add gin plugin

.gitignore

@@ -13,3 +13,5 @@
 
 # Dependency directories (remove the comment below to include it)
 # vendor/
+
+.vscode

examples/simple/main.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/gin-gonic/gin"
+	kgin "github.com/go-kratos/gin"
+	"github.com/go-kratos/kratos/v2"
+	"github.com/go-kratos/kratos/v2/errors"
+	"github.com/go-kratos/kratos/v2/middleware"
+	"github.com/go-kratos/kratos/v2/middleware/recovery"
+	"github.com/go-kratos/kratos/v2/transport"
+	"github.com/go-kratos/kratos/v2/transport/http"
+)
+
+func customMiddleware(handler middleware.Handler) middleware.Handler {
+	return func(ctx context.Context, req interface{}) (reply interface{}, err error) {
+		if tr, ok := transport.FromServerContext(ctx); ok {
+			fmt.Println("operation:", tr.Operation())
+		}
+		reply, err = handler(ctx, req)
+		return
+	}
+}
+
+func main() {
+	router := gin.Default()
+	router.Use(kgin.Middlewares(recovery.Recovery(), customMiddleware))
+	router.GET("/helloworld/:name", func(ctx *gin.Context) {
+		name := ctx.Param("name")
+		if name == "error" {
+			kgin.Error(ctx, errors.Unauthorized("auth_error", "no authentication"))
+		} else {
+			ctx.JSON(200, map[string]string{"welcome": name})
+		}
+	})
+
+	httpSrv := http.NewServer(http.Address(":8000"))
+	httpSrv.HandlePrefix("/", router)
+
+	app := kratos.New(
+		kratos.Name("gin"),
+		kratos.Server(
+			httpSrv,
+		),
+	)
+	if err := app.Run(); err != nil {
+		log.Fatal(err)
+	}
+}

gin.go

@@ -0,0 +1,92 @@
+package gin
+
+import (
+	"context"
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+	"github.com/go-kratos/kratos/v2/errors"
+	"github.com/go-kratos/kratos/v2/middleware"
+	thttp "github.com/go-kratos/kratos/v2/transport/http"
+)
+
+const (
+	baseContentType = "application"
+)
+
+type errorRender struct {
+	body        []byte
+	contentType string
+}
+
+// Render (JSON) writes data with custom ContentType.
+func (er *errorRender) Render(w http.ResponseWriter) error {
+	_, err := w.Write(er.body)
+	return err
+}
+
+// WriteContentType (JSON) writes JSON ContentType.
+func (er *errorRender) WriteContentType(w http.ResponseWriter) {
+	w.Header().Set("Content-Type", er.contentType)
+
+}
+
+// Error encodes the object to the HTTP response.
+func Error(c *gin.Context, err error) {
+	if err == nil {
+		c.Status(http.StatusOK)
+		return
+	}
+	codec, _ := thttp.CodecForRequest(c.Request, "Accept")
+	se := errors.FromError(err)
+	body, err := codec.Marshal(se)
+	if err != nil {
+		c.Status(http.StatusInternalServerError)
+		return
+	}
+	contentType := codec.Name()
+	code := int(se.Code)
+	c.Render(code, &errorRender{body: body, contentType: contentType})
+	return
+}
+
+// ContentType returns the content-type with base prefix.
+func ContentType(subtype string) string {
+	return strings.Join([]string{baseContentType, subtype}, "/")
+}
+
+// Middlewares return middlewares wrapper
+func Middlewares(m ...middleware.Middleware) gin.HandlerFunc {
+	chain := middleware.Chain(m...)
+	return func(c *gin.Context) {
+		next := func(ctx context.Context, req interface{}) (interface{}, error) {
+			c.Next()
+			var err error
+			if c.Writer.Status() >= 400 {
+				err = errors.Errorf(c.Writer.Status(), errors.UnknownReason, errors.UnknownReason)
+			}
+			return c.Writer, err
+		}
+		next = chain(next)
+		ctx := NewGinContext(c.Request.Context(), c)
+		c.Request = c.Request.WithContext(ctx)
+		if ginCtx, ok := FromGinContext(ctx); ok {
+			thttp.SetOperation(ctx, ginCtx.FullPath())
+		}
+		next(c.Request.Context(), c.Request)
+	}
+}
+
+type ginKey struct{}
+
+// NewGinContext returns a new Context that carries gin.Context value.
+func NewGinContext(ctx context.Context, c *gin.Context) context.Context {
+	return context.WithValue(ctx, ginKey{}, c)
+}
+
+// FromGinContext returns the gin.Context value stored in ctx, if any.
+func FromGinContext(ctx context.Context) (c *gin.Context, ok bool) {
+	c, ok = ctx.Value(ginKey{}).(*gin.Context)
+	return
+}

go.mod

@@ -0,0 +1,8 @@
+module github.com/go-kratos/gin
+
+go 1.15
+
+require (
+	github.com/gin-gonic/gin v1.7.2
+	github.com/go-kratos/kratos/v2 v2.0.0
+)