/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* C E D A R
* S O L U T I O N S "Software done right."
* S O F T W A R E
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* Copyright (c) 2013 Kenneth J. Pronovici.
* All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the Apache License, Version 2.0.
* See LICENSE for more information about the licensing terms.
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* Author : Kenneth J. Pronovici <pronovic@ieee.org>
* Language : Java 6
* Project : Common Java Functionality
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
package com.cedarsolutions.dao.domain;
import java.util.HashMap;
import java.util.Map;
import com.cedarsolutions.shared.domain.TranslatableDomainObject;
import com.flipthebird.gwthashcodeequals.EqualsBuilder;
import com.flipthebird.gwthashcodeequals.HashCodeBuilder;
/**
* Controls pagination state for back-end queries.
* @see <a href="https://code.google.com/p/cedar-common/wiki/Pagination">The wiki for notes on pagination for non-GAE platforms</a>
* @author Kenneth J. Pronovici <pronovic@ieee.org>
*/
@SuppressWarnings("serial")
public class Pagination extends TranslatableDomainObject {
/** The configured page size. */
protected int pageSize;
/** The current page number. */
protected int pageNumber;
/** Whether there is any page data. */
protected boolean hasData;
/** Whether there is a previous page. */
protected boolean hasPrevious;
/** Whether there is a next page. */
protected boolean hasNext;
/** Whether the total number of pages is finalized. */
protected boolean isTotalFinalized;
/** The total number of pages so far, possibly not finalized. */
protected int totalPages;
/** The total number of rows so far, possibly not finalized. */
protected int totalRows;
/**
* Current datastore location for pagination, useful for platforms that have such a concept.
* This is an opaque value from the perspective of a DAO client.
* For GAE, this is the cursor for the current page, as from Cursor.toWebSafeString().
*/
protected String current;
/** A map from page number datastore location, useful for platforms that have such a concept. */
protected Map<Integer, String> cursors;
/** A map from page number to number of rows on the page. */
protected Map<Integer, Integer> counts;
/** Default constructor, for GWT's benefit. */
public Pagination() {
}
/** Create pagination for a specific page size. */
public Pagination(int pageSize) {
this.pageSize = pageSize;
this.pageNumber = 1;
this.hasData = false;
this.hasPrevious = false;
this.hasNext = false;
this.isTotalFinalized = false;
this.totalPages = 0;
this.totalRows = 0;
this.current = null;
this.cursors = new HashMap<Integer, String>();
this.counts = new HashMap<Integer, Integer>();
}
/** Copy constructor. */
protected Pagination(Pagination source) {
this.pageSize = source.pageSize;
this.pageNumber = source.pageNumber;
this.hasData = source.hasData;
this.hasPrevious = source.hasPrevious;
this.hasNext = source.hasNext;
this.isTotalFinalized = source.isTotalFinalized;
this.totalPages = source.totalPages;
this.totalRows = source.totalRows;
this.current = source.current;
this.cursors = new HashMap<Integer, String>(source.cursors);
this.counts = new HashMap<Integer, Integer>(source.counts);
}
/**
* Current datastore location for pagination, useful for platforms that have such a concept.
* This is an opaque value from the perspective of a DAO client.
* For GAE, this is the cursor for the current page, as from Cursor.toWebSafeString().
*/
public String getCurrent() {
return current;
}
/** Get the configured page size. */
public int getPageSize() {
return pageSize;
}
/** Get the current page number. */
public int getPageNumber() {
return pageNumber;
}
/**
* Get the next page number.
* This value cannot advance below 1.
*/
public int getPreviousPageNumber() {
if (pageNumber <= 1) {
return 1;
} else {
return pageNumber - 1;
}
}
/**
* Get the next page number.
* If the total is finalized, this value cannot advance beyond the total.
*/
public int getNextPageNumber() {
if (this.isTotalFinalized) {
if (pageNumber >= totalPages) {
return totalPages;
} else {
return pageNumber + 1;
}
} else {
return pageNumber + 1;
}
}
/** Whether there is page data. */
public boolean hasData() {
return hasData;
}
/** Whether there is a previous page. */
public boolean hasPrevious() {
return hasPrevious;
}
/** Whether there is a next page. */
public boolean hasNext() {
return hasNext;
}
/** Whether the total number of pages is finalized. */
public boolean isTotalFinalized() {
return isTotalFinalized;
}
/** The total number of pages so far, possibly not finalized. */
public int getTotalPages() {
return totalPages;
}
/** The total number of rows so far, possibly not finalized. */
public int getTotalRows() {
return totalRows;
}
/** Make a copy of the object. */
public Pagination copy() {
return new Pagination(this);
}
/**
* Return pagination for the previous page.
* @return Pagination for the previous page, or for the current page if there is no previous page.
*/
public Pagination previous() {
return page(getPreviousPageNumber());
}
/**
* Return pagination for the next page.
* @return Pagination for the next page, or for the current page if there is no next page.
*/
public Pagination next() {
return page(getNextPageNumber());
}
/**
* Return pagination for the requested page.
* @param pageNumber Page number to retrieve
* @return Pagination for the requested page, or for the current page if the requested page is unknown.
*/
public Pagination page(int pageNumber) {
Pagination copy = this.copy();
String cursor = cursors.get(pageNumber);
if (cursor != null) {
copy.pageNumber = pageNumber;
copy.current = cursor;
} else {
if (pageNumber < 1) {
cursor = cursors.get(1);
if (cursor != null) {
copy.pageNumber = 1;
copy.current = cursor;
}
} else if (pageNumber > totalPages) {
cursor = cursors.get(totalPages);
if (cursor != null) {
copy.pageNumber = totalPages;
copy.current = cursor;
}
}
}
return copy;
}
/**
* Update the pagination state in place.
* @param current Cursor for current page
* @param next Cursor for next page, null if no next page exists
*/
public void update(String current, String next, int count) {
hasData = true;
this.current = current;
cursors.put(pageNumber, this.current);
counts.put(pageNumber, count);
if (next == null) {
isTotalFinalized = true;
} else {
cursors.put(getNextPageNumber(), next);
}
hasPrevious = false;
if (pageNumber != getPreviousPageNumber()) {
hasPrevious = cursors.get(getPreviousPageNumber()) != null;
}
hasNext = false;
if (pageNumber != getNextPageNumber()) {
hasNext = cursors.get(getNextPageNumber()) != null;
}
totalPages = cursors.size();
totalRows = this.calculateTotalRows();
}
/** Calculate the total number of rows based on the counts map. */
private int calculateTotalRows() {
int total = 0;
for (Integer value : this.counts.values()) {
total += value;
}
return total;
}
/** Compare this object to another object. */
@Override
public boolean equals(Object obj) {
Pagination other = (Pagination) obj;
return new EqualsBuilder()
.append(this.pageSize, other.pageSize)
.append(this.pageNumber, other.pageNumber)
.append(this.current, other.current)
.isEquals();
}
/** Generate a hash code for this object. */
@Override
public int hashCode() {
return new HashCodeBuilder()
.append(this.pageSize)
.append(this.pageNumber)
.append(this.current)
.toHashCode();
}
}