一个分页支持类

参考了http://www.iteye.com/article/14657?page=3#comments文章中的PaginationSupport类实现，略微扩展了一下。

[code]
import java.util.List;

/**
* ps.getItems()得到已分页好的结果集
* ps.getIndexes()得到分页索引的数组
* ps.getTotalCount()得到总结果数
* ps.getStartIndex()当前分页索引
* ps.getNextIndex()下一页索引
* ps.getPreviousIndex()上一页索引
* @see http://www.iteye.com/article/14657?page=3#comments
*/
public class PageSupport {

public final static int PAGESIZE = 30;

private int pageSize = PAGESIZE;

private List items;

private int totalCount;

private int[] indexes = new int[0];

private int startIndex = 0;

public PageSupport(List items, int totalCount) {
setPageSize(PAGESIZE);
setTotalCount(totalCount);
setItems(items);
setStartIndex(0);
}

public PageSupport(List items, int totalCount, int startIndex) {
setPageSize(PAGESIZE);
setTotalCount(totalCount);
setItems(items);
setStartIndex(startIndex);
}

public PageSupport(List items, int totalCount, int pageSize, int startIndex) {
setPageSize(pageSize);
setTotalCount(totalCount);
setItems(items);
setStartIndex(startIndex);
}

public List getItems() {
return items;
}

public void setItems(List items) {
this.items = items;
}

public int getPageSize() {
return pageSize;
}

public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}

public int getTotalCount() {
return totalCount;
}

public void setTotalCount(int totalCount) {
if (totalCount > 0) {
this.totalCount = totalCount;
// 81/10 = 8
int count = totalCount / pageSize;
if (totalCount % pageSize > 0)
count++;
indexes = new int[count];
for (int i = 0; i < count; i++) {
indexes[i] = pageSize * i;
}
} else {
this.totalCount = 0;
}
}

public int[] getIndexes() {
return indexes;
}

public void setIndexes(int[] indexes) {
this.indexes = indexes;
}

public int getStartIndex() {
return startIndex;
}

public void setStartIndex(int startIndex) {
if (totalCount <= 0)
this.startIndex = 0;
else if (startIndex >= totalCount)
this.startIndex = indexes[indexes.length - 1];
else if (startIndex < 0)
this.startIndex = 0;
else {
this.startIndex = indexes[startIndex / pageSize];
}
}

public int getNextIndex() {
int nextIndex = getStartIndex() + pageSize;
if (nextIndex >= totalCount)
return getStartIndex();
else
return nextIndex;
}

public int getPreviousIndex() {
int previousIndex = getStartIndex() - pageSize;
if (previousIndex < 0)
return 0;
else
return previousIndex;
}


//--------------------------------------------------------------

/**
* 末页索引
*/
public int getLastIndex(){
return getIndexes()[getIndexes().length-1];
}

/**
* 分页总数
*/
public int getTotalPageNum(){
return getIndexes().length;
}

/**
* 获得当前页码
*/
public int getCurrentPageNum(){
int[] indexs = getIndexes();
int startIndex = getStartIndex();
int i=0;
for(i=0;i<indexs.length;i++){
if(startIndex == indexs[i])
break;
}
return (i+1);
}

/**
* 根据页码获得分页索引值 pagenum>=1
*/
public int getIndexByPageNum(int pagenum){
if(pagenum<=1)
return 0;
if(pagenum>getTotalPageNum())
return getLastIndex();
return getIndexes()[pagenum-1];
}

public boolean hasPreviousPage(){
return getStartIndex()==0?false:true;
}

public boolean hasNextPage(){
return (getCurrentPageNum() == getTotalPageNum())?false:true;
}

private String queryString = null;

public String getQueryString() {
return queryString;
}

public void setQueryString(String queryString) {
this.queryString = queryString;
}

}
[/code]