trimlob.java

Java示例100

/*
 * This sample shows how to trim BLOBs and CLOBs.
 * It needs jdk1.2 or later version and classes12.zip
 * It drops, creates, and populates table basic_lob_table
 * including columns of blob, clob data types in the database
 */

// You need to import the java.sql package to use JDBC
import java.sql.*;

// You need to import the oracle.sql package to use
// oracle.sql.BLOB
import oracle.sql.*;

public class TrimLob
{
  public static void main (String args []) throws SQLException
  {
    // Load the Oracle JDBC driver
    DriverManager.registerDriver(new oracle.jdbc.OracleDriver());

    String url = "jdbc:oracle:oci8:@";
    try {
      String url1 = System.getProperty("JDBC_URL");
      if (url1 != null)
        url = url1;
    } catch (Exception e) {
      // If there is any security exception, ignore it
      // and use the default
    }

    // Connect to the database
    Connection conn =
      DriverManager.getConnection (url, "hr", "hr");
    // It's faster when auto commit is off
    conn.setAutoCommit (false);

    // Create a Statement
    Statement stmt = conn.createStatement ();

    try
    {
      stmt.execute ("drop table basic_lob_table");
    }
    catch (SQLException e)
    {
      // An exception could be raised here if the
      // table did not exist already.
    }

    // Create a table containing a BLOB and a CLOB
    stmt.execute ("create table basic_lob_table (x varchar2 (30), " + 
                                 "b blob, c clob)");

    // Populate the table
    stmt.execute ("insert into basic_lob_table values ('one', " +
                  "'010101010101010101010101010101', " +
                  "'onetwothreefour')");

    // Select the lobs
    ResultSet rset = stmt.executeQuery
                          ("select * from basic_lob_table for update");
    while (rset.next ())
    {
      // Get the lobs
      BLOB blob = (BLOB) rset.getObject (2);
      CLOB clob = (CLOB) rset.getObject (3);

      // Show the original lob length
      System.out.println ("Open the lobs");
      System.out.println ("blob.length()="+blob.length());
      System.out.println ("clob.length()="+clob.length());

      // Trim the lobs
      System.out.println ("Trim the lob to legnth = 6");
      blob.trim (6);
      clob.trim (6);

      // Show the lob length after trim()
      System.out.println ("Open the lobs");
      System.out.println ("blob.length()="+blob.length());
      System.out.println ("clob.length()="+clob.length());
    }

    // Close the ResultSet
    rset.close ();

    // Close the Statement 
    stmt.close ();
  
    // Close the connection
    conn.close ();
  }
}