ssh2通用分页

最新推荐文章于 2025-08-17 22:19:48 发布

转载最新推荐文章于 2025-08-17 22:19:48 发布 · 70 阅读

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原文链接：http://www.cnblogs.com/liuhaixu/p/3665722.html

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本文介绍了一个通用的分页查询解决方案，包括自定义Page类、利用反射获取泛型类型、使用Hibernate进行分页查询等关键步骤，并展示了如何在Service层调用这些方法。

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第一步：新建一个Page类

  1: package org.ewms2rbac.model;

2:

  3: import java.util.ArrayList;

  4: import java.util.List;

5:

  6: public class Page<T> {

  7: 	protected int pageNo = 1;

  8: 	protected int pageSize = 1;

  9: 	protected List<T> result = new ArrayList<T>();

 10: 	protected long totalCount = -1;

11:

 12: 	public Page() {

 13: 	}

14:

 15: 	public Page(final int pageSize) {

 16: 		setPageSize(pageSize);

 17: 	}

18:

 19: 	/**

 20: 	 * 获得当前页的页号,序号从1开始,默认为1.

 21: 	 */

 22: 	public int getPageNo() {

 23: 		return pageNo;

 24: 	}

25:

 26: 	/**

 27: 	 * 设置当前页的页号,序号从1开始,低于1时自动调整为1.

 28: 	 */

 29: 	public void setPageNo(final int pageNo) {

 30: 		this.pageNo = pageNo;

31:

 32: 		if (pageNo < 1) {

 33: 			this.pageNo = 1;

 34: 		}

 35: 	}

36:

 37: 	/**

 38: 	 * 获得每页的记录数量,默认为1.

 39: 	 */

 40: 	public int getPageSize() {

 41: 		return pageSize;

 42: 	}

43:

 44: 	/**

 45: 	 * 设置每页的记录数量,低于1时自动调整为1.

 46: 	 */

 47: 	public void setPageSize(final int pageSize) {

 48: 		this.pageSize = pageSize;

49:

 50: 		if (pageSize < 1) {

 51: 			this.pageSize = 1;

 52: 		}

 53: 	}

54:

 55: 	/**

 56: 	 * 根据pageNo和pageSize计算当前页第一条记录在总结果集中的位置,序号从1开始.

 57: 	 */

 58: 	public int getFirst() {

 59: 		return ((pageNo - 1) * pageSize) + 1;

 60: 	}

61:

 62: 	/**

 63: 	 * 取得页内的记录列表.

 64: 	 */

 65: 	public List<T> getResult() {

 66: 		return result;

 67: 	}

68:

 69: 	public void setResult(final List<T> result) {

 70: 		this.result = result;

 71: 	}

72:

 73: 	/**

 74: 	 * 取得总记录数, 默认值为-1.

 75: 	 */

 76: 	public long getTotalCount() {

 77: 		return totalCount;

 78: 	}

79:

 80: 	public void setTotalCount(final long totalCount) {

 81: 		this.totalCount = totalCount;

 82: 	}

83:

 84: 	/**

 85: 	 * 根据pageSize与totalCount计算总页数, 默认值为-1.

 86: 	 */

 87: 	public long getTotalPages() {

 88: 		if (totalCount < 0)

 89: 			return -1;

90:

 91: 		long count = totalCount / pageSize;

 92: 		if (totalCount % pageSize > 0) {

 93: 			count++;

 94: 		}

 95: 		return count;

 96: 	}

97:

 98: 	/**

 99: 	 * 是否还有下一页.

100: 	 */

101: 	public boolean isHasNext() {

102: 		return (pageNo + 1 <= getTotalPages());

103: 	}

104:

105: 	/**

106: 	 * 取得下页的页号, 序号从1开始. 当前页为尾页时仍返回尾页序号.

107: 	 */

108: 	public int getNextPage() {

109: 		if (isHasNext())

110: 			return pageNo + 1;

111: 		else

112: 			return pageNo;

113: 	}

114:

115: 	/**

116: 	 * 是否还有上一页.

117: 	 */

118: 	public boolean isHasPre() {

119: 		return (pageNo - 1 >= 1);

120: 	}

121:

122: 	/**

123: 	 * 取得上页的页号, 序号从1开始. 当前页为首页时返回首页序号.

124: 	 */

125: 	public int getPrePage() {

126: 		if (isHasPre())

127: 			return pageNo - 1;

128: 		else

129: 			return pageNo;

130: 	}

131: }

132:

第二步：事务不支持泛型，新建一个帮助类如果返回的是一个泛型可通过此帮助类ReflectionUtils

直接返回该泛型类，避免报错。

  1: package org.ewms2rbac.utils;

2:

  3: import java.lang.reflect.ParameterizedType;

  4: import java.lang.reflect.Type;

5:

  6: public class ReflectionUtils {

7:

  8: 	public static Class getSuperClassGenricType(final Class clazz) {

9:

 10: 		Type genType = clazz.getGenericSuperclass();

11:

 12: 		if (!(genType instanceof ParameterizedType)) {

 13: 			return Object.class;

 14: 		}

15:

 16: 		Type[] params = ((ParameterizedType) genType).getActualTypeArguments();

17:

 18: 		if (!(params[0] instanceof Class)) {

 19: 			return Object.class;

 20: 		}

21:

 22: 		return (Class) params[0];

 23: 	}

24:

 25: }

26:

第三步：创建HibernateBaseDao

  1: package org.ewms2rbac.dao;

2:

  3: import java.io.Serializable;

  4: import java.lang.reflect.ParameterizedType;

  5: import java.util.List;

6:

  7: import org.apache.commons.lang.StringUtils;

  8: import org.ewms2rbac.model.Page;

  9: import org.ewms2rbac.utils.ReflectionUtils;

 10: import org.hibernate.Criteria;

 11: import org.hibernate.Query;

 12: import org.hibernate.criterion.Criterion;

13:

 14: import org.springframework.orm.hibernate3.support.HibernateDaoSupport;

15:

 16: public class HibernateBaseDao<T, ID extends Serializable> extends

 17: 		HibernateDaoSupport {

 18: 	private Class<T> entityClass;

19:

 20: 	public HibernateBaseDao() {

 21: 		entityClass = ReflectionUtils.getSuperClassGenricType(getClass());

 22: 	}

23:

 24: 	public Query createQuery(final String queryString, final Object... values) {

 25: 		Query query = getSession().createQuery(queryString);

 26: 		if (values != null) {

 27: 			for (int i = 0; i < values.length; i++) {

 28: 				query.setParameter(i, values[i]);

 29: 			}

 30: 		}

 31: 		return query;

 32: 	}

33:

 34: 	public T findUnique(final String hql, final Object... values) {

 35: 		return (T) createQuery(hql, values).uniqueResult();

 36: 	}

 37: 	/**

 38: 	 * 按HQL分页查询.

 39: 	 *

 40: 	 * @param page

 41: 	 *            分页参数.不支持其中的orderBy参数.

 42: 	 * @param hql

 43: 	 *            hql语句.

 44: 	 * @param values

 45: 	 *            数量可变的查询参数,按顺序绑定.

 46: 	 *

 47: 	 * @return 分页查询结果, 附带结果列表及所有查询时的参数.

 48: 	 */

 49: 	@SuppressWarnings("unchecked")

 50: 	public Page<T> findPage(final Page<T> page, final String hql,

 51: 			final Object... values) {

 52: 		Query q = createQuery(hql, values);

53:

 54: 		long totalCount = countHqlResult(hql, values);

 55: 		page.setTotalCount(totalCount);

56:

 57: 		setPageParameter(q, page);

 58: 		List result = q.list();

 59: 		page.setResult(result);

 60: 		return page;

 61: 	}

62:

 63: 	/**

 64: 	 * 设置分页参数到Query对象,辅助函数.

 65: 	 */

 66: 	protected Query setPageParameter(final Query q, final Page<T> page) {

 67: 		//hibernate的firstResult的序号从0开始

 68: 		q.setFirstResult(page.getFirst() - 1);

 69: 		q.setMaxResults(page.getPageSize());

 70: 		return q;

 71: 	}

72:

 73: 	/**

 74: 	 * 执行count查询获得本次Hql查询所能获得的对象总数.

 75: 	 */

 76: 	protected long countHqlResult(final String hql, final Object... values) {

 77: 		Long count = 0L;

 78: 		String fromHql = hql;

 79: 		//select子句与order by子句会影响count查询,进行排除.

 80: 		fromHql = "from " + StringUtils.substringAfter(fromHql, "from");

 81: 		fromHql = StringUtils.substringBefore(fromHql, "order by");

82:

 83: 		String countHql = "select count(*) " + fromHql;

84:

 85: 		try {

 86: 			count = (Long)findUnique(countHql, values);

 87: 		} catch (Exception e) {

 88: 			e.printStackTrace();

 89: 		}

 90: 		return count;

 91: 	}

 92: }

93:

第四步：在service中进行查询

从Action中传过page来

  1: public Page<User> getAllUserForPage(Page<User> page)

  2: 	{

  3: 		return userDao.findPage(page, "from User u order by u.id ");

  4: 	}

转载于:https://www.cnblogs.com/liuhaixu/p/3665722.html