Adding chapter 8

chapter8/custom_client_timeout.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"time"
+)
+
+func main() {
+	cc := &http.Client{Timeout: time.Second}
+	res, err := cc.Get("http://goinpracticebook.com")
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	b, _ := ioutil.ReadAll(res.Body)
+	res.Body.Close()
+	fmt.Printf("%s", b)
+}

chapter8/custom_request_delete.go

@@ -0,0 +1,12 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+)
+
+func main() {
+	req, _ := http.NewRequest("DELETE", "http://example.com/foo/bar", nil)
+	res, _ := http.DefaultClient.Do(req)
+	fmt.Printf("%s", res.Status)
+}

chapter8/get_custom_error.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"os"
+)
+
+type Error struct {
+	HTTPCode int    `json:"-"`
+	Code     int    `json:"code,omitempty"`
+	Message  string `json:"message"`
+}
+
+func (e Error) Error() string {
+	fs := "HTTP: %d, Code: %d, Message: %s"
+	return fmt.Sprintf(fs, e.HTTPCode, e.Code, e.Message)
+}
+
+func get(u string) (*http.Response, error) {
+	res, err := http.Get(u)
+	if err != nil {
+		return res, err
+	}
+
+	if res.StatusCode < 200 || res.StatusCode >= 300 {
+		if res.Header.Get("Content-Type") != "application/json" {
+			sm := "Unknown error. HTTP status: %s"
+			return res, fmt.Errorf(sm, res.Status)
+		}
+		b, _ := ioutil.ReadAll(res.Body)
+		res.Body.Close()
+		var data struct {
+			Er Error `json:"error"`
+		}
+		err = json.Unmarshal(b, &data)
+		if err != nil {
+			sm := "Unable to parse json: %s. HTTP status: %s"
+			return res, fmt.Errorf(sm, err, res.Status)
+		}
+		data.Er.HTTPCode = res.StatusCode
+
+		return res, data.Er
+	}
+
+	return res, nil
+}
+
+func main() {
+	res, err := get("http://localhost:8080")
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	b, _ := ioutil.ReadAll(res.Body)
+	res.Body.Close()
+	fmt.Printf("%s", b)
+}

chapter8/get_semantic_version_api.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+)
+
+func main() {
+	ct := "applicaiton/vnd.mytodos.json; version=2.0"
+	req, _ := http.NewRequest("GET", "http://localhost:8080/test", nil)
+	req.Header.Set("Accept", ct)
+	res, _ := http.DefaultClient.Do(req)
+	if res.Header.Get("Content-Type") != ct {
+		fmt.Println("Unexpected content type returned")
+		return
+	}
+	b, _ := ioutil.ReadAll(res.Body)
+	res.Body.Close()
+	fmt.Printf("%s", b)
+}

chapter8/http_custom_error.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+)
+
+type Error struct {
+	HTTPCode int    `json:"-"`
+	Code     int    `json:"code,omitempty"`
+	Message  string `json:"message"`
+}
+
+func JSONError(w http.ResponseWriter, e Error) {
+	data := struct {
+		Er Error `json:"error"`
+	}{e}
+	b, err := json.Marshal(data)
+	if err != nil {
+		http.Error(w, "Internal Server Error", 500)
+		return
+	}
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(e.HTTPCode)
+	fmt.Fprint(w, string(b))
+}
+
+func diaplayError(w http.ResponseWriter, r *http.Request) {
+	e := Error{
+		HTTPCode: http.StatusForbidden,
+		Code:     123,
+		Message:  "An Error Occurred",
+	}
+	JSONError(w, e)
+}
+
+func main() {
+	http.HandleFunc("/", diaplayError)
+	http.ListenAndServe(":8080", nil)
+}

chapter8/http_error.go

@@ -0,0 +1,12 @@
+package main
+
+import "net/http"
+
+func diaplayError(w http.ResponseWriter, r *http.Request) {
+	http.Error(w, "An Error Occurred", http.StatusForbidden)
+}
+
+func main() {
+	http.HandleFunc("/", diaplayError)
+	http.ListenAndServe(":8080", nil)
+}

chapter8/http_timeout_handling.go

@@ -0,0 +1,109 @@
+package main
+
+import (
+	// "io"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func main() {
+	file, err := os.Create("ff.dmg")
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	defer file.Close()
+
+	location := "https://download-installer.cdn.mozilla.net/pub/firefox/releases/40.0.3/mac/en-US/Firefox%2040.0.3.dmg"
+	err = download(location, file, 100)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	fi, err := file.Stat()
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	fmt.Printf("Got it with %v bytes downloaded", fi.Size())
+}
+
+func download(location string, file *os.File, retries int64) error {
+	req, err := http.NewRequest("GET", location, nil)
+	if err != nil {
+		return err
+	}
+	fi, err := file.Stat()
+	if err != nil {
+		return err
+	}
+	current := fi.Size()
+	if current > 0 {
+		start := strconv.FormatInt(current, 10)
+		req.Header.Set("Range", "bytes="+start+"-")
+	}
+
+	cc := &http.Client{Timeout: 5 * time.Minute}
+	res, err := cc.Do(req)
+	if err != nil && hasTimedOut(err) {
+		if retries > 0 {
+			return download(location, file, retries-1)
+		}
+		return err
+	} else if err != nil {
+		return err
+	}
+
+	if res.StatusCode < 200 || res.StatusCode >= 300 {
+		errFmt := "Unsuccess HTTP request. Status: %s"
+		return fmt.Errorf(errFmt, res.Status)
+	}
+
+	if res.Header.Get("Accept-Ranges") != "bytes" {
+		retries = 0
+	}
+
+	_, err = io.Copy(file, res.Body)
+	if err != nil && hasTimedOut(err) {
+		if retries > 0 {
+			return download(location, file, retries-1)
+		}
+		return err
+	} else if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func hasTimedOut(err error) bool {
+	switch err := err.(type) {
+	case *url.Error:
+		if err, ok := err.Err.(net.Error); ok && err.Timeout() {
+			return true
+		}
+	case net.Error:
+		if err.Timeout() {
+			return true
+		}
+	case *net.OpError:
+		if err.Timeout() {
+			return true
+		}
+	}
+
+	errTxt := "use of closed network connection"
+	if err != nil && strings.Contains(err.Error(), errTxt) {
+		return true
+	}
+
+	return false
+}

chapter8/parse_arbitrary_json.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+)
+
+var ks = []byte(`{
+"firstName": "Jean",
+"lastName": "Bartik",
+"age": 86,
+"education": [
+	{
+		"institution": "Northwest Missouri State Teachers College",
+		"degree": "Bachelor of Science in Mathematics"
+	},
+	{
+		"institution": "University of Pennsylvania",
+		"degree": "Masters in English"
+	}
+],
+"spouse": "William Bartik",
+"children": [
+	"Timothy John Bartik",
+	"Jane Helen Bartik",
+	"Mary Ruth Bartik"
+]
+}`)
+
+func main() {
+	var f interface{}
+	err := json.Unmarshal(ks, &f)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	fmt.Println(f)
+
+	m := f.(map[string]interface{})
+	fmt.Println(m["firstName"])
+
+	fmt.Print("interface{} ")
+	printJSON(f)
+}
+
+func printJSON(v interface{}) {
+	switch vv := v.(type) {
+	case string:
+		fmt.Println("is string", vv)
+	case float64:
+		fmt.Println("is float64", vv)
+	case []interface{}:
+		fmt.Println("is an array:")
+		for i, u := range vv {
+			fmt.Print(i, " ")
+			printJSON(u)
+		}
+	case map[string]interface{}:
+		fmt.Println("is an object:")
+		for i, u := range vv {
+			fmt.Print(i, " ")
+			printJSON(u)
+		}
+	default:
+		fmt.Println("Unknown type")
+	}
+}