package org.pagination;

import java.util.List;

public interface Pagination<T> {

public Integer getTotalElements();

public List<T> getPageList();

}

 

package org.pagination;

import java.util.List;

public interface QueryHandler<T> {

public Integer getCount();

public List<T> getData(Integer pageIndex, Integer pageSize);

}

 

 

package org.pagination.impl;

import java.util.List;

import org.pagination.Pagination;

import org.pagination.QueryHandler;

public class DefaultPagination<T> implements Pagination<T> {

private Integer totalElements;

private List<T> pageList;

private QueryHandler<T> queryHandler;

private Integer pageIndex;

private Integer pageSize;

private Integer totalPages;

public DefaultPagination(Integer pageIndex,Integer pageSize,QueryHandler<T> queryHandler) {

this.queryHandler = queryHandler;

setTotalElements();//初始化总行数

setPageSize(pageSize);//修正页大小

calcTotalPage();//计算总页数

setPageIndex(pageIndex);//修正页码

setPageList();//初始化当前页数据

}

private void setTotalElements() {

totalElements = queryHandler.getCount();

}

private void setPageSize(Integer pageSize) {

if (pageSize < 1) {

this.pageSize = 1;

} else if (pageSize > totalElements && totalElements > 0) {

this.pageSize = totalElements;

} else {

this.pageSize = pageSize;

}

}

private void calcTotalPage(){

if (pageSize > 0) {

totalPages = (totalElements + pageSize - 1) / pageSize;

}

} 

private void setPageIndex(Integer pageIndex) {

if (pageIndex < 1) {

this.pageIndex = 1;

} else if (pageIndex > totalPages && totalPages > 0) {

this.pageIndex = totalPages;

} else {

this.pageIndex = pageIndex;

}

}

private void setPageList() {

pageList = queryHandler.getData(pageIndex, pageSize);

}

@Override

public Integer getTotalElements() {

return totalElements;

}

@Override

public List<T> getPageList() {

return pageList;

}

}