NVLFilter.java

package ca.sqlpower.sql;

/**
 * NVLFilter simulates a SQL NVL() function on a WebResultSet column.
 *
 * @author Jonathan Fuerth
 * @version $Id$
 */
public class NVLFilter implements ColumnFilter {

	String nullValue;
	
	/**
	 * Constructs a new NVLFilter which substitutes
	 * <code>nullValue</code> for nulls.
	 *
	 * @param nullValue The value to substitute for nulls.
	 */	 
	public NVLFilter(String nullValue) {
		this.nullValue=nullValue;
	}

	/**
	 * Makes a new NVLFilter which substitutes "?" for nulls.
	 *
	 * @return The new NVLFilter.
	 */
    public static ColumnFilter getInstance() {
        return (ColumnFilter)new NVLFilter("?");
    }

	/**
	 * Converts null values to a pre-determined string, returning
	 * non-null values unchanged.
	 *
	 * @param in The input string
	 * @return <code>in</code> if <code>in != null</code>; the value
	 * of the <code>nullValue</code> property otherwise.
	 */
    public String filter(String in) {
		if(in==null) {
			return nullValue;
		} else {
			return in;
		}
    }

	/**
	 * Gets the value of nullValue
	 *
	 * @return the value of nullValue
	 */
	public String getNullValue() {
		return this.nullValue;
	}

	/**
	 * Sets the value of nullValue
	 *
	 * @param argNullValue Value to assign to this.nullValue
	 */
	public void setNullValue(String argNullValue){
		this.nullValue = argNullValue;
	}
}