ETag¶

Automatic ETag generation for HTTP caching with conditional request support.

Usage¶

app.Use(middleware.ETag)

How It Works¶

The ETag middleware:

1. Captures response body for GET/HEAD requests
2. Generates SHA-1 hash of the content
3. Sets ETag header with the hash
4. Returns 304 Not Modified if client sends matching If-None-Match

// Client sends: If-None-Match: "a1b2c3d4e5f6g7h8"
// If content hash matches, returns 304 with no body

Example¶

package main

import (
    "github.com/gomarten/marten"
    "github.com/gomarten/marten/middleware"
)

func main() {
    app := marten.New()
    app.Use(middleware.ETag)

    app.GET("/data", func(c *marten.Ctx) error {
        return c.JSON(200, marten.M{
            "items": []string{"a", "b", "c"},
        })
    })

    app.Run(":8080")
}

Behavior¶

Benefits¶

• Reduces bandwidth for unchanged resources
• Improves client-side caching
• Zero configuration required
• Works with any response content

Notes¶

• ETag is generated from response body content
• Only applies to successful (2xx) responses
• Automatically handles If-None-Match validation