引言

在前面上一次的实战中，我们搭建了dapr的本地开发环境，并且部署了dapr官方的Hello World示例代码，为了加深对Dapr的理解，在本文中使用go 和 java语言重写Dapr的官方示例代码

Dapr的官方示例代码Hello World的分析

dapr示例

在服务端中提供了三个对Order的处理逻辑：增加订单，查询订单和删除订单，这三个业务处理都是以REST的方式对外提供服务，而这三个业务处理都会通过Dapr Runtime与Redis交互来完成数据的存放，读取和删除；而python所开发的客户端，周期的通过Dapr Runtime去调用服务端的增加订单的接口

官方示例代码重新实现

服务端的代码分为两个部分：提供的REST服务 和 访问Redis，后面将对这两个部分进行分析

使用golang实现服务端

提供REST服务

REST服务这部分的开发与一般的rest服务的开发并没有什么不同之处，所以在这里我选择自己比较熟悉的echo框架作为了开发框架，分别开发了order的增查删的接口，代码如下：
路由注册部分，完整代码参考

    e := echo.New()    e.POST("/neworder", orderResource.Neworder)    e.GET("/order", orderResource.Queryorders)    e.DELETE("/order/:id", orderResource.DeleteOrder)

REST请求处理部分，完整代码参考

func (o *OrderResource) Neworder(c echo.Context) error {    data := &Data{}    err := c.Bind(data)    if err != nil {        return err    }    err = o.cache.Add(data)    if err != nil {        return c.String(500, err.Error())    }    return c.String(200, "add success")}func (o *OrderResource) Queryorders(c echo.Context) error {    data, err := o.cache.Query()    if err != nil {        return c.String(500, err.Error())    }    return c.JSON(200, data)}func (o *OrderResource) DeleteOrder(c echo.Context) error {    id := c.Param("id")    err := o.cache.delete(id)    if err != nil {        return c.String(500, err.Error())    }    return c.String(200, "delete success")}

在这里需要关注的一点就是在这里注册的path和访问这个rest接口的path还是有所不同，通过Dapr来访问时，还需要增加http://xxxx:<DAPR_HTTP_PORT>/v1.0/invoke/<APP_ID>/method/<Method> 来访问才行，如下：

http://localhost:3500/v1.0/invoke/nodeapp/method/neworder

访问redis

要通过Dapr runtime去访问redis服务，必须按照Dapr的state规范来实现（注:Dapr中所涉及到的规范，将在以后的文章中来进行介绍）
相关代码如下,完整代码请参考

func (cache *CacheService) Add(data *Data) error {    request := cache.httpclient.Post()    request.Path(cache.stateUrl)    state := &State{        Key:   "order",        Value: data,    }    states := []*State{state}    response, err := request.JSON(&states).Send()    if err != nil {        return err    }    if !response.Ok {        return fmt.Errorf("add state error,statuCode:%d,messag:%s", response.StatusCode, response.String())    }    log.Info("Successfully persisted state.")    return nil}func (cache *CacheService) Query() (*Data, error) {    request := cache.httpclient.Get()    request.Path(cache.stateUrl + "/order")    response, err := request.Send()    if err != nil {        return nil, err    }    if !response.Ok {        return nil, fmt.Errorf("query state error,statuCode:%d,messag:%s", response.StatusCode, response.String())    }    data := &Data{}    err = response.JSON(&data)    return data, err}func (cache *CacheService) delete(id string) error {    request := cache.httpclient.Delete()    request.Path(cache.stateUrl + "/" + id)    request.AddHeader("Content-Type", "application/json")    response, err := request.Send()    if err != nil {        return err    }    if !response.Ok {        return fmt.Errorf("delete state error,id:%s,statuCode:%d,messag:%s", id, response.StatusCode, response.String())    }    return nil}

使用java实现客户端

相关代码如下，完整代码参考

public class DaprHelloworldClientApplication {    private final static String bodyTmpl="{"data": {"orderId": "%s"}}";    public static void main(String[] args) throws IOException, InterruptedException {        Thread sendThread = new Thread(new Runnable() {            public void run() {                int i=0;                while(!Thread.interrupted()){                    try {                        Thread.sleep(5000);                        i++;                        String body=String.format(bodyTmpl,String.valueOf(i));                        sendRequest(body);                    } catch (Exception e) {                        e.printStackTrace();                    }                }            }        });        sendThread.start();        Thread.sleep(5*60*60*1000);    }    public static void sendRequest(String body) throws IOException {    String httpPort = System.getenv("DAPR_HTTP_PORT");    if (httpPort == null) {        httpPort = "3500";    }    String resultUrl = "http://localhost:" + httpPort + "/v1.0/invoke/goapp/method/neworder";    URL url = new URL(resultUrl);    HttpURLConnection connection = (HttpURLConnection) url.openConnection();    connection.setRequestMethod("POST");    connection.setRequestProperty("Content-Type", "application/json;charset=UTF-8");    connection.setRequestProperty("Connection", "Keep-Alive");    connection.setUseCaches(false);    connection.setDoOutput(true);    connection.setDoInput(true);    System.out.println("request body:"+body);    DataOutputStream out = new DataOutputStream(connection.getOutputStream());    out.write(body.getBytes("UTF-8"));    out.flush();    out.close();    connection.connect();    BufferedReader bReader = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));    String line, resultStr = "";    while (null != (line = bReader.readLine())) {        resultStr += line;    }    System.out.println(resultStr);    bReader.close();}}

在上面的代码中，比较特殊的情况是其访问服务端REST的URL是："http://localhost:" + httpPort + "/v1.0/invoke/goapp/method/neworder"

小结

从上面的代码看来使用Drap后，REST的开发并没有变的麻烦，并且访问Redis的代码还更加的简洁，不在需要使用特定的redis客户端，这样降低了业务开发人员的学习成本，向着云原生又迈进的一步

部署程序

用于使用java开发，所以整个系统都使用maven来进行编译，当然在

启动服务端

dapr run --app-id goapp --app-port 3000 --port 3500 ./helloworld-serverℹ️  Starting Dapr with id goapp. HTTP Port: 3500. gRPC Port: 39669== APP ==== APP ==    ____    __== APP ==   / __/___/ /  ___== APP ==  / _// __/ _ / _ == APP == /___/__/_//_/___/ v4.1.16== APP == High performance, minimalist Go web framework== APP == https://echo.labstack.com== APP == ____________________________________O/_______== APP ==                                     O== APP == ⇨ http server started on [::]:3000

启动客户端

 dapr run --app-id javaapp `java -jar dapr-helloworld-client-0.0.1-SNAPSHOT-jar-with-dependencies.jar`

在启动客户端后，可以在服务端的终端上看到如下的代码输出：

== APP == {"time":"2020-06-01T07:25:37.690025853-04:00","level":"INFO","prefix":"-","file":"cache_service.go","line":"48","message":"Successfully persisted state."}== APP == {"time":"2020-06-01T07:25:42.712922528-04:00","level":"INFO","prefix":"-","file":"cache_service.go","line":"48","message":"Successfully persisted state."}== APP == {"time":"2020-06-01T07:25:47.725423292-04:00","level":"INFO","prefix":"-","file":"cache_service.go","line":"48","message":"Successfully persisted state."}

总结

通过用java和golang开发了官方的实例代码，个人感觉dapr对代码的限制比较少，开发难度不大，在后面的实战中，将试试在Kubernetes来部署Dapr

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