How to connect to multiple MySQL databases as per the header in REST API request - mysql

Question

I'm creating a multi tenant spring boot - JPA application.
In this application, I want to connect to MySQL Databases using DB name which is sent through API request as header.
I checked many multi tenant project samples online but still can't figure out a solution.
Can anyone suggest me a way to do this?

Answer 1

You can use AbstractRoutingDataSource to achieve this. AbstractRoutingDataSource requires information to know which actual DataSource to route to(referred to as Context), which is provided by determineCurrentLookupKey() method. Using example from here.
Define Context like:
public enum ClientDatabase {
CLIENT_A, CLIENT_B
}
Then you need to define Context Holder which will be used in determineCurrentLookupKey()
public class ClientDatabaseContextHolder {
private static ThreadLocal<ClientDatabase> CONTEXT = new ThreadLocal<>();
public static void set(ClientDatabase clientDatabase) {
Assert.notNull(clientDatabase, "clientDatabase cannot be null");
CONTEXT.set(clientDatabase);
}
public static ClientDatabase getClientDatabase() {
return CONTEXT.get();
}
public static void clear() {
CONTEXT.remove();
}
}
Then you can extend AbstractRoutingDataSource like below:
public class ClientDataSourceRouter extends AbstractRoutingDataSource {
#Override
protected Object determineCurrentLookupKey() {
return ClientDatabaseContextHolder.getClientDatabase();
}
}
Finally, DataSource bean configuration:
#Bean
public DataSource clientDatasource() {
Map<Object, Object> targetDataSources = new HashMap<>();
DataSource clientADatasource = clientADatasource();
DataSource clientBDatasource = clientBDatasource();
targetDataSources.put(ClientDatabase.CLIENT_A,
clientADatasource);
targetDataSources.put(ClientDatabase.CLIENT_B,
clientBDatasource);
ClientDataSourceRouter clientRoutingDatasource
= new ClientDataSourceRouter();
clientRoutingDatasource.setTargetDataSources(targetDataSources);
clientRoutingDatasource.setDefaultTargetDataSource(clientADatasource);
return clientRoutingDatasource;
}

Answer 2

https://github.com/wmeints/spring-multi-tenant-demo
Following this logic, I can solve it now. Some of the versions need to be upgraded and the codes as well.
Spring Boot version have changed.
org.springframework.boot
spring-boot-starter-parent
2.1.0.RELEASE
Mysql version has been removed.
And some small changed in MultitenantConfiguration.java
#Configuration
public class MultitenantConfiguration {
#Autowired
private DataSourceProperties properties;
/**
* Defines the data source for the application
* #return
*/
#Bean
#ConfigurationProperties(
prefix = "spring.datasource"
)
public DataSource dataSource() {
File[] files = Paths.get("tenants").toFile().listFiles();
Map<Object,Object> resolvedDataSources = new HashMap<>();
if(files != null) {
for (File propertyFile : files) {
Properties tenantProperties = new Properties();
DataSourceBuilder dataSourceBuilder = DataSourceBuilder.create(this.getClass().getClassLoader());
try {
tenantProperties.load(new FileInputStream(propertyFile));
String tenantId = tenantProperties.getProperty("name");
dataSourceBuilder.driverClassName(properties.getDriverClassName())
.url(tenantProperties.getProperty("datasource.url"))
.username(tenantProperties.getProperty("datasource.username"))
.password(tenantProperties.getProperty("datasource.password"));
if (properties.getType() != null) {
dataSourceBuilder.type(properties.getType());
}
resolvedDataSources.put(tenantId, dataSourceBuilder.build());
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
}
// Create the final multi-tenant source.
// It needs a default database to connect to.
// Make sure that the default database is actually an empty tenant database.
// Don't use that for a regular tenant if you want things to be safe!
MultitenantDataSource dataSource = new MultitenantDataSource();
dataSource.setDefaultTargetDataSource(defaultDataSource());
dataSource.setTargetDataSources(resolvedDataSources);
// Call this to finalize the initialization of the data source.
dataSource.afterPropertiesSet();
return dataSource;
}
/**
* Creates the default data source for the application
* #return
*/
private DataSource defaultDataSource() {
DataSourceBuilder dataSourceBuilder = DataSourceBuilder.create(this.getClass().getClassLoader())
.driverClassName(properties.getDriverClassName())
.url(properties.getUrl())
.username(properties.getUsername())
.password(properties.getPassword());
if(properties.getType() != null) {
dataSourceBuilder.type(properties.getType());
}
return dataSourceBuilder.build();
}
}
This change is here due to the DataSourceBuilder has been moved to another path and its constructor has been changed.
Also changed the MySQL driver class name in application.properties like this
spring.datasource.driver-class-name=com.mysql.jdbc.Driver