Examples of Handling HTTP Requests and Responses in Go

When developing web applications in Go, understanding how to handle HTTP requests and responses is essential. This capability allows developers to create robust APIs and serve dynamic content. Below are three diverse examples demonstrating different scenarios for handling HTTP requests and responses in Go.

Example 1: Basic GET Request Handler

Context

This example illustrates a simple HTTP server that responds to GET requests. This is a foundational use case for serving static content or data.

package main

import (
    "fmt"
    "net/http"
)

func helloHandler(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "text/plain")
    fmt.Fprintf(w, "Hello, World!")
}

func main() {
    http.HandleFunc("/hello", helloHandler)
    http.ListenAndServe(":8080", nil)
}

Notes

To test this example, run the server and navigate to http://localhost:8080/hello in your browser.
The response will be a simple text message, demonstrating how to set the content type and write to the response body.

Example 2: Handling JSON Data with POST Requests

Context

In this example, we create an HTTP server that handles POST requests and processes JSON data. This is commonly used in RESTful APIs.

package main

import (
    "encoding/json"
    "fmt"
    "net/http"
)

type User struct {
    Name  string `json:"name"`
    Email string `json:"email"`
}

func userHandler(w http.ResponseWriter, r *http.Request) {
    if r.Method != http.MethodPost {
        http.Error(w, "Invalid request method", http.StatusMethodNotAllowed)
        return
    }

    var user User
    decoder := json.NewDecoder(r.Body)
    if err := decoder.Decode(&user); err != nil {
        http.Error(w, err.Error(), http.StatusBadRequest)
        return
    }

    response := fmt.Sprintf("Received user: %s with email: %s", user.Name, user.Email)
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(http.StatusOK)
    json.NewEncoder(w).Encode(map[string]string{"message": response})
}

func main() {
    http.HandleFunc("/user", userHandler)
    http.ListenAndServe(":8080", nil)
}

Notes

To test this example, send a POST request to http://localhost:8080/user with a JSON body like { "name": "John", "email": "john@example.com" }.
The server will respond with a JSON message confirming the received user data.

Example 3: Error Handling and Custom Responses

Context

This example demonstrates how to handle errors gracefully and provide custom responses based on the HTTP request status. This can enhance user experience by giving clear feedback.

package main

import (
    "fmt"
    "net/http"
)

func errorHandler(w http.ResponseWriter, r *http.Request) {
    http.Error(w, "Page not found", http.StatusNotFound)
}

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        if r.URL.Path != "/" {
            errorHandler(w, r)
            return
        }
        fmt.Fprintf(w, "Welcome to the Home Page!")
    })
    http.ListenAndServe(":8080", nil)
}

Notes

In this example, if a user navigates to any path other than the root, they will receive a 404 error message.
This is a simple method for managing error responses, making your application more user-friendly.

These examples provide a solid foundation for handling HTTP requests and responses in Go. By understanding these patterns, developers can build more complex and interactive web applications.