[英]Post Request with PostgreSQL and json-api returns an empty body
After a POST request, i was expecting to have a last inserted record marshalled into json, but instead returns an empty body. 在POST请求之后,我期望将最后插入的记录编组到json中,但是返回一个空的正文。 What am i not doing well?
我做得不好吗?
package models
import (
"encoding/json"
"errors"
"flag"
"fmt"
"log"
"net/http"
"strconv"
"github.com/go-chi/chi"
"github.com/google/jsonapi"
"github.com/thedevsaddam/renderer"
"github.com/xo/dburl"
)
var rnd = renderer.New()
var flagVerbose = flag.Bool("v", false, "verbose")
var FlagURL = flag.String("url", "postgres://postgres:@127.0.0.1/sweb", "url")
// Page represents a row from 'public.pages'.
type Page struct {
Tag string `jsonapi:"attr,tag"` // tag
Body string `jsonapi:"attr,body"` // body
Slug string `jsonapi:"attr,slug"` // slug
Title string `jsonapi:"attr,title"` // title
ID int `jsonapi:"primary,pages"` // id
Link string `jsonapi:"attr,link"` // link
// xo fields
_exists, _deleted bool
}
func (page Page) JSONAPILinks() *jsonapi.Links {
return &jsonapi.Links{
"self": fmt.Sprintf("https://%d", page.ID),
}
}
I believe this is the culprit. 我相信这是罪魁祸首。 After inserting a record, it should return the last inserted record as specified.
插入记录后,它应返回指定的最后插入的记录。
func (p *Page) PInsert(db XODB) (*Page, error) {
var err error
// if already exist, bail
if p._exists {
return p, errors.New("insert failed: already exists")
}
// sql insert query, primary key provided by sequence
const sqlstr = `INSERT INTO public.pages (` +
`tag, body, slug, title` +
`) VALUES (` +
`$1, $2, $3, $4` +
`) RETURNING id, tag, body, title`
// run query
XOLog(sqlstr, p.Tag, p.Body, p.Slug, p.Title)
err = db.QueryRow(sqlstr, p.Tag, p.Body, p.Slug, p.Title).Scan(&p.ID, &p.Tag, &p.Body, &p.Title)
if err != nil {
return p, err
}
// set existence
p._exists = true
return p, nil
}
Update updates the Page in the database and return last inserted records. Update更新数据库中的Page,并返回最后插入的记录。 The same should apply for the Update function
同样适用于更新功能
func (p *Page) Update(db XODB) (*Page, error) {
var err error
// if doesn't exist, bail
if !p._exists {
return p, errors.New("update failed: does not exist")
}
// if deleted, bail
if p._deleted {
return p, errors.New("update failed: marked for deletion")
}
// sql query
const sqlstr = `UPDATE public.pages SET (` +
`tag, body, slug, title` +
`) = ( ` +
`$1, $2, $3, $4` +
`) WHERE id = $5`
// run query
XOLog(sqlstr, p.Tag, p.Body, p.Slug, p.Title, p.ID)
_, err = db.Exec(sqlstr, p.Tag, p.Body, p.Slug, p.Title, p.ID)
return p, err
}
func (p *Page) PSave(db XODB) (*Page, error) {
if p.Exists() {
return p.Update(db)
}
return p.PInsert(db)
}
func NewPage(w http.ResponseWriter, r *http.Request) {
db, err := dburl.Open(*FlagURL)
defer db.Close()
if err != nil {
log.Fatal(err)
}
var page Page
//page := new(Page)
if err := jsonapi.UnmarshalPayload(r.Body, &page); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
p, err := page.PSave(db)
if err != nil {
fmt.Println(err)
if err := jsonapi.MarshalPayload(w, p); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
fmt.Println(err)
}
}
w.Header().Set("Content-Type", jsonapi.MediaType)
w.WriteHeader(http.StatusCreated)
}
This is the last function i believe the issue is happening from. 这是我认为问题发生的最后功能。 the last inserted record supposed to be marshalled into json.
最后插入的记录应该被编组到json中。
Your last section of code contains a number of mistakes. 您的最后一段代码包含许多错误。 The relevant section (without the useless and obfuscating Printlns) is:
相关部分(没有无用且晦涩难懂的Printlns)是:
p, err := page.PSave(db)
if err != nil {
if err := jsonapi.MarshalPayload(w, p); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
}
}
w.Header().Set("Content-Type", jsonapi.MediaType)
w.WriteHeader(http.StatusCreated)
And the primary mistake is that json.MarshalPayload
is only called when err != nil
. 而且主要的错误是
json.MarshalPayload
仅在err != nil
时才被调用。 In other words, you only serialize the page if you failed to save it. 换句话说, 只有在保存页面失败 时才对页面进行序列化。
The secondary mistake is that jsonapi.MarshalPayload
will call Write
on the http.ResponseWriter
. 第二个错误是
jsonapi.MarshalPayload
将在http.ResponseWriter
上调用Write
。 This turns all subsequent calls to Header().Set
and WriteHeader
into no-ops. 这会将对
Header().Set
和WriteHeader
所有后续调用转换为无操作。
More correct code would look like this. 更正确的代码如下所示。
// 1. Save the page in the database, bail on error
p, err := page.PSave(db)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
// 2. Marshal the page into an intermediate buffer, bail on error
var buf bytes.Buffer
if err := jsonapi.MarshalPayload(&buf, p); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
// 3. Write the entire response; failures to write the intermediate buffer
// cannot be communicated over HTTP
w.Header().Set("Content-Type", jsonapi.MediaType)
w.WriteHeader(http.StatusCreated)
if _, err := buf.WriteTo(w); err != nil {
log.Printf("failed to write response: %v", err)
return
}
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