Golang Echo bind path param and json body separately

Question

I am using Echo web framework in Golang and I wrote this code

package main

import (
    "github.com/labstack/echo/v4"
    "net/http"
)

type ProjectPath struct {
    ID string `param:"id"`
}

type ProjectBody struct {
    Name string `json:"name"`
}

func main() {
    e := echo.New()

    e.POST("/project/:id", getProjectHandler)

    e.Start(":8080")
}

func getProjectHandler(c echo.Context) error {
    path := new(ProjectPath)
    if err := c.Bind(path); err != nil {
        return err
    }

    body := new(ProjectBody)
    if err := c.Bind(body); err != nil {
        return err
    }

    // Access the fields separately
    projectID := path.ID
    projectName := body.Name

    // Do something with the path and body fields...

    // Return a response
    return c.String(http.StatusOK, "Project ID: "+projectID+", Project Name: "+projectName)
}

I am trying to bind a path param and json body separately in a post request but I am getting an EOF error while trying to run it.

I am using replit for testing and the server is running on: https://echotest.sandeepacharya.repl.co

Curl Post Request:

 curl -X POST https://echotest.sandeepacharya.repl.co/project/123 -H "Content-Type: application/json" -d '{"name":"Sandeep"}'

Response:

{"message":"EOF"}

Answer 1

Bind() reads request body directly from the socket and once read it can't read again, hence the EOF error

https://github.com/labstack/echo/issues/782#issuecomment-317503513

The issue is occured due to that you are attempted to bind the request body twice. The second c.Bind() will raise an error because the request body has already been read and consumed.

if you want to read the request with different struct, you can follow this approach

package main

import (
    "fmt"
    "net/http"

    "github.com/labstack/echo/v4"
)

type ProjectPath struct {
    ID string `param:"id"`
}

type ProjectBody struct {
    Name string `json:"name"`
}

type ProjectRequest struct {
    ProjectPath
    ProjectBody
}

func main() {
    e := echo.New()

    e.POST("/project/:id", getProjectHandler)

    e.Start(":8080")
}

func getProjectHandler(c echo.Context) error {

    project := new(ProjectRequest)
    if err := c.Bind(project); err != nil {
        fmt.Println("Error happened due to::", err)
        return err
    }

    // Access the fields separately
    projectID := project.ID
    projectName := project.Name

    // Do something with the path and body fields...

    // Return a response
    return c.String(http.StatusOK, "Project ID: "+projectID+", Project Name: "+projectName)
}

or you can use only one struct to bind the request

type ProjectRequest struct {
    Name string `json:"name"`
    ID string `param:"id"`
}

Answer 2

If you want to do the binding separately then you'll need to use the source specific bind methods. These methods however are NOT available in the context, instead they are implemented by the DefaultBinder.

See also: https://echo.labstack.com/guide/binding/#direct-source

func getProjectHandler(c echo.Context) error {
    path := new(ProjectPath)
    if err := (&echo.DefaultBinder{}).BindPathParams(c, path); err != nil {
        return err
    }

    body := new(ProjectBody)
    if err := (&echo.DefaultBinder{}).BindBody(c, body); err != nil {
        return err
    }

    // Access the fields separately
    projectID := path.ID
    projectName := body.Name

    // Do something with the path and body fields...

    // Return a response
    return c.String(http.StatusOK, "Project ID: "+projectID+", Project Name: "+projectName)
}