Spring oracle datasource does not destroy connection

Question

I use oracle.jdbc.pool.OracleDataSource for Oracle Pooling connections, but it seems the connections stay alive in the database. Today I got an error while connecting to Oracle Database:

ORA-12516: TNS:listener could not find available handler with matching protocol stack

And I was told by our database administrator that too many open connections stay in "IDLE" mode from my application.

I use ojdbc7:

<dependency>
    <groupId>com.oracle</groupId>
    <artifactId>ojdbc7</artifactId>
    <version>12.1.0.1</version>
</dependency>

Spring applicationContext.xml file:

<bean id="dataSource" class="oracle.jdbc.pool.OracleDataSource" destroy-method="close"> 
    <property name="URL" value="${jdbc.url}" /> 
    <property name="user" value="${jdbc.username}" /> 
    <property name="password" value="${jdbc.password}" /> 
    <property name="connectionCachingEnabled" value="true" /> 
</bean>

The DbConnect class:

import java.sql.Connection;
import java.sql.SQLException;
import javax.sql.DataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

@Repository
public class DbConnect {

  @Autowired
  private DataSource dataSource;

  public Connection getConnection() throws SQLException {
      return dataSource.getConnection();
  }
}

Also I use jdk7 try-with-resources syntax in my dao level for connections:

 @Autowired
 private DbConnect dbConnect;

 public List<User> getAllUsers() {
    List<User> list = new ArrayList<>();

    try(Connection connection = dbConnect.getConnection()) {
        try(PreparedStatement preparedStatement = connection.prepareStatement("select * from V_USERS t")) {
            try(ResultSet resultSet = preparedStatement.executeQuery()) {
                while(resultSet.next()) {
                    list.add(RowFetcher.fetchUser(resultSet));
                }
            }
        }
    }
    catch(Exception e) {
        log.error(e.getMessage(), e);
    }

    return list;
}

Cannot figure out where is the actual problem. Should I use c3p0 instead of OracleDataSource? Is there any bug in ojdbc7 or error in my code?

Thanks in advance!

Answer 1

You can set dataSource limit properties to control the size of the cache.

<property name="connectionCacheProperties">
  <props>
     <prop key="MinLimit">${jdbc.limit.min}</prop>
     <prop key="MaxLimit">${jdbc.limit.max}</prop>
     <prop key="InitialLimit">${jdbc.limit.init}</prop>
  </props>
</property>

Answer 2

The whole point of a pool is to keep connections open. However I'm not sure if the OracleDataSource is an actual pool or that you need to OracleConnectionPoolDataSource.

Instead of using a plain Oracle pool I suggest using HikariCP. The page on configuration options and the defaults.

In that case your datasource would look like

<bean id="dataSource" class="com.zaxxer.hikari.HikariDataSource"> 
    <property name="datasourceClassName" value="oracle.jdbc.pool.OracleDataSource" />
    <property name="dataSourceProperties">
        <props>
            <prop key="URL" value="${jdbc.url}" /> 
            <prop key="user" value="${jdbc.username}" /> 
            <prop key="password" value="${jdbc.password}" /> 
            <prop key="connectionCachingEnabled" value="true" />
        </props>
    </property>
</bean>

Note: There is also a nice page on pool sizing (which is actually from Oracle!).

I would also suggest, to cleanup your code, to remove the DbConnect class and inject (or create) a JdbcTemplate to use instead of working with the plain connection. Saves you managing all the JDBC objects.

private final JdbcTemplate jdbcTemplate;

@Autowired
public YourRepository(DataSource ds) {
    this.jdbcTemplate=new JdbcTemplate(ds);
}

public List<User> getAllUsers() {
    List<User> list = new ArrayList<>();
    return this.jdbcTemplate("select * from V_USERS t", new RowMapper() {
        public User mapRow(ResultSet rs, int row) throws SQLException {
            return RowFetcher.fetchUser(rs);
        }
    });
}

Answer 3

We have Universal Connection Pool (UCP) which is the Java connection pool.
Refer to UCP with Spring for more configuration details.

Answer 4

Try to use different data source org.apache.commons.dbcp.BasicDataSource.t works for me