JDBC当中Scrollable和Updatable ResultSet的用法和Helloworld例子

马克-to-win：在前面的jdbc的Helloworld程序当中，我们接触了最简单的 Statement。那种Statement的光标只能向前移。意思就是访问完2，只能继续访问3，不能再回过头来访问1。还有就是当我们查询数据库的时候，我们不能同时修改数据库。但在现实生活当中，我们确实有这种需求，就是如果当我们正在查询一个数据库的时候，发现某个数据有问题，想当时就修改它。对付这种情况，sun公司专门提供了一种新的Statement。即Scrollable（可滚动的，可向前可向后）和Updatable（可更新的）的 Statement。即con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
马克- to-win：马克 java社区：防盗版实名手机尾号： 73203。

1.Update（更新） a row程序

以下这个程序就把第二条row的id更改成了“11”。

例：5.1.1

/*when do this experiment, if it is sql server，pls make sure you have a primary key in your table.*/
import java.sql.*;
public class TestMark_to_win {
    public static void main(String[] args) throws SQLException,
            ClassNotFoundException {

            Class.forName("com.mysql.jdbc.Driver");
            Connection con = java.sql.DriverManager.getConnection(
                    "jdbc:mysql://localhost:3306/test", "root", "1234");
            String s = "select * from login";
        /* A default ResultSet object is not updatable and has a cursor that
             * moves forward only. Thus, you can iterate through it only once
             * and only from the first row to the last row. It is possible to
             * produce ResultSet objects that are scrollable and/or updatable.
             */
            Statement stm = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
                            ResultSet.CONCUR_UPDATABLE);
            ResultSet rs = stm.executeQuery(s);
            /* boolean absolute(int row) Moves the cursor to the given row
             * number in this ResultSet object.who is 1? experimentally,but
             * undocumentally, the order is based on the primary key column.
             */
            rs.absolute(2);
     /* public void updateString(String columnName,string s)throws SQLException
             * Updates the designated column with a string value. The updater
             * methods are used to update column values in the current row or
             * the insert row. The updater methods do not update the underlying
             * database; instead the updateRow or insertRow methods are called
             * to update the database. */
            rs.updateString("id", "11");
            // rs.cancelRowUpdates();
            /* public void updateRow() throws SQLException Updates the
             * underlying database with the new contents of the current row of
             * this ResultSet object.*/
            rs.updateRow();
            rs.close();
            stm.close();
            con.close();
    }
}

2.insert a row程序

下面的程序在第二个row的后面插入了一个新的row（因为rs.absolute(2);）实际上，当你取回一个ResultSet后，和这个 ResultSet联系在一起的，还有一个叫InsertRow的特殊的row。它就像是一个特殊的缓冲区。rs.moveToInsertRow(); 就把你的光标指向它了，接着你把你要插入的数据先放在这个缓冲区里。当你执行rs.insertRow()的时候，这个特殊的row里的数据，就被插入到数据库当中了。

例：5.2.1

/*when do this experiment, if it is sql server，pls make sure you have a primary key in your table.*/
import java.sql.*;
public class TestMark_to_win {
    public static void main(String[] args) throws SQLException,
            ClassNotFoundException {

        Class.forName("com.mysql.jdbc.Driver");
        Connection con = java.sql.DriverManager.getConnection(
                "jdbc:mysql://localhost:3306/test", "root", "1234");
        String s = "select * from login";
        /*
         * A default ResultSet object is not updatable and has a cursor that
         * moves forward only. Thus, you can iterate through it only once and
         * only from the first row to the last row. It is possible to produce
         * ResultSet objects that are scrollable and/or updatable.
         */
        Statement stm = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
                ResultSet.CONCUR_UPDATABLE);
        ResultSet rs = stm.executeQuery(s);
        rs.absolute(2);
        /* public void moveToInsertRow() throws SQLException Moves
         * the cursor to the insert row. The current cursor position is
         * remembered while the cursor is positioned on the insert row. The
         * insert row is a special row associated with an updatable result set.
         * It is essentially a buffer where a new row may be constructed by
         * calling the updater methods prior to inserting the row into the
         * result set.
         */
        rs.moveToInsertRow();
        rs.updateString("id", "2.5");
        rs.updateString("name", "qqq");
        /* public void insertRow() throws SQLException Inserts the contents of
         * the insert row into this ResultSet object and into the database.
         */
        rs.insertRow();


        rs.close();
        stm.close();
        con.close();

    }
}