go 55 lines · 9 steps

Injecting a scoped GORM query via Gin middleware

A Gin middleware pre-builds a soft-delete-aware GORM session and hands it to every handler in a route group.

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Gin Intermediate middleware dependency-injection request-context soft-delete query-scoping

1package middleware
2 
3import (
4	"github.com/gin-gonic/gin"
5	"gorm.io/gorm"
6)
7 
8const scopedDBKey = "scopedDB"
9 
10func InjectActiveScope(db *gorm.DB) gin.HandlerFunc {
11	return func(c *gin.Context) {
12		scoped := db.WithContext(c.Request.Context()).
13			Where("deleted_at IS NULL").
14			Session(&gorm.Session{NewDB: true})
15 
16		c.Set(scopedDBKey, scoped)
17		c.Next()
18	}
19}
20 
21func ScopedDB(c *gin.Context) *gorm.DB {
22	if v, ok := c.Get(scopedDBKey); ok {
23		if db, ok := v.(*gorm.DB); ok {
24			return db
25		}
26	}
27	panic("scopedDB not present: InjectActiveScope middleware missing on this route group")
28}
29 
30func RegisterArticleRoutes(r *gin.Engine, db *gorm.DB) {
31	articles := r.Group("/articles", InjectActiveScope(db))
32 
33	articles.GET("", func(c *gin.Context) {
34		var list []Article
35		if err := ScopedDB(c).Order("published_at DESC").Find(&list).Error; err != nil {
36			c.JSON(500, gin.H{"error": "failed to load articles"})
37			return
38		}
39		c.JSON(200, list)
40	})
41 
42	articles.GET("/:id", func(c *gin.Context) {
43		var article Article
44		err := ScopedDB(c).First(&article, "id = ?", c.Param("id")).Error
45		if err == gorm.ErrRecordNotFound {
46			c.JSON(404, gin.H{"error": "not found"})
47			return
48		}
49		if err != nil {
50			c.JSON(500, gin.H{"error": "lookup failed"})
51			return
52		}
53		c.JSON(200, article)
54	})
55}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Middleware can precompute a request-scoped dependency and stash it in the context for handlers to reuse.
2Building a GORM session once with a base filter keeps soft-delete logic in one place instead of every query.
3A typed accessor that panics on a missing key turns a wiring mistake into a loud, immediate failure.

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