阶段2（上）：后端专题 Go/Gin/PostgreSQL/MySQL/Redis/MQ/gRPC 的课程、企业场景、面试题和可运行示例
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// Package unifiedapi 演示企业后台接口规范：统一响应、业务错误码、请求 ID、参数校验中文提示、panic 兜底。
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package unifiedapi
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import (
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"crypto/rand"
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"encoding/hex"
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"errors"
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"fmt"
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"log/slog"
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"net/http"
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"reflect"
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"strings"
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"sync"
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"github.com/gin-gonic/gin"
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"github.com/gin-gonic/gin/binding"
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"github.com/go-playground/validator/v10"
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)
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// AppError 业务错误：HTTP 状态码 + 业务错误码 + 给用户看的提示
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type AppError struct {
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Status int
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Code int
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Message string
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}
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func (e *AppError) Error() string { return e.Message }
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var (
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ErrNotFound = &AppError{http.StatusNotFound, 40400, "资源不存在"}
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ErrInternal = &AppError{http.StatusInternalServerError, 50000, "服务器开小差了，请稍后再试"}
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)
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func Invalid(msg string) *AppError { return &AppError{http.StatusBadRequest, 40000, msg} }
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// Body 统一响应格式
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type Body struct {
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Code int `json:"code"`
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Message string `json:"message"`
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Data any `json:"data"`
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RequestID string `json:"request_id"`
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}
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func OK(c *gin.Context, status int, data any) {
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c.JSON(status, Body{Code: 0, Message: "ok", Data: data, RequestID: c.GetString("requestID")})
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}
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func writeErr(c *gin.Context, e *AppError) {
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c.AbortWithStatusJSON(e.Status, Body{Code: e.Code, Message: e.Message, RequestID: c.GetString("requestID")})
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}
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// RequestID 沿用客户端传来的 X-Request-ID，没有就生成一个，并写回响应头
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func RequestID() gin.HandlerFunc {
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return func(c *gin.Context) {
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id := c.GetHeader("X-Request-ID")
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if id == "" || len(id) > 64 {
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b := make([]byte, 8)
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_, _ = rand.Read(b)
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id = hex.EncodeToString(b)
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}
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c.Set("requestID", id)
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c.Header("X-Request-ID", id)
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c.Next()
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}
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}
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// Errors 统一把处理函数里 c.Error(err) 记录的错误和 panic 转成统一响应；内部错误不把细节暴露给用户
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func Errors(log *slog.Logger) gin.HandlerFunc {
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return func(c *gin.Context) {
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defer func() {
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if r := recover(); r != nil {
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log.Error("panic", "request_id", c.GetString("requestID"), "panic", r)
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writeErr(c, ErrInternal)
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}
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}()
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c.Next()
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if len(c.Errors) == 0 || c.Writer.Written() {
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return
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}
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err := c.Errors.Last().Err
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var ae *AppError
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if errors.As(err, &ae) {
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writeErr(c, ae)
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return
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}
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log.Error("internal error", "request_id", c.GetString("requestID"), "err", err)
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writeErr(c, ErrInternal)
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}
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}
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var setupOnce sync.Once
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// useJSONFieldNames 让校验错误里显示 JSON 字段名（title）而不是结构体字段名（Title）
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func useJSONFieldNames() {
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if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
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v.RegisterTagNameFunc(func(f reflect.StructField) string {
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name := strings.Split(f.Tag.Get("json"), ",")[0]
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if name == "" || name == "-" {
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return f.Name
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}
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return name
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})
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}
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}
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// Bind 解析并校验 JSON，失败时记录一个用户能看懂的错误
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func Bind(c *gin.Context, req any) bool {
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err := c.ShouldBindJSON(req)
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if err == nil {
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return true
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}
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var ve validator.ValidationErrors
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if errors.As(err, &ve) {
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msgs := make([]string, 0, len(ve))
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for _, fe := range ve {
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switch fe.Tag() {
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case "required":
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msgs = append(msgs, fmt.Sprintf("%s 不能为空", fe.Field()))
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case "max":
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msgs = append(msgs, fmt.Sprintf("%s 长度不能超过 %s", fe.Field(), fe.Param()))
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case "oneof":
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msgs = append(msgs, fmt.Sprintf("%s 只能是 %s 之一", fe.Field(), fe.Param()))
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default:
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msgs = append(msgs, fmt.Sprintf("%s 不合法", fe.Field()))
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}
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}
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_ = c.Error(Invalid(strings.Join(msgs, "；")))
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} else {
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_ = c.Error(Invalid("请求体格式错误"))
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}
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return false
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}
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type Task struct {
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ID int `json:"id"`
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Title string `json:"title"`
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Priority string `json:"priority"`
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}
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type CreateTask struct {
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Title string `json:"title" binding:"required,max=50"`
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Priority string `json:"priority" binding:"omitempty,oneof=low normal high"`
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}
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// New 组装路由
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func New(log *slog.Logger) *gin.Engine {
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setupOnce.Do(useJSONFieldNames)
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var mu sync.Mutex
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tasks := map[int]Task{}
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next := 1
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r := gin.New()
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r.Use(RequestID(), Errors(log))
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api := r.Group("/api")
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api.POST("/tasks", func(c *gin.Context) {
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var req CreateTask
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if !Bind(c, &req) {
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return
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}
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mu.Lock()
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t := Task{ID: next, Title: req.Title, Priority: req.Priority}
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tasks[t.ID] = t
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next++
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mu.Unlock()
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OK(c, http.StatusCreated, t)
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})
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api.GET("/tasks/:id", func(c *gin.Context) {
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var id int
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if _, err := fmt.Sscan(c.Param("id"), &id); err != nil {
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_ = c.Error(Invalid("id 必须是整数"))
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return
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}
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mu.Lock()
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t, ok := tasks[id]
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mu.Unlock()
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if !ok {
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_ = c.Error(ErrNotFound)
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return
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}
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OK(c, http.StatusOK, t)
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})
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api.GET("/boom", func(c *gin.Context) { panic("数据库连接串 postgres://secret 泄漏测试") })
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api.GET("/db-error", func(c *gin.Context) { _ = c.Error(errors.New("pq: relation \"tasks\" does not exist")) })
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return r
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}
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