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   *  to you under the Apache License, Version 2.0 (the
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  package org.apache.cayenne.datasource;
  
  import javax.sql.DataSource;
  
  import org.apache.cayenne.CayenneRuntimeException;
  
  /**
   * Turns unpooled DataSource to a connection pool. Normally you won't be
   * creating this builder explicitly. Call
   * {@link DataSourceBuilder#pool(int, int)} method instead.
   * 
   * @since 4.0
   */
  public class PoolingDataSourceBuilder {
  
  	private DataSourceBuilder nonPoolingBuilder;
  	private PoolingDataSourceParameters poolParameters;
  
  	public PoolingDataSourceBuilder(DataSourceBuilder nonPoolingBuilder) {
  		this.nonPoolingBuilder = nonPoolingBuilder;
  		this.poolParameters = new PoolingDataSourceParameters();
  
  		poolParameters.setMinConnections(1);
  		poolParameters.setMaxConnections(1);
  		poolParameters.setMaxQueueWaitTime(UnmanagedPoolingDataSource.MAX_QUEUE_WAIT_DEFAULT);
  	}
  
  	public PoolingDataSourceBuilder minConnections(int minConnections) {
  		poolParameters.setMinConnections(minConnections);
  		return this;
  	}
  
  	public PoolingDataSourceBuilder maxConnections(int maxConnections) {
  		poolParameters.setMaxConnections(maxConnections);
  		return this;
  	}
  
  	public PoolingDataSourceBuilder maxQueueWaitTime(long maxQueueWaitTime) {
  		poolParameters.setMaxQueueWaitTime(maxQueueWaitTime);
  		return this;
  	}
  
  	public PoolingDataSourceBuilder validationQuery(String validationQuery) {
  		poolParameters.setValidationQuery(validationQuery);
  		return this;
  	}
  
  	/**
  	 * Builds a pooling DataSource that needs to be explicitly closed by the
  	 * caller when no longer in use.
  	 */
  	public PoolingDataSource build() {
  
  		// sanity checks...
  		if (poolParameters.getMaxConnections() < 0) {
  			throw new CayenneRuntimeException("Maximum number of connections can not be negative (%d)."
  					, poolParameters.getMaxConnections());
  		}
  
  		if (poolParameters.getMinConnections() < 0) {
  			throw new CayenneRuntimeException("Minimum number of connections can not be negative (%d)"
  					, poolParameters.getMinConnections());
  		}
  
  		if (poolParameters.getMinConnections() > poolParameters.getMaxConnections()) {
  			throw new CayenneRuntimeException("Minimum number of connections can not be bigger then maximum.");
  		}
  
  		DataSource nonPooling = nonPoolingBuilder.build();
  		return buildManaged(buildPooling(nonPooling));
  	}
  
  	private UnmanagedPoolingDataSource buildPooling(DataSource nonPoolingDataSource) {
  		return new UnmanagedPoolingDataSource(nonPoolingDataSource, poolParameters);
  	}
  
  	private PoolingDataSource buildManaged(UnmanagedPoolingDataSource dataSource) {
  		return new ManagedPoolingDataSource(dataSource);
  	}
  
  }
  