Use CORS in Beego framework to solve cross-domain problems

With the development of web applications and the globalization of the Internet, more and more applications need to make cross-domain requests. Cross-domain requests are a common problem for front-end developers, and it can cause applications to not work properly. In this case, one of the best ways to solve the problem of cross-origin requests is to use CORS.

In this article, we will focus on how to use CORS to solve cross-domain problems in the Beego framework.

What is a cross-domain request?

In web applications, cross-domain requests refer to sending requests from a web page of one domain name to a server of another domain name. Typically, request and response data are in the same domain, meaning they use the same protocol, port, and protocol type. However, browsers usually prohibit cross-domain requests for security reasons.

For projects with separate front-end and back-end, cross-domain request issues are very common. For example, when writing an application using Vue on the front end, you may need to send an Ajax request to a certain backend server to get data. If the front-end server and the back-end server are not under the same domain name, the browser will reject the request and display an error even if the request is written correctly at the code level. This is a cross-domain request problem.

What is CORS?

CORS is the abbreviation of Cross-Origin Resource Sharing. It is a mechanism based on the HTTP protocol that allows web applications to access cross-domain resources. The emergence of the CORS mechanism is mainly to solve the above-mentioned cross-domain request problems.

The CORS mechanism is implemented by the browser, which uses additional HTTP headers to tell the browser which sources are allowed to access cross-origin resources. When requesting, the browser will check the response header information. If the Access-Control-Allow-Origin field exists in the response header information, and the value of this field matches the requested domain name and port number, the browser allows the cross-domain request.

Using CORS in Beego

In Beego, we can use the beego-cors library to implement the CORS mechanism. The following is the installation method of the beego-cors library:

go get github.com/astaxie/beego/plugins/cors

After installation, we need to import the beego-cors library into the application.

import "github.com/astaxie/beego/plugins/cors"

Configuring CORS in the router

Next, we will introduce how to use CORS in Beego. If your application is a new project, then you can set it when initializing the application as follows:

package main

import (
    "github.com/astaxie/beego"
    "github.com/astaxie/beego/plugins/cors"
)

func main() {
    beego.BConfig.Listen.HTTPAddr = "0.0.0.0"
    beego.BConfig.Listen.HTTPPort = 8080

    beego.InsertFilter("*", beego.BeforeRouter, cors.Allow(&cors.Options{
        AllowOrigins: []string{"*"},
        AllowMethods: []string{"PUT", "PATCH", "GET", "POST", "DELETE", "OPTIONS"},
        AllowHeaders: []string{"Origin", "Content-Type", "Authorization"},
        ExposeHeaders: []string{"Content-Length", "Access-Control-Allow-Origin"},
        AllowCredentials: true,
    }))

    beego.Run()
}

In the above code, we added a filter named cors using the InsertFilter method . This filter works on all requests, so we use the * wildcard to specify the router.

In the Allow method, we configure the sources, methods and headers to be allowed. Here we use * to allow all origins. Of course, you can also use specific domain names or IP addresses to limit allowed sources. Content type, authorization and source header are also set according to the actual situation.

In the AllowCredentials field, we set it to true, which means that cross-domain requests are allowed to send credential information such as cookies.

Configuring CORS in Controller

In addition to configuring CORS in the router, we can also configure CORS in the Controller. This method can be configured for each Controller and has higher flexibility. The details are as follows:

package controllers

import (
    "github.com/astaxie/beego"
    "github.com/astaxie/beego/plugins/cors"
)

type TestController struct {
    beego.Controller
}

func (c *TestController) Get() {
    origin := c.Ctx.Request.Header.Get("Origin")
    c.Ctx.Output.Header("Access-Control-Allow-Origin", origin)
    c.Ctx.Output.Header("Access-Control-Allow-Credentials", "true")
    c.Ctx.Output.Header("Access-Control-Allow-Methods", "POST, GET, PUT, DELETE, OPTIONS")
    c.Ctx.Output.Header("Access-Control-Allow-Headers", "Content-Type,Authorization")
    c.Ctx.Output.Header("Content-Type", "application/json; charset=utf-8")

    c.Ctx.Output.Body([]byte("Hello, world!"))
}

In the above code, we first obtain the Origin field of the request header, and then set it as the Access-Control-Allow-Origin response header. This is an important step in the CORS mechanism because it tells the browser which sources we allow to access resources.

We also set the Access-Control-Allow-Credentials, Access-Control-Allow-Methods and Access-Control-Allow-Headers response headers. Their functions are to allow sending of credential information, allowed request methods and allowed request header fields.

Finally, we use the Output.Body method to send the response data to the client.

Summary

In this article, we introduced what cross-domain requests are, the CORS mechanism, and how to use CORS to solve cross-domain problems in the Beego framework. For projects with separate front-end and back-end, cross-domain requests are a common problem. Using the CORS mechanism can solve this problem very well. The CORS mechanism can be easily implemented in Beego using the beego-cors library. Hope this article is helpful to you.

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