Output the size of a list
I am trying to output the size of a list onto my page using JSF and EL. E.g., I have a managed bean, say myBean, which has a property, say myList. I would like to do the following:
<h:outputText value="#{myBean.myList.size}" />
Of course this does not work, since there is no getSize method on java.util.List. The EL interpreter tries to coerce size into an index and I get a NumberFormatException.
Any ideas?
FYI, I am using facelets but I do not think that matters in this case.
Thanks,
Ray
# 1
I've subclassed an ArrayList into a DtoList which provides object-sorting functionality and which also implements a method "public int getSize() { return super.size(); }". Useful for JSF =)
I'll be so kind to share the source:
package net.balusc.datareflector.dto;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.Set;
/**
* Extended ArrayList to hold data transfer objects (DTO's).
*
* @author balusc@xs4all.nl
*/
public class DtoList<Dto extends BaseDto> extends ArrayList<Dto> {
// Init
private String sortField;
private boolean sortAscending;
// Constructor --
/**
* Default constructor.
*/
public DtoList() {
// Keep it alive.
}
/**
* Create new DtoList based on the given Collection.
* @param collection The given Collection.
*/
public DtoList(Collection<Dto> collection) {
super(collection);
}
// Actions
/**
* Override ArrayList#add(), null DTO's are not allowed.
* @see java.util.ArrayList#add(java.lang.Object)
*/
public boolean add(Dto dto) {
if (dto != null) {
return super.add(dto);
}
return false;
}
/**
* Sort this list.
*/
public void sort() {
if (sortField != null) {
Collections.sort(this, new DtoComparator<BaseDto>(this));
} else {
Collections.sort(this);
}
}
/**
* Sort this list.
* @param sortField The The sort field..
*/
public void sort(String sortField) {
setSortField(sortField);
sort();
}
/**
* Sort this list.
* @param sortField The sort field.
* @param sortAscending Sort ascending?
*/
public void sort(String sortField, boolean sortAscending) {
setSortField(sortField, sortAscending);
sort();
}
/**
* Filter duplicates.
*/
public void unique() {
Set<Dto> set = new LinkedHashSet<Dto>(this);
super.clear();
super.addAll(set);
}
// Dto getters --
/**
* Shifts first DTO of this list.
* @return First DTO of list.
*/
public Dto getFirst() {
if (super.size() == 0) {
return null;
}
return super.remove(0);
}
/**
* Pops last DTO of this list.
* @return Last DTO of this list.
*/
public Dto getLast() {
if (super.size() == 0) {
return null;
}
return super.remove(size() - 1);
}
/**
* Useful for JSF. For example #{myBean.myDtoList.size} will be possible.
* @return The list size
*/
public int getSize() {
return super.size();
}
// Sorting getters -
/**
* @return The sort field.
*/
public String getSortField() {
return sortField;
}
/**
* @return Sort ascending?
*/
public boolean isSortAscending() {
return sortAscending;
}
/**
* @return Sort descending?
*/
public boolean isSortDescending() {
return !sortAscending;
}
// Sorting setters -
/**
* @param sortField The sort field.
*/
public void setSortField(String sortField) {
if (sortField != null && sortField.equals(this.sortField)) {
sortAscending = !sortAscending; // Reverse sort.
} else {
this.sortField = sortField; // New field.
sortAscending = true; // Set default order.
}
}
/**
* @param sortField The sort field.
* @param sortAscending Sort ascending?
*/
public void setSortField(String sortField, boolean sortAscending) {
this.sortField = sortField;
this.sortAscending = sortAscending;
}
}
