Vertx 实例变量在尝试从其方法访问时为 null

Question

下面是垂直

package com.api.redis.gateway.verticle;
import java.util.UUID;
import io.vertx.core.json.JsonObject;
import io.vertx.ext.web.RoutingContext;
import io.vertx.redis.RedisClient;
import io.vertx.redis.RedisOptions;
public class SimpleRestChild extends SimpleRestServer{
RedisClient client;

@Override
public void start() {
// TODO Auto-generated method stub
super.start();
client = RedisClient.create(vertx, new RedisOptions().setHost("127.0.0.1").setPort(6379));
client.subscribe("channelForServiceToPublish", handler -> {
if(handler.succeeded())
System.out.println("SimpleRestServer subscibed to the channel successfully");
});
}
public void handleSubscription(RoutingContext routingContext) {
JsonObject requestAsJson = routingContext.getBodyAsJson();
requestAsJson.put("uuid", getUUID());
// this client object is null.
client.set("request", requestAsJson.toString(), handler ->{
System.out.println("Simple server is setting value to redis client");
if(handler.succeeded()) {
System.out.println("Key and value is stored in Redis Server");
}else if(handler.failed()) {
System.out.println("Key and value is failed to be stored on Redis Server with cause : "+ handler.cause().getMessage());
}
});

client.publish("channelForServerToPublish", "ServiceOne", handler -> {
if(handler.succeeded()) {
System.out.println("Simple Server published message successfully");
}else if(handler.failed()) {
System.out.println("Simple Server failed to published message");
}
});
routingContext.vertx().eventBus().consumer("io.vertx.redis.channelForServiceToPublish", handler -> {
client.get("response", res ->{
if(res.succeeded()) {
JsonObject responseAsJson = new JsonObject(res.result());
if(responseAsJson.getString("uuid").equalsIgnoreCase(requestAsJson.getString("uuid"))) {
routingContext.response().setStatusCode(200).end(res.result());
}
}else if(res.failed()) {
System.out.println("Failed to get message from Redis Server");
routingContext.response().setStatusCode(500).end("Server Error ");
}
});

});
}
private String getUUID() {
UUID uid = UUID.randomUUID();
return uid.toString();
}

}

下面是部署上述顶点的主顶点，并且在向 httpserver 发出任何请求时，都会调用它的 hanlder 方法。

package com.api.redis.gateway.verticle;
import io.vertx.core.AbstractVerticle;
import io.vertx.ext.web.Router;
import io.vertx.ext.web.handler.BodyHandler;
import io.vertx.redis.RedisClient;
import io.vertx.redis.RedisOptions;

public class SimpleRestServer extends AbstractVerticle{

@Override
public void start(){
int http_port = 9001;
vertx.deployVerticle("com.api.redis.gateway.verticle.SimpleRestChild", handler -> {
if(handler.succeeded()) {
System.out.println(" SimpleRestChild deployed successfully");
}
});
Router router = Router.router(vertx);
router.route().handler(BodyHandler.create());
SimpleRestChild child = null;
try {
child = (SimpleRestChild) Class.forName("com.api.redis.gateway.verticle.SimpleRestChild").newInstance();
} catch (InstantiationException | IllegalAccessException | ClassNotFoundException e) {
e.printStackTrace();
}
router.route("/subscription").handler(child::handleSubscription);
vertx.createHttpServer().requestHandler(router::accept).listen(http_port);
System.out.println("Server started at port : " + http_port);
}

}

当为任何"/subscription"请求调用 handleSubscription 时，客户端对象显示为 null。

根据我的理解，这里正在创建两个对象。一个带有 start((，另一个没有 start((。

我想初始化一次Redisclient。当 handleSubscription(( 被调用以请求 "/subscription" 时使用此对象。

如何实现这一点？

如何解决此问题。

Answer 1

请求可能在客户端初始化实际完成之前传入。

AbstractVerticle有两种start()变体：

• start()，以及
• start(Future<Void> startFuture)

应使用带有Future参数的重载版本来执行潜在的长时间运行的初始化，这些初始化在将 Verticle 视为已部署和准备就绪之前是必需的。(文档中有一个专门讨论此主题的部分(。

因此，您可以尝试按如下方式更改代码：

public class SimpleRestChild extends SimpleRestServer {
RedisClient client;
@Override
public void start(Future<Void> startFuture) {
client = ...
// important point below is that this Verticle's
// deployment status depends on whether or not
// the client initialization succeeds
client.subscribe("...", handler -> {
if(handler.succeeded()) {
startFuture.complete();
} else {
startFuture.fail(handler.cause());
}
);
}

}

和：

public class SimpleRestServer extends AbstractVerticle {
@Override
public void start(Future<Void> startFuture) {
int http_port = 9001;
vertx.deployVerticle("...", handler -> {
// if the child Verticle is successfully deployed
// then move on to completing this Verticle's
// initialization
if(handler.succeeded()) {
Router router = ...
...
// if the server is successfully installed then
// invoke the Future to signal this Verticle
// is deployed
vertx.createHttpServer()
.requestHandler(router::accept)
.listen(http_port, handler -> {
if(handler.succeeded()) {
startFuture.complete();
} else {
startFuture.fail(handler.cause());
}
});
} else {
startFuture.fail(handler.cause());
}
}

使用这种类型的方法，Verticles将仅在请求的所有依赖资源完全初始化时为其提供服务。