gs-consuming-web-service

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:spring_version: current :toc: :project_id: gs-consuming-web-service :spring_version: current :spring_boot_version: 2.3.2.RELEASE :icons: font :source-highlighter: prettify

This guide walks you through the process of consuming a SOAP-based web service with Spring.

== What You Will Build

You will build a client that fetches country data from a remote, WSDL-based web service by using http://en.wikipedia.org/wiki/SOAP[SOAP]. You can find out more about the country service and run the service yourself by following https://spring.io/guides/gs/producing-web-service/[this guide].

The service provides country data. You will be able to query data about a country based on its name.

== What You Need

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NOTE: If you read link:/guides/gs/producing-web-service[Producing a SOAP web service], you might wonder why this guide does not use spring-boot-starter-ws? That Spring Boot starter is only for server-side web services. That starter brings on board such things as embedded Tomcat, which is not needed to make a web call.

== Run the Target Web Service Locally

Follow the steps in the https://spring.io/guides/gs/producing-web-service/[companion guide] or clone the https://github.com/spring-guides/gs-producing-web-service[repository] and run the service (for example, by using mvn spring-boot:run) from its complete directory. You can verify that it works by visiting http://localhost:8080/ws/countries.wsdl in your browser. If you don't do this you will see a confusing exception in your build later from the JAXB tooling.

[[scratch]] == Starting with Spring Initializr

For all Spring applications, you should start with the https://start.spring.io[Spring Initializr]. The Initializr offers a fast way to pull in all the dependencies you need for an application and does a lot of the setup for you. This example needs only the Spring Web Services dependency.

To initialize the project:

. Navigate to https://start.spring.io. This service pulls in all the dependencies you need for an application and does most of the setup for you. . Choose either Gradle or Maven and the language you want to use. This guide assumes that you chose Java. . Click Dependencies and select Spring Web Services. . Click Generate. . Download the resulting ZIP file, which is an archive of a web application that is configured with your choices.

NOTE: If your IDE has the Spring Initializr integration, you can complete this process from your IDE.

NOTE: You can also fork the project from Github and open it in your IDE or other editor.

== Modify the Build Files

The build files created by the Spring Initializr need quite a bit of work for this guide. Also, the modifications to pom.xml (for Maven) and build.gradle (for Gradle) differ substantially.

=== Maven

For Maven, you need to add a dependency, a profile, and a WSDL generation plugin.

The following listing shows the dependency you need to add in Maven:

==== [source,xml,indent=0]

include::complete/pom.xml[tags=dependency]

====

The following listing shows the profile you need to add in Maven if you want it to work with Java 11:

==== [source,xml,indent=0]

include::complete/pom.xml[tags=profile]

====

The <> section describes the WSDL generation plugin.

The following listing shows the final pom.xml file:

==== [source,xml,indent=0]

include::complete/pom.xml[]

====

=== Gradle

For Gradle, you need to add a dependency, a configuration, a bootJar section, and a WSDL generation plugin.

The following listing shows the dependency you need to add in Gradle:

==== [source,xml,indent=0]

include::complete/build.gradle[tags=dependency]

====

Note the exclusion of Tomcat. If Tomcat is allowed to run in this build, you get a port collision with the Tomcat instance that provides the country data.

The following listing shows the bootJar section you need to add in Gradle:

==== [source,xml,indent=0]

include::complete/build.gradle[tags=bootjar]

====

The <> section describes the WSDL generation plugin.

The following listing shows the final build.gradle file:

==== [source,xml,indent=0]

include::complete/build.gradle[]

====

[[initial]] == Generate Domain Objects Based on a WSDL

The interface to a SOAP web service is captured in http://en.wikipedia.org/wiki/Web_Services_Description_Language[WSDL]. JAXB provides a way to generate Java classes from WSDL (or rather, the XSD contained in the <Types/> section of the WSDL). You can find the WSDL for the country service at http://localhost:8080/ws/countries.wsdl.

To generate Java classes from the WSDL in Maven, you need the following plugin setup:

==== [source,xml,indent=0]

include::complete/pom.xml[tags=wsdl]

====

This setup will generate classes for the WSDL found at the specified URL, putting those classes in the com.example.consumingwebservice.wsdl package. To generate that code run ./mvnw compile and then look in target/generated-sources if you want to check that it worked.

To do the same with Gradle, you will need the following in your build file:

==== [source,java,tabsize=2,indent=0]

include::complete/build.gradle[tags=wsdl]

====

As Gradle does not (yet) have a JAXB plugin, it involves an Ant task, which makes it a bit more complex than in Maven. To generate that code run ./gradlew compileJava and then look in build/generated-sources if you want to check that it worked.

In both cases, the JAXB domain object generation process has been wired into the build tool's lifecycle, so you need not run any extra steps once you have a successful build.

== Create a Country Service Client

To create a web service client, you have to extend the http://docs.spring.io/spring-ws/sites/2.0/apidocs/org/springframework/ws/client/core/support/WebServiceGatewaySupport.html[WebServiceGatewaySupport] class and code your operations, as the following example (from src/main/java/com/example/consumingwebservice/CountryClient.java) shows:

==== [source,java,tabsize=2]

include::complete/src/main/java/com/example/consumingwebservice/CountryClient.java[]

====

The client contains one method (getCountry) that does the actual SOAP exchange.

In this method, both the GetCountryRequest and the GetCountryResponse classes are derived from the WSDL and were generated in the JAXB generation process (described in <>). It creates the GetCountryRequest request object and sets it up with the country parameter (the name of the country). After printing out the country name, it uses the http://docs.spring.io/spring-ws/sites/2.0/apidocs/org/springframework/ws/client/core/WebServiceTemplate.html[WebServiceTemplate] supplied by the WebServiceGatewaySupport base class to do the actual SOAP exchange. It passes the GetCountryRequest request object (as well as a SoapActionCallback to pass on a http://www.w3.org/TR/2000/NOTE-SOAP-20000508/#_Toc478383528[SOAPAction] header with the request) as the WSDL described that it needed this header in the <soap:operation/> elements. It casts the response into a GetCountryResponse object, which is then returned.

== Configuring Web Service Components

Spring WS uses Spring Framework's OXM module, which has the Jaxb2Marshaller to serialize and deserialize XML requests, as the following example (from src/main/java/com/example/consumingwebservice/CountryConfiguration.java) shows:

==== [source,java,tabsize=2]

include::complete/src/main/java/com/example/consumingwebservice/CountryConfiguration.java[]

====

The marshaller is pointed at the collection of generated domain objects and will use them to both serialize and deserialize between XML and POJOs.

The countryClient is created and configured with the URI of the country service shown earlier. It is also configured to use the JAXB marshaller.

== Run the Application

This application is packaged up to run from the console and retrieve the data for a given country name, as the following listing (from src/main/java/com/example/consumingwebservice/ConsumingWebServiceApplication.java) shows:

==== [source,java,tabsize=2]

include::complete/src/main/java/com/example/consumingwebservice/ConsumingWebServiceApplication.java[]

====

The main() method defers to the http://docs.spring.io/spring-boot/docs/{spring_boot_version}/api/org/springframework/boot/SpringApplication.html[SpringApplication] helper class, providing CountryConfiguration.class as an argument to its run() method. This tells Spring to read the annotation metadata from CountryConfiguration and to manage it as a component in the Spring application context.

NOTE: This application is hard-coded to look up 'Spain'. Later in this guide, you will see how to enter a different symbol without editing the code.

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Logging output is displayed. The service should be up and running within a few seconds.

The following listing shows the initial response:

==== [source]

Requesting country data for Spain

<getCountryRequest>Spain...</getCountryRequest>

====

You can plug in a different country by running the following command:

==== [source,bash]

java -jar build/libs/gs-consuming-web-service-0.1.0.jar Poland

====

Then the response changes to the following:

==== [source]

Requesting location for Poland

<getCountryRequest>Poland...</getCountryRequest>

====

== Summary

Congratulations! You have just developed a client to consume a SOAP-based web service with Spring.

== See Also

The following guides may also be helpful:

• https://spring.io/guides/gs/producing-web-service/[Producing a SOAP web service]
• https://spring.io/guides/gs/spring-boot/[Building an Application with Spring Boot]

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