Creating datasource in java

Interface DataSource

A factory for connections to the physical data source that this DataSource object represents. An alternative to the DriverManager facility, a DataSource object is the preferred means of getting a connection. An object that implements the DataSource interface will typically be registered with a naming service based on the Java Naming and Directory (JNDI) API.

1. Basic implementation — produces a standard Connection object
2. Connection pooling implementation — produces a Connection object that will automatically participate in connection pooling. This implementation works with a middle-tier connection pooling manager.
3. Distributed transaction implementation — produces a Connection object that may be used for distributed transactions and almost always participates in connection pooling. This implementation works with a middle-tier transaction manager and almost always with a connection pooling manager.

A DataSource object has properties that can be modified when necessary. For example, if the data source is moved to a different server, the property for the server can be changed. The benefit is that because the data source’s properties can be changed, any code accessing that data source does not need to be changed.

A driver that is accessed via a DataSource object does not register itself with the DriverManager . Rather, a DataSource object is retrieved through a lookup operation and then used to create a Connection object. With a basic implementation, the connection obtained through a DataSource object is identical to a connection obtained through the DriverManager facility.

An implementation of DataSource must include a public no-arg constructor.

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Interface DataSource

A factory for connections to the physical data source that this DataSource object represents. An alternative to the DriverManager facility, a DataSource object is the preferred means of getting a connection. An object that implements the DataSource interface will typically be registered with a naming service based on the Java Naming and Directory (JNDI) API.

1. Basic implementation — produces a standard Connection object
2. Connection pooling implementation — produces a Connection object that will automatically participate in connection pooling. This implementation works with a middle-tier connection pooling manager.
3. Distributed transaction implementation — produces a Connection object that may be used for distributed transactions and almost always participates in connection pooling. This implementation works with a middle-tier transaction manager and almost always with a connection pooling manager.

A DataSource object has properties that can be modified when necessary. For example, if the data source is moved to a different server, the property for the server can be changed. The benefit is that because the data source’s properties can be changed, any code accessing that data source does not need to be changed.

A driver that is accessed via a DataSource object does not register itself with the DriverManager . Rather, a DataSource object is retrieved through a lookup operation and then used to create a Connection object. With a basic implementation, the connection obtained through a DataSource object is identical to a connection obtained through the DriverManager facility.

An implementation of DataSource must include a public no-arg constructor.

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Spring Boot DataSource Configuration

A DataSource is a factory for connections to a physical database. This tutorial will discuss what is a datasource and how to create and customize the DataSource bean in Spring boot applications.

1. 1. What is DataSource?
2. 2. Configuring a DataSource
   • 2.1. Maven Dependency
   • 2.2. Properties Configuration
   • 2.3. Java Configuration
   • 2.4. JNDI DataSource
3. 3. Configuring Connection Pooling
   • 3.1. HikariCP, Tomcat Pooling and Commons DBCP2
   • 3.2. Customizing Default Values
4. 4. Configuring Multiple DataSources with Spring Boot
5. 5. Conclusion

The DataSource works as a factory for providing database connections. It is an alternative to the DriverManager facility. A datasource uses a URL along with username/password credentials to establish the database connection.

In Java, a datasource implements the javax.sql.DataSource interface. This datasource will typically be registered with the JNDI service and can be discovered using its JNDI name.

We may use a datasource to obtain the following:

• standard Connection object
• a connection that can be used in connection pooling
• a connection that can be used in distributed transactions and connection pooling

2. Configuring a DataSource

Spring boot allows defining datasource configuration in following ways:

During application startup, the DataSourceAutoConfiguration checks for DataSource.class (or EmbeddedDatabaseType.class) on the classpath and a few other things before configuring a DataSource bean for us.

If not already defined, include spring-boot-starter-data-jpa to the project that transitively brings all necessary dependencies including JDBC drivers for various databases e.g. mysql-connector-java for connecting to MySQL database.

 org.springframework.boot spring-boot-starter-data-jpa 

If we plan to use an embedded database at some step (e.g., testing), we can import H2 DB separately.

2.2. Properties Configuration

DataSource configuration is provided by configuration properties entries ( spring.datasource.* ) in application.properties file. The properties configuration decouples the configuration from the application code. This way, we can import the datasource configurations from even external configuration provider systems.

Below given configuration shows sample properties for H2, MySQL, Oracle and SQL Server databases.

We often do not need to specify the driver-class-name , since Spring Boot can deduce it for the most databases from the connection url.

# H2 DB spring.datasource.url=jdbc:h2:file:C:/temp/test spring.datasource.username=sa spring.datasource.password= spring.datasource.driverClassName=org.h2.Driver spring.jpa.database-platform=org.hibernate.dialect.H2Dialect # MySQL spring.datasource.url=jdbc:mysql://localhost:3306/test spring.datasource.username=dbuser spring.datasource.password=dbpass spring.datasource.driver-class-name=com.mysql.jdbc.Driver spring.jpa.database-platform=org.hibernate.dialect.MySQL5InnoDBDialect # Oracle spring.datasource.url=jdbc:oracle:thin:@localhost:1521:orcl spring.datasource.username=dbuser spring.datasource.password=dbpass spring.datasource.driver-class-name=oracle.jdbc.OracleDriver spring.jpa.database-platform=org.hibernate.dialect.Oracle10gDialect # SQL Server spring.datasource.url=jdbc:sqlserver://localhost;databaseName=springbootdb spring.datasource.username=dbuser spring.datasource.password=dbpass spring.datasource.driverClassName=com.microsoft.sqlserver.jdbc.SQLServerDriver spring.jpa.hibernate.dialect=org.hibernate.dialect.SQLServer2012Dialect

The recommended way to create a DataSource bean is using DataSourceBuilder class within a class annotated with the @Configuration annotation.

Given is an example bean for H2 DB. Please configure other beans as necessary.

@Configuration public class JpaConfig < @Bean public DataSource dataSource() < DataSourceBuilder dataSourceBuilder = DataSourceBuilder.create(); dataSourceBuilder.driverClassName("org.h2.Driver"); dataSourceBuilder.url("jdbc:h2:file:C:/temp/test"); dataSourceBuilder.username("sa"); dataSourceBuilder.password(""); return dataSourceBuilder.build(); >>

Suppose we deploy our Spring Boot application to an application server. In that case, we might want to configure and manage the DataSource using the Application Server’s built-in features and access it using JNDI.

We can do this using the spring.datasource.jndi-name property.

#JBoss defined datasource using JNDI spring.datasource.jndi-name = java:jboss/datasources/testDB

3. Configuring Connection Pooling

3.1. HikariCP, Tomcat Pooling and Commons DBCP2

For a pooling datasource to be created, Spring boot verifies that a valid Driver class is available. If we set spring.datasource.driver-class-name property then the mentioned driver class must be found and loaded.

• The auto-configuration first tries to find and configure HikariCP. If HikariCP is available, it always chooses it.
• Otherwise, if the Tomcat Pooling is found, it is configured.
• If neither HikariCP nor the Tomcat Pooling datasource is available, then Commons DBCP2 is used if found on the classpath.

The spring-boot-starter-data-jpa starter automatically get a dependency to HikariCP .

3.2. Customizing Default Values

It is also possible to fine-tune implementation-specific settings by using their respective prefix ( spring.datasource.hikari.* , spring.datasource.tomcat.* , and spring.datasource.dbcp2.* ).

For example, we can use the below properties to customize a DBCP2 connection pool.

spring.datasource.dbcp2.initial-size = 50 spring.datasource.dbcp2.max-idle = 50 spring.datasource.dbcp2.default-query-timeout = 10000 spring.datasource.dbcp2.default-auto-commit = true

4. Configuring Multiple DataSources with Spring Boot

To configure multiple data sources, create as many bean definitions as you want but mark one of the DataSource instances as @Primary.

Remember that if we create our own DataSource bean then auto-configuration backs off. In this case, we are responsible for providing configurations for all datasource beans.

@Configuration public class JpaConfig < @Bean(name = "h2DataSource") public DataSource h2DataSource() < DataSourceBuilder dataSourceBuilder = DataSourceBuilder.create(); dataSourceBuilder.driverClassName("org.h2.Driver"); dataSourceBuilder.url("jdbc:h2:file:C:/temp/test"); dataSourceBuilder.username("sa"); dataSourceBuilder.password(""); return dataSourceBuilder.build(); >@Bean(name = "mysqlDataSource") @Primary public DataSource mysqlDataSource() < DataSourceBuilder dataSourceBuilder = DataSourceBuilder.create(); dataSourceBuilder.url("jdbc:mysql://localhost/testdb"); dataSourceBuilder.username("dbuser"); dataSourceBuilder.password("dbpass"); return dataSourceBuilder.build(); >>

While autowiring the datasource, spring boot will prefer the primary datasource i.e., “mysqlDataSource”. To autowire another non-primary datasource, use @Qualifier annotation.

@Autowired DataSource dataSource;

@Autowired @Qualifier("h2DataSource") DataSource dataSource;

Spring boot provides straightforward ways to create datasource beans – either using properties configuration or using java configuration. Spring boot offers ready-made auto configuration to use which can be further customized with advanced options in application.properties file.

Spring boot tries to find and configure connection pooling, first HikariCP, second Tomcat pooling, and finally Commons DBCP2. HikariCP comes inbuilt with spring-boot-starter-jdbc or spring-boot-starter-data-jpa starters.

We can configure multiple datasources, and we must mark as one of them @Primary . The primary datasource is autowired by default, and other datasources need to be autowired along with @Qualifier annotation.

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