Go与Web服务

最新推荐文章于 2024-11-04 23:57:39 发布

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最新推荐文章于 2024-11-04 23:57:39 发布

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分类专栏： Go

本文链接：https://blog.youkuaiyun.com/weixin_39777626/article/details/86165867

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本文深入探讨了Go语言在Web服务开发中的应用，包括如何使用Go处理XML和JSON数据，创建RESTful API，以及实现CRUD操作。文章详细讲解了数据解析和生成的过程，展示了Go语言在现代Web开发中的强大功能。

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Web服务

定义：与其他软件程序进行交互的软件程序
注意：终端用户不是人类而是软件程序

前后台通信方式

	SOAP	REST
全称	Simple Object Access Protocal（简单对象访问协议）	Representational State Transfer（具体状态传输）
实质	一种协议	一种设计理念
功能	用于交换定义在XML里面的结构化数据，能够跨越不同的网络协议并在不同的编程模型中使用	用于设计那些通过标准的几个动作来操纵资源，并以此来进行相互交流的程序
区别	功能驱动	数据驱动
关注点	API的设计	被发送报文的格式
使用的数据类型	XML	JSON

注意：在REST只允许用户使用指定的几个HTTP方法操纵资源，不允许用户对资源执行任意的动作，为此要发送特殊请求时，可以使用以下方法：

将动作转换为资源
将动作转换为资源的属性

如：要发送以下请求时可以这么做

ACTIVATE /user/456 HTTP/1.1

way1：

POST /user/456/activation HTTP/1.1
{“date”：“2015-05-15T13:05:05z”}

way2:

PATCH /user/456 HTTP/1.1
{"active":"true"}

通过Go分析和创建XML

分析XML

步骤：

创建用于存储XML数据的结构
使用xml.Unmarshal将XML数据解封到结构里面

post.xml

<?xml version="1.0" encoding="utf-8"?>
<post id="1">
	<content>Hello World!</content>
	<author id="2">Sau Sheong</author>
</post>

xml.go

package main

import (
	"encoding/xml"
	"fmt"
	"io/ioutil"
	"os"
)

type Post struct {
	XMLName xml.Name `xml:"post"`
	Id      string   `xml:"id,attr"`
	Content string   `xml:"content"`
	Author  Author   `xml:"author"`
	Xml     string   `xml:",innerxml"`
}

type Author struct {
	Id   string `xml:"id,attr"`
	Name string `xml:",chardata"`
}

func main() {
	xmlFile, err := os.Open("post.xml")
	if err != nil {
		fmt.Println("Error opening XML file:", err)
		return
	}
	defer xmlFile.Close()
	xmlData, err := ioutil.ReadAll(xmlFile)
	if err != nil {
		fmt.Println("Error reading XML data:", err)
		return
	}

	var post Post
	xml.Unmarshal(xmlData, &post)
	fmt.Println(post)
}

使用Decoder
post.xml

<?xml version="1.0" encoding="utf-8"?>
<post id="1">
	<content>Hello World!</content>
	<author id="2">Sau Sheong</author>
	<comments>
		<comment id="1">
			<content>Have a good day!</content>
			<author id="3">Adam</author>
		</comment>
		<comment id="2">
			<content>How are you today?</content>
			<author id="4">Betty</author>
		</comment>
	</comments>
</post>

xml.go

package main

import (
	"encoding/xml"
	"fmt"
	"io"
	"os"
)

type Post struct {
	XMLName  xml.Name  `xml:"post"`
	Id       string    `xml:"id,attr"`
	Content  string    `xml:"content"`
	Author   Author    `xml:"author"`
	Xml      string    `xml:",innerxml"`
	Comments []Comment `xml:"comments>comment"`
}

type Author struct {
	Id   string `xml:"id,attr"`
	Name string `xml:",chardata"`
}

type Comment struct {
	Id      string `xml:"id,attr"`
	Content string `xml:"content"`
	Author  Author `xml:"author"`
}

func main() {
	xmlFile, err := os.Open("post.xml")
	if err != nil {
		fmt.Println("Error opening XML file:", err)
		return
	}
	defer xmlFile.Close()

	decoder := xml.NewDecoder(xmlFile)
	for {
		t, err := decoder.Token()
		if err == io.EOF {
			break
		}
		if err != nil {
			fmt.Println("Error decodeing XML into tokens:", err)
			return
		}

		switch se := t.(type) {
		case xml.StartElement:
			if se.Name.Local == "comment" {
				var comment Comment
				decoder.DecodeElement(&comment, &se)
				fmt.Println(comment)
			}
		}
	}
}

创建XML

使用Marshal函数

package main

import (
	"encoding/xml"
	"fmt"
	"io/ioutil"
)

type Post struct {
	XMLName xml.Name `xml:"post"`
	Id      string   `xml:"id,attr"`
	Content string   `xml:"content"`
	Author  Author   `xml:"author"`
}

type Author struct {
	Id   string `xml:"id,attr"`
	Name string `xml:",chardata"`
}

func main() {
	post := Post{
		Id:      "1",
		Content: "Hello World!",
		Author: Author{
			Id:   "2",
			Name: "Sau Sheong",
		},
	}

	output, err := xml.Marshal(&post)
	if err != nil {
		fmt.Println("Error marshalling to XML:", err)
		return
	}
	err = ioutil.WriteFile("post.xml", output, 0644)
	if err != nil {
		fmt.Println("Error writing XML to file:", err)
		return
	}
}

生成的post.xml文件

<post id="1"><content>Hello World!</content><author id="2">Sau Sheong</author></post>

使用MarshalIndent函数

package main

import (
	"encoding/xml"
	"fmt"
	"io/ioutil"
)

type Post struct {
	XMLName xml.Name `xml:"post"`
	Id      string   `xml:"id,attr"`
	Content string   `xml:"content"`
	Author  Author   `xml:"author"`
}

type Author struct {
	Id   string `xml:"id,attr"`
	Name string `xml:",chardata"`
}

func main() {
	post := Post{
		Id:      "1",
		Content: "Hello World!",
		Author: Author{
			Id:   "2",
			Name: "Sau Sheong",
		},
	}

	output, err := xml.MarshalIndent(&post, "", "\t")
	if err != nil {
		fmt.Println("Error marshalling to XML:", err)
		return
	}
	err = ioutil.WriteFile("post.xml", []byte(xml.Header+string(output)), 0644)
	if err != nil {
		fmt.Println("Error writing XML to file:", err)
		return
	}
}

生成的post.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<post id="1">
	<content>Hello World!</content>
	<author id="2">Sau Sheong</author>
</post>

手动将Go结构编码至XML
过程：

1.创建结构&填充数据
2.创建XML文件（存储XML数据）
3.创建编码器（编码结构）
4.编码器将结构编码至XML文件

代码

package main

import (
	"encoding/xml"
	"fmt"
	"os"
)

type Post struct {
	XMLName xml.Name `xml:"post"`
	Id      string   `xml:"id,attr"`
	Content string   `xml:"content"`
	Author  Author   `xml:"author"`
}

type Author struct {
	Id   string `xml:"id,attr"`
	Name string `xml:",chardata"`
}

func main() {
	post := Post{
		Id:      "1",
		Content: "Hello World!",
		Author: Author{
			Id:   "2",
			Name: "Sau Sheong",
		},
	}

	xmlFile, err := os.Create("post.xml")
	if err != nil {
		fmt.Println("Error creating XML file:", err)
		return
	}
	encoder := xml.NewEncoder(xmlFile)
	encoder.Indent("", "\t")
	err = encoder.Encode(&post)
	if err != nil {
		fmt.Println("Error encoding XML to file:", err)
		return
	}
}

通过Go分析和创建JSON

分析JSON

post.json

{
	"id":1,
	"content":"Hello World!",
	"author":{
		"id":2,
		"name":"Sau Sheong"
	},
	"comments":[
		{
			"id":3,
			"content":"Have a good day!",
			"author":"Adam"
		},
		{
			"id":4,
			"content":"How are you today?",
			"author":"Betty"
		}
	]
}

JSON分析程序

package main

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

type Post struct {
	Id       int    `json:"id,attr"`
	Content  string    `json:"content"`
	Author   Author    `json:"author"`
	Comments []Comment `json:"comments"`
}

type Author struct {
	Id   int `json:"id,attr"`
	Name string `json:",chardata"`
}

type Comment struct {
	Id      int    `json:"id"`
	Content string `json:"content"`
	Author  string `json:"author"`
}

func main() {
	jsonFile, err := os.Open("post.json")
	if err != nil {
		fmt.Println("Error opening JSON file:", err)
		return
	}
	defer jsonFile.Close()
	jsonData, err := ioutil.ReadAll(jsonFile)
	if err != nil {
		fmt.Println("Error reading JSON data:", err)
		return
	}

	var post Post
	json.Unmarshal(jsonData, &post)
	fmt.Println(post)
}

使用Decoder

package main

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
)

type Post struct {
	Id       int       `json:"id,attr"`
	Content  string    `json:"content"`
	Author   Author    `json:"author"`
	Comments []Comment `json:"comments"`
}

type Author struct {
	Id   int    `json:"id,attr"`
	Name string `json:",chardata"`
}

type Comment struct {
	Id      int    `json:"id"`
	Content string `json:"content"`
	Author  string `json:"author"`
}

func main() {
	jsonFile, err := os.Open("post.json")
	if err != nil {
		fmt.Println("Error opening JSON file:", err)
		return
	}
	defer jsonFile.Close()

	decoder := json.NewDecoder(jsonFile)
	for {
		var post Post
		err := decoder.Decode(&post)
		if err == io.EOF {
			break
		}
		if err != nil {
			fmt.Println("Error decoding Json:", err)
			return
		}
		fmt.Println(post)
	}
}

创建JSON

将结构封装为JSON

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
)

type Post struct {
	Id       int       `json:"id,attr"`
	Content  string    `json:"content"`
	Author   Author    `json:"author"`
	Comments []Comment `json:"comments"`
}

type Author struct {
	Id   int    `json:"id,attr"`
	Name string `json:",chardata"`
}

type Comment struct {
	Id      int    `json:"id"`
	Content string `json:"content"`
	Author  string `json:"author"`
}

func main() {
	post := Post{
		Id:      1,
		Content: "Hello World!",
		Author: Author{
			Id:   2,
			Name: "Sau Sheong",
		},
		Comments: []Comment{
			Comment{
				Id:      3,
				Content: "Have a great day!",
				Author:  "Adam",
			},
			Comment{
				Id:      4,
				Content: "How are you today?",
				Author:  "Betty",
			},
		},
	}

	output, err := json.MarshalIndent(&post, "", "\t\t")
	if err != nil {
		fmt.Println("Error marshalling to JSON:", err)
		return
	}
	err = ioutil.WriteFile("post.json", output, 0644)
	if err != nil {
		fmt.Println("Error writing JSON to File:", err)
		return
	}
}

使用Encoder

package main

import (
	"encoding/json"
	"fmt"
	"os"
)

type Post struct {
	Id       int       `json:"id,attr"`
	Content  string    `json:"content"`
	Author   Author    `json:"author"`
	Comments []Comment `json:"comments"`
}

type Author struct {
	Id   int    `json:"id,attr"`
	Name string `json:",chardata"`
}

type Comment struct {
	Id      int    `json:"id"`
	Content string `json:"content"`
	Author  string `json:"author"`
}

func main() {
	post := Post{
		Id:      1,
		Content: "Hello World!",
		Author: Author{
			Id:   2,
			Name: "Sau Sheong",
		},
		Comments: []Comment{
			Comment{
				Id:      3,
				Content: "Have a great day!",
				Author:  "Adam",
			},
			Comment{
				Id:      4,
				Content: "How are you today?",
				Author:  "Betty",
			},
		},
	}

	jsonFile, err := os.Create("post.json")
	if err != nil {
		fmt.Println("Error creating JSON file:", err)
		return
	}
	encoder := json.NewEncoder(jsonFile)
	err = encoder.Encode(&post)
	if err != nil {
		fmt.Println("Error encoding JSON to file:", err)
		return
	}
}

创建Go Web服务

server,go

package main

import (
	"encoding/json"
	"net/http"
	"path"
	"strconv"
)

type Post struct {
	Id      int    `json:"id"`
	Content string `json:"content"`
	Author  string `json:"author"`
}

func main() {
	server := http.Server{
		Addr: "127.0.0.1:8080",
	}
	http.HandleFunc("/post/", handleRequest)
	server.ListenAndServe()
}

func handleRequest(w http.ResponseWriter, r *http.Request) {
	var err error
	switch r.Method {
	case "GET":
		err = handleGet(w, r)
	case "POST":
		err = handlePost(w, r)
	case "PUT":
		err = handlePut(w, r)
	case "DELETE":
		err = handleDelete(w, r)
	}
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
}

func handleGet(w http.ResponseWriter, r *http.Request) (err error) {
	id, err := strconv.Atoi(path.Base(r.URL.Path))
	if err != nil {
		return
	}
	post, err := retrieve(id)
	if err != nil {
		return
	}
	output, err := json.MarshalIndent(&post, "", "\t\t")
	if err != nil {
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.Write(output)
	return
}

func handlePost(w http.ResponseWriter, r *http.Request) (err error) {
	len := r.ContentLength
	body := make([]byte, len)
	r.Body.Read(body)
	var post Post
	json.Unmarshal(body, &post)
	err = post.create()
	if err != nil {
		return
	}
	w.WriteHeader(200)
	return
}

func handlePut(w http.ResponseWriter, r *http.Request) (err error) {
	id, err := strconv.Atoi(path.Base(r.URL.Path))
	if err != nil {
		return
	}
	post, err := retrieve(id)
	if err != nil {
		return
	}
	len := r.ContentLength
	body := make([]byte, len)
	r.Body.Read(body)
	json.Unmarshal(body, &post)
	err = post.update()
	if err != nil {
		return
	}
	w.WriteHeader(200)
	return
}

func handleDelete(w http.ResponseWriter, r *http.Request) (err error) {
	id, err := strconv.Atoi(path.Base(r.URL.Path))
	if err != nil {
		return
	}
	post, err := retrieve(id)
	if err != nil {
		return
	}
	err = post.delete()
	if err != nil {
		return
	}
	w.WriteHeader(200)
	return
}

data.go

package main

import (
	"database/sql"

	_ "github.com/lib/pq"
)

var Db *sql.DB

func init() {
	var err error
	Db, err = sql.Open("postgres", "user=postgres dbname=testdb password=***********  sslmode=disable")
	if err != nil {
		panic(err)
	}
}

func retrieve(id int) (post Post, err error) {
	post = Post{}
	err = Db.QueryRow("select id,content,author from posts where id=$1", id).Scan(&post.Id, &post.Content, &post.Author)
	return
}

func (post *Post) create() (err error) {
	statement := "insert into posts (content,author) values ($1,$2) returning id"
	stmt, err := Db.Prepare(statement)
	if err != nil {
		return
	}
	defer stmt.Close()
	err = stmt.QueryRow(post.Content, post.Author).Scan(&post.Id)
	return
}

func (post *Post) update() (err error) {
	_, err = Db.Exec("update posts set content=$2,author=$3 where id=$1", post.Id, post.Content, post.Author)
	return
}

func (post *Post) delete() (err error) {
	_, err = Db.Exec("delete from posts where id=$1", post.Id)
	return
}

创建

curl -i -X POST -H "Content-Type:application/json" -d '{"content":"My first post","author":"Sau Sheong"}' http://127.0.0.1:8080/post/

获取

curl -i -X GET http://127.0.0.1.:8080/post/1

更新

curl -i -X PUT -H "Content-Type:application/json" -d '{"content":"Updated psot","author":"Sau Sheong"}' http://127.0.0.1:8080/post/1

删除

curl -i -X DELETE http://127.0.0.1:8080/post/1