DelegatingDataSource incorrectly implements java.sql.Wrapper [SPR-9770]

[spring-projects-issues]

Juan M. Tula opened SPR-9770 and commented

Status Quo

Spring's DelegatingDataSource does not correctly implement the java.sql.Wrapper interface.

Analysis

According to the documentation for the unwrap() and isWrapper() methods, if the receiver implements the received interface, it should return itself, something like this:

public <T> T unwrap(Class<T> iface) throws SQLException {
	T result;
	if(iface.isInstance(this)) {
		result = iface.cast(this);
	} else {
		result = getTargetDataSource().unwrap(iface);
	}
	return result;
}

But the implementation is currently this:

public <T> T unwrap(Class<T> iface) throws SQLException {
	return getTargetDataSource().unwrap(iface);
}

So, a call to new DelegatingDataSource().unwrap(DelegatingDataSource.class) will fail instead of returning itself.

---

Affects: 3.1 GA

Reference URL: http://docs.oracle.com/javase/6/docs/api/java/sql/Wrapper.html?is-external=true

Issue Links:

• AbstractRoutingDataSource does not allow to unwrap the underlying datasource [SPR-9856] #14489 AbstractRoutingDataSource does not allow to unwrap the underlying datasource

0 votes, 6 watchers

[spring-projects-issues]

Phil Webb commented

#140

[spring-projects-issues]

Juergen Hoeller commented

Good catch! AbstractDataSource and DelegatingDataSource consistently implement JDBC 4.0's Wrapper interface now.

Juergen

[spring-projects-issues]

Hernan J. Gonzalez commented

Shouldn't we also look at AbstractRoutingDataSource.isWrapper()? I think it should override the parent, so that the isInstance matching is done, not with respect to the class itself (well, perhaps also with the class itself) but also (mainly) with the currently routed datasource.

(it might be debatable if the Wrapper interface behaviour can change for a given object in runtime, i'd say yes)

Case in point: I have a RoutingDataSource than can route to a org.apache.commons.dbcp.BasicDataSource pool or a plain jdbc datasource. I expected I can ask myRoutingDataSource.isWrapperFor(org.apache.commons.dbcp.BasicDataSource.class) to check if I'm using the pooled data source, and to retrieve the wrapped dbcp object. Currently, I can't.

[spring-projects-issues]

Sam Brannen commented

Hernan,

Could you please create a new JIRA issue to address your concerns regarding AbstractRoutingDataSource?

Thanks,

Sam

[spring-projects-issues]

Hernan J. Gonzalez commented

Sam: done, I hope it's ok: https://jira.springsource.org/browse/DATAJDBC-35

[spring-projects-issues]

Sam Brannen commented

Hernan,

Thanks for creating that JIRA issue.

Please note that I've moved it from the Spring Data JDBC project to the Spring Framework project where it belongs (#14489).

Sam