What are the purposes and common methods of Context in the Gin framework?

The purpose and common methods of the Context in the Gin framework are as follows:

1. Purpose of Context

gin.Context is a core component of the Gin framework. It is passed throughout the request processing lifecycle, providing methods to access requests and responses, as well as the ability to store request-scoped data.

Main purposes of Context:

• Access and manipulate HTTP requests
• Build and return HTTP responses
• Store and retrieve request-scoped data
• Control request processing flow
• Manage error information
• Access route parameters and query parameters

2. Request-related methods

Get request information:

go
// Get request method
c.Request.Method

// Get request URL
c.Request.URL

// Get request headers
c.GetHeader("Content-Type")
c.Request.Header.Get("Authorization")

// Get client IP
c.ClientIP()

// Get User-Agent
c.GetHeader("User-Agent")

Get request parameters:

go
// Get query parameters
c.Query("name")
c.DefaultQuery("name", "default")
c.QueryArray("ids")

// Get form parameters
c.PostForm("username")
c.DefaultPostForm("username", "guest")

// Get route parameters
c.Param("id")

// Get raw request body
c.GetRawData()

3. Response-related methods

Return JSON response:

go
c.JSON(200, gin.H{"message": "success"})
c.JSON(200, User{Name: "John", Age: 30})

Return other format responses:

go
// XML
c.XML(200, gin.H{"message": "success"})

// YAML
c.YAML(200, gin.H{"message": "success"})

// String
c.String(200, "Hello, %s", name)

// HTML
c.HTML(200, "index.html", gin.H{"title": "Home"})

// File
c.File("path/to/file")
c.FileAttachment("path/to/file", "filename")

// Redirect
c.Redirect(302, "/login")

4. Data storage methods

Store and retrieve data:

go
// Store data
c.Set("user", user)
c.Set("requestID", requestID)

// Get data
user, exists := c.Get("user")
if exists {
    u := user.(*User)
}

// Get specific type data
userID := c.GetInt("userID")
userName := c.GetString("userName")

5. Flow control methods

Control request processing flow:

go
// Continue to execute next middleware
c.Next()

// Interrupt request processing
c.Abort()
c.AbortWithStatus(404)
c.AbortWithStatusJSON(400, gin.H{"error": "invalid input"})

// Deferred execution (executed after all middleware)
defer func() {
    // Cleanup logic
}()

6. Error handling methods

Error handling:

go
// Add error
c.Error(errors.New("something went wrong"))

// Get errors
errors := c.Errors
lastError := c.Errors.Last()

7. Other common methods

go
// Get Gin engine instance
c.Engine

// Get current route
c.FullPath()

// Get request Content-Type
c.ContentType()

// Check if it's a WebSocket request
c.IsWebsocket()

// Check if it's an AJAX request
c.IsAborted()

// Get binder
c.ShouldBindJSON(&obj)
c.ShouldBindQuery(&obj)

8. Context lifecycle

The lifecycle of Context is bound to a single HTTP request:

1. Context is created when the request arrives
2. Context is passed through the middleware chain
3. Context is destroyed after request processing is complete
4. Do not use Context directly in goroutines, need to use c.Copy()

9. Usage notes

1. Do not store Context in global variables
2. When using Context in goroutines, need to call c.Copy()
3. Context is thread-safe, but stored data needs to ensure thread safety
4. Reasonably use c.Set() and c.Get() to pass data
5. When using c.Abort(), ensure subsequent logic does not execute
6. Avoid storing large amounts of data in Context

Understanding the purpose and common methods of Context is very important for developing Gin applications, it is the bridge connecting requests and responses.