Sql条件查询筛选数据

先来一个jsp效果显示图：

下面开始代码部分：

在Dao中添加一个具有安照筛选条件的查询方法：

Sql查询语句：select * from goods ( where ...........)

//通过要筛选的条件查找符合条件的商品
    public List<Goods> findFiltrate(String cate,String brand,double minPrice,double maxPrice,int page) throws SQLException {
        if(page < 1){
            page = 1;
        }
        String sql = "select * from tdb_goods";
        ArrayList<Object> plist = new ArrayList<Object>();
        //通过传入的筛选条件拼接sql查询语句（最好写在Service中，可直接传拼接好的sql语句和需要替换的参数数组Object[] params）
        if(cate != null || brand != null || (minPrice >= 0 && maxPrice > minPrice)){
            sql += " where ";
            if(cate != null){
                if(brand == null && !(minPrice >=0 && maxPrice > minPrice)){
                    sql += " goods_cate=? ";
                }else{
                    sql += " goods_cate=? and";
                }
                plist.add(cate);
            }
            if(brand != null){
                if(!(minPrice >=0 && maxPrice > minPrice)){
                    sql += " brand_name=? ";
                }else{
                    sql += " brand_name=? and";
                }
                plist.add(brand);
            }
            if(minPrice >=0 && maxPrice > minPrice){
                sql += " goods_price > ? and goods_price < ? ";
                plist.add(minPrice);
                plist.add(maxPrice);
            }
        }
        sql +=" limit ?,?";
        plist.add((page - 1) * pagesize);
        plist.add(pagesize);
        Object[] params = plist.toArray();
        QueryRunner queryRunner = new QueryRunner(JDBCUtil_DBCP.getDataSource());
        List<Goods> list = null;
        try {
            list = (List<Goods>) queryRunner.query(sql, new BeanListHandler(Goods.class),params);
        } catch (SQLException e) {
            throw new SQLException(e);
        }
        return list;
    }

Dao中省略了获取筛选条件的代码

中间省略Service（调用方法就行了）

Servlet：

import java.io.IOException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.hyl.bean.Goods;
import com.hyl.service.Service;

public class MyServlet extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");
        Service service = new Service();
        
        List<String> cate = service.findAllcate();
        List<String> brand = service.findAllbrand();
        String ncate = null;
        String nbrand = null;
        double minPrice = 0;
        double maxPrice = 0;
        if(req.getParameter("cate")==null||"All".equals(req.getParameter("cate"))){
            req.setAttribute("ncate","All");
            ncate = null;
        }else{
            ncate = req.getParameter("cate");
            req.setAttribute("ncate", ncate);
        }
        if(req.getParameter("brand")==null||"All".equals(req.getParameter("brand"))){
            req.setAttribute("nbrand","All");
            nbrand = null;
        }else{
            nbrand = req.getParameter("brand");
            req.setAttribute("nbrand", nbrand);
        }
        
        try{
            minPrice = Double.parseDouble(req.getParameter("minPrice"));
            req.setAttribute("minPrice", minPrice);
        }catch(Exception e){
            minPrice = 0;
        }
        try{
            maxPrice = Double.parseDouble(req.getParameter("maxPrice"));
            req.setAttribute("maxPrice", maxPrice);
        }catch(Exception e){
            maxPrice = 0;
        }
        int maxpage = service.getmaxPage(ncate,nbrand,minPrice,maxPrice);
        if(req.getParameter("page")==null){
            req.setAttribute("page", 1); 
        }else if(Integer.parseInt(req.getParameter("page"))>maxpage){
            req.setAttribute("page", maxpage);
        }else if(Integer.parseInt(req.getParameter("page"))==0){
            req.setAttribute("page", maxpage);
        }else{
            req.setAttribute("page", Integer.parseInt(req.getParameter("page"))); 
        }
        List<Goods> list = service.show_goos(ncate,nbrand,minPrice,maxPrice,Integer.parseInt(req.getAttribute("page").toString()));
        req.setAttribute("maxpage", maxpage); 
        req.setAttribute("list", list); 
        req.setAttribute("cate", cate); 
        req.setAttribute("brand", brand); 
        getServletContext().getRequestDispatcher("/goods.jsp").forward(req, resp);

    }
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        doPost(req, resp);
    }
}

jsp：

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>

<title>goods page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
</head>
<!-- 请忽略，include 的另一个登录的头部 -->
<jsp:include page="head.jsp"></jsp:include>
<body>
    <div align="center"><h3 style="color: blue">商&nbsp;&nbsp;品&nbsp;&nbsp;信&nbsp;&nbsp;息&nbsp;&nbsp;表</h3></div>
    <div style="margin-top: 25px" align="center">
        <form id="form_id" action="myservlet" method="post">
            <table style=" 1300px" border="1px">
                <tr>
                    <td>编号</td>
                    <td>商品</td>
                    <td>类型<select name="cate" onchange="select(1)">
                            <option>${ncate}</option>
                            <option value="All">All</option>
                            <c:forEach var="c" items="${cate}">
                                <option value="${c}">${c}</option>
                            </c:forEach>
                    </select></td>
                    <td>厂商<select name="brand" onchange="select(1)">
                            <option>${nbrand}</option>
                            <option value="All">All</option>
                            <c:forEach var="b" items="${brand}">
                                <option value="${b}">${b}</option>
                            </c:forEach>
                    </select></td>
                    <td>价格<input type="text" name="minPrice" style="50px;"
                        value="${minPrice}">--<input type="text"
                        style="50px;" name="maxPrice" value="${maxPrice}"><input
                        type="submit" value="搜索"></td>
                    <td>是否出售</td>
                    <td>是否售空</td>
                </tr>
                <c:choose>
                    <c:when test="${empty list}">
                        <tr>
                            <td colspan="7">未找到符合条件的数据</td>
                        </tr>
                    </c:when>
                    <c:otherwise>
                        <c:forEach var="g" items="${list}">
                            <tr>
                                <td>${g.goods_id}</td>
                                <td>${g.goods_name}</td>
                                <td>${g.goods_cate}</td>
                                <td>${g.brand_name}</td>
                                <td>${g.goods_price}</td>
                                <td>${g.is_show}</td>
                                <td>${g.is_saleoff}</td>
                            </tr>
                        </c:forEach>
                    </c:otherwise>
                </c:choose>
            </table>
        </form>
        <c:if test="${page!=1}">
            <span onclick="select(1)">首页</span>&nbsp;
        </c:if>
        <c:if test="${page>1}">
            <span onclick="select('${page-1}')">上一页</span>&nbsp;
        </c:if>
        <c:forEach begin="1" step="1" end="${maxpage}" var="a">
            <c:choose>
                <c:when test="${page==a}">
                    <span onclick="select('${a}')" style="color: red">${a}</span>&nbsp;
                </c:when>
                <c:otherwise>
                    <span onclick="select('${a}')">${a}</span>&nbsp;
                </c:otherwise>
            </c:choose>
        </c:forEach>
        <c:if test="${page<maxpage}">
            <span onclick="select('${page+1}')">下一页</span>&nbsp;
        </c:if>
        <c:if test="${page!=maxpage}">
            <span onclick="select('${maxpage}')">尾页</span>&nbsp;
        </c:if>
    </div>

</body>
<script type="text/javascript">
    //当select组件中值发生了变化就会调用该函数 标签的onchange属性
    function select(page) {
        var form = document.getElementById("form_id");
        form.action = "myservlet?page=" + page;
        form.submit();
    };
    
</script>
</html>

筛选结果如下：

补：模糊查找 

Sql = "select * from table where colnum like ? "
params = new Object[]{ "%" + value + "%"};//中间含有value；
params = new Object[]{ value + "%" };//以value开头；
params = new Object[]{ "%" + value };//以value结尾；

在MySql中 ‘_’ 占一个字符 '%' 占0个或者0个以上；

‘_’与‘%’可结合使用；

Over