Update of /cvsroot/displaytag/table-ben/src/com/tablelib/core/util
In directory sc8-pr-cvs1:/tmp/cvs-serv11620
Added Files:
BeanSorter.java
Log Message:
--- NEW FILE: BeanSorter.java ---
/**
* $Id: BeanSorter.java,v 1.1 2003/07/18 13:23:49 javabencom Exp $
*
* Status: Under Development
*
* Todo
* - implementation
* - documentation (javadoc, examples, etc...)
* - junit test cases
**/
package com.tablelib.core.util;
import org.apache.commons.beanutils.PropertyUtils;
import java.lang.reflect.InvocationTargetException;
import java.util.Comparator;
import com.tablelib.tags.Decorator;
/**
* This utility class is used to sort the list that the table is viewing
* based on arbitrary properties of objects contained in that list. The
* only assumption made is that the object returned by the property is
* either a native type, or implements the Comparable interface.
*
* If the property does not implement Comparable, then this little sorter
* object will just assume that all objects are the same, and quietly do
* nothing (so you should check for Comparable objecttypes elsewhere as
* this object won't complain).
**/
public class BeanSorter implements Comparator {
private String property;
private Decorator dec;
/**
* BeanSorter is a decorator of sorts, you need to initialize it with
* the property name of the object that is to be sorted (getXXX method
* name). This property should return a Comparable object.
*/
public static Comparator asComparator(String property, Decorator dec) {
BeanSorter ret = new BeanSorter();
ret.property = property;
ret.dec = dec;
return ret;
}
/**
* Compares two objects by first fetching a property from each object
* and then comparing that value. If there are any errors produced while
* trying to compare these objects then a RunTimeException will be
* thrown as any error found here will most likely be a programming
* error that needs to be quickly addressed (like trying to compare
* objects that are not comparable, or trying to read a property from a
* bean that is invalid, etc...)
*
* @throws java.lang.RuntimeException if there are any problems making a comparison
* of the object properties.
*/
public int compare(Object o1, Object o2) throws RuntimeException {
if (property == null) {
throw new NullPointerException("Null property provided which " +
"prevents BeanSorter sort");
}
try {
Object p1 = PropertyUtils.getProperty(o1, property);
Object p2 = PropertyUtils.getProperty(o2, property);
if (p1 instanceof Comparable && p2 instanceof Comparable) {
Comparable c1 = (Comparable) p1;
Comparable c2 = (Comparable) p2;
return c1.compareTo(c2);
} else {
throw new RuntimeException("Object returned by property \"" +
property + "\" is not a Comparable object");
}
} catch (IllegalAccessException e) {
throw new RuntimeException("IllegalAccessException thrown while " +
"trying to fetch property \"" + property + "\" during sort");
} catch (InvocationTargetException e) {
throw new RuntimeException("InvocationTargetException thrown while " +
"trying to fetch property \"" + property + "\" during sort");
} catch (NoSuchMethodException e) {
throw new RuntimeException("NoSuchMethodException thrown while " +
"trying to fetch property \"" + property + "\" during sort");
}
}
/**
* Is this Comparator the same as another one...
*/
public boolean equals(Object obj) {
if (obj == this) return true;
if (obj instanceof BeanSorter == false) return false;
if (this.property == null) return false;
return this.property.equals(((BeanSorter) obj).property);
}
}
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