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一个使用github.com/gorilla/mux实现REST API Service的例子，主要内容包括：
GET/POST方法，如何接收path参数，query参数，以及POST body参数
如何设置返回状态码，如何返回JSON数据body
验证Handler函数是同步的还是异步的，单线程的还是多线程的
GET方法
发布一个GET REST API，接收client请求，并解析URL带的查询参数，最后返回JSON数据。
main.go
package main
import (
"flag"
"fmt"
"log"
"net/http"
"github.com/gorilla/mux"
)
var (
hostname string
port int
)
func init() {
flag.StringVar(&hostname, "hostname", "0.0.0.0", "The hostname or IP on which the REST server will listen")
flag.IntVar(&port, "port", 8080, "The port on which the REST server will listen")
}
func main() {
flag.Parse()
var address = fmt.Sprintf("%s:%d", hostname, port)
log.Println("REST service listening on", address)
// register router
router := mux.NewRouter().StrictSlash(true)
router.
HandleFunc("/api/service/get", MyGetHandler).
Methods("GET")
// start server listening
err := http.ListenAndServe(address, router)
if err != nil {
log.Fatalln("ListenAndServe err:", err)
}
log.Println("Server end")
}
handle.go
package main
import (
"encoding/json"
"fmt"
"io/ioutil"
"net/http"
"github.com/gorilla/mux"
)
func MyGetHandler(w http.ResponseWriter, r *http.Request) {
// parse query parameter
vals := r.URL.Query()
param, _ := vals["servicename"] // get query parameters
// composite response body
var res = map[string]string{"result":"succ", "name":param[0]}
response, _ := json.Marshal(res)
w.Header().Set("Content-Type", "application/json")
w.Write(response)
}
运行
# on server
$ go build && ./main
2017/09/16 15:04:23 REST service listening on 0.0.0.0:8080
# on client
$ curl -X GET http://localhost:8080/api/service/get?servicename=myname
{"name":"myname","result":"succ"}
POST方法
这个例子client发送POST消息，并使用path变量，同时附带JSON格式body消息体，server端解析body内容，并返回JSON信息。
这里只给出POST相关代码，其他框架的代码请参考GET方法
main.go
// register router
router := mux.NewRouter().StrictSlash(true)
router.
HandleFunc("/api/service/get", MyGetHandler).
Methods("GET")
router.
HandleFunc("/api/service/{servicename}/post", MyPostHandler).
Methods("POST")
handle.go
func MyPostHandler(w http.ResponseWriter, r *http.Request) {
// parse path variable
vars := mux.Vars(r)
servicename := vars["servicename"]
// parse JSON body
var req map[string]interface{}
body, _ := ioutil.ReadAll(r.Body)
json.Unmarshal(body, &req)
servicetype := req["servicetype"].(string)
// composite response body
var res = map[string]string{"result":"succ", "name":servicename, "type":servicetype}
response, _ := json.Marshal(res)
w.Header().Set("Content-Type", "application/json")
w.Write(response)
}
运行
$ curl -X POST -d '{"servicetype":"mytype"}' http://localhost:8080/api/service/myservice/post
{"name":"myservice","result":"succ","type":"mytype"}
HTTP 返回值
上面例子返回的都是200 OK，如何可以根据服务运行状态返回不同的状态码呢？
以GET方法为例
handler.go
func MyGetHandler(w http.ResponseWriter, r *http.Request) {
var res map[string]string = make(map[string]string)
var status = http.StatusOK
vals := r.URL.Query()
param, ok := vals["name"]
if (!ok) {
res["result"] = "fail"
res["error"] = "required parameter name is missing"
status = http.StatusBadRequest
} else {
res["result"] = "succ"
res["name"] = param[0]
status = http.StatusOK
}
response, _ := json.Marshal(res)
w.WriteHeader(status)
w.Header().Set("Content-Type", "application/json")
w.Write(response)
}
运行结果
第一个请求，返回200 OK
$ curl -v -X GET http://localhost:8080/api/service/get?name=myname
* Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 8080 (#0)
> GET /api/service/get?name=myname HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.43.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Date: Sat, 16 Sep 2017 07:41:38 GMT
< Content-Length: 33
< Content-Type: text/plain; charset=utf-8
<
* Connection #0 to host localhost left intact
{"name":"myname","result":"succ"}
第二个请求，返回400 Bad Request
$ curl -v -X GET http://localhost:8080/api/service/get
* Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 8080 (#0)
> GET /api/service/get HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.43.0
> Accept: */*
>
< HTTP/1.1 400 Bad Request
< Date: Sat, 16 Sep 2017 07:41:42 GMT
< Content-Length: 62
< Content-Type: text/plain; charset=utf-8
<
* Connection #0 to host localhost left intact
{"error":"required parameter name is missing","result":"fail"}
Handler函数是同步的还是异步的
在前面的例子中我们看到了，w http.ResponseWriter可以用来设置返回信息的Status值，Header信息，以及Body内容，如果我们什么也不做，会出什么结果呢，验证
handler.go
func MyGetHandler(w http.ResponseWriter, r *http.Request) {
// do nothing
}
测试
$ curl -v -X GET http://localhost:8080/api/service/get?name=myname
* Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 8080 (#0)
> GET /api/service/get?name=myname HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.43.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Date: Sat, 16 Sep 2017 07:50:18 GMT
< Content-Length: 0
< Content-Type: text/plain; charset=utf-8
<
* Connection #0 to host localhost left intact
可以看到client正常的收到了200 OK的返回码。
再做一个例子，让Handler sleep一段时间
func MyGetHandler(w http.ResponseWriter, r *http.Request) {
time.Sleep(5*time.Second);
}
客户端
$ time curl -v -X GET http://localhost:8080/api/service/get?name=myname
* Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 8080 (#0)
> GET /api/service/get?name=myname HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.43.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Date: Sat, 16 Sep 2017 07:56:12 GMT
< Content-Length: 0
< Content-Type: text/plain; charset=utf-8
<
* Connection #0 to host localhost left intact
real 0m5.081s
user 0m0.005s
sys 0m0.009s
可以看到client在5秒之后正常的返回了，那么我们的结论是Handler函数返回的时候，client也就收到了server的返回；所以handler是一个同步调用函数。然后紧接着我们自然想到另一个问题。
Handler函数是单线程的还是多线程的
第一个问题，不同的handler能否同时进来
handler.go
func MyGetHandler(w http.ResponseWriter, r *http.Request) {
log.Println("entry of MyGetHandler")
time.Sleep(10*time.Second);
log.Println("exit of MyGetHandler")
}
func MyPostHandler(w http.ResponseWriter, r *http.Request) {
log.Println("entry of MyPostHandler")
time.Sleep(2*time.Second);
log.Println("exit of MyPostHandler")
}
测试
打开三个终端，一个运行server，一个调用MyGetHander，另一个调用 MyPostHandler。
终端1: server
2017/09/16 16:12:32 entry of MyGetHandler
2017/09/16 16:12:35 entry of MyPostHandler
2017/09/16 16:12:37 exit of MyPostHandler
2017/09/16 16:12:42 exit of MyGetHandler
终端2: MyGetHandler
$ date && time curl -X GET http://localhost:8080/api/service/get?name=myname
Sat Sep 16 16:12:32 CST 2017
real 0m10.020s
user 0m0.006s
sys 0m0.006s
终端2: MyPostHandler
$ date && time curl -X POST -d '{"servicetype":"mytype"}' http://localhost:8080/api/service/myservice/post
Sat Sep 16 16:12:35 CST 2017
real 0m2.017s
user 0m0.005s
sys 0m0.005s
通过比较时间戳，我们可以发现GetHandler已经在处理了，此时PostHandler刚进来，然后PostHander退出后，GetHander再退出，因此不同的Handler的执行方式是多线程的，多个请求可以冲入。
第2个问题，同一个handler能否同时进来
handler.go
func MyGetHandler(w http.ResponseWriter, r *http.Request) {
log.Println("entry of MyGetHandler")
vals := r.URL.Query()
param, ok := vals["name"]
if (ok) {
log.Println("name=", param[0])
}
time.Sleep(5*time.Second);
log.Println("exit of MyGetHandler")
}
测试
和第一个问题一样采用三个终端
终端1: server
2017/09/16 16:18:17 entry of MyGetHandler
2017/09/16 16:18:17 name= myname1
2017/09/16 16:18:19 entry of MyGetHandler
2017/09/16 16:18:19 name= myname2
2017/09/16 16:18:22 exit of MyGetHandler
2017/09/16 16:18:24 exit of MyGetHandler
终端2: MyGetHandler
$ date && time curl -X GET http://localhost:8080/api/service/get?name=myname1
Sat Sep 16 16:18:17 CST 2017
real 0m5.032s
user 0m0.005s
sys 0m0.009s
终端2: MyPostHandler
$ date && time curl -X GET http://localhost:8080/api/service/get?name=myname2
Sat Sep 16 16:18:19 CST 2017
real 0m5.021s
user 0m0.006s
sys 0m0.006s
结论是同一个Handler函数也是可以重入的。