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WebClient doc update #2064
WebClient doc update #2064
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WebClient Introduction
WebClient is an HTTP client for Helidon SE 2.0. It handles the responses to the HTTP requests in a reactive way.
Helidon WebClient provides the following features:
Reactive approach
Allows you to execute HTTP requests and handle the responses without having to wait for the server response. When the response is received, the client requests only the amount of data that it can handle at that time. So, there is no overflow of memory.
Builder-like setup and execution
Creates every client and request as a builder pattern. This improves readability and code maintenance.
Redirect chain
Follows the redirect chain and perform requests on the correct endpoint by itself.
Tracing, metrics and security propagation
Automatically propagates the configured tracing, metrics and security settings of the Helidon WebServer to the WebClient and uses them during request and response.
Configuring the WebClient
The WebClient default configuration may be suitable in most use cases. However, you can configure it to suit your specific requirements.
Example of a WebClient Configuration
Example of Yaml WebClient Configuration
Client functional settings
Default client headers and cookies
Client service configuration
Proxy configuration
TLS configuration
Creating the WebClient
You can create WebClient by executing
WebClient.create()
method. This will create an instance of client with default settings and without a base uri set.To change the default settings and register additional services, you can use simple builder that allows you to customize the client behavior.
Example
Creating and Executing the WebClient Request
WebClient executes requests to the target endpoints and returns specific response type.
It offers variety of methods to specify the type of request you want to execute:
put()
get()
method(String methodName)
These methods set specific request type based on their name or parameter to the new instance of
WebClientRequesBuilder
and return this instance based on configurations for specific request type.You can set configuration for every request type before it is sent as described in Request Configuration.
For the final execution, use the following methods with variations and different parameters:
Single<T> submit(Object entity, Class<T> responseType)
Single<T> request(Class<T> responseType)
Example
Request Configuration
The request settings are based on the following optional parameters, and change when a specific request is executed.
uri("http://example.com")
Overrides baseUri from WebClient
path("/path")
Adds path to the uri
queryParam("query", "parameter")
Adds query parameter to the request
fragment("someFragment")
Adds fragment to the request
headers(headers → headers.addAccept(MediaType.APPLICATION_JSON))
Adds header to the request
WebClientRequestBuilder
class also provides specific header methods that help the user to set a particular header. The methods are:contentType
(MediaType contentType)accept
(MediaType… mediaTypes)For more details, see the Request Headers API.
Adding JSON Processing Media Support to the WebClient
JSON Processing (JSON-P) media support is not present in the WebClient by default. So, in this case, you must first register it before making a request. This example shows how to register
JsonpSupport
using the following two methods.Example
Adds JSON-P reader to all client requests.
Adds JSON-P writer to all client requests.
Adds JSON-P writer and reader to all client requests.
/////////////////////////////////////////////////////////////////////////////// Copyright (c) 2020 Oracle and/or its affiliates. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. /////////////////////////////////////////////////////////////////////////////// // Updated the examples to register JSON-P Support for WebClient = WebClient Introduction :pagename: WebClient-Introduction :description: Helidon WebClient :keywords: helidon, se, rest, httpclient, webclient, reactive WebClient is an HTTP client for Helidon SE 2.0. It handles the responses to the HTTP requests in a reactive way. Helidon WebClient provides the following features: * *Reactive approach* + Allows you to execute HTTP requests and handle the responses without having to wait for the server response. When the response is received, the client requests only the amount of data that it can handle at that time. So, there is no overflow of memory. * *Builder-like setup and execution* + Creates every client and request as a builder pattern. This improves readability and code maintenance. * *Redirect chain* + Follows the redirect chain and perform requests on the correct endpoint by itself. * *Tracing, metrics and security propagation* + Automatically propagates the configured tracing, metrics and security settings of the Helidon WebServer to the WebClient and uses them during request and response. == Configuring the WebClient The WebClient default configuration may be suitable in most use cases. However, you can configure it to suit your specific requirements. === Example of a WebClient Configuration [source,java] ---- Config config = Config.create(); WebClient client = WebClient.builder() .baseUri("http://localhost") .config(config.get("client")) .build(); ---- === Example of Yaml WebClient Configuration [source, java] ---- client: connect-timeout-millis: 2000 read-timeout-millis: 2000 follow-redirects: true <1> max-redirects: 5 cookies: automatic-store-enabled: true default-cookies: - name: "env" value: "dev" headers: - name: "Accept" value: ["application/json","text/plain"] <2> services: config: metrics: - methods: ["PUT", "POST", "DELETE"] - type: METER name-format: "client.meter.overall" - type: TIMER # meter per method name-format: "client.meter.%1$s" - methods: ["GET"] type: COUNTER errors: false name-format: "client.counter.%1$s.success" description: "Counter of successful GET requests" - methods: ["PUT", "POST", "DELETE"] type: COUNTER success: false name-format: "wc.counter.%1$s.error" description: "Counter of failed PUT, POST and DELETE requests" - methods: ["GET"] type: GAUGE_IN_PROGRESS name-format: "client.inprogress.%2$s" description: "In progress requests to host" tracing: proxy: use-system-selector: false host: "hostName" port: 80 no-proxy: ["localhost:8080", ".helidon.io", "192.168.1.1"] <3> tls: server: disable-hostname-verification: false trust-all: false truststore: keystore-resource-path: "path to the keystore" keystore-type: "JKS" keystore-passphrase: "password" trust-store: true <4> client: keystore: keystore-resource-path: "path to client keystore" keystore-passphrase: "password" trust-store: true <5> ---- <1> Client functional settings <2> Default client headers and cookies <3> Proxy configuration <4> SSL configuration <5> Client service configuration == Creating the WebClient You can create WebClient by executing `WebClient.create()` method. This will create an instance of client with default settings and without a base uri set. To change the default settings and register additional services, you can use simple builder that allows you to customize the client behavior. === Example .Create a WebClient with simple builder: [source,java] ---- WebClient client = WebClient.builder() .baseUri("http://localhost") .build(); ---- == Creating and Executing the WebClient Request WebClient executes requests to the target endpoints and returns specific response type. It offers the following methods to specify the type of request you want to execute: * `put()` * `get()` * `method(String methodName)` These methods set specific request type based on their name or parameter to the new instance of `WebClientRequesBuilder` and return this instance based on configurations for specific request type. You can set configuration for every request type before it is sent as described in <>. For the final execution, use the following methods with variations and different parameters: * `CompletionStage submit(Object entity, Class responseType)` * `CompletionStage request(Class responseType)` === Example .Execute a simple GET request to endpoint: [source,java] ---- CompletionStage response = client.get() .path("/endpoint") .request(String.class); ---- === Request Configuration The request settings are based on the following optional parameters, and change when a specific request is executed. |=== |Parameter |Description |`uri("http://example.com")` |Overrides baseUri from WebClient |`path("/path")` |Adds path to the uri |`queryParam("query", "parameter")` |Adds query parameter to the request |`fragment("someFragment")` |Adds fragment to the request |`headers(headers -> headers.addAccept(MediaType.APPLICATION_JSON))` |Adds header to the request |=== `WebClientRequestBuilder` class also provides specific header methods that help the user to set a particular header. The methods are: * `contentType` (MediaType contentType) * `accept` (MediaType... mediaTypes) For more details, see the https://helidon.io/docs/latest/apidocs/io/helidon/webserver/RequestHeaders.html[Request Headers] API. == Adding JSON Processing Media Support to the WebClient JSON Processing (JSON-P) media support is not present in the WebClient by default. So, in this case, you must first register it before making a request. This example shows how to register `JsonpSupport` using the following two methods. === Example [source,java] .Register JSON-P support to the WebClient. ---- WebClient.builder() .baseUri("http://localhost") .addReader(JsonpSupport.reader()) <1> .addWriter(JsonpSupport.writer()) <2> .addMediaService(JsonpSupport.create()) <3> .build(); ---- <1> Adds JSON-P reader to all client requests. <2> Adds JSON-P writer to all client requests. <2> Adds JSON-P writer and reader to all client requests. [source,java] .Register JSON-P support only to the specific request. ---- WebClient webClient = WebClient.create(); WebClientRequestBuilder requestBuilder = webClient.get(); requestBuilder.writerContext().registerWriter(JsonSupport.writer()); <1> requestBuilder.readerContext().registerReader(JsonSupport.reader()); <2> requestBuilder.request(JsonObject.class) ---- <1> Adds JSON-P writer only to this request. <2> Adds JSON-P reader only to this request. == Maven Coordinates The <> page describes how you should declare dependency management for Helidon applications. You must declare the following dependency in your project's pom.xml: [source,xml,subs="verbatim,attributes"] ---- io.helidon.webclient helidon-webclient <1> ---- <1> Dependency on WebClient.
Adds JSON-P writer only to this request.
Adds JSON-P reader only to this request.
Maven Coordinates
The Managing Dependencies page describes how you should declare dependency management for Helidon applications. You must declare the following dependency in your project’s pom.xml:
Dependency on WebClient.