Chapter 5. Creating a virtual database as a fat JAR

The Datasources.java file adds a class to represent a connection to a data source. The file also establishes a prefix in the ConfigurationProperties argument (spring.datasource.sampledb). This prefix must be used in the names of data source properties that you specify in the application.properties file.

You can define multiple data sources in Datasources.java by adding multiple classes, each with its own prefix designation. In each case you must add corresponding entries to the DDL file and to the datasources properties in the CR file.

To associate the Java bean with the data source that is defined in your DDL file, the bean name must be the same as the name of the SERVER and resource-name properties in the DDL file. For example, the following sample file establishes a connection to a PostgreSQL database called sampledb, which is the name that is assigned in the DDL file to the data source SERVER object and to its resource-name definition.

package com.example;

import javax.sql.DataSource;

import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class DataSources {

    @ConfigurationProperties(prefix = "spring.datasource.sampledb") 1
    @Bean
    public DataSource sampledb() {    2
        return DataSourceBuilder.create().build();
    }

}

When you create a virtualization as a fat JAR, you must supply an application.properties file. You can define some static properties for your virtual database application in an application.properties file in the /src/main/resource directory. Static properties are configuration settings that remain constant across different environments. After you deploy a virtual database on OpenShift, any modifications that you make to the application.properties file are not effective unless you rebuild and redeploy your virtual database.

You must prefix data source properties that you define in the application.properties file, with the configuration properties string that is specified in the Datasources.java file. The prefix establishes a connection between the properties and the Java class.

For example, if you establish the configuration properties prefix spring.datasource.sampledb in the Datasources.java file, then you must precede the names of the properties that you define in the application.properties file with that string, as in the following property definitions:

spring.datasource.sampledb.username=<username>
spring.datasource.sampledb.password=<password>

After you develop a virtual database from the teiid-springboot starter, you deploy the resulting JAR to Maven repository. You then create a YAML custom resource file for deploying the virtual database to OpenShift.

The CR file for deploying a virtual database created as a fat JAR resembles the CR that you use to deploy a virtual database that is created as a Maven artifact, as described in Section 4.1, “Creating a custom resource (CR) to deploy a Maven artifact”. Only the Maven GAV coordinates differ. In this case, the CR provides the Maven coordinates of the JAR file.

After you create the CR YAML file, you can run the Data Virtualization Operator to deploy the virtual database to OpenShift.