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Hibernate3的DetachedCriteria实现分页查询

2007-08-06 09:47 627 查看
Hibernate3提供了DetachedCriteria，使得我们可以在Web层构造detachedCriteria，然后调用业务层Bean，进行动态条件查询，根据这一功能，我设计了通用的抽象Bean基类和分页类支持，代码来自于Quake Wang的javaeye-core包的相应类，然后又做了很多修改。

分页支持类：

java 代码
java 代码
/**
* Created on 2005-7-12
*/
package com.javaeye.common.business;
import java.io.Serializable;
import java.util.List;
import org.hibernate.Criteria;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.criterion.DetachedCriteria;
import org.hibernate.criterion.Projections;
import org.springframework.orm.hibernate3.HibernateCallback;
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;
import com.javaeye.common.util.PaginationSupport;
public abstract class AbstractManager extends HibernateDaoSupport {
private boolean cacheQueries = false;
private String queryCacheRegion;
public void setCacheQueries(boolean cacheQueries) {
this.cacheQueries = cacheQueries;
}
public void setQueryCacheRegion(String queryCacheRegion) {
this.queryCacheRegion = queryCacheRegion;
}
public void save(final Object entity) {
getHibernateTemplate().save(entity);
}
public void persist(final Object entity) {
getHibernateTemplate().save(entity);
}
public void update(final Object entity) {
getHibernateTemplate().update(entity);
}
public void delete(final Object entity) {
getHibernateTemplate().delete(entity);
}
public Object load(final Class entity, final Serializable id) {
return getHibernateTemplate().load(entity, id);
}
public Object get(final Class entity, final Serializable id) {
return getHibernateTemplate().get(entity, id);
}
public List findAll(final Class entity) {
return getHibernateTemplate().find("from " + entity.getName());
}
public List findByNamedQuery(final String namedQuery) {
return getHibernateTemplate().findByNamedQuery(namedQuery);
}
public List findByNamedQuery(final String query, final Object parameter) {
return getHibernateTemplate().findByNamedQuery(query, parameter);
}
public List findByNamedQuery(final String query, final Object[] parameters) {
return getHibernateTemplate().findByNamedQuery(query, parameters);
}
public List find(final String query) {
return getHibernateTemplate().find(query);
}
public List find(final String query, final Object parameter) {
return getHibernateTemplate().find(query, parameter);
}
public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria) {
return findPageByCriteria(detachedCriteria, PaginationSupport.PAGESIZE, 0);
}
public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria, final int startIndex) {
return findPageByCriteria(detachedCriteria, PaginationSupport.PAGESIZE, startIndex);
}
public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria, final int pageSize,
final int startIndex) {
return (PaginationSupport) getHibernateTemplate().execute(new HibernateCallback() {
public Object doInHibernate(Session session) throws HibernateException {
Criteria criteria = detachedCriteria.getExecutableCriteria(session);
int totalCount = ((Integer) criteria.setProjection(Projections.rowCount()).uniqueResult()).intValue();
criteria.setProjection(null);
List items = criteria.setFirstResult(startIndex).setMaxResults(pageSize).list();
PaginationSupport ps = new PaginationSupport(items, totalCount, pageSize, startIndex);
return ps;
}
}, true);
}
public List findAllByCriteria(final DetachedCriteria detachedCriteria) {
return (List) getHibernateTemplate().execute(new HibernateCallback() {
public Object doInHibernate(Session session) throws HibernateException {
Criteria criteria = detachedCriteria.getExecutableCriteria(session);
return criteria.list();
}
}, true);
}
public int getCountByCriteria(final DetachedCriteria detachedCriteria) {
Integer count = (Integer) getHibernateTemplate().execute(new HibernateCallback() {
public Object doInHibernate(Session session) throws HibernateException {
Criteria criteria = detachedCriteria.getExecutableCriteria(session);
return criteria.setProjection(Projections.rowCount()).uniqueResult();
}
}, true);
return count.intValue();
}
}

render_code();

用户在web层构造查询条件detachedCriteria，和可选的startIndex，调用业务bean的相应findByCriteria方法，返回一个PaginationSupport的实例ps。

ps.getItems()得到已分页好的结果集
ps.getIndexes()得到分页索引的数组
ps.getTotalCount()得到总结果数
ps.getStartIndex()当前分页索引
ps.getNextIndex()下一页索引
ps.getPreviousIndex()上一页索引

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评论 共 46 条 发表评论
downpour 2005-07-16 00:04

连续看了两篇robbin有关DetachedCriteria的介绍，感觉真的不错，尤其是上面的示例代码，让我着实觉得该对我原来的分页查询做一下代码重构了。

我把原本我的做法也提供出来供大家讨论吧：

首先，为了实现分页查询，我封装了一个Page类：

代码
代码
/*Created on 2005-4-14*/
package org.flyware.util.page;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* @author Joa
*
*/
public class PageUtil {
private static final Log logger = LogFactory.getLog(PageUtil.class);
/**
* Use the origin page to create a new page
* @param page
* @param totalRecords
* @return
*/
public static Page createPage(Page page, int totalRecords){
return createPage(page.getEveryPage(), page.getCurrentPage(), totalRecords);
}
/**
* the basic page utils not including exception handler
* @param everyPage
* @param currentPage
* @param totalRecords
* @return page
*/
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, totalPage,
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;
}
}

render_code();

上面的这两个对象与具体的业务逻辑无关，可以独立和抽象。

面对一个具体的业务逻辑：分页查询出User，每页10个结果。具体做法如下：
1. 编写一个通用的结果存储类Result，这个类包含一个Page对象的信息，和一个结果集List：

代码
代码
/*Created on 2005-7-15*/
package com.adt.service;
import net.sf.hibernate.HibernateException;
import org.flyware.util.page.Page;
import com.adt.bo.Result;
/**
* @author Joa
*/
public interface UserManager {
public Result listUser(Page page) throws HibernateException;
}

render_code();

代码
代码
/*Created on 2005-7-15*/
package com.adt.dao;
import java.util.List;
import org.flyware.util.page.Page;
import net.sf.hibernate.HibernateException;
/**
* @author Joa
*/
public interface UserDAO extends BaseDAO {
public List getUserByName(String name) throws HibernateException;
public int getUserCount() throws HibernateException;
public List getUserByPage(Page page) throws HibernateException;
}

render_code();

代码
代码
/*Created on 2005-6-17*/
package com.adt.action.user;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.flyware.util.page.Page;
import com.adt.bo.Result;
import com.adt.service.UserService;
import com.opensymphony.xwork.Action;
/**
* @author Joa
*/
public class ListUser implements Action {
private static final Log logger = LogFactory.getLog(ListUser.class);
private UserService userService;
private Page page;
private List users;
/*
* (non-Javadoc)
*
* @see com.opensymphony.xwork.Action#execute()
*/
public String execute() throws Exception {
Result result = userService.listUser(page);
page = result.getPage();
users = result.getContent();
return SUCCESS;
}
/**
* @return Returns the page.
*/
public Page getPage() {
return page;
}
/**
* @return Returns the users.
*/
public List getUsers() {
return users;
}
/**
* @param page
*            The page to set.
*/
public void setPage(Page page) {
this.page = page;
}
/**
* @param users
*            The users to set.
*/
public void setUsers(List users) {
this.users = users;
}
/**
* @param userService
*            The userService to set.
*/
public void setUserService(UserService userService) {
this.userService = userService;
}
}

render_code();

上面的代码似乎看不出什么地方设置了page的相关初值，事实上，可以通过配置文件来进行配置，例如，我想每页显示10条记录，那么只需要：

代码
<?xml version="1.0"?>
<!DOCTYPE xwork PUBLIC "-//OpenSymphony Group//XWork 1.0//EN" "http://www.opensymphony.com/xwork/xwork-1.0.dtd">
<xwork>
<package name="user" extends="webwork-interceptors">
<!-- The default interceptor stack name -->
<default-interceptor-ref name="myDefaultWebStack"/>
<action name="listUser" class="com.adt.action.user.ListUser">
<param name="page.everyPage">10</param>
<result name="success">/user/user_list.jsp</result>
</action>
</package>
</xwork>

render_code();

这样就可以通过配置文件和OGNL的共同作用来对page对象设置初值了。并可以通过随意修改配置文件来修改每页需要显示的记录数。

注：上面的<param>的配置，还需要webwork和Spring整合的配合。

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