Hibernate+Spring+Struts2整合开发中的一个分页显示方案
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Hibernate+Spring+Struts2整合开发中的一个分页显示方案
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1、DAO层接口的设计，在MemberDao接口中定义了如下两个方法：
public interface MemberDao{
???
??? //省略了其他的代码
???
??? /** *//**
???? * 分页查询
???? * @param hql 查询的条件
???? * @param offset 开始记录
???? * @param length 一次查询几条记录
???? * @return
???? */
??? public List queryForPage(final String hql,final int offset,final int length);
???
??? /** *//**
???? * 查询所有记录数
???? * @param hql 查询的条件
???? * @return 总记录数
???? */
??? public int getAllRowCount(String hql);
}
2、DAO层实现类MemberDaoImpl对上面两个方法的实现如下：
public class MemberDaoImpl extends HibernateDaoSupport implements MemberDao {
?????? //省略了其他的代码???
??? /** *//**
???? * 分页查询
???? * @param hql 查询的条件
???? * @param offset 开始记录
???? * @param length 一次查询几条记录
???? * @return
???? */
??? public List queryForPage(final String hql,final int offset,final int length){
??????? List list = getHibernateTemplate().executeFind(new HibernateCallback(){
??????????? public Object doInHibernate(Session session) throws HibernateException,SQLException{
??????????????? Query query = session.createQuery(hql);
??????????????? query.setFirstResult(offset);
??????????????? query.setMaxResults(length);
??????????????? List list = query.list();
??????????????? return list;
??????????? }
??????? });
??????? return list;
??? }
???
???
??? /** *//**
???? * 查询所有记录数
???? * @return 总记录数
???? */
??? public int getAllRowCount(String hql){
??????? return getHibernateTemplate().find(hql).size();
??? }
}
??????? 细心的读者会发现，这个类继承了HibernateDaoSupport类，HibernateDaoSupport是Spring提供的对Hibernate支持的类，getHibernateTemplate().executeFind(new HibernateCallback(){....})方法中的参数，我们使用了接口回调，在其参数内，我们能像原生的Hibernate一样调用query.setFirstResult(offset)和query.setMaxResults(length)来实现分页查询功能。
3、下面我们来新建一个保存分页信息的类PageBean,具体代码如下：
public class PageBean {
???
??? private List list;??????? //要返回的某一页的记录列表
???
??? private int allRow;???????? //总记录数
??? private int totalPage;??????? //总页数
??? private int currentPage;??? //当前页
??? private int pageSize;??????? //每页记录数
???
??? private boolean isFirstPage;??? //是否为第一页
??? private boolean isLastPage;??????? //是否为最后一页
??? private boolean hasPreviousPage;??? //是否有前一页
??? private boolean hasNextPage;??????? //是否有下一页
???
???
??? public List getList() {
??????? return list;
??? }
??? public void setList(List list) {
??????? this.list = list;
??? }
??? public int getAllRow() {
??????? return allRow;
??? }
??? public void setAllRow(int allRow) {
??????? this.allRow = allRow;
??? }
??? public int getTotalPage() {
??????? return totalPage;
??? }
??? public void setTotalPage(int totalPage) {
??????? this.totalPage = totalPage;
??? }
??? public int getCurrentPage() {
??????? return currentPage;
??? }
??? public void setCurrentPage(int currentPage) {
??????? this.currentPage = currentPage;
??? }
??? public int getPageSize() {
??????? return pageSize;
??? }
??? public void setPageSize(int pageSize) {
??????? this.pageSize = pageSize;
??? }
???
??? /** *//**
???? * 初始化分页信息
???? */
??? public void init(){
??????? this.isFirstPage = isFirstPage();
??????? this.isLastPage = isLastPage();
??????? this.hasPreviousPage = isHasPreviousPage();
??????? this.hasNextPage = isHasNextPage();
??? }
???
??? /** *//**
???? * 以下判断页的信息,只需getter方法(is方法)即可
???? * @return
???? */
???
??? public boolean isFirstPage() {
??????? return currentPage == 1;??? // 如是当前页是第1页
??? }
??? public boolean isLastPage() {
??????? return currentPage == totalPage;??? //如果当前页是最后一页
??? }
??? public boolean isHasPreviousPage() {
??????? return currentPage != 1;??????? //只要当前页不是第1页
??? }
??? public boolean isHasNextPage() {
??????? return currentPage != totalPage;??? //只要当前页不是最后1页
??? }
???
???
??? /** *//**
???? * 计算总页数,静态方法,供外部直接通过类名调用
???? * @param pageSize 每页记录数
???? * @param allRow 总记录数
???? * @return 总页数
???? */
??? public static int countTotalPage(final int pageSize,final int allRow){
??????? int totalPage = allRow % pageSize == 0 ? allRow/pageSize : allRow/pageSize+1;
??????? return totalPage;
??? }
???
??? /** *//**
???? * 计算当前页开始记录
???? * @param pageSize 每页记录数
???? * @param currentPage 当前第几页
???? * @return 当前页开始记录号
???? */
??? public static int countOffset(final int pageSize,final int currentPage){
??????? final int offset = pageSize*(currentPage-1);
??????? return offset;
??? }
???
??? /** *//**
???? * 计算当前页,若为0或者请求的URL中没有"?page=",则用1代替
???? * @param page 传入的参数(可能为空,即0,则返回1)
???? * @return 当前页
???? */
??? public static int countCurrentPage(int page){
??????? final int curPage = (page==0?1:page);
??????? return curPage;
??? }
}
4、Service层接口的设计：
public interface MemberService {
??? //省略其他的代码
??? /** *//**
???? * 分页查询
???? * @param currentPage 当前第几页
???? * @param pageSize 每页大小
???? * @return 封闭了分页信息(包括记录集list)的Bean
???? */
??? public PageBean queryForPage(int pageSize,int currentPage);
}
5、Service层实现类的部分内码如下：
public class MemberServiceImpl implements MemberService {
?
? //通过applicationContext.xml配置文件注入MemberDao的值
??? private MemberDao memberDao;
??? public void setMemberDao(MemberDao memberDao) {
??????? this.memberDao = memberDao;
??? }
???
??? /** *//**
???? * 分页查询
???? * @param currentPage 当前第几页
???? * @param pageSize 每页大小
???? * @return 封闭了分页信息(包括记录集list)的Bean
???? */
??? public PageBean queryForPage(int pageSize,int page){
??????? final String hql = "from Member";??????? //查询语句
??????? int allRow = memberDao.getAllRowCount(hql);??? //总记录数
??????? int totalPage = PageBean.countTotalPage(pageSize, allRow);??? //总页数
??????? final int offset = PageBean.countOffset(pageSize, page);??? //当前页开始记录
??????? final int length = pageSize;??? //每页记录数
??????? final int currentPage = PageBean.countCurrentPage(page);
??????? List<Member> list = memberDao.queryForPage(hql,offset, length);??????? //"一页"的记录
???????
??????? //把分页信息保存到Bean中
??????? PageBean pageBean = new PageBean();
??????? pageBean.setPageSize(pageSize);???
??????? pageBean.setCurrentPage(currentPage);
??????? pageBean.setAllRow(allRow);
??????? pageBean.setTotalPage(totalPage);
??????? pageBean.setList(list);
??????? pageBean.init();
??????? return pageBean;
??? }
6、在Struts2中调用queryForPageMemberService层的queryForPage（）方法即可return一个包含分页信息、符合条件的结果集list， 代码如下：
public class ListMember extends ActionSupport{
??? //通过applicationContext.xml配置文件注入memberService的值
??? private MemberService memberService;
??? public void setMemberService(MemberService memberService) {
??????? this.memberService = memberService;
??? }
???
??? private int page;??? //第几页
???
??? private PageBean pageBean;??? //包含分布信息的bean
???
??? public int getPage() {
??????? return page;
??? }
??? public void setPage(int page) {??????? //若URL中无此参数,会默认为第1页
??????? this.page = page;
??? }
??? public PageBean getPageBean() {
??????? return pageBean;
??? }
??? public void setPageBean(PageBean pageBean) {
??????? this.pageBean = pageBean;
??? }
??? @Override
??? public String execute() throws Exception {
??????? //分页的pageBean,参数pageSize表示每页显示记录数,page为当前页
??????? this.pageBean = memberService.queryForPage(2, page);
??????? return SUCCESS;
??? }
}
7、最后在listMember.jsp页面中，用到了Struts2标签：
<s:iterator value="pageBean.list">
??????????? <s:property value="title"/>
??????????? <a href="getArticle.action?id=<s:property value="id"/>">modify</a>
??????????? <a href="deleteArticle.action?id=<s:property value="id"/>" onclick="return askDel()"/>delete</a><br/>
??????? </s:iterator>
??????? 共<s:property value="pageBean.allRow"/> 条记录
??????? 共<s:property value="pageBean.totalPage"/> 页
??????? 当前第<s:property value="pageBean.currentPage"/>页<br/>
???????
??????? <s:if test="%{pageBean.currentPage == 1}">
??????????? 第一页 上一页
??????? </s:if>
??????? <s:else>
??????????? <a href="listMyArticle.action?page=1">第一页</a>
??????????? <a href="listMyArticle.action?page=<s:property value="%{pageBean.currentPage-1}"/>">上一页</a>
??????? </s:else>
??????? <s:if test="%{pageBean.currentPage != pageBean.totalPage}">
??????????? <a href="listMyArticle.action?page=<s:property value="%{pageBean.currentPage+1}"/>">下一页</a>
??????????? <a href="listMyArticle.action?page=<s:property value="pageBean.totalPage"/>">最后一页</a>
??????? </s:if>
??????? <s:else>
??????????? 下一页 最后一页
??????? </s:else>
