In this series of workshop we will build few micro services using spring boot, docker and then deploy them into kubernetes. So, Lets get started.<\/p>\n
First we need to define a problem statement to begin with. Lets say we want to build a order management system.<\/strong><\/p>\n Identifying domains<\/strong><\/p>\n First step would be to understand what domains are required, for simplicity lets assume we need the following domains:<\/p>\n Orders Now that we know what we are building, let\u2019s start developing.<\/strong><\/p>\n In this workshop, we would be using the following<\/p>\n Spring boot for micro services First Microservice : Products <\/strong> Step 1: Set up spring boot application using spring initialiser.<\/strong> group id : com.anirudhbhatnagar Click generate project and download the zipped project. Create a new directory called \u201corder_management_system\u201d. Unzip the project in a folder and copy its contents into a this new directory.<\/p>\n Import the project into your favourite IDE and we are good to start. Check if the setup is working fine by running the project in a terminal:<\/p>\n The build would fail with DataSourceBeanCreationException, this happened because we added PostgresSQL dependency in our project but did not configure the data source by giving the DB credentials and its uri. Lets do that in next step.<\/p>\n Step 2: Configure database<\/strong> This will start a postgres server on port 5432 in your local and initialise an empty DB \u201cpostgres_db\u201d with username \u201cdbuser\u201d and password \u201cpassword\u201d. Once the database is up and running, we will now configure the datasource our spring boot application. One the ways and perhaps the easiest one with spring boot is to define data source URI and database credentials in the application.properties file. Spring boot will auto configure the data source using these credentials. Open the application.properties file in the project and add below :<\/p>\n Now, that we have configured the database for our application, lets run the gradle build again. Build :<\/p>\n If everything is fine, then this time the build should pass. Run :<\/p>\n Now we will have an application running at : http:\/\/localhost:8080\/<\/a> But as we have not implemented any service it will give a 404. In order to get it working, lets add some code.<\/p>\n NOTE : if you are using postgres version you may get this error :<\/p>\n This exception appears because JPA (Hibernate) supported by Atomikos is trying to verify PostgreSQL CLOB feature. This feature is not implemented by JDBC driver, so driver throws an unimportant exception. to fix this, add following to your application.properties file :<\/p>\n This will disable driver\u2019s feature detection (we will not be using this feature anyways)<\/p>\n<\/blockquote>\n Step 3: Add the code in product service<\/strong> Lombok<\/strong> The add the annotations on the class \u201cProduct\u201d<\/p>\n The meaning of annotations: And in order to create this table in the database, we need to set jpa hibernate auto-ddl as true. To do that add the following line to application.properties file :<\/p>\n spring.jpa.hibernate.ddl-auto=create<\/p>\n<\/blockquote>\n We also added : @GeneratedValue and @Id to the field Id, to tell hibernate to auto generate value for the id when creating a new entry in the table.<\/p>\n Add Controller<\/strong> Annotate the class with \u201c@RestController\u201d to extend this class into a Servlet which exposes the webservices. Create the endpoints with the annotation \u201d @GetMapping\u201d<\/p>\n Add Repository<\/strong> Inject productRepository into ProductController so that we can use productRepository in ProductController to pass product request object received in controller to repository to fetch and persist.<\/p>\n Now we have product service up and running with following endpoints :<\/p>\n GET \/products \u2013 gets all the products See the entire code here<\/a>.<\/p>\n Dockerise the app<\/strong> Build :<\/p>\n Run :<\/p>\n This should start a service at localhost:8080<\/p>\n Test the application :<\/strong> Http POST http:\/\/localhost:8080\/products.\u00a0<\/a>Header : Content-Type application\/json<\/p>\n And the products can be fetched by : GET http:\/\/localhost:8080\/products<\/a><\/p>\n In the next workshop, we would look into the following :<\/p>\n Spring cloud, Ribbon for Service Discovery and client side load balancing\n
\nProducts
\nCustomers or Users
\nShopping Cart<\/p>\n<\/blockquote>\n\n
\nPostgres for Database
\nGradle for build
\nDocker for containers<\/p>\n<\/blockquote>\n
\nLets build our first micro-service for products, we will call it product service, this will contain the details of the products.<\/p>\n
\nGo to https:\/\/start.spring.io\/<\/a><\/code> and genereate a gradle<\/code> project with Java<\/code> and SpringBoot 2.1.0\u00a0<\/code>And provide the following values :<\/p>\n\n
\nartifact : productService
\ndependecies : Web, Jpa, postgresSQL<\/p>\n<\/blockquote>\n.\/gradlew build<\/pre>\n
\nWe need a database to persist the product details for the product service.
\nFor this we need 2 things :
\n\u2013 A running postgres database
\n\u2013 Configure its details in spring
\nLets first create a local postgres database. We can use a docker image to have a local postgres DB running. In order to have a postgres database server running as docker image, we need to have docker in our system. Use this link<\/a> to install docker in your mac (Similar links can be found for Windows and Linux).
\nOnce docker is installed in your machine. Pull a latest postgres image and run it in your local. We will also initialise a database with username and password to be used. Run the following command in your terminal :<\/p>\n$ docker run --name oms_postgres -p 5432:5432 -e POSTGRES_USER=dbuser -e POSTGRES_DB=products_db -e POSTGRES_PASSWORD=password -d postgres<\/pre>\n
spring.datasource.url=jdbc:postgresql:\/\/localhost:5432\/products_db\r\nspring.datasource.username=dbuser\r\nspring.datasource.password=password\r\nspring.jpa.hibernate.dialect=org.hibernate.dialect.PostgreSQLDialect<\/pre>\n
.\/gradlew build<\/pre>\n
.\/gradlew bootRun<\/pre>\n
\n
java.sql.SQLFeatureNotSupportedException: Method org.postgresql.jdbc.PgConnection.createClob() is not yet implemented.<\/pre>\n
spring.jpa.properties.hibernate.jdbc.lob.non_contextual_creation=true<\/pre>\n
\nNow that our service and database is setup, we can start writing some code for our product service. Make a package with the name : \u201cdomain\u201d inside the package \u201ccom.anirudhbhatnagar.productService\u201d and create a new Java class \u201cProduct\u201d with attributes:<\/p>\nid\r\nname\r\ndescription\r\nsku<\/pre>\n
\nWe would use Lombok<\/a> to add constructors, getter, setter, and builder methods for our bean. To use lombok add its dependency to build.gradle file :<\/p>\ncompileOnly 'org.projectlombok:lombok:1.18.4'<\/pre>\n
@Entity\r\n@Builder\r\n@AllArgsConstructor\r\n@NoArgsConstructor\r\n@Getter\r\npublic class Product {\r\n\r\n @Id\r\n @GeneratedValue(strategy = GenerationType.AUTO)\r\n private Long id;\r\n private String name;\r\n private String description;\r\n private String sku;\r\n}<\/pre>\n
\n1. @Entity tell spring boot JPA to treat this class as an entity and persist it the database.
\n2. @Builder \u2013 this lmobok annotation adds builder method to our class for creating objects using builder pattern.
\n3. @AllArgsConstructor \u2013 this lmobok annotation adds an all arguments constructor to the class, Builder method needs this method.
\n4. @NoArgsConstructor \u2013 this lmobok annotation adds a default constructor to the class, JPA needs this constructor to fetch the entities.
\n5. @Getter \u2013 this lombok annotation adds getters to all the fields in the class, this is required to fetch individual attributes of the product, this is also used by Jackson to serialise\/deserialise the fields.<\/p>\n\n
\nAdd a controller to implement expose web services and serialise\/deserialise the request using Jackson. Make a package with the name : \u201ccontroller\u201d inside the package \u201ccom.anirudhbhatnagar.productService\u201d and create a new Java class \u201cProductController\u201d inside it.<\/p>\n@RestController\r\npublic class ProductController {\r\n\r\n @GetMapping(\"\/products\")\r\n public List getProducts() {\r\n return Collections.EMPTY_LIST;\r\n }\r\n\r\n @PostMapping(\"\/products\")\r\n public Product save(@RequestBody Product product) {\r\n return null;\r\n }\r\n}<\/pre>\n
\nAdd JPA repository to persist products in the database. Make a package with the name : \u201crepository\u201d inside the package \u201ccom.anirudhbhatnagar.productService\u201d and create a new interface \u201cProductRepository\u201d inside it:<\/p>\npublic interface ProductRepository extends JpaRepository {\r\n}<\/pre>\n@RestController\r\npublic class ProductController {\r\n\r\n private ProductRepository productRepository;\r\n\r\n @Autowired\r\n public ProductController(ProductRepository productRepository) {\r\n this.productRepository = productRepository;\r\n }\r\n\r\n @GetMapping(\"\/products\")\r\n public List getProducts() {\r\n return productRepository.findAll();\r\n }\r\n\r\n @PostMapping(\"\/products\")\r\n public Product save(@RequestBody Product product) {\r\n return productRepository.save(product);\r\n }\r\n}<\/pre>\n
\nPOST \/products \u2013 creates a new product<\/p>\n
\nCreate a file named \u201cdockerFile\u201d in the root folder of the application and add the following contents into it :<\/p>\nFROM openjdk:8-jdk-alpine\r\nVOLUME \/tmp\r\nCOPY build\/libs\/*.jar app.jar\r\nENTRYPOINT [\"java\",\"-Djava.security.egd=file:\/dev\/.\/urandom\",\"-jar\",\"\/app.jar\"]\r\nEXPOSE 8080<\/pre>\n
docker build .<\/pre>\n
docker run -p 8080:8080 [image-id]<\/pre>\n
\nUsing postman or any other similar tool, submit this request to create a product :<\/p>\n{\r\n\"name\" : \"Nike shoes\",\r\n\"description\" : \"mens shoes size 10\",\r\n\"sku\" : \"1234asc\"\r\n}<\/pre>\n\n
\nOpenFeign Client
\nKubernetes for container management
\nAPI gateways<\/p>\n<\/blockquote>\n