如下面图片所示：进行模糊查询
前端的页面代码： 注意：请选择那里的value="" 一定要写
<body><form action="SearchStuServlet" method="post"><table border="1px" width="700" align="center" ><tr > <td colspan="8">按姓名查询：<input type="text" name = "sname"> 按性别查询：<select name ="sex"><option value ="">--请选择--</option><option value ="男">男</option><option value ="女">女</option></select> <input type="submit" value="查询"> <a href="add.jsp">添加</a></td></tr>…………</table></form>
</body>
SearchStuServlet的代码：
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {try {//编码格式request.setCharacterEncoding("utf-8");//获取页面填写的信息String sname = request.getParameter("sname");String sex = request.getParameter("sex");System.out.println(sex+""+sname);//获取数据库中的数据StuService service = new StuServiceImpl();List<Student> stu = service.searchStu(sname, sex);//将获取的数据存储到session中HttpSession session = request.getSession();session.setAttribute("list", stu);//跳转页面request.getRequestDispatcher("list.jsp").forward(request, response);} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}这里要分析一下：
如果只有姓名 ，select * from stu where sname like ? ;
如果只有性别 ， select * from stu where gender = ?
如果两个都有 select * from stu where sname like ? and gender=?
如果两个都没有就查询所有。
Dao层代码：注意在这里只能用list集合来接收这个参数，因为参数的个数不是固定的
@Overridepublic List<Student> searchStudent(String sname, String sgender) throws SQLException {System.out.println("现在要执行模糊查询了，收到的name ="+sname + "==genser=="+sgender); QueryRunner runner = new QueryRunner(JDBCUtil02.getDataSource()); //String sql = "select * from stu where sname=? or sgender=?"; /** 这里要分析一下：* 如果只有姓名 ，select * from stu where sname like ? ;* 如果只有性别 ， select * from stu where gender = ?* 如果两个都有 select * from stu where sname like ? and gender=?* 如果两个都没有就查询所有。*/String sql = "select * from stu where 1=1 ";List<String> list = new ArrayList<String> (); //判断有没有姓名， 如果有，就组拼到sql语句里面if(sname!=null && sname.length()!=0){sql = sql +" and sname like ?";list.add("%"+sname+"%");}//判断有没有性别，有的话，就组拼到sql语句里面。if(sex!=null && sex.length()!=0){sql = sql +" and sex = ?";list.add(sex);}return queryRunner.query(sql, new BeanListHandler<Student>(Student.class),list.toArray());}说明：这里的runner.query()的第三个参数是可变参数，可以接收0个参数，即查询全部，可以接收一个参数，即查询性别或者姓名，可以接收两个参数，即性别和姓名连起来一起进行模糊查询 可变参数用数组接收，所以list转为数组
如果Dao层不用runner.query() 的可变的参数。直接用if else也是可以写出来模糊查询的 ，思路都是一样的
代码如下：只不过比较麻烦
/*** 模糊查询*/public List<Student> searchStu(String sname, String sex) throws SQLException {System.out.println("sanme="+sname+"sex="+sex);ComboPooledDataSource dataSource = new ComboPooledDataSource();QueryRunner queryRunner = new QueryRunner(dataSource);String sql = "select * from ddd where 1=1";//如果两个都有 select * from stu where sname like ? and gender=?if((sname!=null && sname.length()!=0)&&(sex!=null && sex.length()!=0)){sql = sql +" and sname like ? and sex=?";sname = "%"+sname+"%";return queryRunner.query(sql, new BeanListHandler<Student>(Student.class),sname,sex);}else if((sname!=null && sname.length()!=0)||(sex!=null && sex.length()!=0)){//如果只有姓名 ，select * from stu where sname like ? ;if(sname!=null && sname.length()!=0){sql = sql +" and sname like ? ";sname = "%"+sname+"%";return queryRunner.query(sql, new BeanListHandler<Student>(Student.class),sname);}// 如果只有性别 ， select * from stu where gender = ?if(sex!=null && sex.length()!=0){sql = sql +" and sex=?";return queryRunner.query(sql, new BeanListHandler<Student>(Student.class),sex);}}else{//如果两个都没有就查询所有。return queryRunner.query(sql, new BeanListHandler<Student>(Student.class));} return null;}
