笔记1

1.要想在 jsp 中向Servlet 传递数据，要么使用超链接，要么使用表单，要么使用session来传递，用request传递不过来

<%--用session传递::Servlet页面只能接收java代码中的session对象--%>
<%
    String name = (String) request.getAttribute("name");
    session.setAttribute("name",name);
%>

<%--Servlet.java--%>
 //从jsp接收数据（用request来传递，Servlet接收不到！）
//        String name = request.getParameter("name");
//        System.out.println(name);
        String name = (String) request.getSession().getAttribute("name");
        System.out.println(name);

2.从 jsp 页面通过表单传递数据：

在Servlet中可以通过 request.getParameter("name"); 来获取

3.设置编码格式

        //设置编译格式
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

4.   1对应第一个问号，2对应第二个问号......

                String sql = "insert into renkou01(hubie,type,mianji,num,name,id,sex,nation,educate) values(?,?,?,?,?,?,?,?,?)";
                preparedStatement = null;
                preparedStatement = connection.prepareStatement(sql);
                preparedStatement.setString(1, hubie);
                preparedStatement.setString(2, type);
                preparedStatement.setString(3, mianji);
                preparedStatement.setString(4, num);
                preparedStatement.setString(5, name);
                preparedStatement.setString(6, id);
                preparedStatement.setString(7, sex);
                preparedStatement.setString(8, nation);
                preparedStatement.setString(9, educate);

            String sql = "select * from renkou01 where name=?";
            PreparedStatement preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, name);

5.判断一个字符串是否为整数

    private boolean isNumeric(String str) {
        for (int i = str.length();--i>=0;){
            if (!Character.isDigit(str.charAt(i))){
                return false;
            }
        }
        return true;
    }

6.在Servlet.java页面编写内容在浏览器中显示：

            PrintWriter write = response.getWriter();
            write.write("面积不是整数");
            write.close();   

7.模糊查询

            String name=request.getParameter("name");
            Connection connection = DBUtil.getConnection();
            String sql = "select * from renkou01 where name like ?";
//            String sql = "select * from renkou01 where name like '%"+name+"%'";
            PreparedStatement preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1,"%"+name+"%");
            ResultSet rs= preparedStatement.executeQuery();            

8.

            String name = (String) request.getSession().getAttribute("name");
            Connection connection = DBUtil.getConnection();
            String sql="update renkou01 set hubie=?,type=?,mianji=?,num=?,nation=?,educate=? where name=?";
            PreparedStatement preparedStatement=connection.prepareStatement(sql);
            preparedStatement.setString(1,hubie);
            preparedStatement.setString(2,type);
            preparedStatement.setString(3,mianji);
            preparedStatement.setString(4,num);
            preparedStatement.setString(7,name);
//            preparedStatement.setString(6,id);
//            preparedStatement.setString(5,sex);
            preparedStatement.setString(5,nation);
            preparedStatement.setString(6,educate);
            int rs=preparedStatement.executeUpdate();
            if(rs>0){
                writer.write("修改成功");
            }
            else{
                writer.write("修改失败");
            }                

 9.key键对应的值不可以修改

key键，报错为java.lang.RuntimeException: java.sql.SQLIntegrityConstraintViolationException: Duplicate entry 'XXX' for key 'XXXXX' - yuanse - 博客园 (cnblogs.com)

10.JSP中超链接传参

JSP中超链接如何传参数?_半张饭卡的博客-CSDN博客_jsp超链接传递参数

11.模糊查询

MySQL模糊查询用法大全（正则、通配符、内置函数等）__陈哈哈的博客-CSDN博客_模糊查询

12.java中字符串的分割

java字符串的拆分_Java中的字符串分割 ._铁帅的博客-CSDN博客