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 …
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…
In this post I'll look at Springs messaging support and how it can be used to integrate with Message Oriented Middleware (MOM) offerings such as Apache ActiveMQ. Although the sample application in this post will use ActiveMQ as its message broker, the application itself is vendor agnostic and can integrate with any JMS compliant messaging platform. I've kept the application as loosely coupled from ActiveMQ as possible and will highlight the bits that would need to change if you were to choose another message platform such as IBM MQSeries.
The sample code in this post will be built and deployed as a simple web application. Obviously this doesn't have to be the case but I've chosen to build a web app as these type of enterprise integration components tend to be deployed as web applications in the real world. The sample app will be built using the following stack. Apache ActiveMQ - JMS Message Broker(not part of the actual application but used to test our…
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…
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 Boot makes it easier to build Spring based applications by focusing on convention over configuration. Following standard Spring Boot conventions we can minimize the configuration required to get an application up and running. The use of an embedded servlet container allows us to package the application as an executable JAR and simply invoke it on the command line to launch the application.
One of my favorite things about Boot is its emphasis on production readiness. Out of the box it provides a number of key non functional features, such as metrics, health checks and externalized configuration. In the past these types of features would have been written from scratch (or more worrying, not at all), before an application could be considered production ready.
This tutorial is an introduction to Spring Boot and describes the steps required to build and test a simple JPA backed REST service. The code is intended to be simple, easy to follow and provide readers with a template for b…
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…
In this post I’ll show you how to use Quartz scheduling with a Spring application. Quartz can be easily integrated with Spring to invoke schedule tasks that call your existing business logic. One of the things I really like about Springs support for Quartz is that you don't have to write any Quartz specific code or amend your existing code to use Quartz scheduling. You simply configure Quartz alongside your existing bean definitions and point it at the logic that you'd like to invoke.
Our Spring/Quartz example will be built as a stand alone
Java application using the following. Spring 3.1MavenQuartz 1.6
It is assumed that readers have a basic knowledge of Spring and Maven. To help you
get an example running quickly I’ll add a link to the full source code at the bottom of this post. Once you download the Maven project simply
import it into Eclipse and run a Maven build.
Creating a simple Project
We'll start off by creating a very simple Spring project like …
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…