Hard Code

Problem You want to boost application performance by loading data from a cache and prevent the network trip to the persistent store (and also the query execution). This can be achieved by loading data from a cache. However, you want to load data on demand or lazily. Also, you want the application to control the cache data management – loading, eviction, and retrieval. Forces Improve performance by loading data from cache lazily. Application code controls cache data management. The underlying caching system does not provide read-through, write-through/write-behind strategies (strange really ??). Solution Use cache aside design pattern to solve the problems outlined above. This is also one of many caching patterns/strategies. I believe it is named in this because aside from managing the data store, application code is responsible for managing the cache also. Let's now try to understand how this caching technique works and then explore how it solves the proble...

Setup and Configure Spring Cloud Config Server Project Spring Cloud Config Server is just another Spring Boot application. It provides several infrastructure micro services to centralize access to configuration information backed by a version controlled (well at least in the case of default GIT storage) repository. Step 1 - Create a Spring Boot project in STS with the dependencies shown in Figure 2. Figure 1 - Creating Spring Boot project to setup Spring Cloud Config Server Figure 2 - Spring Cloud Config Server dependencies Click on 'Finish' to complete the creation of the Spring Boot project in STS. The build.gradle file is shown in listing below. There is only one dependency to the Spring Cloud Config Server. Also Spring Cloud release train 'Dalston.SR1'. Step 2 - Annotate the class containing main method The next step is to annotate the ConfigServerInfraApplication class with  @EnableConfigServer That's all is needed on the Java si...

So far I have been using an in-memory H2 database or Mockito for testing the lead microservice. To make the transition towards using the Spring Cloud Config server, I need to upgrade the micro-application to use MariaDB . I will be adding the configuration in the application.yml  the file which in the subsequent post will move over to the config server store. I will also be using Flyway to make it easy to maintain the database schema changes in future. I will use this post to introduce Flyway in the mix. Spring Boot also provides first class integration with Flyway. I am using Flyway as its really quick and easy to get started, minimal learning curve (no DSL) and I am comfortable with it having used it in the past. Assumptions MariaDB 10 is installed Basic familiarity with Flyway Heidi SQL client is installed. Step 1 - Update build.gradle to include the MariaDB JDBC and Flyway dependencies. Do not forget to do a Gradle refresh on your IDE (I am using STS 3.8.4 on...

Last month I wrote a primer on concepts around 12 factor app . Before getting into the details of the Spring Cloud Config Server, I must refresh on the principle #3 from the list presented in that post. 3 –  Configuration Store config in the environment s Configuration information must be separate from the source code. This may seem so obvious, but often we are guilty of leaving critical configuration parameters in the scattered in the code. Instead, applications should have environment specific configuration files. The sensitive information like database password or API key should be stored in these environment configuration files in encrypted format.  The key takeaways from this postulate for a cloud-native microservices application are: Do not store configuration as part of the deployable unit (in the case of lead microservice - inside the jar or war if you are still deploying war like the good old days). Instead, store it in an external location and make it...

In this post, I am going to show how to unit test the business layer of the lead microservice that I am developing. A couple of things to keep in mind to write the unit test for the business layer. These tests run must very fast for quick feedback. Only the business layer is involved and hence the web layer and repository layer should not be started. In other words, the Spring web tier beans should not be created and neither any database connections should be used. (This helps to achieve #1).  The repository layer will be mocked using Mockito. The fluent assert from AssertJ library will be used.  The source code of the lead business unit test is shown in listing below. Most of the test methods are straight forward. However, the testDelete  the method needs some explanation. Here the findOne method is mocked/stubbed. This ensures that correct lead object is returned by the stub method. The other thing to note is that the verify the method for saving method...

This post continues from the last one . I will try to complete the lead microservice in this post. I will be focusing primarily on the CRUD operation. In CRM applications, that is the primary set of operations. I will start by creating the exception class. Later I would show how to use this exception class and Spring Rest exception handling and build a robust error handling around the API calls. Listing 1 - BusinessException.java Next step would be to introduce the service class. Since this is CRUD most of the functionality can be encapsulated in an abstract parent service class. Any specific feature like convert lead to opportunity can be implemented in the LeadService class. Listing 2 - AbstractBaseBusinessDelegate.java And then finally the LeadService implementation class is shown in Listing 3. Listing 3 - LeadBusinessDelegate.java Note that this code will not compile. In order to get this to compile, you will need to add 2 new dependencies for the...

This is a continuation of my previous post where I listed the key domain components of CRM. For sake of simplicity, I will focus on just two key components - Lead and Opportunity respectively. These two modules will help me explore end to microservice implementation. I will be primarily using Spring framework's support to deliver the microservices. I am deliberating on a nice interesting Javascript framework for the front end. More on this later. Goal For the time being, I am just going to focus on building the backend and cloud enable it. Then slowly I am going to add the front end and security to the backend and front end. I will also explore the complete Sping Cloud gamut of projects and beyond. I will then deliberate on cloud-native applications, transactions and actually making this application suitable to run on virtually any cloud. I will also explore cloud and microservices application design patterns. Last but not the least we also need to check where this application...

The 12-factor app guideline was published by Heroku the platform as a service (PaaS) provider (now a part of Salesforce.com). These were a set of principles/best practices that one needed to follow to build applications on the Heroku PaaS. Over time, this has become the de-facto standard for building web applications on the cloud or more precisely cloud-native applications. The original 12-factor app guideline is available at 12factor.net and was not really meant for microservices. In this post, I will try to go over the 12-factor app guidelines and check how they fit into microservices architecture. 1 – Codebase One codebase tracked in revision control, many deploys The application codebase should be maintained in a version control system (VCS).All developers should have easy access to VCS.There is only one codebase per application in the VCS, but there can be multiple deployment copies of this application codebase. For example, an application can be deployed in di...