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Using Mule with Web Services

Mule ESB allows different integration scenarios using Web services:

Here we explore in a deeper way what options exist in each of these scenarios and direct you to other documentation sources and examples.

CXF Module Overview

Before explaining the different Web service scenarios that you can accomplish using Mule ESB, it is important to understand that the main technology on which it relies on is Apache CXF. Apache CXF is an open-source services framework that helps you build and develop services using front-end programming APIs, like JAX-WS and JAX-RS. Mule ESB now bundles the CXF Module that provides Web services integration for consuming existing Web services and building new ones.

As of the latest version of Mule ESB, the CXF Module is the recommended way to work with with Web services.

Consuming Web Services

If you invoke an existing Web service, you usually build a Web service client to perform the call. If you have ever experienced this, you will understand it requires some code generation—​you can learn about different ways to accomplish this with Apache CXF here).

With Mule ESB you can simplify the way Web services can be consumed, but mainly you have many features out-of-the-box when invoking the service (e.g, security) and to handle and process the results, such as transformations and using the results in a complex flow.

Mule ESB provides different alternatives to consume web services:

  1. Generate and use a client from a WSDL

  2. Use a Client Based on the Interface of a JAX-WS Service

  3. Use a client based on the interface of a "simple" frontend web service

  4. Use the JAX-WS Java Client API

Generate and use a client from a WSDL

This is a good approach when you need to consume third-party web services or in other cases where you don’t have the web service code.

When consuming a web service this way, do the following:

  1. Generate a CXF client using the WSDL to Java tool from CXF or the Maven plugin.

  2. Configure the client in the Mule configuration XML file using the <cxf:jaxws-client> component.

  3. Configure an endpoint in the Mule configuration XML file that will be the transport to request the service (usually HTTP).

For more information, you can check the Consuming Web Services with CXF documentation.

Use a Client Based on the Interface of a JAX-WS Service

If you have access to the code used to build the Web service, you can build a client for your JAX-WS services with no need to generate a client from the WSDL.

To consume a web service this way, do the following:

  1. Copy your service interface and all your data objects locally.

  2. Configure the client in the Mule configuration XML file using the <cxf:jaxws-client> component.

  3. Configure an endpoint in the Mule configuration XML file that will be the transport to request the service (usually HTTP).

For more information, read the Consuming Web Services with CXF documentation.

Use a Client Based on the Interface of a "Simple" Front-End Web Service

If you are not using the JAX-WS service, you have a copy of your service interface and all your data objects locally, and the service is simple enough you may consider building a client for your simple front end-based services without generating a client from the WSDL.

In order to consume a Web service this way, do the following:

  1. Copy your service interface and all your data objects locally.

  2. Configure the client in the Mule configuration XML file using the cxf:simple-client> component.

  3. Configure an endpoint in the Mule configuration XML file that will be the transport to request the service (usually HTTP).

For more information, read the Consuming Web Services with CXF documentation.

Use the JAX-WS Java Client API

You can also use a Web service client API to communicate with Web services outside of Mule configurations. This means that you can invoke services from within your Java classes that can then be used from within Mule ESB.

As before, based on whether you will use the WSDL or whether you’ve built your service via "code-first" methodologies, there are two ways to use CXF clients:

Exposing Web Services

Mule ESB can be used to host your own Web services. In the same way you can consume Web services from Mule ESB, you can also build and expose them. Here are three different ways to do this:

  1. Create a JAX-WS Service.

  2. Create a WSDL First JAX-WS Service.

  3. Create a Simple Front-End Web Service.

Create a JAX-WS Service

The JAX-WS specification is a series of APIs and annotations to help you build web services. To build and expose a Web service this way you will need to accomplish the following:

  1. Write a Java class that represent Web services (with the @WebService annotation) to expose its methods so that they can be invoked remotely.

  2. Configure the endpoint that will be accepting requests to the Web service (usually a HTTP inbound endpoint).

  3. Configure the service in the Mule configuration XML file using the <cxf:jaxws-service> component.

For more information, read the Creating a JAX-WS Service documentation.

Create a WSDL First JAX-WS Service

This is where you first define the WSDL and then code the web services. To build a Web service this way and configure it in Mule you should:

  1. Generate your Web service interface from your WSDL using WSDL to Java tool from CXF or the Maven plugin.

  2. Write the service implementation class that implements your service interface.

  3. Configure the endpoint that will be accepting requests to the Web service, usually a HTTP inbound endpoint.

  4. Configure the service in the Mule XML configuration file using the <cxf:jaxws-service> component.

For more information, read the Creating a WSDL First JAX-WS Service documentation.

Create a Simple Front-End Web Service

This is the best approach if you want to create a simple Web service out of an existing POJO. In this way, you need not use annotations, and though writing an interface is not required, it is recommended as it will make the Web service easy to consume. To build a Web service this way and configure it in Mule, do the following:

  1. Use an existing simple Java class (POJO) or write a new one.

  2. Configure the endpoint that will be accepting requests to the Web service (usually a HTTP inbound endpoint).

  3. Configure the service in the Mule configuration XML file using the <cxf:jaxws-service> component.

For more information, read the Creating a simple front-end Web service documentation.

Proxying Web Services

Using Mule ESB as a Web service proxy is a feature that you may want to use when:

  • You need to add security to an existing 3rd party web service (you don’t have the code or own the infrastructure).

  • You need to add or remove HTTP headers.

  • You need to validate or transform input or output of the Web service.

  • You may need to transform the SOAP envelope.

  • You may want to take advantage of the CXF Web service standards support to use WS-Security, WS-Addressing or to enforce WS-Policy assertions.

  • Introduce custom error handling.

There are many other scenarios where you may also need to consider proxying Web services.

You have two types of proxying:

Web Service Proxy Pattern

For simple use cases, you may consider using the Web Service Proxy Pattern, particularly when you don’t need to accomplish much message processing. From Mule, you can use Using Mule Configuration Patterns to configure (with minor XML configuration) a specific integration feature.

References

For more information and complete documentation, please read the following: