四、大数据
1.mysql数据库也可以直至在数据库中保存大文本和大二进制数据,
Text
TINYTEXT(255)、TEXT(64k)、MEDIUMTEXT(16M)和LONGTEXT(4G)
Blob
TINYBLOB、BLOB、MEDIUMBLOB和LONGBLOB
2.JDBC去操作大文本:
~插入大文本:
ps = conn.prepareStatement("insert into Demo2Text values(null,?,?)");
ps.setString(1, "钢铁是怎样练成");
File file = new File("1.txt");
ps.setCharacterStream(2, new FileReader(file), (int) file.length());
//1.Exception in thread "main" java.lang.AbstractMethodError: com.mysql.jdbc.PreparedStatement.setCharacterStream(ILjava/io/Reader;J)V
//ps.setCharacterStream(2, new FileReader(file), file.length());第三个参数是long型的是从1.6才开始支持的,驱动里还没有开始支持。
//解决方案:ps.setCharacterStream(2, new FileReader(file), (int)file.length());
//2.Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
//文件大小过大,导致PreparedStatement中数据多大占用内存,内存溢出
//-Xms256M-Xmx256M
//3.com.mysql.jdbc.PacketTooBigException: Packet for query is too large (10886466 > 1048576). You can change this value on the server by setting the max_allowed_packet' variable.
//数据库连接传输用的包不够大,传输大文本时报此错误
//在my.ini中配置max_allowed_packet指定包的大小
~查询大文本:
Reader rd = rs.getCharacterStream("content");
3.JDBC操作大二进制
~插入:
ps = conn.prepareStatement("insert into Demo3Blob values(null,?,?)");
ps.setString(1, "梦想的力量");
File file = new File("1.mp3");
ps.setBinaryStream(2, new FileInputStream(file), (int) file.length());
~查询
InputStream in = rs.getBinaryStream("content");