Two folders in the file system as a virtual folder in the path of the site address (web server in Go)

When php editor Youzi introduced the virtual folder in the web server path, he mentioned two folders in the file system as part of the site address. In the Go language, this concept of virtual folders is widely used in the path settings of web servers. By including these two folders as part of the site address, more flexible file path management and access control can be achieved. This design pattern not only simplifies the organization of site files, but also provides better security and maintainability. Through the concept of virtual folders, developers can manage and control site resources more conveniently.

Question content

There are two folders "files1" and "files2" in my file system.

I can host a folder in the file system as a virtual folder in the site address path like this:

http.Handle("/public/", http.StripPrefix("/public/", http.FileServer(http.Dir("./files1"))))

How to host the contents of the "files1" and "files2" folders on the same path of the site address "/public/"?

Solution

A simple solution is to implement the http.filesystem interface.

This is the demo:

package main

import (
    "errors"
    "io/fs"
    "net/http"
)

func main() {
    http.handle("/public/", http.stripprefix("/public/", http.fileserver(mergeddir{
        dir1: "./files1",
        dir2: "./files2",
    })))

    http.listenandserve(":8080", nil)
}

type mergeddir struct {
    dir1 http.dir // dir1 will be tried first so it has higher priority.
    dir2 http.dir
}

func (d mergeddir) open(name string) (http.file, error) {
    f, err := d.dir1.open(name)

    if err != nil {
        if errors.is(err, fs.errnotexist) {
            return d.dir2.open(name)
        }
    }

    return f, err
}

I have tested with this directory structure:

├── files1
│   ├── f1-1.txt
│   └── f1-sub
│       └── f1-s.txt
└── files2
    ├── f1-1.txt
    ├── f2-1.txt
    └── f2-sub
        └── f2-s.txt

There are two f1-1.txt. Since files1 is tried first, the one in files1 is served.

renew:

As requested by the author, another version of mergeddir supports multiple directories:

type mergedDir struct {
    Dirs []http.Dir
}

func (d mergedDir) Open(name string) (http.File, error) {
    for _, dir := range d.Dirs {
        f, err := dir.Open(name)
        if err == nil {
            return f, nil
        }
        if !errors.Is(err, fs.ErrNotExist) {
            return f, err
        }
    }

    return nil, fs.ErrNotExist
}

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