JDBC Tutorials - Herong's Tutorial Examples - Version 2.21, by Dr. Herong Yang

Retrieving CLOB Values with getCharacterStream() Method

This section describes how to retrieve CLOB values with the ResultSet.getCharacterStream() method.

CLOB values can also be retrieved with the getCharacterStream() method on the ResultSet object, which will return a Reader object. Then you can read the CLOB values from the Reader object with the read() method. The sample program below shows you how to create Reader objects with the getCharacterStream() method. A utility method is included to read all characters from a Ready object and save them in a file.

/**
 * OracleClobGetCharacterStream.java
 * Copyright (c) 2007 by Dr. Herong Yang. All rights reserved.
 */
import java.io.*;
import java.sql.*;
public class OracleClobGetCharacterStream {
  public static void main(String [] args) {
    Connection con = null;
    try {
      oracle.jdbc.pool.OracleDataSource ds 
        = new oracle.jdbc.pool.OracleDataSource();
      ds.setDriverType("thin");
      ds.setServerName("localhost");
      ds.setPortNumber(1521);
      ds.setDatabaseName("XE");
      ds.setUser("Herong");
      ds.setPassword("TopSecret");
      con = ds.getConnection();


// Retrieving CLOB value with getCharacterStream()
      Statement sta = con.createStatement(); 
      ResultSet res = sta.executeQuery("SELECT * FROM Article"); 
      int i = 0;
      while (res.next() && i<3) {
        i++;
        System.out.println("Record ID: "+res.getInt("ID"));
        System.out.println("   Subject = "+res.getString("Subject"));
        Reader bodyOut = res.getCharacterStream("Body");
        String fileOut = "ClobOut_"+res.getInt("ID")+".txt";
        saveReader(fileOut,bodyOut);
        bodyOut.close();
        System.out.println("   Body = (Saved in "+fileOut+")");
      }
      res.close();

      sta.close();
      con.close();
    } catch (Exception e) {
      System.err.println("Exception: "+e.getMessage());
      e.printStackTrace();
    }
  }
  public static void saveReader(String name, Reader body) {
    int c;
    try {
      Writer f = new FileWriter(name);
      while ((c=body.read())>-1) {
        f.write(c);
      }
      f.close();
    } catch (Exception e) {
      System.err.println("Exception: "+e.getMessage());
      e.printStackTrace();
    }
  }
}

The output looked correct:

C:\>java -cp .;\local\lib\ojdbc14.jar OracleClobGetCharacterStream

Record ID: 1
   Subject = Test on INSERT statement
   Body = (Saved in ClobOut_1.txt)

Record ID: 2
   Subject = Test of the setString() method
   Body = (Saved in ClobOut_2.txt)

Record ID: 3
   Subject = Test of setCharacterStream() methods
   Body = (Saved in ClobOut_3.txt)

I checked file ClobOut_3.txt. The CLOB value, the OracleClobGetCharacterStream.java, program was corrected saved.

Table of Contents

 About This Book

 JDBC (Java Database Connectivity) Introduction

 Downloading and Installing JDK - Java SE

 Installing and Running Java DB - Derby

 Derby (Java DB) JDBC Driver

 Derby (Java DB) JDBC DataSource Objects

 Java DB (Derby) - DML Statements

 Java DB (Derby) - ResultSet Objects of Queries

 Java DB (Derby) - PreparedStatement

 MySQL Installation on Windows

 MySQL JDBC Driver (MySQL Connector/J)

 MySQL - PreparedStatement

 MySQL - Reference Implementation of JdbcRowSet

 MySQL - JBDC CallableStatement

 MySQL CLOB (Character Large Object) - TEXT

 MySQL BLOB (Binary Large Object) - BLOB

 Oracle Express Edition Installation on Windows

 Oracle JDBC Drivers

 Oracle - Reference Implementation of JdbcRowSet

 Oracle - PreparedStatement

 Oracle - JBDC CallableStatement

Oracle CLOB (Character Large Object) - TEXT

 Overview of CLOB (Character Large Object)

 Create Tables with CLOB Columns

 Inserting CLOB Values with SQL INSERT Statements

 Inserting CLOB Values with setString() Method

 Inserting CLOB Values with setCharacterStream() Method

 Closing InputStream Too Early on setCharacterStream()

 Retrieving CLOB Values with getString() Method

Retrieving CLOB Values with getCharacterStream() Method

 Retrieving CLOB Values with getClob() Method

 Inserting CLOB Values with setClob() Method

 Oracle BLOB (Binary Large Object) - BLOB

 Microsoft SQL Server 2005 Express Edition

 Microsoft JDBC Driver for SQL Server - sqljdbc.jar

 Microsoft JDBC Driver - Query Statements and Result Sets

 Microsoft JDBC Driver - DatabaseMetaData Object

 Microsoft JDBC Driver - DDL Statements

 Microsoft JDBC Driver - DML Statements

 SQL Server - PreparedStatement

 SQL Server CLOB (Character Large Object) - TEXT

 SQL Server BLOB (Binary Large Object) - BLOB

 JDBC-ODBC Bridge Driver - sun.jdbc.odbc.JdbcOdbcDriver

 JDBC-ODBC Bridge Driver - Flat Text Files

 JDBC-ODBC Bridge Driver - MS Access

 JDBC-ODBC Bridge Driver - MS SQL Server

 Summary of JDBC Drivers and Database Servers

 Additional Tutorial Notes to Be Added

 References

 PDF Printing Version

Retrieving CLOB Values with getCharacterStream() Method - Updated in 2014, by Dr. Herong Yang