CLOB + java

原文：
http://www.experts-exchange.com/Programming/Languages/Java/Q_20274035.html?cid=335

Title:  CLOB + java
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Question: I am trying to use the sample code I found in the oracle doc's for to update my db. However, although it looks like it is updating the clob - when I check the db it is not updated see below code.

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import java.sql.*;                                           // line 1
import java.io.*;
import java.util.*;

// Importing the Oracle Jdbc driver package
// makes the code more readable
import oracle.jdbc.driver.*;

// Import this to get CLOB and BLOB classes
import oracle.sql.*;

public class test1
{
  public static void main (String args [])
       throws Exception
  {
    // Load the Oracle JDBC driver
    DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());

    // Connect to the database. You can put a database
    // name after the @ sign in the connection URL.
    Connection conn =
      DriverManager.getConnection ("jdbc:oracle:oci8:@dev", "IS5_DEV", "IS5_DEV");

    // It's faster when auto commit is off
    conn.setAutoCommit (false);                             // line 26

    // 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 but we gleefully ignore it
    }                                                       // line 38

    // Create a table containing a BLOB and a CLOB             line 40
    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')");
    stmt.execute ("INSERT INTO basic_lob_table VALUES ('two',
   '0202020202020202020202020202', 'twothreefourfivesix')");
                                                            // line 49
    System.out.println ("Dumping lobs");
 */
    // Select the lobs
    ResultSet rset = stmt.executeQuery ("SELECT * FROM is_ui_layout FOR UPDATE");
    while (rset.next ())
    {
      // Get the lobs

      CLOB clob = ((OracleResultSet)rset).getCLOB (6);

      // Print the lob contents
      //dumpClob (conn, clob);

      // Change the lob contents
      fillClob (conn, clob, 2000);
    }
                                                            // line 68
    System.out.println ("Dumping lobs again");

    rset = stmt.executeQuery ("SELECT * FROM is_ui_layout");
    while (rset.next ())
    {
      // Get the lobs

      CLOB clob = ((OracleResultSet)rset).getCLOB (6);

      // Print the lobs contents

      dumpClob (conn, clob);
    }
  }                                                         // line 82

  // Utility function to dump Clob contents
  static void dumpClob (Connection conn, CLOB clob)
    throws Exception
  {
    // get character stream to retrieve clob data
    Reader instream = clob.getCharacterStream();

    // create temporary buffer for read                        line 91
    char[] buffer = new char[10];

    // length of characters read
    int length = 0;

    // fetch data                                              line 98
    while ((length = instream.read(buffer)) != -1)
    {
      System.out.print("Read " + length + " chars: ");

      for (int i=0; i<length; i++)
        System.out.print(buffer[i]);
      System.out.println();
    }

    // Close input stream
    instream.close();
  }                                                        // line 108

                                               // line 135
   // Utility function to put data in a Clob
  static void fillClob (Connection conn, CLOB clob, long length)
    throws Exception
  {
    Writer outstream = clob.getCharacterOutputStream();

    int i = 0;
    int chunk = 10;

    while (i < length)
    {
      outstream.write(i + "hello world", 0, chunk);        // line 147

      i += chunk;
      if (length - i < chunk)
          chunk = (int) length - i;
    }
    outstream.close();
  }                                                                                                                  // line 154

}