContent
function allows you to serve content with precise control over the HTTP response headers. Unlike http.ServeFile
, which serves files directly from the filesystem, http.ServeContent
allows you to serve content from any io.ReadSeeker
source, such as an in-memory buffer or a dynamically generated stream. This function is particularly useful when you need to customize the response headers or serve content that is not stored as a file on disk.
http.ServeContent Function Syntax
The syntax for the http.ServeContent
function is as follows:
func ServeContent(w http.ResponseWriter, r *http.Request, name string, modtime time.Time, content io.ReadSeeker)
Parameters:
w
: Thehttp.ResponseWriter
used to write the HTTP response.r
: The*http.Request
representing the incoming HTTP request.name
: A string specifying the name of the content being served (used to determine theContent-Type
).modtime
: Atime.Time
value representing the last modification time of the content, used to set theLast-Modified
header.content
: Anio.ReadSeeker
representing the content to be served. This could be a file, a buffer, or any other readable and seekable data source.
Returns:
- The function does not return any value. It writes the content directly to the HTTP response.
Examples
Basic Usage
This example demonstrates how to use the http.ServeContent
function to serve content from a file with custom control over the response headers.
Example
package main
import (
"net/http"
"os"
"time"
)
func main() {
// Register a handler for serving content
http.HandleFunc("/content", func(w http.ResponseWriter, r *http.Request) {
// Open the file to be served
file, err := os.Open("example.txt")
if err != nil {
http.Error(w, "File not found", http.StatusNotFound)
return
}
defer file.Close()
// Get the file information to obtain the modification time
fileInfo, err := file.Stat()
if err != nil {
http.Error(w, "Could not get file info", http.StatusInternalServerError)
return
}
// Serve the file content with http.ServeContent
http.ServeContent(w, r, fileInfo.Name(), fileInfo.ModTime(), file)
})
// Start the server on port 8080
http.ListenAndServe(":8080", nil)
}
Explanation:
- The code opens a file (
example.txt
) and serves its content usinghttp.ServeContent
. - The
ServeContent
function sets appropriate headers such asContent-Type
,Content-Length
, andLast-Modified
based on the file's metadata.
Serving Dynamic Content with Custom Headers
This example shows how to serve dynamically generated content with custom headers using http.ServeContent
.
Example
package main
import (
"bytes"
"net/http"
"time"
)
func main() {
// Register a handler for serving dynamic content
http.HandleFunc("/dynamic", func(w http.ResponseWriter, r *http.Request) {
// Generate dynamic content
content := "Hello, this is dynamically generated content."
contentReader := bytes.NewReader([]byte(content))
// Serve the content with a custom modification time
http.ServeContent(w, r, "dynamic.txt", time.Now(), contentReader)
})
// Start the server on port 8080
http.ListenAndServe(":8080", nil)
}
Explanation:
- The example generates dynamic content in memory and serves it using
http.ServeContent
. - A
bytes.Reader
is used as theio.ReadSeeker
to serve the content, with a custom modification time set to the current time.
Serving a File with Custom HTTP Headers
This example demonstrates how to serve a file while customizing HTTP headers like Content-Disposition
.
Example
package main
import (
"net/http"
"os"
"time"
)
func main() {
// Register a handler for serving a file with custom headers
http.HandleFunc("/download", func(w http.ResponseWriter, r *http.Request) {
// Open the file to be served
file, err := os.Open("example.pdf")
if err != nil {
http.Error(w, "File not found", http.StatusNotFound)
return
}
defer file.Close()
// Get the file information
fileInfo, err := file.Stat()
if err != nil {
http.Error(w, "Could not get file info", http.StatusInternalServerError)
return
}
// Set a custom Content-Disposition header
w.Header().Set("Content-Disposition", "attachment; filename=\"example.pdf\"")
// Serve the file content
http.ServeContent(w, r, fileInfo.Name(), fileInfo.ModTime(), file)
})
// Start the server on port 8080
http.ListenAndServe(":8080", nil)
}
Explanation:
- The code serves a PDF file (
example.pdf
) and sets aContent-Disposition
header to prompt the user to download the file. http.ServeContent
handles the content delivery, while the custom header ensures the file is presented as a download.
Real-World Use Case
Serving Video Content with Custom HTTP Headers
In real-world applications, http.ServeContent
can be used to serve video content while providing appropriate headers for streaming, such as Content-Range
and Accept-Ranges
.
Example: Serving Video with Streaming Support
package main
import (
"net/http"
"os"
"time"
)
func main() {
// Register a handler for serving video content
http.HandleFunc("/video", func(w http.ResponseWriter, r *http.Request) {
// Open the video file to be served
videoFile, err := os.Open("video.mp4")
if err != nil {
http.Error(w, "Video file not found", http.StatusNotFound)
return
}
defer videoFile.Close()
// Get the file information
fileInfo, err := videoFile.Stat()
if err != nil {
http.Error(w, "Could not get video file info", http.StatusInternalServerError)
return
}
// Serve the video content with streaming support
http.ServeContent(w, r, fileInfo.Name(), fileInfo.ModTime(), videoFile)
})
// Start the server on port 8080
http.ListenAndServe(":8080", nil)
}
Explanation:
- The code serves a video file (
video.mp4
) usinghttp.ServeContent
, allowing clients to stream the video with support for range requests. - The function handles setting the appropriate headers for video streaming, such as
Accept-Ranges
andContent-Range
.
Conclusion
The http.ServeContent
function in Go is used for serving content with fine-grained control over the HTTP response headers. It is particularly useful when you need to serve dynamically generated content, non-file content, or files with custom HTTP headers. By leveraging http.ServeContent
, you can provide a robust and flexible solution for delivering content over HTTP, ensuring that the appropriate metadata and headers are included in the response.
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