public String query(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        /*

         * 1. 封装表单数据到Customer对象中，它只有四个属性（cname、gender、cellphone、email）

         *   它就是一个条件

         * 2. 使用Customer调用service方法，得到List<Customer>

         * 3. 保存到request域中

         * 4. 转发到list.jsp

         */

        Customer criteria = CommonUtils.toBean(request.getParameterMap(), Customer.class);

        List<Customer> cstmList = customerService.query(criteria);

        request.setAttribute("cstmList", cstmList);

        return "/list.jsp";

    }

    /**

     * 多条件组合查询

     * @param criteria

     * @return

     */

    public List<Customer> query(Customer criteria) {

        return customerDao.query(criteria);

    }

/**

 * 领域对象 与表单和数据库表对应

 *

 * @author cxf

 *

 */

public class Customer {

    /*

     * 对应数据库表

     */

    private String cid;// 主键

    private String cname;// 客户名称

    private String gender;// 客户性别

    private String birthday;// 客户生日

    private String cellphone;// 客户手机

    private String email;// 客户邮箱

    private String description;// 客户的描述

    public String getCid() {

        return cid;

    }

    public void setCid(String cid) {

        this.cid = cid;

    }

    public String getCname() {

        return cname;

    }

    public void setCname(String cname) {

        this.cname = cname;

    }

    public String getGender() {

        return gender;

    }

    public void setGender(String gender) {

        this.gender = gender;

    }

    public String getBirthday() {

        return birthday;

    }

    public void setBirthday(String birthday) {

        this.birthday = birthday;

    }

    public String getCellphone() {

        return cellphone;

    }

    public void setCellphone(String cellphone) {

        this.cellphone = cellphone;

    }

    public String getEmail() {

        return email;

    }

    public void setEmail(String email) {

        this.email = email;

    }

    public String getDescription() {

        return description;

    }

    public void setDescription(String description) {

        this.description = description;

    }

    @Override

    public String toString() {

        return "Customer [cid=" + cid + ", cname=" + cname + ", gender="

                + gender + ", birthday=" + birthday + ", cellphone="

                + cellphone + ", email=" + email + ", description="

                + description + "]";

    }

}

 /**

     * 多条件组合查询

     * @param criteria

     * @return

     */

    public List<Customer> query(Customer criteria) {

        try {

            /*

             * 1. 给出sql模板

             * 2. 给出参数

             * 3. 调用query方法，使用结果集处理器：BeanListHandler

             */

            /*

             * 一、　给出sql模板

             * 二、　给出参数！

             */

            /*

             * 1. 给出一个sql语句前半部

             */

            StringBuilder sql = new StringBuilder("select * from t_customer where 1=1");

            /*

             * 2. 判断条件，完成向sql中追加where子句

             */

            /*

             * 3. 创建一个ArrayList，用来装载参数值

             */

            List<Object> params = new ArrayList<Object>();

            String cname = criteria.getCname();

            if(cname != null && !cname.trim().isEmpty()) {

                sql.append(" and cname like ?");

                params.add("%" + cname + "%");

            }

            String gender = criteria.getGender();

            if(gender != null && !gender.trim().isEmpty()) {

                sql.append(" and gender=?");

                params.add(gender);

            }

            String cellphone = criteria.getCellphone();

            if(cellphone != null && !cellphone.trim().isEmpty()) {

                sql.append(" and cellphone like ?");

                params.add("%" + cellphone + "%");

            }

            String email = criteria.getEmail();

            if(email != null && !email.trim().isEmpty()) {

                sql.append(" and email like ?");

                params.add("%" + email + "%");

            }

            /*

             * 三、执行query

             */

            return qr.query(sql.toString(),

                    new BeanListHandler<Customer>(Customer.class),

                    params.toArray());

        } catch(SQLException e) {

            throw new RuntimeException(e);

        }

    }