可滚动结果集与分页技术
可滚动的结果集
Statement st =
connection.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
ResultSet rs = st.executeQuery(sql);
rs.beforeFirst();//定位到第一行的前面
rs.afterLast();//定位到最后一行的下一行去，若想读数据则向前移
rs.first();//定位到第一行
rs.isFirst();//判断是不是第一行
rs.last();//定位到最后一行
rs.isLast();//判断是不是最后一行
rs.absolute(9);//定位到那一行
rs.moveToInsertRow();
public class ScrollTest {
public static void main(String[] args) throws SQLException {
scroll();
}
static void scroll() throws SQLException {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
// 2.建立连接
conn = JdbcUtils.getConnection();
st = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
ResultSet.CONCUR_READ_ONLY);
rs = st
.executeQuery("select id, name, money, birthday from user where id<10");
while (rs.next()) {
System.out.println(rs.getObject("id") + "\t"
+ rs.getObject("name") + "\t"
+ rs.getObject("birthday") + "\t"
+ rs.getObject("money"));
}
System.out.println("------------");
rs.absolute(5);//定位到第5行去
if (rs.previous()){//定位到前一行去
System.out.println(rs.getObject("id") + "\t"
+ rs.getObject("name") + "\t"
+ rs.getObject("birthday") + "\t"
+ rs.getObject("money"));
}
} finally {
JdbcUtils.free(rs, st, conn);
}
}
//用可流动的结果集进行分页
static void scroll2() throws SQLException {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
// 2.建立连接
conn = JdbcUtils.getConnection();
st = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
ResultSet.CONCUR_READ_ONLY);
rs = st
.executeQuery("select id, name, money, birthday from user");
while (rs.next()) {
System.out.println(rs.getObject("id") + "\t"
+ rs.getObject("name") + "\t"
+ rs.getObject("birthday") + "\t"
+ rs.getObject("money"));
}
System.out.println("------------");
rs.absolute(150);//定位到150行
int i = 0;
while (rs.next() && i < 10) { //向下读取10条记录
i++;
System.out.println(rs.getObject("id") + "\t"
+ rs.getObject("name") + "\t"
+ rs.getObject("birthday") + "\t"
+ rs.getObject("money"));
}
} finally {
JdbcUtils.free(rs, st, conn);
}
}
//说明，这种分页效率很低,它是由先读到内存当中去,然后再选择哪些列.这种方法就为了那些不支技分页的数据库使用的.
}