JAVA学习笔记(五十五)- 元数据 MetaData和可滚动的结果集

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元数据 Meta Data

/* * 元数据 Meta Data */public class Test03 {    Connection conn = null;    PreparedStatement pstmt=null;    ResultSet rs = null;    public void test(){        conn=DBUtil.getConnection();        try {            DatabaseMetaData dbmd=conn.getMetaData();             //获取数据库元数据            System.out.println(dbmd.getDatabaseProductName());            System.out.println(dbmd.getDatabaseProductVersion());            System.out.println(dbmd.getDriverName());            System.out.println(dbmd.getDriverVersion());            pstmt=conn.prepareStatement("select username,password from user");            rs=pstmt.executeQuery();            //获取结果集元数据            ResultSetMetaData rsmd=rs.getMetaData();            System.out.println(rsmd.getColumnCount());            System.out.println(rsmd.getColumnName(1));            System.out.println(rsmd.getColumnName(2));        } catch (SQLException e) {            e.printStackTrace();        }    }    public static void main(String[] args) {        new Test03().test();    }}

可滚动的结果集

/* * 可滚动的结果集 */public class Test04 {    Connection conn = null;    PreparedStatement pstmt = null;    ResultSet rs = null;    // 读取到指定用户时插入一条记录    public void test01() {        String sql = "select * from user";        try {            conn = DBUtil.getConnection();            pstmt = conn.prepareStatement(sql,                    ResultSet.TYPE_SCROLL_INSENSITIVE,                    ResultSet.CONCUR_UPDATABLE);            rs = pstmt.executeQuery(); // 可滚动结果集，可以更新表            while (rs.next()) {                String name = rs.getString("username");                if (name.equals("tom")) {// 判断当前读取的用户                    // 将光标移动到插入行，插入行实际上就是一个缓冲区，用来准备数据                    rs.moveToInsertRow();                    rs.updateString("username", "alex");                    rs.updateString("password", "999");                    // 提交缓冲区中的数据                    rs.insertRow();                    System.out.println("插入用户成功！");                    // 将光标移动到当前行，即插入记录前的那条记录                    rs.moveToCurrentRow();                }                System.out.println(rs.getInt(1) + "," + rs.getString(2) + ","                        + rs.getString(3));            }        } catch (SQLException e) {            e.printStackTrace();        } finally {            DBUtil.closeAll(rs, pstmt, conn);        }    }    // 删除指定用户    public void test02() {        String sql = "select * from user";        try {            conn = DBUtil.getConnection();            pstmt = conn.prepareStatement(sql,                    ResultSet.TYPE_SCROLL_INSENSITIVE,                    ResultSet.CONCUR_UPDATABLE);            rs = pstmt.executeQuery();            while (rs.next()) {                String name = rs.getString("username");                if (name.equals("bbb")) {                    rs.deleteRow();// 删除当前行                    //rs.next();// 删除后将光标下移                    System.out.println("删除用户成功");                }                System.out.println(rs.getInt(1) + "," + rs.getString(2) + ","                        + rs.getString(3));            }        } catch (SQLException e) {            e.printStackTrace();        } finally {            DBUtil.closeAll(rs, pstmt, conn);        }    }    //移动游标    public void test03() {        String sql = "select * from user";        try {            conn = DBUtil.getConnection();            pstmt = conn.prepareStatement(sql,                    ResultSet.TYPE_SCROLL_INSENSITIVE,                    ResultSet.CONCUR_UPDATABLE);            rs = pstmt.executeQuery();            while (rs.next()) {                String name = rs.getString("username");                if (name.equals("s001")) {                    rs.relative(3);                }                System.out.println(rs.getInt(1) + "," + rs.getString(2) + ","                        + rs.getString(3));            }        } catch (SQLException e) {            e.printStackTrace();        } finally {            DBUtil.closeAll(rs, pstmt, conn);        }    }    public static void main(String[] args) {        new Test04().test03();    }}

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