Vert.x Web Client（Web客户端）是一个异步的 HTTP 和 HTTP/2 客户端。
Web Client使得发送 HTTP 请求以及从 Web 服务器接收 HTTP 响应变得更加便捷，同时提供了额外的高级功能，例如：
JSON体的编码和解码
请求和响应泵
请求参数的处理
统一的错误处理
提交表单
制作Web Client的目的并非为了替换Vert.x Core中的 HttpClient ，
而是基于该客户端，扩展并保留其便利的设置和特性，例如请求连接池（Pooling），HTTP/2的支持，
流水线／管线的支持等。当您需要对 HTTP 请求和响应做细微粒度控制时，您应当使用
HttpClient 。
另外Web Client并未提供 WebSocket API，此时您应当使用 HttpClient 。
如需使用Vert.x Web Client，请先加入以下依赖：
Maven (在 pom.xml 文件中):
<dependency>
<groupId>io.vertx</groupId>
<artifactId>vertx-web-client</artifactId>
<version>3.6.2</version>
</dependency>Gradle (在 build.gradle 文件中):
dependencies {
compile 'io.vertx:vertx-web-client:3.6.2'
}Vert.x Web Client使用Vert.x Core的API，如您对此还不熟悉，请先熟悉
HttpClient 的一些基本概念。
您可使用缺省设置创建一个 WebClient ：
WebClient client = WebClient.create(vertx);您亦可使用配置选项来创建客户端：
WebClientOptions options = new WebClientOptions()
.setUserAgent("My-App/1.2.3");
options.setKeepAlive(false);
WebClient client = WebClient.create(vertx, options);Web Client配置选项继承自 HttpClient 配置选项，使用时可根据实际情况选择。
如已在程序中创建 HttpClient，可用以下方式复用：
WebClient client = WebClient.wrap(httpClient);一般情况下，HTTP GET，OPTIONS以及HEAD请求没有请求体，可用以下方式发送无请求体的HTTP Requests（HTTP请求）：
WebClient client = WebClient.create(vertx);
// Send a GET request
client
.get(8080, "myserver.mycompany.com", "/some-uri")
.send(ar -> {
if (ar.succeeded()) {
// Obtain response
HttpResponse<Buffer> response = ar.result();
System.out.println("Received response with status code" + response.statusCode());
} else {
System.out.println("Something went wrong " + ar.cause().getMessage());
}
});
// Send a HEAD request
client
.head(8080, "myserver.mycompany.com", "/some-uri")
.send(ar -> {
if (ar.succeeded()) {
// Obtain response
HttpResponse<Buffer> response = ar.result();
System.out.println("Received response with status code" + response.statusCode());
} else {
System.out.println("Something went wrong " + ar.cause().getMessage());
}
});您可用以下链式方式向请求URI添加查询参数
client
.get(8080, "myserver.mycompany.com", "/some-uri")
.addQueryParam("param", "param_value")
.send(ar -> {
if (ar.succeeded()) {
// Obtain response
HttpResponse<Buffer> response = ar.result();
System.out.println("Received response with status code" + response.statusCode());
} else {
System.out.println("Something went wrong " + ar.cause().getMessage());
}
});在请求URI中的参数将会被预填充
HttpRequest<Buffer> request = client.get(8080, "myserver.mycompany.com", "/some-uri?param1=param1_value¶m2=param2_value");
// Add param3
request.addQueryParam("param3", "param3_value");
// Overwrite param2
request.setQueryParam("param2", "another_param2_value");设置请求URI将会自动清除已有的查询参数
HttpRequest<Buffer> request = client.get(8080, "myserver.mycompany.com", "/some-uri");
// Add param1
request.addQueryParam("param1", "param1_value");
// Overwrite param1 and add param2
request.uri("/some-uri?param1=param1_value¶m2=param2_value");如需要发送请求体，可使用相同的API并在最后加上 sendXXX 方法发送相应的请求体。
例如用 sendBuffer 方法发送一个缓冲体：
client
.post(8080, "myserver.mycompany.com", "/some-uri")
.sendBuffer(buffer, ar -> {
if (ar.succeeded()) {
// Ok
}
});有时候我们并不希望将所有数据一次性全部读入内存，因为文件太大或希望同时处理多个请求，希望每个请求仅使用最小的内存。出于此目的，Web Client可用
sendStream 方法发送流式数据 ReadStream<Buffer>
（例如 AsyncFile 便是一个 ReadStream<Buffer>）：
client
.post(8080, "myserver.mycompany.com", "/some-uri")
.sendStream(stream, ar -> {
if (ar.succeeded()) {
// Ok
}
});Web Client会为您设置好传输泵以平滑传输流。如果流长度未知则使用分块传输（chunked transfer）。
如已知流的大小，可在HTTP协议头中设置 content-length 属性
fs.open("content.txt", new OpenOptions(), fileRes -> {
if (fileRes.succeeded()) {
ReadStream<Buffer> fileStream = fileRes.result();
String fileLen = "1024";
// Send the file to the server using POST
client
.post(8080, "myserver.mycompany.com", "/some-uri")
.putHeader("content-length", fileLen)
.sendStream(fileStream, ar -> {
if (ar.succeeded()) {
// Ok
}
});
}
});此时POST方法不会使用分块传输。
有时您需要在请求体中使用JSON格式，可使用 sendJsonObject 方法发送 JsonObject ：
client
.post(8080, "myserver.mycompany.com", "/some-uri")
.sendJsonObject(new JsonObject()
.put("firstName", "Dale")
.put("lastName", "Cooper"), ar -> {
if (ar.succeeded()) {
// Ok
}
});在Java，Groovy以及Kotlin语言中，您亦可使用 sendJson 方法发送POJO（Plain Old Java Object），该方法会自动调用 Json.encode
方法将 POJO 映射为 JSON：
client
.post(8080, "myserver.mycompany.com", "/some-uri")
.sendJson(new User("Dale", "Cooper"), ar -> {
if (ar.succeeded()) {
// Ok
}
});|
Note
|
Json.encode 方法使用Jackson的 mapper将 POJO 映射成 JSON。
|
您可使用 sendForm
方法发送HTTP表单。
MultiMap form = MultiMap.caseInsensitiveMultiMap();
form.set("firstName", "Dale");
form.set("lastName", "Cooper");
// Submit the form as a form URL encoded body
client
.post(8080, "myserver.mycompany.com", "/some-uri")
.sendForm(form, ar -> {
if (ar.succeeded()) {
// Ok
}
});缺省情况下，提交表单的请求头中的 content-type 属性值为 application/x-www-form-urlencoded，您亦可将其设置为 multipart/form-data：
MultiMap form = MultiMap.caseInsensitiveMultiMap();
form.set("firstName", "Dale");
form.set("lastName", "Cooper");
// Submit the form as a multipart form body
client
.post(8080, "myserver.mycompany.com", "/some-uri")
.putHeader("content-type", "multipart/form-data")
.sendForm(form, ar -> {
if (ar.succeeded()) {
// Ok
}
});If you want to upload files and send attributes, you can create a MultipartForm and
use sendMultipartForm.
MultipartForm form = MultipartForm.create()
.attribute("imageDescription", "a very nice image")
.binaryFileUpload("imageFile", "image.jpg", "/path/to/image", "image/jpeg");
// Submit the form as a multipart form body
client
.post(8080, "myserver.mycompany.com", "/some-uri")
.sendMultipartForm(form, ar -> {
if (ar.succeeded()) {
// Ok
}
});您可使用以下方式填充请求头：
HttpRequest<Buffer> request = client.get(8080, "myserver.mycompany.com", "/some-uri");
MultiMap headers = request.headers();
headers.set("content-type", "application/json");
headers.set("other-header", "foo");此处 Headers 是一个 MultiMap 对象，提供了增加、设置以及删除头属性操作的入口。HTTP头的某些特定属性允许设置多个值。
您亦可通过 putHeader 方法写入头属性：
HttpRequest<Buffer> request = client.get(8080, "myserver.mycompany.com", "/some-uri");
request.putHeader("content-type", "application/json");
request.putHeader("other-header", "foo");send 方法可被重复多次调用，这使得配置以及重用
HttpRequest 对象变得更加便捷：
HttpRequest<Buffer> get = client.get(8080, "myserver.mycompany.com", "/some-uri");
get.send(ar -> {
if (ar.succeeded()) {
// Ok
}
});
// Same request again
get.send(ar -> {
if (ar.succeeded()) {
// Ok
}
});请注意， HttpRequest 对象是可变的。
所以在修改缓存中的对象之前，您应当使用 copy 方法先复制一份拷贝：
HttpRequest<Buffer> get = client.get(8080, "myserver.mycompany.com", "/some-uri");
get.send(ar -> {
if (ar.succeeded()) {
// Ok
}
});
// The "get" request instance remains unmodified
get.copy().putHeader("a-header", "with-some-value").send(ar -> {
if (ar.succeeded()) {
// Ok
}
});您可通过 timeout 方法设置超时时间。
client
.get(8080, "myserver.mycompany.com", "/some-uri")
.timeout(5000)
.send(ar -> {
if (ar.succeeded()) {
// Ok
} else {
// Might be a timeout when cause is java.util.concurrent.TimeoutException
}
});若请求在设定时间内没返回任何数据，则一个超时异常将会传递给响应处理代码。
Web Client请求发送之后，返回的结果将会被包装在异步结果 HttpResponse 中。
当响应被成功接收到之后，相应的回调函数将会被触发。
client
.get(8080, "myserver.mycompany.com", "/some-uri")
.send(ar -> {
if (ar.succeeded()) {
HttpResponse<Buffer> response = ar.result();
System.out.println("Received response with status code" + response.statusCode());
} else {
System.out.println("Something went wrong " + ar.cause().getMessage());
}
});|
Warning
|
缺省状况下，响应会被完全缓冲读入内存，请用 BodyCodec.pipe 方法将响应写入流。
|
缺省状况下，响应以缓冲形式提供，并不提供任何形式的解码。
可用 BodyCodec 将响应定制成以下类型：
普通字符串
JSON对象
将JSON映射成POJO
响应体编解码器对二进制数据流解码，以节省您在响应处理中的代码。
使用 BodyCodec.jsonObject 将结果解码为JSON对象：
client
.get(8080, "myserver.mycompany.com", "/some-uri")
.as(BodyCodec.jsonObject())
.send(ar -> {
if (ar.succeeded()) {
HttpResponse<JsonObject> response = ar.result();
JsonObject body = response.body();
System.out.println("Received response with status code" + response.statusCode() + " with body " + body);
} else {
System.out.println("Something went wrong " + ar.cause().getMessage());
}
});在Java，Groovy以及Kotlin语言中，JSON对象可被解码映射成POJO：
client
.get(8080, "myserver.mycompany.com", "/some-uri")
.as(BodyCodec.json(User.class))
.send(ar -> {
if (ar.succeeded()) {
HttpResponse<User> response = ar.result();
User user = response.body();
System.out.println("Received response with status code" + response.statusCode() + " with body " +
user.getFirstName() + " " + user.getLastName());
} else {
System.out.println("Something went wrong " + ar.cause().getMessage());
}
});当响应结果较大时，请使用 BodyCodec.pipe
方法。响应体编解码器将响应结果压入 WriteStream
并在最后发出成功或失败的信号。
client
.get(8080, "myserver.mycompany.com", "/some-uri")
.as(BodyCodec.pipe(writeStream))
.send(ar -> {
if (ar.succeeded()) {
HttpResponse<Void> response = ar.result();
System.out.println("Received response with status code" + response.statusCode());
} else {
System.out.println("Something went wrong " + ar.cause().getMessage());
}
});最后，如您对响应结果不感兴趣，可用 BodyCodec.none
废弃响应体。
client
.get(8080, "myserver.mycompany.com", "/some-uri")
.as(BodyCodec.none())
.send(ar -> {
if (ar.succeeded()) {
HttpResponse<Void> response = ar.result();
System.out.println("Received response with status code" + response.statusCode());
} else {
System.out.println("Something went wrong " + ar.cause().getMessage());
}
});若无法预知响应内容类型，您依旧可以在获取结果之后，用 bodyAsXXX() 方法将其转换成特定的类型
client
.get(8080, "myserver.mycompany.com", "/some-uri")
.send(ar -> {
if (ar.succeeded()) {
HttpResponse<Buffer> response = ar.result();
// Decode the body as a json object
JsonObject body = response.bodyAsJsonObject();
System.out.println("Received response with status code" + response.statusCode() + " with body " + body);
} else {
System.out.println("Something went wrong " + ar.cause().getMessage());
}
});|
Warning
|
这种方式仅对响应结果为缓冲体有效。 |
缺省状况下，客户端将会依照30x状态码自动重定向，您可使用 WebClientOptions 予以配置：
WebClient client = WebClient.create(vertx, new WebClientOptions().setFollowRedirects(false));客户端将会执行最多达`16`次重定向，该参数亦可在 WebClientOptions 配置：
WebClient client = WebClient.create(vertx, new WebClientOptions().setMaxRedirects(5));Vert.x Web Client可用与 HttpClient 相同方式配置HTTPS协议。
您可对每个请求单独设置：
client
.get(443, "myserver.mycompany.com", "/some-uri")
.ssl(true)
.send(ar -> {
if (ar.succeeded()) {
// Obtain response
HttpResponse<Buffer> response = ar.result();
System.out.println("Received response with status code" + response.statusCode());
} else {
System.out.println("Something went wrong " + ar.cause().getMessage());
}
});或使用绝对路径：
client
.getAbs("https://myserver.mycompany.com:4043/some-uri")
.send(ar -> {
if (ar.succeeded()) {
// Obtain response
HttpResponse<Buffer> response = ar.result();
System.out.println("Received response with status code" + response.statusCode());
} else {
System.out.println("Something went wrong " + ar.cause().getMessage());
}
});RxJava的 HttpRequest 提供了原版API的响应式版本，
rxSend 方法返回一个可被订阅的 Single<HttpResponse<Buffer>> ，
故单个 Single 可被多次订阅。
Single<HttpResponse<Buffer>> single = client
.get(8080, "myserver.mycompany.com", "/some-uri")
.rxSend();
// Send a request upon subscription of the Single
single.subscribe(response -> System.out.println("Received 1st response with status code" + response.statusCode()), error -> System.out.println("Something went wrong " + error.getMessage()));
// Send another request
single.subscribe(response -> System.out.println("Received 2nd response with status code" + response.statusCode()), error -> System.out.println("Something went wrong " + error.getMessage()));获取到的 Single 可与其它RxJava API自然组合成链式处理
Single<String> url = client
.get(8080, "myserver.mycompany.com", "/some-uri")
.rxSend()
.map(HttpResponse::bodyAsString);
// Use the flatMap operator to make a request on the URL Single
url
.flatMap(u -> client.getAbs(u).rxSend())
.subscribe(response -> System.out.println("Received response with status code" + response.statusCode()), error -> System.out.println("Something went wrong " + error.getMessage()));之前的例子可写成
Single<HttpResponse<JsonObject>> single = client
.get(8080, "myserver.mycompany.com", "/some-uri")
.putHeader("some-header", "header-value")
.addQueryParam("some-param", "param value")
.as(BodyCodec.jsonObject())
.rxSend();
single.subscribe(resp -> {
System.out.println(resp.statusCode());
System.out.println(resp.body());
});当发送请求体为 Flowable<Buffer> 时，应使用 sendStream ：
Flowable<Buffer> body = getPayload();
Single<HttpResponse<Buffer>> single = client
.post(8080, "myserver.mycompany.com", "/some-uri")
.rxSendStream(body);
single.subscribe(resp -> {
System.out.println(resp.statusCode());
System.out.println(resp.body());
});当订阅时， body 将会被订阅，其内容将会被用于请求中。