Fix issue #4094:By using structure encapsulation parameters to achieve the purpose of user-defined JSON rendering, while not changing the functions implemented by the original code

Signed-off-by: 朱宗辉 <1050527083@qq.com>

context.go

@@ -52,6 +52,26 @@ const ContextRequestKey ContextKeyType = 0
 // abortIndex represents a typical value used in abort functions.
 const abortIndex int8 = math.MaxInt8 >> 1
 
+// defaultJsonRenderName, default JSON render name
+const defaultJsonRenderName string = "render.JSON"
+
+// jsonRenderRegistry, storing JSON render types and their corresponding creation factory functions
+var jsonRenderRegistry = make(map[string]func(data any) render.Render)
+
+// RegisterJsonRender allows users to register JSON render factory functions
+func (c *Context) RegisterJsonRender(name string, jsonRender func(data any) render.Render) {
+	jsonRenderRegistry[name] = jsonRender
+}
+
+// createInstance, Create a JSON render instance through a factory function
+func createInstance(name string, data any) render.Render {
+	jsonRender, exists := jsonRenderRegistry[name]
+	if !exists {
+		return jsonRenderRegistry[defaultJsonRenderName](data)
+	}
+	return jsonRender(data)
+}
+
 // Context is the most important part of gin. It allows us to pass variables between middleware,
 // manage the flow, validate the JSON of a request and render a JSON response for example.
 type Context struct {
@@ -90,6 +110,15 @@ type Context struct {
 	// sameSite allows a server to define a cookie attribute making it impossible for
 	// the browser to send this cookie along with cross-site requests.
 	sameSite http.SameSite
+
+	// jsonRenderName the name of the JSON render currently used. The default value is render.JSON
+	// this is used to get the JSON render type when executing the c.JSON function.
+	jsonRenderName string
+}
+
+// SetJSONRender set the name of the current JSON render
+func (c *Context) SetJSONRender(jsonRenderName string) {
+	c.jsonRenderName = jsonRenderName
 }
 
 /************************************/
@@ -109,6 +138,9 @@ func (c *Context) reset() {
 	c.queryCache = nil
 	c.formCache = nil
 	c.sameSite = 0
+	// registering a default JSON renderer
+	c.jsonRenderName = defaultJsonRenderName
+	c.RegisterJsonRender(defaultJsonRenderName, render.NewJSON)
 	*c.params = (*c.params)[:0]
 	*c.skippedNodes = (*c.skippedNodes)[:0]
 }
@@ -1095,7 +1127,7 @@ func (c *Context) JSONP(code int, obj any) {
 // JSON serializes the given struct as JSON into the response body.
 // It also sets the Content-Type as "application/json".
 func (c *Context) JSON(code int, obj any) {
-	c.Render(code, render.JSON{Data: obj})
+	c.Render(code, createInstance(c.jsonRenderName, obj))
 }
 
 // AsciiJSON serializes the given struct as JSON into the response body with unicode to ASCII string.