JdbcTemplate — logging the dataSource connection url

Question

Hi,

is there a way to log the JdbcTemplate's DataSource connection URL in Java?

The field exists in the DataSource, but there ain't a getter to access it. Of course I could read the DataSource properties from the application context xml, but I'd like to do it the other way.

Answer 1

If the field exists, would you consider using reflection to access it? The approach may not be future-proof but may be sufficient for your needs.

Answer 2

I know you said you didn't want to have to get it from the context xml, but I can't see an easy and non-fragile way around it.

In Spring 2.0 and greater you can use the <util:property-path /> element to reference a property of another bean. Let's say your DataSource is declared like so (note: I'm going to use the p-namespace throughout for brevity):

<bean id="dataSource" class="com.example.SimpleDataSource"
    p:user="db_user"
    p:password="letmein"
    p:driverClass="com.example.CabDriver"
    p:jdbcUrl="jdbc:example:@localhost:1729:magicdb" />

I'm assuming that your JdbcTemplate is being used by some data access object. Let's say it looks like this:

public class SimpleDao implements ExampleDao {
    private JdbcTemplate jdbcTemplate;

    public void setDataSource(DataSource dataSource) {
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }
}

So the Spring config to construct this DAO is like so:

<bean id="dao" class="com.example.SimpleDao"
    p:dataSource-ref="dataSource" />

Now to our problem: how to get the JdbcUrl property into our DAO? Let's add a setter:

public class SimpleDao implements ExampleDao {
    private String jdbcUrl;
    // ...
    public void setJdbcUrl(String jdbcUrl) {
        this.jdbcUrl = jdbcUrl;
    }
    // ...

And finally we inject this using the aforementioned <util:property-path /> element:

<bean id="dao" class="com.example.SimpleDao"
    p:dataSource-ref="dataSource">
    <property name="jdbcUrl>
        <util:property-path path="dataSource.jdbcUrl" />
    </property>
</bean>

The URL is available from the bean named dataSource using getJdbcUrl (note that this is on the concrete DataSource, not the interface), so the property-path element tells Spring to get the value from there and use it as the value for the DAO's property.

This isn't too much code (it's one setter and one extra property) and you're guaranteed to always have the same value injected into both beans.