In the previous step we initialized a spring boot project so that we can start development. In this step we\u2019re going to setup the persistence tier of the customer service.<\/p>\n\n\n\n
I like to start with the data model at the persistence level and work up. Since the datastore is usually the \u2018foundation\u2019 of your applications it makes sense to me. We\u2019re going to use liquibase define a database \u2018contract\u2019, spring data jpa to create the data access layer and then H2 as an in-memory data store for testing.<\/p>\n\n\n\n
First, lets setup liquibase. In What we\u2019re doing here is defining the columns of our database table in a way that is compatible across DB platforms. Liquibase will read this configuration and generate the correct DB statements for your database. This \u2018contract\u2019 will work against H2, postgres, mysql, etc\u2026 without making any changes to your DDL. We\u2019re also defining a sequence that we\u2019ll use to manage the primary key on our table.<\/p><\/blockquote>\n\n\n\n However, we also need to define how these changelogs will be executed. We can do that via a changelog master. In This will tell the application on startup to execute all of the changelogs in the defined directory. Since they\u2019re ordered by the file name convention, they will execute in the correct order. Additionally, on startup the application will detect which changelogs are currently applied to the database and will apply any changes that it detects have not been applied.<\/p><\/blockquote>\n\n\n\n Now lets create the data access object that will interact with the data repository. Create this package in In the We\u2019re making a lot of use of Lombok here. If you\u2019re not familiar with it, it may be somewhat strange. Lombok uses the annotations to define code to generate at compile time. Here we\u2019re using it to generate getters, setters, toString, etc\u2026 which are all defined here<\/a>. I\u2019m also using builder <\/a>and some constructor<\/a> annotations. It keeps us from having to write a lot of boiler plate java code and speeds up our development time in addition to making the code very easy to read which also speeds up our development and debug time.<\/p><\/blockquote>\n\n\n\n In the We\u2019re using spring data jpa to generate the boilerplate CRUD functions so we don\u2019t have to. We can also use this class to access the database directly, which we\u2019ll use in testing<\/p><\/blockquote>\n\n\n\n Lets see if we can actually write into a table and access the data using the DAO we just wrote. In If you run the test, you should bet a green check \/ success.<\/p>\n\n\n\n We can look at the logs and see what just happened<\/p>\n\n\n\n These lines are telling us that we\u2019re going to start a datasource and hook it up to in memory H2 database that spring starts up for us.<\/p><\/blockquote>\n\n\n\n These lines are telling us that liquibase is using Hibernate to translate our liquibase changelog file into H2 dialect and then executing it.<\/p><\/blockquote>\n\n\n\n These lines are telling us that the unit test created a transaction for the duration of the test and then rolled it back when it finished. So we don\u2019t have to worry about stale test data contaminating our database during future test runs. This test is now idempotent and we can run it as much as we want and it will return the database to the original state.<\/p><\/blockquote>\n\n\n\n Confirm our build still works:<\/p>\n\n\n\n and if we have success we should commit<\/p>\n\n\n\n I\u2019m going to try and keep each step in its own branch. That way, if you\u2019re following along you can see each stage. I hated articles that had stages but the git repo was the \u2018final product\u2019 and it was difficult to see how the code or service evolved. I\u2019ll try and prevent that from happening here.<\/p><\/blockquote>\n\n\n\n I\u2019m also going to merge this branch back into master so that I can use it as a baseline for the next step.<\/p>\n\n\n\nsrc\/main\/resources<\/code> create a directory structure for db\/changelog\/migrations<\/code>. First lets use liquibase to define a DDL for our database table. We\u2019re going to try and follow liquibase best practices<\/a>. In src\/main\/resources\/db\/changelog\/migrations<\/code> create a file called 0001-init-customer-table.yaml<\/code>. Inside that file lets define our customer table like this:<\/p>\n\n\n\ndatabaseChangeLog:\n - changeSet:\n id: create-customer-table\n author: brianrook\n changes:\n - createTable:\n catalogName: medium\n tableName: customer\n columns:\n - column:\n name: customer_id\n type: bigint\n constraints:\n primaryKey: true\n nullable: false\n - column:\n name: first_name\n type: varchar(100)\n constraints:\n nullable: false\n - column:\n name: last_name\n type: varchar(100)\n constraints:\n nullable: false\n - column:\n name: phone_number\n type: varchar(20)\n - column:\n name: email\n type: varchar(150)\n constraints:\n nullable: false\n - column:\n name: create_timestamp\n type: timestamp\n constraints:\n nullable: false\n defaultValueComputed: CURRENT_TIMESTAMP\n - column:\n name: modify_timestamp\n type: timestamp\n constraints:\n nullable: false\n defaultValueComputed: CURRENT_TIMESTAMP\n - createSequence:\n sequenceName: customer_seq\n incrementBy: 1<\/code><\/pre>\n\n\n\nsrc\/main\/resources\/db\/changelog<\/code> create a file called db.changelog-master.yaml<\/code> with this content:<\/p>\n\n\n\ndatabaseChangeLog:\n - includeAll:\n path: db\/changelog\/migrations\/<\/code><\/pre>\n\n\n\nCreate the Entity<\/h3>\n\n\n\n
src\/main\/java com.brianrook.medium.customer.dao.entity<\/code><\/p>\n\n\n\nentity <\/code>directory create your database entity CustomerEntity<\/code><\/p>\n\n\n\npackage com.brianrook.medium.customer.dao.entity;\n\nimport lombok.Data;\n\nimport javax.persistence.*;\n\n@Data\n@Entity\n@Table(name = \"customer\")\n@Builder\n@NoArgsConstructor\n@AllArgsConstructor\npublic class CustomerEntity {\n @Id\n @SequenceGenerator(name = \"customer_seq\", sequenceName = \"customer_seq\", allocationSize = 1)\n @GeneratedValue(strategy = GenerationType.SEQUENCE<\/em>, generator = \"customer_seq\")\n @Column(name = \"customer_id\")\n private Long customerId;\n\n @Column(name = \"first_name\")\n private String firstName;\n @Column(name = \"last_name\")\n private String lastName;\n @Column(name = \"phone_number\", nullable = false, unique = true)\n private String phoneNumber;\n @Column(name = \"email\", nullable = false, unique = true)\n private String email;\n}<\/code><\/pre>\n\n\n\nCreate the DAO<\/h3>\n\n\n\n
com.brianrook.medium.customer.dao<\/code> directory create a java interface called CustomerDAO<\/code>. Add this content:<\/p>\n\n\n\npackage com.brianrook.medium.customer.dao;\n\nimport com.brianrook.medium.customer.dao.entity.CustomerEntity;\nimport org.springframework.data.repository.CrudRepository;\nimport org.springframework.stereotype.Repository;\n\n@Repository\npublic interface CustomerDAO extends CrudRepository<CustomerEntity, Long> {\n}<\/code><\/pre>\n\n\n\nWrite the Test<\/h3>\n\n\n\n
src\/test\/java<\/code> create a package called com.brianrook.medium.customer.dao<\/code>. Create a java test class called CustomerDAOTest<\/code> and add this content.<\/p>\n\n\n\npackage com.brianrook.medium.customer.dao;\n\nimport com.brianrook.medium.customer.dao.entity.CustomerEntity;\nimport org.junit.jupiter.api.Test;\nimport org.junit.jupiter.api.extension.ExtendWith;\nimport org.springframework.beans.factory.annotation.Autowired;\nimport org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;\nimport org.springframework.test.context.junit.jupiter.SpringExtension;\n\nimport java.util.Optional;\n\nimport static org.assertj.core.api.Assertions.assertThat<\/em>;\n\n@ExtendWith(SpringExtension.class)\n@DataJpaTest\npublic class CustomerDAOTest {\n @Autowired\n private CustomerDAO customerDAO;\n\n @Test\n public void testSaveCustomer()\n {\n CustomerEntity testCustomer = CustomerEntity.builder<\/em>()\n .firstName(\"Brian\")\n .lastName(\"Rook\")\n .email(\"test.user@test.com\")\n .phoneNumber(\"303-555-1212\")\n .build();\n\n customerDAO.save(testCustomer);\n\n Optional<CustomerEntity> returnCustomer = customerDAO.findById(testCustomer.getCustomerId());\n\nassertThat<\/em>(returnCustomer.isPresent()).isTrue();\nassertThat<\/em>(returnCustomer.get()).isEqualTo(testCustomer);\n }\n}<\/code><\/pre>\n\n\n\n2020-03-27 16:25:38.530 INFO [,,,] 7636 --- [ main] beddedDataSourceBeanFactoryPostProcessor : Replacing 'dataSource' DataSource bean with embedded version\n2020-03-27 16:25:38.863 INFO [,,,] 7636 --- [ main] o.s.j.d.e.EmbeddedDatabaseFactory : Starting embedded database: url='jdbc:h2:mem:88a922a3-9a84-4153-8c73-085c38168e17;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=false', username='sa'<\/code><\/pre>\n\n\n\n2020-03-27 16:25:39.520 INFO [,,,] 7636 --- [ main] org.hibernate.dialect.Dialect : HHH000400: Using dialect: org.hibernate.dialect.H2Dialect\nHibernate: drop table organizer if exists\nHibernate: drop sequence if exists customer_seq\nHibernate: create sequence customer_seq start with 1 increment by 1\nHibernate: create table organizer (customer_id bigint not null, email varchar(255) not null, first_name varchar(255), last_name varchar(255), phone_number varchar(255) not null, primary key (customer_id))\nHibernate: alter table organizer add constraint UK_s25r3nckqlux0klke4y3yb9u0 unique (email)\nHibernate: alter table organizer add constraint UK_81500y90b5jyslc733s8iisk unique (phone_number)<\/code><\/pre>\n\n\n\n2020-03-27 16:25:40.362 INFO [,,,] 7636 --- [ main] o.s.t.c.transaction.TransactionContext : Began transaction (1) for test context ...\nHibernate: call next value for customer_seq\n2020-03-27 16:25:40.574 INFO [,,,] 7636 --- [ main] o.s.t.c.transaction.TransactionContext : Rolled back transaction for test: ...<\/code><\/pre>\n\n\n\nBuild and Commit<\/h3>\n\n\n\n
mvn clean install<\/code><\/pre>\n\n\n\ngit checkout -b dao\ngit add .\ngit commit -m \"added database repository\"\ngit push --set-upstream origin dao<\/code><\/pre>\n\n\n\ngit checkout master\ngit merge --squash dao\ngit commit -m \"Added DB and DAO\"\ngit push<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"