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Java中带条件的查询

2016-02-18 03:57 676 查看

使用的查询页面能设置复杂的查询条件。其基本原理是把查询条件转化为对应的WHERE子句，然后使用包含该WHERE子句的SQL查询数据库。下面使用tb_person表进行复杂的查询为例：

searchPerson.jsp

<%@ page language="java" pageEncoding="UTF-8" contentType="text/html;charset=UTF-8" %>
<%@ page import="java.sql.ResultSet" %>
<jsp:directive.page import="java.sql.Date"/>
<jsp:directive.page import="java.sql.Timestamp"/>
<jsp:directive.page import="com.helloweenvsfei.util.DbManager"/>
<jsp:directive.page import="com.helloweenvsfei.util.Pagination"/>
<jsp:directive.page import="java.sql.Connection"/>
<jsp:directive.page import="java.sql.Statement"/>
<jsp:directive.page import="java.sql.SQLException"/>
<%!
public String forSQL(String sql){
return sql.replace("'", "\\'");
}
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'listPerson.jsp' starting 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">
<style type="text/css">body, td, th{font-size:12px; text-align:center; }</style>
</head>
<body>
<%
request.setCharacterEncoding("UTF-8");

final int pageSize = 5;

int pageNum = 1;

try{
pageNum = new Integer(request.getParameter("pageNum"));
}catch(Exception e){}

String nameSearch = request.getParameter("name");
String sexSearch = request.getParameter("sex");
String englishNameSearch = request.getParameter("englishName");
String descriptionSearch = request.getParameter("description");
String birthdayStart = request.getParameter("birthdayStart");
String birthdayEnd = request.getParameter("birthdayEnd");

String whereClause = "";

// 模糊匹配
if(nameSearch!=null && nameSearch.trim().length()!=0){
if(whereClause.length() == 0)
whereClause += " name LIKE '%" + forSQL(nameSearch) + "%'";
else
whereClause += " AND name LIKE '%" + forSQL(nameSearch) + "%'";
}
// 精确匹配
if(sexSearch!=null && sexSearch.trim().length()!=0){
if(whereClause.length() == 0)
whereClause += " sex = '" + forSQL(sexSearch) + "' ";
else
whereClause += " AND sex = '" + forSQL(sexSearch) + "' ";
}
if(englishNameSearch!=null && englishNameSearch.trim().length()!=0){
if(whereClause.length() == 0)
whereClause += " english_name LIKE '%" + forSQL(englishNameSearch) + "%' ";
else
whereClause += " AND english_name LIKE '%" + forSQL(englishNameSearch) + "%' ";
}
if(descriptionSearch!=null && descriptionSearch.trim().length()!=0){
if(whereClause.length() == 0)
whereClause += " description LIKE '%" + forSQL(descriptionSearch) + "%' ";
else
whereClause += " AND description LIKE '%" + forSQL(descriptionSearch) + "%' ";
}
if(birthdayStart!=null && birthdayStart.trim().length()!=0){
if(whereClause.length() == 0)
whereClause += " birthday >= '" + birthdayStart + "' ";
else
whereClause += " AND birthday >= '" + birthdayStart + "' ";
}
if(birthdayEnd!=null && birthdayEnd.trim().length()!=0){
if(whereClause.length() == 0)
whereClause += " birthday <= '" + birthdayEnd + "' ";
else
whereClause += " AND birthday <= '" + birthdayEnd + "' ";
}

if(whereClause.length() != 0){
whereClause = " WHERE " + whereClause;
}

String countSQL = " SELECT count(*) FROM tb_person " + whereClause;
int recordCount = DbManager.getCount(countSQL);

int pageCount = (recordCount + pageSize) / pageSize;

String querySQL = " SELECT * FROM tb_person " + whereClause + " LIMIT " + (pageNum-1)*pageSize + ", " + pageSize;

Connection conn = null;
Statement stmt = null;
ResultSet rs = null;

try{
conn = DbManager.getConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery(querySQL);
%>
<form action="searchPerson.jsp" method=get>
<fieldset style='width:80%'>
<legend>查询条件</legend>
<table >
<tr>
<td style="text-align:right; ">姓名</td>
<td style="text-align:left; ">
<input type='text' name='name' value="${ param.name }"/>
</td>
<td style="text-align:right; ">性别</td>
<td style="text-align:left; ">
<select name='sex' />
<option value="">无限制</option>
<option value="男" ${ '男'==param.sex ? 'selected' : '' }>男</option>
<option value="女" ${ '女'==param.sex ? 'selected' : '' }>女</option>
</select>
</td>
</tr>
<tr>
<td style="text-align:right; ">英文名</td>
<td style="text-align:left; ">
<input type='text' name='englishName' value="${ param.englishName }"/>
</td>
<td style="text-align:right; ">备注</td>
<td style="text-align:left; ">
<input type='text' name='description' value="${ param.description }"/>
</td>
</tr>
<tr>
<td colspan=4>
出生日期
从 <input type='text' name='birthdayStart' onfocus="setday(birthdayStart);" value="${ param.birthdayStart }"/>
<img src="images/calendar.gif" onclick="setday(birthdayStart);" />  
到 <input type='text' name='birthdayEnd' onfocus="setday(birthdayEnd);" value="${ param.birthdayEnd }"/>
<img src="images/calendar.gif" onclick="setday(birthdayEnd);" />
</td>
</tr>
<tr>
<td colspan=4>
<input type="submit" value="提交查询">
<input type="reset" value="复位">
</td>
</tr>
</table>
</fieldset>
<br/>
<table bgcolor="#CCCCCC" cellspacing=1 cellpadding=5 width=100%>
<tr bgcolor=#DDDDDD>
<th>ID</th>
<th>姓名</th>
<th>英文名</th>
<th>性别</th>
<th>年龄</th>
<th>生日</th>
<th>备注</th>
<th>记录创建时间</th>
</tr>
<%
// 遍历结果集。rs.next() 返回结果集中是否还有下一条记录。如果有，自动滚动到下一条记录并返回 true
while(rs.next()){

int id = rs.getInt("id");   // 整形类型
int age = rs.getInt("age");

String name = rs.getString("name"); // 字符串类型
String englishName = rs.getString("english_name");
String sex = rs.getString("sex");
String description = rs.getString("description");

Date birthday = rs.getDate("birthday"); // 日期类型，只有日期信息而没有时间信息
Timestamp createTime = rs.getTimestamp("create_time"); // 时间戳类型，既有日期又有时间。

out.println("       <tr bgcolor=#FFFFFF>");
out.println("           <td>" + id + "</td>");
out.println("           <td>" + name + "</td>");
out.println("           <td>" + englishName + "</td>");
out.println("           <td>" + sex + "</td>");
out.println("           <td>" + age + "</td>");
out.println("           <td>" + birthday + "</td>");
out.println("           <td>" + description + "</td>");
out.println("           <td>" + createTime + "</td>");
out.println("       </tr>");
}
%>
</table>
<table align=right><tr><td>
<%= Pagination.getPagination(pageNum, pageCount, recordCount, request.getRequestURI()) %>
</td></tr></table><br/><br/>
<table width='100%'><tr><td style='text-align:center; '>
<br/><br/> <%= "Count SQL: " + countSQL %>
<br/><br/> <%= "Query SQL: " + querySQL %>
</td></tr></table>
</form>
<%
}catch(SQLException e){
out.println("执行SQL：" + querySQL + "时出错：" + e.getMessage());
}finally{
if(rs != null)  rs.close();
if(stmt != null)    stmt.close();
if(conn != null)    conn.close();
}
%>
<script type="text/javascript" src="js/calendar.js"></script>
</body>
</html>

实现分页的代码Pagination.java

Pagination.java

package com.helloweenvsfei.util;

public class Pagination {

/**
*
* @param pageNum
*            当前页数
* @param pageCount
*            总页数
* @param recordCount
*            总记录数
* @param pageUrl
*            页面 URL
* @return
*/
public static String getPagination(int pageNum, int pageCount,
int recordCount, String pageUrl) {

String url = pageUrl.contains("?") ? pageUrl : pageUrl + "?";
if(!url.endsWith("?") && !url.endsWith("&")){
url += "&";
}

StringBuffer buffer = new StringBuffer();
buffer.append("第 " + pageNum + "/" + pageCount + " 页 共 " + recordCount
+ " 记录 ");

buffer.append(pageNum == 1 ? " 第一页 " : " <a href='" + url
+ "pageNum=1'>第一页</a> ");
buffer.append(pageNum == 1 ? " 上一页 " : " <a href='" + url + "pageNum="
+ (pageNum - 1) + "'>上一页</a> ");
buffer.append(pageNum == pageCount ? " 下一页 " : " <a href='" + url
+ "pageNum=" + (pageNum + 1) + "'>下一页</a> ");
buffer.append(pageNum == pageCount ? " 最后一页 " : " <a href='" + url
+ "pageNum=" + pageCount + "'>最后一页</a> ");

buffer.append(" 到 <input type='text' ");
buffer.append("  name='helloweenvsfei_goto_input' ");
buffer.append("  style='width:25px; text-align:center; '> 页 ");
buffer.append(" <input type='button'");
buffer.append("  name='helloweenvsfei_goto_button' value='Go'>");

buffer.append("<script language='javascript'>");
buffer.append("function helloweenvsfei_enter(){");
buffer.append(" if(event.keyCode == 13){");
buffer.append("     helloweenvsfei_goto();");
buffer.append("     return false;");
buffer.append(" }");
buffer.append(" return true;");
buffer.append("} ");
buffer.append("function helloweenvsfei_goto(){");
buffer
.append("   var numText = document.getElementsByName('helloweenvsfei_goto_input')[0].value;");
buffer.append(" var num = parseInt(numText, 10);");
buffer.append(" if(!num){");
buffer.append("     alert('页数必须为数字');   ");
buffer.append("     return;");
buffer.append(" }");
buffer.append(" if(num<1 || num>" + pageCount + "){");
buffer.append("     alert('页数必须大于 1，且小于总页数 " + pageCount + " ');    ");
buffer.append("     return;");
buffer.append(" }");
buffer.append(" location='" + url + "pageNum=' + num;");
buffer.append("}");
buffer
.append("document.getElementsByName('helloweenvsfei_goto_input')[0].onkeypress = helloweenvsfei_enter;");
buffer
.append("document.getElementsByName('helloweenvsfei_goto_button')[0].onclick = helloweenvsfei_goto;");
buffer.append("</script>");

return buffer.toString();
}
}

数据库连接的代码DbManager.java

Dbmanager.java

package com.helloweenvsfei.util;

import java.sql.Connection;
import java.sql.Date;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Timestamp;
import java.sql.Types;

import com.mysql.jdbc.Driver;

public class DbManager {

/**
* 获取默认数据库连接
*
* @return
* @throws SQLException
*/
public static Connection getConnection() throws SQLException {
return getConnection("databaseWeb", "root", "admin");
}

/**
* 获取数据库连接
*
* @param dbName
* @param userName
* @param password
* @return
* @throws SQLException
*/
public static Connection getConnection(String dbName, String userName,
String password) throws SQLException {

String url = "jdbc:mysql://localhost:3306/" + dbName
+ "?characterEncoding=utf-8";

DriverManager.registerDriver(new Driver());

return DriverManager.getConnection(url, userName, password);
}

/**
* 设置 PreparedStatement 参数
*
* @param preStmt
* @param params
* @throws SQLException
*/
public static void setParams(PreparedStatement preStmt, Object... params)
throws SQLException {

if (params == null || params.length == 0)
return;

for (int i = 1; i <= params.length; i++) {
Object param = params[i - 1];
if (param == null) {
preStmt.setNull(i, Types.NULL);
} else if (param instanceof Integer) {
preStmt.setInt(i, (Integer) param);
} else if (param instanceof String) {
preStmt.setString(i, (String) param);
} else if (param instanceof Double) {
preStmt.setDouble(i, (Double) param);
} else if (param instanceof Long) {
preStmt.setDouble(i, (Long) param);
} else if (param instanceof Timestamp) {
preStmt.setTimestamp(i, (Timestamp) param);
} else if (param instanceof Boolean) {
preStmt.setBoolean(i, (Boolean) param);
} else if (param instanceof Date) {
preStmt.setDate(i, (Date) param);
}
}
}

/**
* 执行 SQL，返回影响的行数
*
* @param sql
* @return
* @throws SQLException
*/
public static int executeUpdate(String sql) throws SQLException {
return executeUpdate(sql, new Object[] {});
}

/**
* 带参数执行SQL，返回影响的行数
*
* @param sql
* @param params
* @return
* @throws SQLException
*/
public static int executeUpdate(String sql, Object... params)
throws SQLException {

Connection conn = null;
PreparedStatement preStmt = null;

try {
conn = getConnection();

preStmt = conn.prepareStatement(sql);

setParams(preStmt, params);

return preStmt.executeUpdate();

} finally {
if (preStmt != null)
preStmt.close();
if (conn != null)
conn.close();
}
}

/**
* 获取总数。
*
* @param sql
*            格式必须为 SELECT count(*) FROM ...
* @return
* @throws SQLException
*/
public static int getCount(String sql) throws SQLException {

Connection conn = null;
Statement stmt = null;
ResultSet rs = null;

try {
conn = getConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
rs.next();
return rs.getInt(1);
} finally {
if (rs != null)
rs.close();
if (stmt != null)
stmt.close();
if (conn != null)
conn.close();
}
}

}

注意当客户没有填写姓名时Where条件里不能出现姓名列。程序中对name参数做了判断，如果name为空则不查询name.另外还要注意吧用户填写的信息在查询结果页面上显示。程序运行效果如图所示：

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