SQL语句的拼凑

 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 + "%");
             }