Golang教程：如何通过项目实例学习Gin框架

通过项目实例学习Gin框架

下面通过一个完整的用户管理API项目来演示Gin框架的核心功能：

1. 项目初始化

# 创建项目目录
mkdir gin-user-api && cd gin-user-api

# 初始化Go模块
go mod init gin-user-api

# 安装Gin框架
go get -u github.com/gin-gonic/gin

2. 基础路由示例

// main.go
package main

import (
    "github.com/gin-gonic/gin"
    "net/http"
)

func main() {
    // 创建Gin引擎实例
    r := gin.Default()
    
    // 基础GET路由
    r.GET("/", func(c *gin.Context) {
        c.JSON(http.StatusOK, gin.H{
            "message": "Welcome to User API",
            "status":  "running",
        })
    })
    
    // 带参数的路由
    r.GET("/user/:id", func(c *gin.Context) {
        userID := c.Param("id")
        c.JSON(http.StatusOK, gin.H{
            "user_id": userID,
            "name":    "John Doe",
        })
    })
    
    // 查询参数示例
    r.GET("/search", func(c *gin.Context) {
        query := c.Query("q")
        limit := c.DefaultQuery("limit", "10")
        
        c.JSON(http.StatusOK, gin.H{
            "query": query,
            "limit": limit,
            "results": []string{},
        })
    })
    
    // 启动服务器
    r.Run(":8080")
}

3. 用户管理API完整示例

// models/user.go
package models

type User struct {
    ID       string `json:"id"`
    Username string `json:"username"`
    Email    string `json:"email"`
    Age      int    `json:"age"`
}

// handlers/user_handler.go
package handlers

import (
    "gin-user-api/models"
    "github.com/gin-gonic/gin"
    "net/http"
)

var users = []models.User{
    {ID: "1", Username: "john_doe", Email: "john@example.com", Age: 25},
    {ID: "2", Username: "jane_smith", Email: "jane@example.com", Age: 30},
}

// GetUsers 获取所有用户
func GetUsers(c *gin.Context) {
    c.JSON(http.StatusOK, gin.H{
        "users": users,
        "count": len(users),
    })
}

// GetUserByID 根据ID获取用户
func GetUserByID(c *gin.Context) {
    id := c.Param("id")
    
    for _, user := range users {
        if user.ID == id {
            c.JSON(http.StatusOK, user)
            return
        }
    }
    
    c.JSON(http.StatusNotFound, gin.H{
        "error": "User not found",
    })
}

// CreateUser 创建新用户
func CreateUser(c *gin.Context) {
    var newUser models.User
    
    // 绑定JSON请求体
    if err := c.ShouldBindJSON(&newUser); err != nil {
        c.JSON(http.StatusBadRequest, gin.H{
            "error": "Invalid request data",
        })
        return
    }
    
    // 简单的ID生成
    newUser.ID = string(rune(len(users) + 1 + '0'))
    users = append(users, newUser)
    
    c.JSON(http.StatusCreated, gin.H{
        "message": "User created successfully",
        "user":    newUser,
    })
}

// UpdateUser 更新用户信息
func UpdateUser(c *gin.Context) {
    id := c.Param("id")
    var updatedUser models.User
    
    if err := c.ShouldBindJSON(&updatedUser); err != nil {
        c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid data"})
        return
    }
    
    for i, user := range users {
        if user.ID == id {
            updatedUser.ID = id
            users[i] = updatedUser
            
            c.JSON(http.StatusOK, gin.H{
                "message": "User updated successfully",
                "user":    updatedUser,
            })
            return
        }
    }
    
    c.JSON(http.StatusNotFound, gin.H{"error": "User not found"})
}

// DeleteUser 删除用户
func DeleteUser(c *gin.Context) {
    id := c.Param("id")
    
    for i, user := range users {
        if user.ID == id {
            users = append(users[:i], users[i+1:]...)
            c.JSON(http.StatusOK, gin.H{
                "message": "User deleted successfully",
            })
            return
        }
    }
    
    c.JSON(http.StatusNotFound, gin.H{"error": "User not found"})
}

4. 中间件示例

// middleware/auth.go
package middleware

import (
    "github.com/gin-gonic/gin"
    "net/http"
)

// AuthMiddleware 简单的认证中间件
func AuthMiddleware() gin.HandlerFunc {
    return func(c *gin.Context) {
        token := c.GetHeader("Authorization")
        
        if token != "Bearer valid-token" {
            c.JSON(http.StatusUnauthorized, gin.H{
                "error": "Unauthorized access",
            })
            c.Abort()
            return
        }
        
        c.Next()
    }
}

// LoggingMiddleware 日志中间件
func LoggingMiddleware() gin.HandlerFunc {
    return func(c *gin.Context) {
        // 请求前
        method := c.Request.Method
        path := c.Request.URL.Path
        
        c.Next()
        
        // 请求后
        status := c.Writer.Status()
        println(method, path, status)
    }
}

5. 主程序整合

// main.go
package main

import (
    "gin-user-api/handlers"
    "gin-user-api/middleware"
    "github.com/gin-gonic/gin"
)

func main() {
    r := gin.Default()
    
    // 使用中间件
    r.Use(middleware.LoggingMiddleware())
    
    // 公开路由
    r.GET("/", func(c *gin.Context) {
        c.JSON(200, gin.H{
            "message": "User Management API",
            "version": "1.0.0",
        })
    })
    
    // 用户路由组
    userRoutes := r.Group("/users")
    {
        userRoutes.GET("/", handlers.GetUsers)
        userRoutes.GET("/:id", handlers.GetUserByID)
        
        // 需要认证的路由
        authRoutes := userRoutes.Group("/")
        authRoutes.Use(middleware.AuthMiddleware())
        {
            authRoutes.POST("/", handlers.CreateUser)
            authRoutes.PUT("/:id", handlers.UpdateUser)
            authRoutes.DELETE("/:id", handlers.DeleteUser)
        }
    }
    
    // 文件上传示例
    r.POST("/upload", func(c *gin.Context) {
        file, err := c.FormFile("file")
        if err != nil {
            c.JSON(400, gin.H{"error": err.Error()})
            return
        }
        
        // 保存文件
        c.SaveUploadedFile(file, "./uploads/"+file.Filename)
        
        c.JSON(200, gin.H{
            "message":  "File uploaded successfully",
            "filename": file.Filename,
            "size":     file.Size,
        })
    })
    
    // 静态文件服务
    r.Static("/static", "./static")
    
    // 启动服务器
    r.Run(":8080")
}

6. 测试API

# 启动服务器
go run main.go

# 测试命令示例
curl http://localhost:8080/users/
curl http://localhost:8080/users/1
curl -X POST http://localhost:8080/users/ \
  -H "Authorization: Bearer valid-token" \
  -H "Content-Type: application/json" \
  -d '{"username":"new_user","email":"new@example.com","age":28}'

这个项目实例涵盖了Gin框架的核心功能：路由定义、参数处理、中间件使用、JSON绑定、文件上传和静态文件服务。通过这个完整的CRUD API示例，可以快速掌握Gin框架的实际应用。