JSON, Readers, Writers, Encoding and Decoding JSON Streams

main.go

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"strings"
)

func main() {
	fmt.Println("Default Temp Dir: ", os.TempDir())

	dir, e := ioutil.TempDir(".", "*")
	if e != nil {
		panic(e)
	}
	fmt.Println("Temp Dir: ", dir)

	f, e := ioutil.TempFile(dir, "*")
	if e != nil {
		panic(e)
	}
	fmt.Println("Temp file: ", f.Name())

	defer func() {
		if e := os.Remove(dir); e != nil {
			panic(e)
		}
		fmt.Println("Removed dir: ", dir)
	}()

	defer func() {
		if e := os.Remove(f.Name()); e != nil {
			panic(e)
		}
		fmt.Println("Removed file: ", f.Name())
	}()

	defer func() {
		if e := f.Close(); e != nil {
			panic(e)
		}
		fmt.Println("Closed file: ", f.Name())
	}()

	type Item struct {
		ID   int    `json:"id"`
		Name string `json:"name"`
	}

	var items = []Item{{1, "John"}, {2, "Jane"}}
	if e := json.NewEncoder(f).Encode(items); e != nil {
		panic(e)
	}

	if _, e := f.Seek(0, io.SeekStart); e != nil {
		panic(e)
	}

	dec := json.NewDecoder(f)
	if token, e := dec.Token(); e != nil {
		panic(e)
	} else {
		fmt.Println(token)
	}
	var item Item
	for dec.More() {
		err := dec.Decode(&item)
		if err != nil {
			panic(err)
		}
		fmt.Printf("item=%+v\n", item)
	}
	if token, e := dec.Token(); e != nil {
		panic(e)
	} else {
		fmt.Println(token)
	}

	if _, e := f.Seek(0, io.SeekStart); e != nil {
		panic(e)
	}

	if e := json.NewDecoder(f).Decode(&items); e != nil {
		panic(e)
	}
	fmt.Printf("items=%+v\n", items)

	var buffer bytes.Buffer
	enc := json.NewEncoder(&buffer)
	reader := strings.NewReader(`{"id":1,"name": "John"}{"id":2,"name":"Jane"}`)
	dec = json.NewDecoder(reader)
	for dec.More() {
		if e := dec.Decode(&item); e != nil {
			panic(e)
		}
		fmt.Printf("%+v\n", item)
		if e := enc.Encode(item); e != nil {
			panic(e)
		}
	}
	fmt.Println(buffer.String())
}