分页查询实例
博客专区 > bharals 的博客 > 博客详情
分页查询实例
bharals 发表于7个月前
分页查询实例
  • 发表于 7个月前
  • 阅读 3
  • 收藏 0
  • 点赞 0
  • 评论 0

腾讯云 技术升级10大核心产品年终让利>>>   


package com.hao.bookstore.dao.impl;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import com.hao.bookstore.dao.DAO;
import com.hao.bookstore.db.JDBCUtils;
import com.hao.bookstore.utils.ReflectionUtils;


public class BaseDAO<T> implements DAO<T> {
	
	private QueryRunner queryRunner = new QueryRunner();

	private Class<T> clazz;
	
	public BaseDAO() {
		clazz = ReflectionUtils.getSuperGenericType(getClass());
	}
	
	@Override
	public long insert(String sql, Object... args) {
		
		long id = 0;
		
		Connection connection = null;
		PreparedStatement preparedStatement = null;
		ResultSet resultSet = null;
		
		try {
			connection = JDBCUtils.getConnection();
			preparedStatement = connection.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
			
			if(args != null){
				for(int i = 0; i < args.length; i++){
					preparedStatement.setObject(i + 1, args[i]);
				}
			}
			
			preparedStatement.executeUpdate();
			
			//获取生成的主键值
			resultSet = preparedStatement.getGeneratedKeys();
			if(resultSet.next()){
				id = resultSet.getLong(1);
			}
			
		} catch (Exception e) {
			e.printStackTrace();
		} finally{
			JDBCUtils.release(resultSet, preparedStatement);
		}
		
		return id;
	}

	@Override
	public void update(String sql, Object... args) {
		Connection connection = null;
		
		try {
			connection = JDBCUtils.getConnection();
			queryRunner.update(connection, sql, args);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	@Override
	public T query(String sql, Object... args) {
		
		Connection connection = null;
		
		try {
			connection = JDBCUtils.getConnection();
			return queryRunner.query(connection, sql, new BeanHandler<>(clazz), args);
		} catch (Exception e) {
			e.printStackTrace();
		}
		
		return null;
	}

	@Override
	public List<T> queryForList(String sql, Object... args) {
		Connection connection = null;
		
		try {
			connection = JDBCUtils.getConnection();
			return queryRunner.query(connection, sql, new BeanListHandler<>(clazz), args);
		} catch (Exception e) {
			e.printStackTrace();
		} 
		return null;
	}

	@Override
	public <V> V getSingleVal(String sql, Object... args) {
		Connection connection = null;
		
		try {
			connection = JDBCUtils.getConnection();
			return (V)queryRunner.query(connection, sql, new ScalarHandler(), args);
		} catch (Exception e) {
			e.printStackTrace();
		}
		
		return null;
	}

	@Override
	public void batch(String sql, Object[]... params) {
		Connection connection = null;
		
		try {
			connection = JDBCUtils.getConnection();
			queryRunner.batch(connection, sql, params);
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}

}

package com.hao.bookstore.dao;

import java.util.Collection;
import java.util.List;

import com.hao.bookstore.domain.Book;
import com.hao.bookstore.domain.ShoppingCartItem;
import com.hao.bookstore.web.CriteriaBook;
import com.hao.bookstore.web.Page;


public interface BookDAO {

	/**
	 * 根据 id 获取指定 Book 对象
	 * @param id
	 * @return
	 */
	public abstract Book getBook(int id);
	/**
	 * 根据传入的 CriteriaBook 对象返回对应的 Page 对象
	 * @param cb
	 * @return
	 */
	public abstract Page<Book> getPage(CriteriaBook cb);
	/**
	 * 根据传入的 CriteriaBook 对象返回其对应的记录数
	 * @param cb
	 * @return
	 */
	public abstract long getTotalBookNumber(CriteriaBook cb);
	/**
	 * 根据传入的 CriteriaBook 和 pageSize 返回当前页对应的 List 
	 * @param cb
	 * @param pageNo
	 * @param pageSize
	 * @return
	 */
	public abstract List<Book> getPageList(CriteriaBook cb,int pageSize);
	/**
	 * 返回指定 id 的 book 的 storeNumber 字段的值
	 * @param id
	 * @return
	 */
	public abstract int getStoreNumber(Integer id);
	/**
	 * 根据传入的 ShoppingCartItem 的集合, 
	 * 批量更新 books 数据表的 storenumber 和 salesnumber 字段的值
	 * @param items
	 */
	public abstract void batchUpdateStoreNumberAndSalesAmount(
			Collection<ShoppingCartItem> items);
}


package com.hao.bookstore.dao.impl;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import com.hao.bookstore.dao.BookDAO;
import com.hao.bookstore.domain.Book;
import com.hao.bookstore.domain.ShoppingCartItem;
import com.hao.bookstore.web.CriteriaBook;
import com.hao.bookstore.web.Page;


public class BookDAOImpl extends BaseDAO<Book> implements BookDAO {

	@Override
	public Book getBook(int id) {
		String sql = "SELECT id, author, title, price, publishingDate, " +
				"salesAmount, storeNumber, remark FROM mybooks WHERE id = ?";
		return query(sql, id);
	}

	//3. 
	@Override
	public Page<Book> getPage(CriteriaBook cb) {
		Page<Book> page = new Page<>(cb.getPageNo());
		
		page.setTotalItemNumber(getTotalBookNumber(cb));
		//校验 pageNo 的合法性
		cb.setPageNo(page.getPageNo());
		page.setList(getPageList(cb, 3));
		
		return page;
	}

	//1. 
	@Override
	public long getTotalBookNumber(CriteriaBook cb) {
		String sql = "SELECT count(id) FROM mybooks WHERE price >= ? AND price <= ?";
		return getSingleVal(sql, cb.getMinPrice(), cb.getMaxPrice()); 
	}

	//2. 
	/**
	 * MySQL 分页使用 LIMIT, 其中 fromIndex 从 0 开始。 
	 */
	@Override
	public List<Book> getPageList(CriteriaBook cb, int pageSize) {
		String sql = "SELECT id, author, title, price, publishingDate, " +
				"salesAmount, storeNumber, remark FROM mybooks " +
				"WHERE price >= ? AND price <= ? " +
				"LIMIT ?, ?";
		
		return queryForList(sql, cb.getMinPrice(), cb.getMaxPrice(), 
				(cb.getPageNo() - 1) * pageSize, pageSize);
	}

	@Override
	public int getStoreNumber(Integer id) {
		String sql = "SELECT storeNumber FROM mybooks WHERE id = ?";
		return getSingleVal(sql, id);
	}

	@Override
	public void batchUpdateStoreNumberAndSalesAmount(
			Collection<ShoppingCartItem> items) {
		String sql = "UPDATE mybooks SET salesAmount = salesAmount + ?, " +
				"storeNumber = storeNumber - ? " +
				"WHERE id = ?";
		Object [][] params = null;
		params = new Object[items.size()][3];
		List<ShoppingCartItem> scis = new ArrayList<>(items);
		for(int i = 0; i < items.size(); i++){
			params[i][0] = scis.get(i).getQuantity();
			params[i][1] = scis.get(i).getQuantity();
			params[i][2] = scis.get(i).getBook().getId();
		}
		batch(sql, params);
	}


}


package com.hao.bookstore.web;

import java.util.List;

public class Page<T> {
	private int pageNo;//当前第几页
	private List<T> list;//当前页的 List
	private int pageSize=3;//每页显示多少条记录
	private long totalItemNumber;//共有多少条记录
	
	public Page(int pageNo){
		super();
		this.pageNo=pageNo;
	}

	public int getPageNo() {
		if(pageNo < 0)
			pageNo = 1;
		
		if(pageNo > getTotalPageNumber()){
			pageNo = getTotalPageNumber();
		}
		return pageNo;
	}

	public void setPageNo(int pageNo) {
		this.pageNo = pageNo;
	}

	public List<T> getList() {
		return list;
	}

	public void setList(List<T> list) {
		this.list = list;
	}

	public int getPageSize() {
		return pageSize;
	}

	public void setPageSize(int pageSize) {
		this.pageSize = pageSize;
	}

	public long getTotalItemNumber() {
		return totalItemNumber;
	}

	public void setTotalItemNumber(long totalItemNumber) {
		this.totalItemNumber = totalItemNumber;
	}
	
	//获取总页数
	public int getTotalPageNumber(){
		int totalPageNumber = (int)totalItemNumber/pageSize;
		if(totalItemNumber % pageSize != 0){
			totalPageNumber++;
		}
		return totalPageNumber;
	}
	public boolean isHasNext(){
		if(getPageNo()<getTotalPageNumber()){
			return true;
		}
		return false;
	}
	public boolean isHasPrev(){
		if(getPageNo() > 1){
			return true;
		}
		return false;
	}
	public int getPrevPage(){
		if(isHasPrev()){
			return getPageNo() - 1;
		}
		
		return getPageNo();
	}
	public int getNextPage(){
		if(isHasNext()){
			return getPageNo() + 1;
		}
		
		return getPageNo();
	}
}


<pre name="code" class="java">package com.hao.bookstore.web;

public class CriteriaBook {
	private float minPrice = 0;
	private float maxPrice = Integer.MAX_VALUE;
	
	private int pageNo;

	public float getMinPrice() {
		return minPrice;
	}

	public void setMinPrice(float minPrice) {
		this.minPrice = minPrice;
	}

	public float getMaxPrice() {
		return maxPrice;
	}

	public void setMaxPrice(float maxPrice) {
		this.maxPrice = maxPrice;
	}

	public int getPageNo() {
		return pageNo;
	}

	public void setPageNo(int pageNo) {
		this.pageNo = pageNo;
	}

	public CriteriaBook(float minPrice, float maxPrice, int pageNo) {
		super();
		this.minPrice = minPrice;
		this.maxPrice = maxPrice;
		this.pageNo = pageNo;
	}
}



共有 人打赏支持
粉丝 0
博文 26
码字总数 46307
×
bharals
如果觉得我的文章对您有用,请随意打赏。您的支持将鼓励我继续创作!
* 金额(元)
¥1 ¥5 ¥10 ¥20 其他金额
打赏人
留言
* 支付类型
微信扫码支付
打赏金额:
已支付成功
打赏金额: