package com.walker.db.page;
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import java.util.List;
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import com.walker.db.page.Pager;
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public abstract class AbstractPager implements Pager {
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/* 当前给定的页码索引，如：1 = 第一页 */
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private int pageIndex = DEFAULT_PAGE_INDEX;
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/* 每页设置的数据条数，即：每页显示几条 */
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private int pageSize = DEFAULT_PAGE_SIZE;
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private int pageCount = DEFAULT_PAGE_COUNT;
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private long totalRows = DEFAULT_TOTAL_ROWS;
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public AbstractPager(int pageIndex, int pageSize, long totalRows){
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setPageIndex(pageIndex);
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setPageSize(pageSize);
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if(totalRows > 0)
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setTotalRows(totalRows);
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}
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protected abstract Class<?> buildData();
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@Override
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public boolean isEmpty(){
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return totalRows == 0;
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}
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@Override
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public int getPageCount() {
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return pageCount;
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}
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@Override
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public long getTotalRows() {
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return totalRows;
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}
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@Override
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public void setTotalRows(final long totalRows){
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if(totalRows < 0)
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throw new IllegalArgumentException("totalRows must more than 0.");
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if(totalRows == 0) return;
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// if(totalRows == 0 && this.pageIndex != 1){
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// throw new IndexOutOfBoundsException("Page index out of range: " + this.pageIndex);
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// }
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// else if(this.pageIndex > totalRows){
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// throw new IndexOutOfBoundsException("Page index out of range: " + this.pageIndex);
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// }
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this.totalRows = totalRows;
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this.pageCount = (int)(totalRows / this.pageSize + (totalRows % this.pageSize == 0 ? 0 : 1));
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}
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@Override
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public int getPageIndex() {
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return pageIndex;
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}
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public void setPageIndex(int pageIndex) {
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if(this.pageIndex > DEFAULT_PAGE_INDEX && pageIndex >= DEFAULT_PAGE_INDEX){
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throw new IllegalStateException("can't invoke method of setPageIndex() repeatedly.");
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}
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if (pageIndex < DEFAULT_PAGE_INDEX)
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pageIndex = DEFAULT_PAGE_INDEX;
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this.pageIndex = pageIndex;
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}
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@Override
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public int getPageSize() {
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return pageSize;
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}
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public void setPageSize(int pageSize) {
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if(this.pageSize > DEFAULT_PAGE_SIZE
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&& pageSize >= 0){
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throw new IllegalStateException("can't invoke method of setPageSize() repeatedly."
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+ ", this.pageSize = " + this.pageSize
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+ ", pageSize = " + pageSize);
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}
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if (pageSize < DEFAULT_PAGE_SIZE)
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pageSize = DEFAULT_PAGE_SIZE;
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this.pageSize = pageSize;
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}
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/**
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* 返回分页对象中的第一条记录的索引值
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* @return
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*/
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@Override
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public long getFirstRowIndexInPage(){
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return (this.pageIndex - 1) * this.pageSize;
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}
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/**
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* 返回本页最后一条记录索引值
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* @return
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*/
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@Override
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public long getEndRowIndexPage(){
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long endDataIndex = 0;
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if(totalRows <= 1){
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return endDataIndex;
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}
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long firstDataIndex = getFirstRowIndexInPage();
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if(totalRows >= pageSize){
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// 带分页
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if(hasNextPage()){
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endDataIndex = firstDataIndex + pageSize - 1;
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} else {
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endDataIndex = firstDataIndex + (totalRows - (pageCount - 1)*pageSize) - 1;
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}
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} else {
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// 不带分页
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endDataIndex = totalRows-1;
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}
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return endDataIndex;
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}
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@Override
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public boolean hasNextPage(){
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return this.pageIndex < this.pageCount;
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}
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@Override
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public boolean hasPreviousPage(){
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return this.pageIndex > 1;
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}
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@Override
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public List<Object> getDatasObject(){
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throw new UnsupportedOperationException("error: no implements.");
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}
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public String toString(){
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return new StringBuilder().append("pager: {pageIndex=").append(pageIndex)
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.append(", pageSize=").append(pageSize)
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.append(", pageCount=").append(pageCount)
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.append(", totalRows=").append(totalRows)
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.append("}").toString();
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}
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}
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