JDBC 2.0中的高级数据类型
JDBC 2.0中的高级数据类型,JDBC 2.0中的高级数据类型
例如,我们要向tbl_User表中插入用户的照片,这时就可以使用流将Blob对象导入数据库中:
String sql = "intsert into tbl_User values(?, ?)";
PreparedStatement pstmt = con.prepareStatement(sql) ;
File file = new File("C:/images/photo.jpg") ;
FileInputStream fis = new FileInputStream(file);
pstmt.setString(1, "John");
pstmt.setBinaryStream(2, fis, (int)file.length());
pstmt.executeUpdate();
pstmt.close();
fis.close();
其中SQL语句的第一个参数为用户名,第二个参数为photo,它是一个Blob型对象。这样在将数据插入数据库之后,我们就可以用程序获取该数据了:
String sql = "select photo from tbl_User where username = ?";
PreparedStatement pstmt = con.prepareStatement(selectSQL) ;
pstmt.setString(1, "John");
ResultSet rs = pstmt.executeQuery() ;
rs.next();
Blob blob = rs.getBlob("photo") ;
ImageIcon icon = new ImageIcon(blob.getBytes(1, (int)blob.length())) ;
JLabel photo = new JLabel(icon);
rs.close();
pstmt.close();
类似地,我们也可以对Clob对象进行相应的操作。下面是一个从 ASCII 流中直接将 Clob对象插入数据库中的例子:
String sql = "insert into tbl_Articles values(?,?)";
PreparedStatement pstmt = con.prepareStatement(sql) ;
File file = new File("C:/data/news.txt") ;
FileInputStream fis = new FileInputStream(file);
pstmt.setString(1, "Iraq War");
pstmt.setAsciiStream(2, fis, (int)file.length());
pstmt.executeUpdate();
pstmt.close();
fis.close();
同样,我们也可以用类似的方法将Clob对象从数据库中取出:
String sql = "select content from tbl_Articles where title = ?";
PreparedStatement pstmt = con.prepareStatement(sql) ;
pstmt.setString(1, "Iraq War");
ResultSet rs = pstmt.executeQuery() ;
rs.next() ;
Clob clob = rs.getClob("content") ;
InputStreamReader in = new InputStreamReader(clob.getAsciiStream()) ;
JTextArea text = new JTextArea(readString(in)) ;
rs.close();
pstmt.close();