分页设计 原则
由于每次要将对应页数所需要的数据在jsp或者html等文件中显示出来，所以要将这些数据封装在一个javabean中
，后台都将查询到的数据导入到对应的javabean对象实例中，我们再将该对象存入request作用域，html或者jsp页面
从域中获取所需要的数据
创建LepPage类import java.util.List;
public class LepPage {
/**
* 如果指定的分页大小小于等于0，则义默认分页为20条数据
*/
public static final int DEFAULT_ROW_SIZE = 20;
/**
* 如果指定的分页页码小于等于0，则默认为第一页。
*/
public static final int DEFAULT_PAGE_NUM = 1;
private int pageNo=DEFAULT_PAGE_NUM; // 当前页码
private int pageSize=DEFAULT_ROW_SIZE; // 页面大小
private int totalCount=-1; // 总记录数
private int totalPage=-1; // 总页数
private int startIndex; // 分页开始位置
private int endIndex; // 分页结束位置
private List results; // 返回的结果集
/*
* 是否手动设置过总记录数
* 如果手动设置过，则不自动去计算数据总数。否则，将对SQL语句包装成COUNT语句去查询总记录数
*/
private boolean alreadySetTotolRecode = false;
/*
* 计算总页数
*/
private void calculateTotalPage() {
this.alreadySetTotolRecode = true;
if ( this.totalCount < 0 ) {
this.totalCount = 0;
}
if ( this.totalCount % this.pageSize == 0 ) {
this.totalPage = this.totalCount / this.pageSize;
} else {
this.totalPage = this.totalCount / this.pageSize + 1;
}
}
/**
* 该方法不推荐使用，使用{@code Page(int PageNo, int pageSize)}进行替换
*/
public LepPage() {
super();
}
private void calculatorPageNo() {
this.startIndex = pageNo > 0 ? ((pageNo - 1) * pageSize) : 0;
this.endIndex = pageNo * pageSize;
}
/**
* 构造一个Page对象
* @param pageNo 当前页码
* @param pageSize 页面大小
*/
public LepPage(int pageNo, int pageSize) {
this.pageNo = pageNo;
this.pageSize = pageSize;
calculatorPageNo();
}
public int getPageNo() {
return pageNo;
}
public void setPageNo(int PageNo) {
if ( PageNo <= 0 ) {
this.pageNo = DEFAULT_PAGE_NUM;
}
this.pageNo = PageNo;
calculatorPageNo();
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
if ( pageSize <= 0 ) {
this.pageSize = DEFAULT_ROW_SIZE;
}
this.pageSize = pageSize;
calculatorPageNo();
}
public int getTotalCount() {
return totalCount;
}
public void setTotalCount(int totalCount) {
this.totalCount = totalCount;
// 去计算总页数
calculateTotalPage();
}
public int getTotalPage() {
return totalPage;
}
public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
}
public int getStartIndex() {
return startIndex;
}
public void setStartIndex(int startIndex) {
this.startIndex = startIndex;
}
public int getEndIndex() {
return endIndex;
}
public void setEndIndex(int endIndex) {
this.endIndex = endIndex;
}
public List getResults() {
return results;
}
public void setResults(List results) {
this.results = results;
}
public boolean isAlreadySetTotolRecode() {
return alreadySetTotolRecode;
}
public void setAlreadySetTotolRecode(boolean alreadySetTotolRecode) {
this.alreadySetTotolRecode = alreadySetTotolRecode;
}
@Override
public String toString() {
return "Page{" +
"pageNo=" + pageNo +
", pageSize=" + pageSize +
", totalCount=" + totalCount +
", totalPage=" + totalPage +
", startIndex=" + startIndex +
", endIndex=" + endIndex +
", results=" + results +
", alreadySetTotolRecode=" + alreadySetTotolRecode +
'}';
}
}
Service层编写业务逻辑代码
在Json对象中 添加对应的分页对象返回到前端
