Holon Platform JDBC Module - Reference manual

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1. Introduction

The Holon Platform JDBC module provides base JDBC support to the Holon platform, dealing with javax.sql.DataSource configuration and providing a multi-tenant DataSource implementation.

Futhermore, the module provides integration with the Spring framework relatively to DataSource configuration and DataSource auto-configuration facilities using Spring Boot.

1.1. Sources and contributions

The Holon Platform JDBC module source code is available from the GitHub repository https://github.com/holon-platform/holon-jdbc.

See the repository README file for information about:

The source code structure.
How to build the module artifacts from sources.
Where to find the code examples.
How to contribute to the module development.

2. Obtaining the artifacts

The Holon Platform uses Maven for projects build and configuration. All the platform artifacts are published in the Maven Central Repository, so there is no need to explicitly declare additional repositories in your project pom file.

At the top of each section of this documentation you will find the Maven coordinates (group id, artifact id and version) to obtain the artifact(s) as a dependency for your project.

A BOM (Bill Of Materials) pom is provided to import the available dependencies for a specific version in your projects. The Maven coordinates for the core BOM are the following:

Maven coordinates:

<groupId>com.holon-platform.jdbc</groupId>
<artifactId>holon-jdbc-bom</artifactId>
<version>5.2.4</version>

The BOM can be imported in a Maven project in the following way:

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.holon-platform.jdbc</groupId>
      <artifactId>holon-jdbc-bom</artifactId>
      <version>5.2.4</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

2.1. Using the Platform BOM

The Holon Platform provides an overall Maven BOM (Bill of Materials) to easily obtain all the available platform artifacts.

See Obtain the platform artifacts for details.

3. What’s new in version 5.2.x

The JdbcTransactionOptions API was introduced to provide JDBC transaction configuration options.
The transaction isolation level can be specified using the TransactionIsolation enumeration.
Support for JDK 9+ module system using Automatic-Module-Name.

4. What’s new in version 5.1.x

A DataSource can now be built through the DataSourceBuilder API directly providing the DataSource configuration properties, besides using a configuration property source. See Provide DataSource configuration properties programmatically.
The JdbcConnectionHandler API was introduced to provide DataSource connections lifecycle customization. See the Holon Platform JDBC Datastore Module for a use case.

5. JDBC DataSource creation and configuration

Maven coordinates:

<groupId>com.holon-platform.jdbc</groupId>
<artifactId>holon-jdbc</artifactId>
<version>5.2.4</version>

The Holon platform JDBC module provides an API to create and configure JDBC DataSource instances using a set of configuration properties.

The DataSourceBuilder API can be used to build DataSource instances using a set of configuration properties, represented by the DataSourceConfigProperties property set.

See the next sections to learn how to use the DataSource builder API to create JDBC DataSource instances.

5.1. DataSource configuration properties

The DataSource configuration properties are available from the DataSourceConfigProperties interface, which is a standard ConfigPropertySet API and allows to obtain the configuration property set values from different sources.

The DataSourceConfigProperties property set name prefix is holon.datasource.

The available configuration properties are listed below:

Name Type Meaning

Name	Type	Meaning
holon.datasource. type	String	DataSource type: see DataSource type
holon.datasource. driver-class-name	String	The JDBC Driver class name to use. If not specified, the default DataSource builder tries to auto-detect it form the connection URL
holon.datasource. url	String	JDBC connection url
holon.datasource. username	String	JDBC connection username
holon.datasource. password	String	JDBC connection password
holon.datasource. platform	`DatabasePlatform` enumeration	Database platform to which the DataSource is connected. If not specified, the DataSource builder tries to auto-detect it form the connection URL
holon.datasource. auto-commit	Boolean (`true` / `false`)	The default JDBC driver auto-commit mode
holon.datasource. max-pool-size	Integer number	For connection pooling `DataSource` types, configure the minimum connection pool size
holon.datasource. min-pool-size	Integer number	For connection pooling `DataSource` types, configure the maximum connection pool size
holon.datasource. validation-query	String	For connection pooling `DataSource` types the query to use to validate the connections in the pool
holon.datasource. jndi-name	String	JNDI lookup name for `JNDI` DataSource retrieval strategy

holon.datasource. type

String

DataSource type: see DataSource type

holon.datasource. driver-class-name

String

The JDBC Driver class name to use. If not specified, the default DataSource builder tries to auto-detect it form the connection URL

holon.datasource. url

String

JDBC connection url

holon.datasource. username

String

JDBC connection username

holon.datasource. password

String

JDBC connection password

holon.datasource. platform

DatabasePlatform enumeration

Database platform to which the DataSource is connected. If not specified, the DataSource builder tries to auto-detect it form the connection URL

holon.datasource. auto-commit

Boolean (true / false)

The default JDBC driver auto-commit mode

holon.datasource. max-pool-size

Integer number

For connection pooling DataSource types, configure the minimum connection pool size

holon.datasource. min-pool-size

Integer number

For connection pooling DataSource types, configure the maximum connection pool size

holon.datasource. validation-query

String

For connection pooling DataSource types the query to use to validate the connections in the pool

holon.datasource. jndi-name

String

JNDI lookup name for JNDI DataSource retrieval strategy

The DataSourceConfigProperties property set can be loaded from a number a sources using the default ConfigPropertySet builder API:

DataSourceConfigProperties config = DataSourceConfigProperties.builder().withDefaultPropertySources().build(); (1)

config = DataSourceConfigProperties.builder().withSystemPropertySource().build(); (2)

Properties props = new Properties();
props.put("holon.datasource.url", "jdbc:h2:mem:testdb");
config = DataSourceConfigProperties.builder().withPropertySource(props).build(); (3)

config = DataSourceConfigProperties.builder().withPropertySource("datasource.properties").build(); (4)

config = DataSourceConfigProperties.builder()
    .withPropertySource(
        Thread.currentThread().getContextClassLoader().getResourceAsStream("datasource.properties"))
    .build(); (5)

1	Read the configuration properties from default property sources (i.e. the `holon.properties` file)
2	Read the configuration properties from `System` properties
3	Read the configuration properties from a `Properties` instance
4	Read the configuration properties from the `datasource.properties` file
5	Read the configuration properties from the `datasource.properties` `InputStream`

5.2. Multiple DataSource configuration

When multiple DataSource instances are to be configured and the configuration properties are read from the same property source, a data context id can be used to discern one DataSource configuration property set form another.

From the property source point of view, the data context id is used as a suffix after the configuration property set name (holon.datasource) and before the specific property name.

For example, suppose we have a configuration property set for two different data sources as follows:

datasource.properties

holon.datasource.one.url=jdbc:h2:mem:testdb1
holon.datasource.one.username=sa

holon.datasource.two.url=jdbc:h2:mem:testdb2
holon.datasource.two.username=sa

In the example above, the one and two strings represents two different data context ids.

To build two DataSource instances, one bound to the one configuration property set and the other bound to the two configuration property set, the DataSourceConfigProperties implementation can be obtained as follows, specifying the data context id when obtaining the builder, even using the same property source:

DataSourceConfigProperties config1 = DataSourceConfigProperties.builder("one") (1)
    .withPropertySource("datasource.properties").build();

DataSourceConfigProperties config2 = DataSourceConfigProperties.builder("two") (2)
    .withPropertySource("datasource.properties").build();

1	Obtain a `DataSourceConfigProperties` builder for the `one` data context id
2	Obtain a `DataSourceConfigProperties` builder for the `two` data context id

5.3. Build a DataSource using the `DataSourceBuilder` API

The DataSourceBuilder API can be used to build DataSource instances using the DataSource configuration properties property set.

A DataSourceBuilder API implementation can be otained using the create() static method.

For example, using the following configuration properties file:

datasource.properties

holon.datasource.url=jdbc:h2:mem:testdb
holon.datasource.username=sa
holon.datasource.password=

The DataSourceBuilder API can be used as follows to create a DataSource instance:

DataSourceConfigProperties config = DataSourceConfigProperties.builder()
    .withPropertySource("datasource.properties").build(); (1)

DataSource dataSource = DataSourceBuilder.create().build(config); (2)

1	Create a configuration property set using the `datasource.properties` file as property source
2	Build a `DataSource` instance according to given configuration properties

5.3.1. Provide DataSource configuration properties programmatically

The DataSourceBuilder API can be also used directly providing the DataSource configuration properties. For this purpose, an appropriate builder API can be obtained using the builder() method.

This builder also supports DataSource initialization scripts, which will be executed at DataSource initialization time. The DataSource initialization scripts can be directly provided as a String of SQL statements or specifying classpath resource name (for example a file name).

DataSource dataSource = DataSourceBuilder.builder() (1)
    .type(DataSourceType.HIKARICP) // type
    .url("jdbc:h2:mem:testdb") // jdbc url
    .username("sa") // jdbc username
    .minPoolSize(5) // max pool size
    .withInitScriptResource("init.sql") // init script resource
    .build();

1	Obtain the `DataSource` builder

5.4. DataSource type

When using the DataSourceBuilder API, the concrete DataSource implementation to use can be selected using the type configuration property.

The following type names are supported by default:

com.holonplatform.jdbc.BasicDataSource: Create BasicDataSource instances, to be used typically for testing purposes. It is a simple DataSource implementation, using the java.sql.DriverManager class and returning a new java.sql.Connection from every getConnection call. See BasicDataSource.
com.zaxxer.hikari.HikariDataSource: Create HikariCP connection pooling DataSource instances. The HikariCP library dependency must be available in classpath. All default configuration properties are supported, and additional Hikari-specific configuration properties can be specified using the hikari prefix before the actual property name, for example: holon.datasource.hikari.connectionTimeout.
org.apache.commons.dbcp2.BasicDataSource: Create Apache Commons DBCP 2 connection pooling DataSource instances. The DBCP 2 library dependency must be available in classpath. All default configuration properties are supported, and additional DBCP-specific configuration properties can be specified using the dbcp prefix before the actual property name, for example: holon.datasource.dbcp.maxWaitMillis.
org.apache.tomcat.jdbc.pool.DataSource: Create Tomcat JDBC connection pooling DataSource instances. The tomcat-jdbc library dependency must be available in classpath. All default configuration properties are supported, and additional Tomcat-specific configuration properties can be specified using the tomcat prefix before the actual property name, for example: holon.datasource.tomcat.maxAge.
JNDI: Obtain a DataSource using JNDI. The jndi-name configuration property is required to specify the JNDI name to which the DataSource is bound in the JNDI context.

To use a specific DataSource implementation, the corresponding classes must be available in classpath. So you have to ensure the required dependencies are declared for your project.

For example, to use a HikariCP pooling DataSource implementation, the com.zaxxer.hikari.HikariDataSource type can be specified:

holon.datasource.url=jdbc:h2:mem:testdb
holon.datasource.username=sa
holon.datasource.password=

holon.datasource.type=com.zaxxer.hikari.HikariDataSource

5.4.1. Default DataSource type selection strategy

If the type configuration property is not specified, the default DataSource type selection strategy is defined as follows:

If the HikariCP dependecy is present in classpath, the com.zaxxer.hikari.HikariDataSource type will be used;
If the Apache Commons DBCP 2 dependecy is present in classpath, the org.apache.commons.dbcp2.BasicDataSource type will be used;
If the Tomcat JDBC dependecy is present in classpath, the org.apache.tomcat.jdbc.pool.DataSource type will be used;
Otherwise, the com.holonplatform.jdbc.BasicDataSource type is used as fallback.

5.4.2. DataSourceFactory

The default DataSourceBuilder API implementation delegates DataSource instances creation to a set of concrete DataSourceFactory implementations, each of them bound to a single DataSource type name.

A DataSourceFactory can be registered in the DataSourceBuilder API and used to provide additional DataSource types support or to replace a default type creation strategy with a new one.

The DataSource type name to which the DataSourceFactory is bound is provided by the getDataSourceType() method.

The registration of a DataSourceFactory can be accomplished in two ways:

Direct registration: A DataSourceFactory instance can directly registered in a DataSourceBuilder API using the registerFactory method. Any previous binding with given type will be replaced by the given factory.

class MyDataSourceFactory implements DataSourceFactory { (1)

  @Override
  public String getDataSourceType() {
    return "my.type.name";
  }

  @Override
  public DataSource build(DataSourceConfigProperties configurationProperties) throws ConfigurationException {
    // Build and return a DataSource istance using given configuration properties
    return buildTheDataSourceInstance();
  }

}

void usingTheFactory() {
  DataSourceBuilder builder = DataSourceBuilder.create();
  builder.registerFactory(new MyDataSourceFactory()); (2)
}

1	Create a `DataSourceFactory` implementation
2	Register the factory in the `DataSourceBuilder` API instance

Using the direct DataSourceFactory registration, the registered factories will be available only for the specific DataSourceBuilder API instance.

Java ServiceLoader extensions: The default Java ServiceLoader extensions can be used, providing a file named com.holonplatform.jdbc.DataSourceFactory under the META-INF/services folder, in which to specify the fully qualified name of the DataSourceFactory implementation/s to register. This way, the factory will be automatically registered at DataSourceBuilder API initialization time.

Using the ServiceLoader extensions method, the DataSourceFactory implementations will be available for any DataSourceBuilder API instance.

5.4.3. DataSourcePostProcessor

The DataSourcePostProcessor interface can be used to perform additional DataSource initialization and configuration when using the DataSourceBuilder API.

The postProcessDataSource(…) method is called just after the creation of any DataSource instance, providing the DataSource instance itself, the type name and the DataSourceConfigProperties used to create the DataSource instance.

In order to activate a DataSourcePostProcessor, it must be registered in the DataSourceBuilder API instance used to create the DataSource.

When more than one DataSourcePostProcessor is registered, the invocation order will be the same as the registration order.

The registration of a DataSourcePostProcessor can be accomplished in two ways:

Direct registration: A DataSourcePostProcessor instance can directly registered in a DataSourceBuilder instance using the registerPostProcessor method.

DataSourceBuilder builder = DataSourceBuilder.create();
builder.registerPostProcessor(new DataSourcePostProcessor() { (1)

  @Override
  public void postProcessDataSource(DataSource dataSource, String typeName,
      DataSourceConfigProperties configurationProperties) throws ConfigurationException {
    // perform DataSource post processing
  }
});

1	Register a post processor in the `DataSourceBuilder` API instance

Using the direct DataSourcePostProcessor registration, the registered post processors will be available only for the specific DataSourceBuilder API instance.

Java ServiceLoader extensions: The default Java ServiceLoader extensions can be used, providing a file named com.holonplatform.jdbc.DataSourcePostProcessor under the META-INF/services folder, in which to specify the fully qualified name of the DataSourcePostProcessor implementation/s to register. This way, the post processors will be automatically registered at DataSourceBuilder API initialization time.

Using the ServiceLoader extensions method, the DataSourcePostProcessor implementations will be registered for any DataSourceBuilder API instance.

5.5. BasicDataSource

The BasicDataSource API is made available to create simple, standard javax.sql.DataSource implementations.

The BasicDataSource implementation uses the java.sql.DriverManager class and returns a new java.sql.Connection from every getConnection() call.

This implementation is not designed for production and should be used only for testing purposes.

A fluent builder is provided to create and configure a BasicDataSource instance:

DataSource dataSource = BasicDataSource.builder().url("jdbc:h2:mem:testdb").username("sa") //
    .driverClassName("org.h2.Driver") (1)
    .build();

try (Connection connection = dataSource.getConnection()) {
  // ...
}

dataSource = BasicDataSource.builder().url("jdbc:h2:mem:testdb").username("sa") //
    .database(DatabasePlatform.H2) (2)
    .build();

1	Build a `BasicDataSource` providing driver class name
2	Build a `BasicDataSource` using the `DatabasePlatform` enumeration to obtain the driver class name

6. Multi-tenant DataSource

The Holon platform JDBC module provides a DataSource implementation with multi-tenant support, represented by the MultiTenantDataSource interface.

This DataSource implementation acts as a wrapper for concrete DataSource implementations, one for each tenant id. By default, DataSource instances are reused, so if an instance was already created for a specific tenant id, this one is returned at next tenant connection request.

A reset() method is provided to clear the internal per-tenant DataSource instance cache. To clear only the cached instance for a specific tenant id, the reset(String tenantId) method is provided.

The MultiTenantDataSource implementation relies on the APIs to work properly:

A com.holonplatform.core.tenancy.TenantResolver API instance to obtain the current tenant id.
A TenantDataSourceProvider API implementation, which acts as concrete DataSource instances provider, used to obtain a DataSource for each tenant id.

MultiTenantDataSource dataSource = MultiTenantDataSource.builder().resolver(() -> Optional.of("test")) (1)
    .provider(tenantId -> new DefaultBasicDataSource()) (2)
    .build();

1	Set the `TenantResolver`
2	Set the `TenantDataSourceProvider`

6.1. `TenantResolver` and `TenantDataSourceProvider` lookup strategy

If not directly configured, the TenantResolver and TenantDataSourceProvider implementation can be obtained by default using the Holon Platform Context resources architecture.

The MultiTenantDataSource will try to obtain a TenantResolver and a TenantDataSourceProvider implementation as context resources using the default context keys (i.e. the class names) when they are not directly configured using the appropriate builder methods.

7. Spring framework integration

Maven coordinates:

<groupId>com.holon-platform.jdbc</groupId>
<artifactId>holon-jdbc-spring</artifactId>
<version>5.2.4</version>

The holon-jdbc-spring artifact provides integration with the Spring framework for JDBC DataSource building and configuration, fully supporting multiple DataSource instances configuration and providing Spring Boot auto-configuration facilities.

7.1. DataSource auto-configuration

The EnableDataSource annotation can be used on Spring configuration classes to enable automatic DataSource configuration, using Spring Environment property sources to obtain the DataSource configuration properties, which must be defined according to the DataSource configuration properties property set.

For example, using the following configuration properties:

datasource.properties

holon.datasource.url=jdbc:h2:mem:testdb1
holon.datasource.username=sa

A DataSource bean can be automatically configured using the @EnableDataSource annotation on a Spring configuration class:

@Configuration
@PropertySource("datasource.properties")
@EnableDataSource (1)
class Config {

}

@Autowired
private DataSource dataSource1; (2)

1	Use the `@EnableDataSource` to create a `DataSource` bean instance, using the `datasource.properties` file as property source
2	Obtain the configured `DataSource` bean instance

7.1.1. Multiple `DataSource` configuration

When multiple DataSource instances has to be configured, multiple @EnableDataSource annotations can be used, relying on the data context id specification to discern a configuration property set from another.

The data context id to which the DataSource configuration is bound can be configured using the dataContextId() attribute of the @EnableDataSource annotation.

As described in the Multiple DataSource configuration section, the data context id will be used as a suffix after the configuration property set name (holon.datasource) and before the specific property name.

For example, if the data context id is test, the JDBC connection URL for a DataSource must be configured using a property named holon.datasource.test.url.

When a data context id is defined, a Spring qualifier named the same as the data context id will be associated to the generated DataSource bean definitions, and such qualifier can be later used to obtain the right DataSource instance through dependency injection.

Furthermore, each bean definition will be named using the default DataSource bean name (dataSource) followed by an underscore and by the data context id name. For example: dataSource_test.

For example, given a datasource.properties file defined as follows:

datasource.properties

holon.datasource.one.url=jdbc:h2:mem:testdb1
holon.datasource.one.username=sa

holon.datasource.two.url=jdbc:h2:mem:testdb1
holon.datasource.two.username=sa

To configure the the DataSource bean instances, one bound to the data context id one and another bound to the data context id two, two @EnableDataSource annotations can be used this way:

@Configuration
@PropertySource("datasource.properties")
static class Config {

  @Configuration
  @EnableDataSource(dataContextId = "one") (1)
  static class Config1 {
  }

  @Configuration
  @EnableDataSource(dataContextId = "two") (2)
  static class Config2 {
  }

}

@Autowired
@Qualifier("one") (3)
private DataSource dataSource1;

@Autowired
@Qualifier("two")
private DataSource dataSource2;

1	Enable a `DataSource` bean using the `one` data context id
2	Enable a `DataSource` bean using the `two` data context id
3	The data context id can be used as qualifier to obtain the proper `DataSource` instance

7.1.2. Primary mode

The @EnableDataSource annotation provides a primary() attribute which can be used to control the primary mode of the DataSource bean registration.

If the primary mode is set to PrimaryMode.TRUE, the DataSource bean created with the corresponding annotation will be marked as primary in the Spring application context, meaning that will be the one provided by Spring in case of multiple available candidates, when no specific bean name or qualifier is specified in the dependency injection declaration.

This behaviour is similar to the one obtained with the Spring @Primary annotation at bean definition time.

@Configuration @PropertySource("datasource.properties") class Config {

  @Configuration
  @EnableDataSource(dataContextId = "one", primary = PrimaryMode.TRUE) (1)
  static class Config1 {
  }

  @Configuration
  @EnableDataSource(dataContextId = "two")
  static class Config2 {
  }

}

@Autowired
private DataSource dataSource1; (2)

@Autowired
@Qualifier("two")
private DataSource dataSource2;

1	The `PrimaryMode.TRUE` is configured for the `one` data context id `@EnableDataSource` configuration
2	The `DataSource` bean bound to the `one` data context id can be now obtained without specifyng a qualifier

7.1.3. Transaction management

The @EnableDataSource annotation provides also a enableTransactionManager() attribute, that, if set to true, automatically registers a JDBC PlatformTransactionManager to enable transactions management by using Spring’s transactions infrastructure (for example in order to use @Transactional annotations).

The registered transaction manager will be a standard Spring DataSourceTransactionManager.

@Configuration
@PropertySource("datasource.properties")
@EnableDataSource(enableTransactionManager = true) (1)
class Config {

}

@Transactional
void doSomethingTransactionally() { (2)
  // ...
}

1	Enable a the transaction manager using the configured `DataSource`
2	When a `PlatformTransactionManager` is available, the `@Transactional` annotation can be used

7.1.4. Additional `DataSource` configuration properties

The JDBC Spring integration supports a set of additional DataSource configuration properties, collected in the SpringDataSourceConfigProperties interface, which can be used to configure further DataSource initialization options when the @EnableDataSource annotation is used.

The available additional configuration properties are listed below:

Name	Type	Meaning
holon.datasource. primary	Boolean (true/false)	Marks the DataSource bean as primary, meaning that will be the one provided by the Spring context when no specific name or qualifier is specified
holon.datasource. schema	String	Specifies the the schema (DDL) script to execute when the DataSource is initialized
holon.datasource. data	String	Specifies the the data (DML) script to execute when the DataSource is initialized
holon.datasource. continue-on-error	Boolean (true/false)	Whether to stop schema/data scripts execution if an error occurs
holon.datasource. separator	String	Statement separator in SQL initialization scripts. Default is semicolon.
holon.datasource. sql-script-encoding	String	SQL scripts encoding
holon.datasource. initialize	Boolean (true/false)	Whether to populate the database after DataSource initialization using schema/data scripts (default is true)

Name

Type

Meaning

holon.datasource. primary

Boolean (true/false)

Marks the DataSource bean as primary, meaning that will be the one provided by the Spring context when no specific name or qualifier is specified

holon.datasource. schema

String

Specifies the the schema (DDL) script to execute when the DataSource is initialized

holon.datasource. data

String

Specifies the the data (DML) script to execute when the DataSource is initialized

holon.datasource. continue-on-error

Boolean (true/false)

Whether to stop schema/data scripts execution if an error occurs

holon.datasource. separator

String

Statement separator in SQL initialization scripts. Default is semicolon.

holon.datasource. sql-script-encoding

String

SQL scripts encoding

holon.datasource. initialize

Boolean (true/false)

Whether to populate the database after DataSource initialization using schema/data scripts (default is true)

If the initialize property is set to true (the default) and the script files schema.sql and/or data.sql are available from the standard locations (in the root of the classpath), such scripts are executed to initialize the DataSource, in given order.

The scripts locations can be changed using the schema and data configuration properties.

Additionaly, if the platform configuration property is provided, the schema-{platform}.sql and data-{platform}.sql scripts are executed if available, where {platform} is the value of the platform configuration property.

7.1.5. Using the data context id for `DataSource` initialization

When a data context id is specified, the data context id name will be used as prefix for the default DataSource initialization scripts: {datacontextid}-data-.sql and {datacontextid}-data-.sql.

If one or more script with a matching name pattern is available, it will be executed using the DataSource bean instance which corresponds to the data context id.

For example, given the following configuration properties to configure two DataSource bean instances, one bound to the data context id one and the other bound to the data context id two:

holon.datasource.one.url=jdbc:h2:mem:testdb1
holon.datasource.one.username=sa

holon.datasource.two.url=jdbc:h2:mem:testdb2
holon.datasource.two.username=sa

You can provide different initialization scripts for each DataSource instance, i.e. for each data context id:

For the one data context id DataSource you will provide the initialization files one-schema.sql and one-data.sql;
For the two data context id DataSource you will provide the initialization files two-schema.sql and two-data.sql.

8. Spring Boot integration

Maven coordinates:

<groupId>com.holon-platform.jdbc</groupId>
<artifactId>holon-jdbc-spring-boot</artifactId>
<version>5.2.4</version>

The holon-jdbc-spring-boot artifact provides integration with Spring Boot to enable JDBC DataSource auto-configuration facilities.

8.1. JDBC `DataSource` auto-configuration

This auto-configuration feature is enabled when one of the Holon DataSource configuration properties (holon.datasource.*) is detected in the Spring Environment. See the DataSource configuration properties section for information about the available configuration properties.

It provides automatic DataSource beans registration and configuration following the same strategy adopted by the DataSource auto-configuration annotation described above.

For example, using the given yaml configuration properties:

holon:
  datasource:
    one:
      url: "jdbc:h2:mem:testdb1"
      username: "sa"
    two:
      url: "jdbc:h2:mem:testdb2"
      username: "sa"

The auto-configuration feature will configure two DataSource bean instances:

One DataSource bean instance using the one data context id configuration properties, qualified with the one qualifier.
Another DataSource bean instance using the two data context id configuration properties, qualified with the two qualifier.

So the DataSource bean instances can be obtained using dependency injection this way:

@Autowired
@Qualifier("one")
private DataSource dataSource1;

@Autowired
@Qualifier("two")
private DataSource dataSource2;

To disable this auto-configuration feature the DataSourcesAutoConfiguration class can be excluded:

@EnableAutoConfiguration(exclude={DataSourcesAutoConfiguration.class})

8.2. DataSource `PlatformTransactionManager` auto-configuration

This auto-configuration feature is enabled only if a PlatformTransactionManager bean is not already registered in the Spring context.

It registers a DataSourceTransactionManager bean for each DataSource registered using the Holon DataSource configuration properties (holon.datasource.*), as described in the section above.

If a data context id is defined for multiple DataSource instances, the corresponding PlatformTransactionManager will be qualified with the same data context id name, and such qualifier can be later used to obtain the right PlatformTransactionManager bean instance through dependency injection.

Furthermore, the PlatformTransactionManager bean name when data context id is specified will be assigned using the pattern: transactionManager_{dataContextId}. So, for example, the PlatformTransactionManager bean created for the test data context id will be named transactionManager_test.

To disable this auto-configuration feature the DataSourcesTransactionManagerAutoConfiguration class can be excluded:

@EnableAutoConfiguration(exclude={DataSourcesTransactionManagerAutoConfiguration.class})

8.3. Spring Boot starters

The following starter artifacts are available to provide a quick project configuration setup using the Maven dependency system:

1. Default JDBC starter provides the dependencies to the Holon JDBC Spring and Spring Boot integration artifacts, in addition to default Holon core Spring Boot starters (see the documentation for further information) and the core Spring Boot starter (spring-boot-starter):

Maven coordinates:

<groupId>com.holon-platform.jdbc</groupId>
<artifactId>holon-starter-jdbc</artifactId>
<version>5.2.4</version>

2. JDBC starter with HikariCP DataSource provides the same dependencies as the default JDBC starter, adding the HikariCP pooling DataSource dependency.

This way, the HikariCP DataSource will be selected by default by the DataSource auto-configuration strategy if the DataSource type is not explicitly specified using the corresponding configuration property.

Maven coordinates:

<groupId>com.holon-platform.jdbc</groupId>
<artifactId>holon-starter-jdbc-hikaricp</artifactId>
<version>5.2.4</version>

See the Spring Boot starters documentation for details about the Spring Boot starters topic and the core Spring Boot starter features.

9. Loggers

By default, the Holon platform uses the SLF4J API for logging. The use of SLF4J is optional: it is enabled when the presence of SLF4J is detected in the classpath. Otherwise, logging will fall back to JUL (java.util.logging).

The logger name for the JDBC module is com.holonplatform.jdbc.

10. System requirements

10.1. Java

The Holon Platform JDBC module requires Java 8 or higher.

Holon Platform JDBC Module - Reference manual

1. Introduction

1.1. Sources and contributions

2. Obtaining the artifacts

2.1. Using the Platform BOM

3. What’s new in version 5.2.x

4. What’s new in version 5.1.x

5. JDBC DataSource creation and configuration

5.1. DataSource configuration properties

5.2. Multiple DataSource configuration

5.3. Build a DataSource using the DataSourceBuilder API

5.3.1. Provide DataSource configuration properties programmatically

5.4. DataSource type

5.4.1. Default DataSource type selection strategy

5.4.2. DataSourceFactory

5.4.3. DataSourcePostProcessor

5.5. BasicDataSource

6. Multi-tenant DataSource

6.1. TenantResolver and TenantDataSourceProvider lookup strategy

7. Spring framework integration

7.1. DataSource auto-configuration

7.1.1. Multiple DataSource configuration

7.1.2. Primary mode

7.1.3. Transaction management

7.1.4. Additional DataSource configuration properties

7.1.5. Using the data context id for DataSource initialization

8. Spring Boot integration

8.1. JDBC DataSource auto-configuration

8.2. DataSource PlatformTransactionManager auto-configuration

8.3. Spring Boot starters

9. Loggers

10. System requirements

10.1. Java

5.3. Build a DataSource using the `DataSourceBuilder` API

6.1. `TenantResolver` and `TenantDataSourceProvider` lookup strategy

7.1.1. Multiple `DataSource` configuration

7.1.4. Additional `DataSource` configuration properties

7.1.5. Using the data context id for `DataSource` initialization

8.1. JDBC `DataSource` auto-configuration

8.2. DataSource `PlatformTransactionManager` auto-configuration