decodecasefragment.java

用Java实现的23个常用设计模式源代码

//$Id: DecodeCaseFragment.java,v 1.5.2.5 2003/11/27 16:10:00 oneovthafew Exp $
package net.sf.hibernate.sql;

import java.util.Iterator;
import java.util.Map;
import net.sf.hibernate.util.StringHelper;
import org.apache.commons.collections.SequencedHashMap;

/**
 An Oracle-style DECODE function.
 <br>
 <code>decode(pkvalue, key1, 1, key2, 2, ..., 0)</code>
 <br>

 @author Simon Harris
 */
public class DecodeCaseFragment extends CaseFragment {

	private String returnColumnName;

	private Map cases = new SequencedHashMap();

	public CaseFragment setReturnColumnName(String returnColumnName) {
		this.returnColumnName = returnColumnName;
		return this;
	}

	public CaseFragment setReturnColumnName(String returnColumnName, String suffix) {
		return setReturnColumnName( new Alias(suffix).toAliasString(returnColumnName) );
	}

	public CaseFragment addWhenColumnNotNull(String alias, String columnName, String value) {
		cases.put( StringHelper.qualify(alias, columnName), value );
		return this;
	}

	public String toFragmentString() {
		StringBuffer buf = new StringBuffer( cases.size() * 15 + 10 );

		Iterator iter = cases.entrySet().iterator();
		while ( iter.hasNext() ) {
			Map.Entry me = (Map.Entry) iter.next();

			if ( "0".equals( me.getValue() ) ) {
				buf.insert( 0, me.getKey() );
			} 
			else {
				buf.append(", ")
					.append( me.getKey() )
					.append(", ")
					.append( me.getValue() );
			}
		}

		buf.insert(0, "decode (").append(",0 )");
		if (returnColumnName!=null) {
			buf.append(" as ")
				.append(returnColumnName);
		}
		return buf.toString();
	}
}