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Controlling Database Connections
Using DataSource
Spring obtains a connection to the database through a DataSource
. A DataSource
is
part of the JDBC specification and is a generalized connection factory. It lets a
container or a framework hide connection pooling and transaction management issues
from the application code. As a developer, you need not know details about how to
connect to the database. That is the responsibility of the administrator who sets up
the datasource. You most likely fill both roles as you develop and test code, but you
do not necessarily have to know how the production data source is configured.
When you use Spring’s JDBC layer, you can obtain a data source from JNDI, or you can
configure your own with a connection pool implementation provided by a third party.
Traditional choices are Apache Commons DBCP and C3P0 with bean-style DataSource
classes;
for a modern JDBC connection pool, consider HikariCP with its builder-style API instead.
You should use the DriverManagerDataSource and SimpleDriverDataSource classes
(as included in the Spring distribution) only for testing purposes! Those variants do not
provide pooling and perform poorly when multiple requests for a connection are made.
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The following section uses Spring’s DriverManagerDataSource
implementation.
Several other DataSource
variants are covered later.
To configure a DriverManagerDataSource
:
-
Obtain a connection with
DriverManagerDataSource
as you typically obtain a JDBC connection. -
Specify the fully qualified class name of the JDBC driver so that the
DriverManager
can load the driver class. -
Provide a URL that varies between JDBC drivers. (See the documentation for your driver for the correct value.)
-
Provide a username and a password to connect to the database.
The following example shows how to configure a DriverManagerDataSource
:
-
Java
-
Kotlin
-
Xml
@Bean
DriverManagerDataSource dataSource() {
DriverManagerDataSource dataSource = new DriverManagerDataSource();
dataSource.setDriverClassName("org.hsqldb.jdbcDriver");
dataSource.setUrl("jdbc:hsqldb:hsql://localhost:");
dataSource.setUsername("sa");
dataSource.setPassword("");
return dataSource;
}
@Bean
fun dataSource() = DriverManagerDataSource().apply {
setDriverClassName("org.hsqldb.jdbcDriver")
url = "jdbc:hsqldb:hsql://localhost:"
username = "sa"
password = ""
}
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="${jdbc.driverClassName}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</bean>
<context:property-placeholder location="jdbc.properties"/>
The next two examples show the basic connectivity and configuration for DBCP and C3P0. To learn about more options that help control the pooling features, see the product documentation for the respective connection pooling implementations.
The following example shows DBCP configuration:
-
Java
-
Kotlin
-
Xml
@Bean(destroyMethod = "close")
BasicDataSource dataSource() {
BasicDataSource dataSource = new BasicDataSource();
dataSource.setDriverClassName("org.hsqldb.jdbcDriver");
dataSource.setUrl("jdbc:hsqldb:hsql://localhost:");
dataSource.setUsername("sa");
dataSource.setPassword("");
return dataSource;
}
@Bean(destroyMethod = "close")
fun dataSource() = BasicDataSource().apply {
driverClassName = "org.hsqldb.jdbcDriver"
url = "jdbc:hsqldb:hsql://localhost:"
username = "sa"
password = ""
}
<bean id="dataSource" class="org.apache.commons.dbcp2.BasicDataSource" destroy-method="close">
<property name="driverClassName" value="${jdbc.driverClassName}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</bean>
<context:property-placeholder location="jdbc.properties"/>
The following example shows C3P0 configuration:
-
Java
-
Kotlin
-
Xml
@Bean(destroyMethod = "close")
ComboPooledDataSource dataSource() throws PropertyVetoException {
ComboPooledDataSource dataSource = new ComboPooledDataSource();
dataSource.setDriverClass("org.hsqldb.jdbcDriver");
dataSource.setJdbcUrl("jdbc:hsqldb:hsql://localhost:");
dataSource.setUser("sa");
dataSource.setPassword("");
return dataSource;
}
@Bean(destroyMethod = "close")
fun dataSource() = ComboPooledDataSource().apply {
driverClass = "org.hsqldb.jdbcDriver"
jdbcUrl = "jdbc:hsqldb:hsql://localhost:"
user = "sa"
password = ""
}
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
<property name="driverClass" value="${jdbc.driverClassName}"/>
<property name="jdbcUrl" value="${jdbc.url}"/>
<property name="user" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</bean>
<context:property-placeholder location="jdbc.properties"/>
Using DataSourceUtils
The DataSourceUtils
class is a convenient and powerful helper class that provides
static
methods to obtain connections from JNDI and close connections if necessary.
It supports a thread-bound JDBC Connection
with DataSourceTransactionManager
but
also with JtaTransactionManager
and JpaTransactionManager
.
Note that JdbcTemplate
implies DataSourceUtils
connection access, using it
behind every JDBC operation, implicitly participating in an ongoing transaction.
Implementing SmartDataSource
The SmartDataSource
interface should be implemented by classes that can provide a
connection to a relational database. It extends the DataSource
interface to let
classes that use it query whether the connection should be closed after a given
operation. This usage is efficient when you know that you need to reuse a connection.
Extending AbstractDataSource
AbstractDataSource
is an abstract
base class for Spring’s DataSource
implementations. It implements code that is common to all DataSource
implementations.
You should extend the AbstractDataSource
class if you write your own DataSource
implementation.
Using SingleConnectionDataSource
The SingleConnectionDataSource
class is an implementation of the SmartDataSource
interface that wraps a single Connection
that is not closed after each use.
This is not multi-threading capable.
If any client code calls close
on the assumption of a pooled connection (as when using
persistence tools), you should set the suppressClose
property to true
. This setting
returns a close-suppressing proxy that wraps the physical connection. Note that you can
no longer cast this to a native Oracle Connection
or a similar object.
SingleConnectionDataSource
is primarily a test class. It typically enables easy testing
of code outside an application server, in conjunction with a simple JNDI environment.
In contrast to DriverManagerDataSource
, it reuses the same connection all the time,
avoiding excessive creation of physical connections.
Using DriverManagerDataSource
The DriverManagerDataSource
class is an implementation of the standard DataSource
interface that configures a plain JDBC driver through bean properties and returns a new
Connection
every time.
This implementation is useful for test and stand-alone environments outside of a Jakarta EE
container, either as a DataSource
bean in a Spring IoC container or in conjunction
with a simple JNDI environment. Pool-assuming Connection.close()
calls
close the connection, so any DataSource
-aware persistence code should work. However,
using JavaBean-style connection pools (such as commons-dbcp
) is so easy, even in a test
environment, that it is almost always preferable to use such a connection pool over
DriverManagerDataSource
.
Using TransactionAwareDataSourceProxy
TransactionAwareDataSourceProxy
is a proxy for a target DataSource
. The proxy wraps that
target DataSource
to add awareness of Spring-managed transactions. In this respect, it
is similar to a transactional JNDI DataSource
, as provided by a Jakarta EE server.
It is rarely desirable to use this class, except when already existing code must be
called and passed a standard JDBC DataSource interface implementation. In this case,
you can still have this code be usable and, at the same time, have this code
participating in Spring managed transactions. It is generally preferable to write your
own new code by using the higher level abstractions for resource management, such as
JdbcTemplate or DataSourceUtils .
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See the TransactionAwareDataSourceProxy
javadoc for more details.
Using DataSourceTransactionManager
/ JdbcTransactionManager
The DataSourceTransactionManager
class is a PlatformTransactionManager
implementation for a single JDBC DataSource
. It binds a JDBC Connection
from the specified DataSource
to the currently executing thread, potentially
allowing for one thread-bound Connection
per DataSource
.
Application code is required to retrieve the JDBC Connection
through
DataSourceUtils.getConnection(DataSource)
instead of Java EE’s standard
DataSource.getConnection
. It throws unchecked org.springframework.dao
exceptions
instead of checked SQLExceptions
. All framework classes (such as JdbcTemplate
) use
this strategy implicitly. If not used with a transaction manager, the lookup strategy
behaves exactly like DataSource.getConnection
and can therefore be used in any case.
The DataSourceTransactionManager
class supports savepoints (PROPAGATION_NESTED
),
custom isolation levels, and timeouts that get applied as appropriate JDBC statement
query timeouts. To support the latter, application code must either use JdbcTemplate
or
call the DataSourceUtils.applyTransactionTimeout(..)
method for each created statement.
You can use DataSourceTransactionManager
instead of JtaTransactionManager
in the
single-resource case, as it does not require the container to support a JTA transaction
coordinator. Switching between these transaction managers is just a matter of configuration,
provided you stick to the required connection lookup pattern. Note that JTA does not support
savepoints or custom isolation levels and has a different timeout mechanism but otherwise
exposes similar behavior in terms of JDBC resources and JDBC commit/rollback management.
For JTA-style lazy retrieval of actual resource connections, Spring provides a
corresponding DataSource
proxy class for the target connection pool: see
LazyConnectionDataSourceProxy
.
This is particularly useful for potentially empty transactions without actual statement
execution (never fetching an actual resource in such a scenario), and also in front of
a routing DataSource
which means to take the transaction-synchronized read-only flag
and/or isolation level into account (e.g. IsolationLevelDataSourceRouter
).
LazyConnectionDataSourceProxy
also provides special support for a read-only connection
pool to use during a read-only transaction, avoiding the overhead of switching the JDBC
Connection’s read-only flag at the beginning and end of every transaction when fetching
it from the primary connection pool (which may be costly depending on the JDBC driver).
As of 5.3, Spring provides an extended JdbcTransactionManager variant which adds
exception translation capabilities on commit/rollback (aligned with JdbcTemplate ).
Where DataSourceTransactionManager will only ever throw TransactionSystemException
(analogous to JTA), JdbcTransactionManager translates database locking failures etc to
corresponding DataAccessException subclasses. Note that application code needs to be
prepared for such exceptions, not exclusively expecting TransactionSystemException .
In scenarios where that is the case, JdbcTransactionManager is the recommended choice.
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In terms of exception behavior, JdbcTransactionManager
is roughly equivalent to
JpaTransactionManager
and also to R2dbcTransactionManager
, serving as an immediate
companion/replacement for each other. DataSourceTransactionManager
on the other hand
is equivalent to JtaTransactionManager
and can serve as a direct replacement there.