07: Demos

web/07/demos/00_method_receiver.go

@@ -0,0 +1,26 @@
+package main
+
+import "fmt"
+
+type Person struct {
+	Name string
+	Age  int
+}
+
+// Wert-Receiver: arbeitet auf einer Kopie
+func (p Person) Greet() {
+	fmt.Println("Hallo,", p.Name)
+}
+
+// Zeiger-Receiver: kann das Original ändern
+func (p *Person) Birthday() {
+	p.Age++
+}
+
+func main() {
+	a := Person{Name: "Karl", Age: 30}
+
+	a.Greet()          // Ausgabe: Hallo, Karl
+	a.Birthday()       // Alter wird erhöht
+	fmt.Println(a.Age) // Ausgabe: 31
+}

web/07/demos/01_helloworld_http.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+)
+
+type helloHandler int
+
+func (hello helloHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintf(w, "Hello World %d!", hello)
+}
+
+func main() {
+	var world helloHandler
+	world = 42
+	http.ListenAndServe("localhost:8080", world)
+}

web/07/demos/02_responsewriter_http.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+	"net/http"
+)
+
+type respExampleHandler int
+
+func (hello respExampleHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("my-http-header", "Ein beliebiger Text")
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	w.WriteHeader(http.StatusFound)
+	w.Write([]byte("<h1>Dies ist eine HTML-Überschrift<h1>"))
+}
+
+func main() {
+	var r respExampleHandler
+	http.ListenAndServe("localhost:8080", r)
+}

web/07/demos/03_get_request_http.go

@@ -0,0 +1,36 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+)
+
+type reqExampleHandler int
+
+func (hello reqExampleHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+
+	if r.Method != http.MethodGet {
+		http.Error(w, "Only GET requests are allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	fmt.Println("Method:", r.Method)
+	fmt.Println("URL:", r.URL.String())
+	fmt.Println("Host:", r.Host)
+	fmt.Println("Accept-Header", r.Header.Get("Accept"))
+
+	queryParams := r.URL.Query()
+	fmt.Println("Query Parameters:")
+	for key, values := range queryParams {
+		for _, value := range values {
+			fmt.Printf("  %s = %s\n", key, value)
+		}
+	}
+
+	w.Write([]byte("<h1>GET: http.Request-Beispiel<h1>"))
+}
+
+func main() {
+	var r reqExampleHandler
+	http.ListenAndServe("localhost:8080", r)
+}

web/07/demos/04_post_request_http.go

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+package main
+
+import (
+	"fmt"
+	"net/http"
+)
+
+type formExampleHandler int
+
+func (formHandler formExampleHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+
+	if r.Method != http.MethodPost {
+		http.Error(w, "Only POST requests are allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	// Formulardaten parsen und Überprüfen, ob ungültige Formulardaten gesendet wurde
+	if err := r.ParseForm(); err != nil {
+		http.Error(w, "Fehler beim Parsen des Formulars", http.StatusBadRequest)
+		return
+	}
+
+	// Überprüfen, ob leeres Formular gesendet wurde
+	if len(r.PostForm) == 0 {
+		http.Error(w, "Kein POST-Formular gesendet", http.StatusBadRequest)
+		return
+	}
+
+	// Zugriff auf PostForm-Daten
+	// string mit Wert des Feldes "name"
+	name := r.PostForm.Get("name")
+	// []string mit allen ausgewählten Werten der Checkbox "hobby"
+	hobbies := r.PostForm["hobby"]
+
+	// Ausgabe der Werte
+	fmt.Fprintf(w, "Name: %s\n", name)
+	fmt.Fprintf(w, "Hobbies:\n")
+	for _, h := range hobbies {
+		fmt.Fprintf(w, "- %s\n", h)
+	}
+
+}
+
+func main() {
+	var r formExampleHandler
+	http.ListenAndServe("localhost:8080", r)
+}

web/07/demos/05_encode_json.go

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+package main
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+type jsonEncodeHandler int
+
+type User struct {
+	Firstname string `json:"firstname"`
+	Lastname  string `json:"lastname"`
+	Age       int    `json:"age"`
+}
+
+func (jsonHandler jsonEncodeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	mariam := User{
+		Firstname: "Mariam",
+		Lastname:  "Okonkwo",
+		Age:       25,
+	}
+	json.NewEncoder(w).Encode(mariam)
+}
+
+func main() {
+	var enc jsonEncodeHandler
+	http.ListenAndServe("localhost:8080", enc)
+}

web/07/demos/06_decode_json.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+)
+
+type jsonDecodeHandler int
+
+type User struct {
+	Firstname string `json:"firstname"`
+	Lastname  string `json:"lastname"`
+	Age       int    `json:"age"`
+}
+
+func (jsonHandler jsonDecodeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	var user User
+	json.NewDecoder(r.Body).Decode(&user)
+	fmt.Fprintf(w, "%s %s is %d years old!", user.Firstname, user.Lastname, user.Age)
+}
+
+func main() {
+	var dec jsonDecodeHandler
+	http.ListenAndServe("localhost:8080", dec)
+}

web/07/demos/post_form.html

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+<!DOCTYPE html>
+<html lang="en">
+
+<head>
+	<meta charset="UTF-8">
+	<title>Einfaches Formular für Backend</title>
+</head>
+
+<body>
+	<form method="POST" action="http://localhost:8080">
+		<label for="nameLabel">Name</label>
+		<input name="name" id="nameLabel" />
+		<p>Hobbies:
+			<label><input type="checkbox" name="hobby" value="lesen"> Lesen</label>
+			<label><input type="checkbox" name="hobby" value="kochen"> Kochen</label>
+			<label><input type="checkbox" name="hobby" value="wandern"> Wandern</label>
+		</p>
+		<button type="submit">Absenden</button>
+	</form>
+</body>
+
+</html>