分页查询实例

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;
}
}