Until today I was working with ResultSet
when handling results from queries. But today I read a little about RowSet
and CachedRowset
and I realized they can serve my purposes better. While in all the examples I read where RowSet
and CachedRowSet
were referred to as object, when I tried it myself in my code I realized those are interfaces and in the examples they use some implementation of those interfaces.
Now my question is where do I find those implementations, and is there something official?
Do I need to download them or do they come with the JDK?
The implementations are JRE specific. Oracle (Sun) JRE comes with a bunch of implementations:
com.sun.rowset.JdbcRowSetImpl
com.sun.rowset.CachedRowSetImpl
com.sun.rowset.WebRowSetImpl
com.sun.rowset.FilteredRowSetImpl
com.sun.rowset.JoinRowSetImpl
In Java 1.6 and before, you'd need to construct them yourself:
JdbcRowSet rowSet = new JdbcRowSetImpl();
rowSet.setDataSourceName("jdbc/dbname");
// Or
rowSet.setUrl("jdbc:vendor://host:port/dbname");
rowSet.setUsername("username");
rowSet.setPassword("password");
rowSet.setCommand("SELECT id, name, value FROM tbl");
rowSet.execute();
while (rowSet.next()) {
// ...
}
In Java 1.7 you can get them by a javax.sql.rowset
factory so that you're not dependent of underlying JRE implementation and that you can finetune the implementation of choice if necessary:
RowSetFactory rowSetFactory = RowSetProvider.newFactory();
JdbcRowSet rowSet = rowSetFactory.createJdbcRowSet();
// ...
It only doesn't provide a possibility to pass a ResultSet
on construction. Those implementations doesn't ship with the average JDBC driver (at least, MySQL and PostgreSQL have none). It's basically an extra (optional) layer over JDBC API as the package name prefix javax
hints.
Note that if you get that far by looking into rowsets, then you might want to consider to look into an ORM instead, such as Hibernate or JPA. They provide first/second level cache possibilities.
See also:
- JDBC Guide - Chapter 10 - RowSet
- JDBC RowSet tutorial, by Oracle
- Java 8
javax.sql.rowset
package summary - Source code in OpenJDK 8 for Oracle’s com.sun.rowset implementation, Gnu GPL 2 license with Classpath exception
Add rt.jar in Eclipse Java Build Path. Then you see all the implemention class. Else you can remove the restriction from Eclipse which is not allowing to access rt.jar from jdk. Works for me. I was using jdk1.6 and Eclipse Luna.
来源:https://stackoverflow.com/questions/8217493/implementations-of-rowset-cachedrowset-etc