I've recently written a more up to date version of this post which describes how to build a contract first web service using Apache CXF. Check it out here.
Modern enterprise applications are rarely stand alone and often rely on data and services provided by external systems. In order for different types of systems to communicate there must be a communication protocol of some sort, a standard way of sending and receiving messages in a format that is recognised and supported by all major platforms. SOAP (Simple Object Application Protocol) is such a protocol, and allows applications to communicate by exchanging messages in a standard XML format.
SOAP Web Services provide a platform agnostic integration mechanism that allows disparate systems to exchange data regardless of the platform they are running on. For example, SOAP web services are commonly used to integrate .NET applications with applications running on the Java platform. Almost all modern platforms and …
In this post I'm going to show you how to test a Spring MVC Rest endpoint without deploying your application to a server. In the past, full integration tests were the only meaningful way to test a Spring REST endpoint. This involved spinning up a test server like Tomcat or Jetty, deploying the application, calling the test endpoint, running some assertions and then terminating the server. While this is an effective way to test an endpoint, it isn't particularly fast. We're forced to wait while the entire application is stood up, just to test a single endpoint.
An alternative approach is to unit test by manually instantiating the Controller and mocking out any required dependencies. While such a test will run much faster than a full integration test, its of limited value. The problem is that by manually instantiating the Controller we're bypassing Springs Dispatcher Servlet, and as a result missing out on core features like request URL mapping request deserialization re…
Axis2 is a Java framework that provides comprehensive support for exposing and consuming web services. This short post will look at its SOAP client support and how it can be used to get a simple web service client up and running.
For convenience I'm going to be calling a web service that I recently built as part of another blog post. If you don't already have a web service to call you can grab the full source code for my sample service from github. Simply run a Maven build and deploy the WAR to your Servlet container.
What is a Web Service Client
This post doesn't attempt to explain the detailed inner workings of a web service client, but its still pretty useful to have an idea of what's going on under the hood. Most web service clients provide the following A client side proxy for the remote service we want to call, that allows our application to invoke a SOAP service using a simple method call. The proxy insulates our application from the intricacies of s…
I've been working with Spring Boot for a few years now and I'm a big fan. There are lots of things to like about Spring Boot, but one thing that really stands out for me is the emphasis on production readiness. Production Readiness
Production readiness is about looking beyond functional requirements and ensuring your application can be properly managed and monitored in production. Some key things to consider when thinking about production readiness are... Health checksViewing application configuration - application properties, Environment variables etc. Viewing and altering log configurationViewing application metrics - JVM, classloader, threading and garbage collection. Audibility of key application events
Spring provides all of this functionality out of the box via Spring Boot Actuator, a sub project of Spring Boot. A range of RESTful management and monitoring endpoints are provided so you don't have to implement these features each time you build an application. To enable…
This post provides a brief introduction to Wiremock, showing how it can be used to to quickly and easily mock remote API calls. We'll use Wiremock to write some integration tests for a simple Dropwizard app and show you how it can be put to use in a real world scenario.
Why would I need to mock external API calls?
There are a number of scenarios where it makes sense to mock an external API rather than call a live service. The external API may still be in development and not yet available for integration. In this instance as long as a data contract has been defined (e.g. Swagger spec, WSDL), the remote API can be stubbed based on the data contract. Stubbed endpoints allows a team to continue development even when external APIs isn't fully implemented.You may have little or no control over the external API uptime in development or test. As a result you cannot guarantee it will be available to call when running integration tests. In this instance it makes sense to use mocked respo…
Spring batch is a lightweight framework that provides a solid foundation on which to build robust and scalable batch applications. It provides developers with a set of tried and tested patterns that solve common batch problems and allows developers to focus more on the business requirement and less on complex batch infrastructure. Spring batch contains a variety of out of the box configurable components that can be used to satisfy many of the most common batch use cases. Extensive XML configuration and an extensible programming model mean that these components can be customised and used as building blocks to quickly deliver common batch functionality.
This tutorial will show you how to build a very simple batch application to read fixed length data from a flat file and write it to a database table. This is a common batch use case and should be sufficient to demonstrate some of the fundamental concepts of Spring batch and provide you with a foundation on which to build mor…
Enterprise applications typically contain a number of properties and runtime resources that must be configured before the application is deployed. Property and resource values can either be baked into the artefact at build time using something like Maven Profiles or derived at runtime using Spring Profiles. My preferred approach is to externalise all configuration so that the artefact taken from the build server is environment agnostic and can be deployed onto any environment . For example, we could take a WAR file from our build server and deploy it to our development, UAT or production environments without changing any configuration in the WAR file itself.
Spring Property Configuration
Spring applications use the PropertyPlaceholderConfigurer to load application properties. Property files are typically loaded from the class path but the example below uses a slightly different approach, loading the properties file from a directory outside of the application itself. This allows the…
Docker allows you to package an application with its dependencies, into a light weight, portable container that can run on almost any environment. You can think of a Docker container as a run time, a mini virtual machine that encapsulates your application and its dependencies.
In order to run a container you need a Docker image. An image is like a template that defines everything that will exist within the container. You can almost think of an container as a run time instance of the image it was created from. In this post we'll define and build 3 slightly different Docker images that run a simple Java app.
If you haven't already done so you'll need to install Docker. The official documentation is pretty good so following it step by step should see you up and running in about 15 minutes.
I've installed Docker on Windows and Ubuntu but to be honest I prefer running it on Ubuntu and have found it a bit more reliable than with Docker Toolbox on Windows.…
This post will take you through a step by step guide to building and deploying a simple Java application to the AWS cloud platform. The application will use a few well known AWS services which I'll describe along the way. There is quite a bit of material to cover in this post so the overview of the AWS services will be light. For those interested in finding out more I'll link to the appropriate section of the AWS documentation. Amazon have done a fine job documenting their platform so I'd encourage you to have a read if time permits.
In order to get the sample application up and running you'll need access to AWS. If you don't already have access you can register for a free account which includes access to a bunch of great services and some pretty generous allowances. I'd encourage you to get an account set up now before going any further.
What will the sample application look like?
The application we're going to build is very simple custo…