Consuming a SOAP Service in Spring Boot: A Step-by-Step Guide

Introduction

SOAP (Simple Object Access Protocol) is a protocol for exchanging structured information in web services. While RESTful services dominate modern APIs, SOAP remains essential in enterprise applications due to its robustness, security, and built-in support for transactions.

In this guide, we’ll explore how to consume a SOAP web service in Spring Boot using Spring Web Services (Spring-WS) and JAX-WS.

Prerequisites

Before starting, ensure you have the following:

• Java 8 or later
• Spring Boot 2.x or 3.x
• Maven or Gradle
• A WSDL file or an available SOAP web service

Setting Up the Spring Boot Project

We will create a Spring Boot project to consume a SOAP service using Spring Web Services.

Step 1: Add Dependencies

Include the necessary dependencies in pom.xml:

<dependencies>
    <!-- Spring Web Services -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web-services</artifactId>
    </dependency>
    
    <!-- JAXB for marshalling and unmarshalling -->
    <dependency>
        <groupId>org.springframework.ws</groupId>
        <artifactId>spring-ws-core</artifactId>
    </dependency>
    
    <!-- JAX-WS (optional, for Java-generated classes from WSDL) -->
    <dependency>
        <groupId>javax.xml.ws</groupId>
        <artifactId>jaxws-api</artifactId>
    </dependency>
</dependencies>

Step 2: Generate Java Classes from WSDL

To interact with the SOAP service, we need Java classes that map to the request and response structure. Use the wsimport tool:

wsimport -keep -p com.example.client -d ./src/main/java http://example.com/service?wsdl

This generates the required classes in the com.example.client package.

Step 3: Configure the SOAP Client

Create a SOAPConnector class to handle communication:

import org.springframework.ws.client.core.support.WebServiceGatewaySupport;
import org.springframework.ws.soap.client.core.SoapActionCallback;
import org.springframework.stereotype.Component;

@Component
public class SOAPConnector extends WebServiceGatewaySupport {
    
    public Object callWebService(String url, Object request){
        return getWebServiceTemplate().marshalSendAndReceive(url, request, new SoapActionCallback("http://example.com/action"));
    }
}

Step 4: Define a Service Layer

Create a service class to consume the SOAP service:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class SoapClientService {
    
    @Autowired
    private SOAPConnector soapConnector;
    
    public ResponseType callSoapService(RequestType request) {
        return (ResponseType) soapConnector.callWebService("http://example.com/service", request);
    }
}

Step 5: Create a REST Controller for Testing

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class SoapController {
    
    @Autowired
    private SoapClientService soapClientService;
    
    @GetMapping("/invokeSoap")
    public ResponseType invokeSoap(@RequestParam String param) {
        RequestType request = new RequestType();
        request.setParam(param);
        return soapClientService.callSoapService(request);
    }
}

Testing the SOAP Client

Start the Spring Boot application and call the SOAP service using a REST client like Postman:

GET http://localhost:8080/invokeSoap?param=sampleValue

If configured correctly, the response should return the SOAP service result.

External Resources

• Spring Web Services Documentation
• JAX-WS Reference
• SOAP vs. REST

FAQs

1. What is SOAP in Java?
   SOAP is a protocol for exchanging structured XML-based messages over a network, commonly used in web services.
2. Why use SOAP instead of REST?
   SOAP offers enhanced security, transaction support, and is ideal for enterprise-level applications requiring strict contracts.
3. Can I consume a SOAP service in Spring Boot without WSDL?
   Yes, but using a WSDL allows automatic class generation, making integration easier.
4. What is JAXB, and why is it used?
   JAXB (Java Architecture for XML Binding) is used for converting Java objects to XML and vice versa.
5. How does Spring Boot handle SOAP requests?
   Spring Boot uses Spring Web Services (spring-ws) for sending and receiving SOAP messages.
6. What is the difference between JAX-WS and JAX-RS?
   JAX-WS is for SOAP-based web services, whereas JAX-RS is for RESTful web services.
7. How do I debug SOAP responses in Spring Boot?
   Enable logging with logging.level.org.springframework.ws=DEBUG in application.properties.
8. Can I use Spring Boot with Apache CXF for SOAP services?
   Yes, Apache CXF provides additional features for working with SOAP web services.
9. Is SOAP still relevant today?
   Yes, many enterprises still use SOAP for secure and transactional web services.
10. How do I handle authentication in SOAP services?
    Use WS-Security with security headers or integrate with OAuth for authentication.

Conclusion

Consuming SOAP services in Spring Boot is straightforward with Spring Web Services and JAX-WS. By following this guide, you can integrate SOAP-based APIs seamlessly into your Java applications. With the right setup and best practices, you can ensure robust, secure, and maintainable web service consumption.