java 实现分页技术(Structs+Hibernate+MySQL)

通过Structs+Hibernate+MySQL数据数来实现分页技术的应用.

源程序下载
至于Hibernate, Structs, MySQL的具体用法我就不说了,你可以看源程序来查看详细内容.我们来看看分页应用的相关内容.
架构上和Spring JPetStore没多少区别, 只是没用Spring框架所以Structs中的UserdisplayAction中必须new出各个对象并完成它们之间的关联, 这就是Spring IOC可自动完成的功能. 它也是三层:表现层(Structs), 业务层(POJO), 数据层(Hibernate访问MySQL). 同样业务层通过DAO接口(UserDAO)来访问数据库, 访问数据库的通过Hibernate(在UserDAOImpl中实现). 这一次分页要在业务层中来实现, 业务层同样向表现层提供一个Facada(门面, UserManager接口), 来访问业务. 在UserManagerImpl中通过调用UserDAO来访问数据, 调用POJO来实现分页功能. 看以下关键代码.

先看POJO的分布类吧:

Page.java

package org.flyware.util.page;

public class Page {

private boolean hasPrePage;

private boolean hasNextPage;

private int everyPage;

private int totalPage;

private int currentPage;

private int beginIndex;


public Page(){

}

public Page(int everyPage){
this.everyPage = everyPage;
}

/** The whole constructor */
public Page(boolean hasPrePage, boolean hasNextPage,
int everyPage, int totalPage,
int currentPage, int beginIndex) {
this.hasPrePage = hasPrePage;
this.hasNextPage = hasNextPage;
this.everyPage = everyPage;
this.totalPage = totalPage;
this.currentPage = currentPage;
this.beginIndex = beginIndex;
}

......

public int getTotalPage() {
return totalPage;
}

public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
}

}

PageUtil.java(用来构造Page实例 相当于page工厂)

package org.flyware.util.page;

public class PageUtil {

private static final Log logger = LogFactory.getLog(PageUtil.class);

public static Page createPage(Page page, int totalRecords){

return createPage(page.getEveryPage(), page.getCurrentPage(), totalRecords);
}

public static Page createPage(int everyPage, int currentPage, int totalRecords){
everyPage = getEveryPage(everyPage);

currentPage = getCurrentPage(currentPage);

int beginIndex = getBeginIndex(everyPage, currentPage);

int totalPage = getTotalPage(everyPage, totalRecords);

boolean hasNextPage = hasNextPage(currentPage, totalPage);

boolean hasPrePage = hasPrePage(currentPage);

return new Page(hasPrePage, hasNextPage,
everyPage, tot

alPage,
currentPage, beginIndex);
}

private static int getEveryPage(int everyPage){
return everyPage == 0 ? 10 : everyPage;
}

private static int getCurrentPage(int currentPage){
return currentPage == 0 ? 1 : currentPage;
}

private static int getBeginIndex(int everyPage, int currentPage){
return (currentPage - 1) * everyPage;
}

private static int getTotalPage(int everyPage, int totalRecords){
int totalPage = 0;

if(totalRecords % everyPage == 0)
totalPage = totalRecords / everyPage;
else
totalPage = totalRecords / everyPage + 1 ;

return totalPage;
}

private static boolean hasPrePage(int currentPage){
return currentPage == 1 ? false : true;
}

private static boolean hasNextPage(int currentPage, int totalPage){
return currentPage == totalPage || totalPage == 0 ? false : true;
}


}



业务实现类 UserManaerImpl.java

package com.linan.service.impl;

public class UserManagerImpl implements UserManager {

private UserDAO userDAO;

public void setUserDAO(UserDAO userDAO) {

erDAO = userDAO;

}

//提供业务方法

public Result listUser(Page page) throws HibernateException,

ObjectNotFoundException {

int totalRecords = userDAO.getUserCount();

if(totalRecords == 0)

throw new ObjectNotFoundException("userNotExist", null);

page = PageUtil.createPage(page, totalRecords);

List users = userDAO.getUserByPage(page);

return new Result(page, users);

}

}


DAO数据访问实现类 UserDAOImpl.java

package com.linan.dao.impl;

public class UserDAOImpl implements UserDAO {

...........

public List getUserByPage(Page page) throws HibernateException {

String querySentence = "FROM user in class erlist";

Query query = getSession().createQuery(querySentence);

//实现分页功能

query.setFirstResult(page.getBeginIndex())

.setMaxResults(page.getEveryPage());

return query.list();

}


}

表现层Structs中的Action UserdisplayAction.java

package com.linan.struts.action;

public class UserdisplayAction extends Action {

public ActionForward execute(
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) {

Page page=new Page();

UserManagerImpl userManager=new UserManagerImpl();

UserDAOImpl userDAO=new UserDAOImpl();

userManager.setUserDAO(userDAO);

//掉用业务代理完成分页

Result result=userManager.listUser(page);

List list=result

.getContent();

HttpSession session=request.getSession();

session.setAttribute("list",list);

return mapping.findForward("displayGo");

}

}