Golang可执行文件刷新

Question

I have a function which writes/updates a json. But I need to stop the executable, run go build again and re-run the executable to get the json updated in url.

For example, I have a Handler.go file which takes argument from URL as key and runs an if condition and updates the json. So If json value before building the executable is {"Name":"Sneha"} and i pass parameter "Nair" in the url, the json gets updated in the server as {"Name":"Nair"}, but doesnt get updated in the URL. So I have to stop the executable, run go build again and run the executable again to reflect the new json value {"Name":"Nair"} in the URL.

1. Can somebody please suggest an alternative idea ?

2. Can we run go build or go update inside a function?

Help much appreciated.

PS: I have got URL for goagain.go. But am not sure if that matches my requirement.

Handler.go

func handler(w http.ResponseWriter, r *http.Request) {
    keys, ok := r.URL.Query()["key"]
    if !ok || len(keys) < 1 {
        log.Println("Url Param 'key' is missing")
        return
    }
    key := keys[0]
    log.Println("Url Param 'key' is: " + string(key))
    if key == "java" {

         commands := []string{
        "Version=`java -version`",
        "sed -i -e 's/^\\( *Name: *\\) .*$/        Name:\"Java\",/' Handler.go",
        "sed -i -e 's/^\\( *Version: *\\) .*$/        Version:\" '$Version'\",/' Handler.go",   

    }
        exe_cmd(commands)

    }

    if key == "go" {

         commands := []string{
        "Version=`go version`",
        "sed -i -e 's/^\\( *Name: *\\) .*$/        Name:\"Go\",/' Handler.go",
        "sed -i -e 's/^\\( *Version: *\\) .*$/        Version:\" '$Version'\",/' Handler.go",   

    }
        exe_cmd(commands)

    }

    GetHands := GetHand{

            Name:"java",
            Version:" 1.7.0_71",

            }

if err := json.NewEncoder(w).Encode(GetHands); err != nil {
        panic(err)
    }

So on running this package, the url shows json value : {"name":"java","version":" 1.7.0_71"} If I call url : http://localhost:8080/?key=go this Handler.go gets updated to,

GetHands := GetHand{

        Name:"go",
        Version:" 1.9",

        }

If I stop the executable, run go build again and run executable again the url gets returned as :{"name":"go","version":" 1.9"}

So basically I need dynamic url which on hitting the http:/localhost/?key=go would return go's corresponding value annd htpp://localhost/?key=java would return java's corresponding value. This should be attained without restarting the executable or re-running the go build

Answer 1

Its quite difficult to understand exactly what you want. But I suspect that is essence you simply want to extract the output from a shell command and write it to JSON.

For this there is no need to modify the Handler.go file or do go build. You can simply write the output directly into the GetHand structure.

A basic example is as follows :

    package main

    import (
        "fmt"
        "os/exec"
    )

    var cmds = map[string][]string{
        "go":   []string{"/usr/local/go/bin/go", "version"},
        "java": []string{"java", "-version"},
    }

    type GetHand struct {
        Name    string
        Version string
    }

    func handleKey(key string) (*GetHand, error) {

        cmd := cmds[key]
        if cmd == nil {
            return nil, fmt.Errorf("No such key : %v", key)
        }

        b, err := exec.Command("/usr/local/go/bin/go", "version").Output()
        if err != nil {
            return nil, err
        }
        return &GetHand{
            Name:    key,
            Version: string(b),
        }, nil
    }

    func main() {
        h, err := handleKey("go")
        if err != nil {
            fmt.Println(err)
            return
        }
        fmt.Println(h)

        h, err = handleKey("java")
        if err != nil {
            fmt.Println(err)
            return
        }
        fmt.Println(h)
    }