ansicasefragment.java

来自「用Java实现的23个常用设计模式源代码」· Java 代码 · 共 58 行

//$Id: ANSICaseFragment.java,v 1.4.2.3 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 ANSI SQL CASE expression.
 <br>
 <code>case when ... then ... end as ...</code>
 <br>
 @author Gavin King, Simon Harris
 */
public class ANSICaseFragment 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) + " is not null", value );
		return this;
	}

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

		buf.append("case");

		Iterator iter = cases.entrySet().iterator();
		while ( iter.hasNext() ) {
			Map.Entry me = (Map.Entry) iter.next();
			buf.append(" when ")
				.append( me.getKey() )
				.append(" then ")
				.append( me.getValue() );
		}
		buf.append(" end");
		
		if (returnColumnName!=null) {
			buf.append(" as ")
				.append(returnColumnName);
		}
		
		return buf.toString();
	}
}