// Compile it by
//   javac -classpath /usr/local/pgsql/java/devpgjdbc3.jar psql_lob.java
//
// Run it by
//   java -classpath .:/usr/local/pgsql/java/devpgjdbc3.jar Hello

import java.io.*;
import java.sql.*;
import org.postgresql.largeobject.*;

class Hello
{
  public static void main(String args[]) throws Exception
  {
    Class.forName("org.postgresql.Driver");
    Connection conn = DriverManager.getConnection(
      "jdbc:postgresql://sql.csic.umd.edu/YOUR_USERNAME",
      "YOUR_USERNAME", "YOUR_PASSWROD");
    Statement stat = conn.createStatement();

    //For LargeObject API calls, they must be within a transaction
    conn.setAutoCommit(false);

    //create table, lobid
    stat.executeUpdate("CREATE TABLE hello (lobid int)");

    //create and open a PostgreSQL large object
    LargeObjectManager lobj =
                        ((org.postgresql.PGConnection)conn).getLargeObjectAPI();
    int lobid = lobj.create();
    LargeObject obj = lobj.open(lobid, LargeObjectManager.WRITE);

    //write data to the large object 
    //h+w may be very long, we divide it into short strings
    String h = "hello ", w = "world!";
    obj.write(h.getBytes(), 0, h.length());
    obj.write(w.getBytes(), 0, w.length());
    obj.close();
    
    //insert lobid
    stat.executeUpdate("INSERT INTO hello VALUES (" + lobid + ")");
    
    //select query
    ResultSet res = stat.executeQuery("SELECT * FROM hello ");
    if (res != null)
      for(; res.next();)
      {
        lobid = res.getInt(1);
        obj = lobj.open(lobid, LargeObjectManager.READ);

        byte buf[] = new byte[4];
	int n = obj.size(), k;
        for(int i = 1; i <= n; i += 4)  //get large object part by part
	{
          k = obj.read(buf, 0, 4);
          System.out.println("lob: " + new String(buf, 0, k));
	}
	obj.close();
      }
    res.close();

    stat.close();
    conn.close();
  }
}