分页查询

package com.pojo;

public class Commodity {
    private int c_id;
    private int classify_id;
    private String c_name;
    private double price;
    private int sales;
    private int inventory;

    public int getC_id() {
        return c_id;
    }

    public void setC_id(int c_id) {
        this.c_id = c_id;
    }

    public int getClassify_id() {
        return classify_id;
    }

    public void setClassify_id(int classify_id) {
        this.classify_id = classify_id;
    }

    public String getC_name() {
        return c_name;
    }

    public void setC_name(String c_name) {
        this.c_name = c_name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public int getSales() {
        return sales;
    }

    public void setSales(int sales) {
        this.sales = sales;
    }

    public int getInventory() {
        return inventory;
    }

    public void setInventory(int inventory) {
        this.inventory = inventory;
    }

    @Override
    public String toString() {
        return "Commodity{" +
              "c_id=" + c_id +
              ", classify_id=" + classify_id +
              ", c_name=‘" + c_name + ‘\‘‘ +
              ", price=" + price +
              ", sales=" + sales +
              ", inventory=" + inventory +
              ‘}‘;
    }
}

package com.util;

import com.pojo.Commodity;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class GetSql {

    private Object obj;// 获取某个类的信息
    private Class cla;//反射获取传过来的类的信息
    private String tableName;// 数据库表名
    public GetSql(Object obj){
        this.obj = obj;
        cla = obj.getClass();
        tableName= cla.getName().substring(cla.getName().lastIndexOf(".")+1);
    }
    public static void main(String[] args) {
        GetSql gs = new GetSql(new Commodity());
        Commodity com = new Commodity();
        com.setC_name("sadfsaf");
        System.out.println(gs.getAlter(com));;
    }

    // 通过字段名获取并拼接对象对应的属性值
    private String getValues() {
        String str = "";
        String[] fields = getFields().split(",");
        try {
            for (int i = 0; i < fields.length; i++) {
                // a: 将属性名的首字母替换为大写,再加上get即为get方法名
                String a = "get" + fields[i].replaceFirst(fields[i].substring(0, 1), fields[i].substring(0, 1).toUpperCase());
                Method method = cla.getMethod(a);
                if (fields.length == 1) {

                    if (method.toString().contains("String")) {
                        str += "‘" + method.invoke(obj, null) + "‘";// 通过调用对象的方法获取返回值
                    } else {
                        str += method.invoke(obj, null);
                    }
                } else if (i == fields.length - 1) {
                    if (method.toString().contains("String")) {
                        str += "‘" + method.invoke(obj, null) + "‘";// 通过调用对象的方法获取返回值
                    } else {
                        str += method.invoke(obj, null);
                    }
                } else {
                    if (method.toString().contains("String")) {
                        str += "‘" + method.invoke(obj, null) + "‘" + ",";// 通过调用对象的方法获取返回值
                    } else {
                        str += method.invoke(obj, null) + ",";
                    }
                }
            }
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        return str;
    }

    // 获取并拼接对象的所有字段名
    private String getFields() {
        String str = "";
        // 获取所有的属性名
        Field[] fields = cla.getDeclaredFields();
        for (int i = 0; i < fields.length; i++) {
            String name = fields[i].getName();
            if (fields.length == 1) {
                str += name;
            } else if (i == fields.length - 1) {
                str += name.substring(name.lastIndexOf(".") + 1);
            } else {
                str += name.substring(name.lastIndexOf(".") + 1) + ",";
            }
        }
        return str;
    }

    // 将字段名与值进行拼接
    private String getKeyValues (){
        String[] fieldsName = getFields().split(",");
        String[] values = getValues().split(",");
        String str = "";
        for (int i = 0; i < fieldsName.length; i++) {
            if(fieldsName.length==1){
                str += fieldsName[i]+"="+values[i];
            }else if(i==fieldsName.length-1){
                str += fieldsName[i]+"="+values[i];
            }else {
                str += fieldsName[i]+"="+values[i]+" and ";
            }
        }
        return str;
    }
    // 获取添加的SQL语句
    public String getAdd(){
        return "insert into " +tableName+"("+getFields()+")"+" values("+getValues()+")";
    }
    // 获取删除的SQL语句
    public String getDelete(){
        return "delete from "+ tableName+" where "+getKeyValues();
    }
    // 获取修改的SQL语句,需传一个想要修改
    public String getAlter(Object o){
        String str = new GetSql(o).getKeyValues().replace("and",",");
        return "update "+tableName+" set "+ str +" where "+getKeyValues();
    }
}

package com.service.impl;

import com.dao.BaseDao;
import com.pojo.Commodity;
import com.service.CommodityService;

import java.util.List;

public class CommodityServiceImpl implements CommodityService {

    BaseDao bd = new BaseDao();

    // 分页获取商品信息列表
    public List<Commodity> getPageList(int pageNo, int pageSize) {
        String sql = "select * from Commodity limit "+ (pageNo-1)*pageSize+ ","+pageSize;
        List<Commodity> list = bd.display(sql);

        return list;
    }
    // 查询商品信息
    public List<Commodity> displayAll() {
        return null;
    }
    // 增加商品信息
    public boolean add(Commodity com) {
        return false;
    }
    // 根据商品id查询商品信息
    public Commodity getById() {
        return null;
    }
    // 获取商品总数量
    public int getTotalCount() {
        return 0;
    }
}

<%@ page import="com.util.PageSupport" %>
<%@ page import="com.dao.BaseDao" %>
<%@ page import="com.pojo.Commodity" %>
<%@ page import="com.service.impl.CommodityServiceImpl" %>
<%@ page import="java.util.List" %><%--
  Created by IntelliJ IDEA.
  User: zengt
  Date: 2019-09-28
  Time: 14:02
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<%
    String currentPage = request.getParameter("pageIndex");
    if(currentPage==null){
        // 首次进入
        currentPage = "1";
    }
    PageSupport ps = new PageSupport();
    BaseDao bd = new BaseDao();
    int pageIndex = Integer.parseInt(currentPage);//当前页码
    out.println(pageIndex);
    // 获取新闻总数量
    int totalCount = bd.nums();
    //每页显示几条新闻，页面容量
    int pageSize = 10;
    // 获取总页数
    ps.setCurrentRageNo(pageIndex);
    ps.setPageSize(pageSize);
    ps.setTotalCount(totalCount);
    int totalPage = ps.getTotalPageCount();

    List<Commodity> newsList = new CommodityServiceImpl().getPageList(ps.getCurrentRageNo(),pageSize);
    int i= 0;
    for(Commodity news:newsList) {
        i++;
%>
<h5>
    <%=news.getC_id() %>&nbsp;&nbsp;&nbsp;
    <%=news.getC_name() %>&nbsp;&nbsp;&nbsp;
    <%=news.getPrice() %>
</h5>
<%} %>

<a href="index.jsp?pageIndex=<%=pageIndex-1%>">上一页</a>
<a href="index.jsp?pageIndex=<%=pageIndex+1%>">下一页</a>

</body>
</html>