mysql,sqlserver,oracle三种数据库的大对象存取

mysql 大对象存取:
类型一般应该用mediumblod,
blob只能存2的16次方个byte,
mediumblod是24次方,
一般来说够用了.longblob是32次方有些大.
 
MYSQL默认配置只能存1M大小的文件,要修改配置,WIN版本的在mysql.ini文件中
修改max_allowed_packet,net_buffer_length等几个参数,或直接SET GLOBAL varName=value.
linux版本可以在启动参数后加-max_allowed_packet=xxM等几个参数.
 
MYSQL存大对象最好直接就setBinaryStream,又快又方便.
而不要先插入空再造型成BLOB然后再setBlob
 
例子:
import java.sql.*;
import java.io.*;
public class DBTest {
 
 
  static String driver = "org.gjt.mm.mysql.Driver";
  static String url = "jdbc:mysql://localhost:3306/test";
  static String user = "root";
  static String passwd = "passwd";
  public static void main(String[] args) throws Exception {
    Connection conn = null;
    try {
      Class.forName(driver);
      conn = DriverManager.getConnection(url,user,passwd);
      
      int op = 1;
      //插入
      if (op == 0) {
        PreparedStatement ps = conn.prepareStatement("insert into tb_file values (?,?)");
        ps.setString(1, "aaa.exe");
        InputStream in = new FileInputStream("d:/aaa.exe");
        ps.setBinaryStream(2,in,in.available());
        ps.executeUpdate();
        ps.close();
      }
      else {
        //取出
        PreparedStatement ps = conn.prepareStatement("select * from  tb_file where filename = ?");
        ps.setString(1, "aaa.exe");
        ResultSet rs = ps.executeQuery();
        rs.next();
        InputStream in = rs.getBinaryStream("filecontent");
        System.out.println(in.available());
        FileOutputStream out = new FileOutputStream("d:/bbb.exe");
        byte[] b = new byte[1024];
        int len = 0;
        while ( (len = in.read(b)) != -1) {
          out.write(b, 0, len);