JDBC Tutorials - Herong's Tutorial Examples - 3.10, 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) HerongYang.com. 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) { e.printStackTrace(); } } }
The output looked correct:
herong> Progra~1\java\jdk1.8.0_45\bin\java -cp .;\local\lib\ojdbc14.jar OracleClobGetCharacterStream Record ID: 4 Subject = Error test of setCharacterStream() Body = (Saved in ClobOut_4.txt) Record ID: 3 Subject = Test of setCharacterStream() methods Body = (Saved in ClobOut_3.txt) Record ID: 1 Subject = Test on INSERT statement Body = (Saved in ClobOut_1.txt)
I checked file ClobOut_3.txt. The CLOB value, the OracleClobGetCharacterStream.java, program was corrected saved.
Table of Contents
JDBC (Java Database Connectivity) Introduction
Installing and Running Java DB - Derby
Derby (Java DB) JDBC DataSource Objects
Java DB (Derby) - DML Statements
Java DB (Derby) - ResultSet Objects of Queries
Java DB (Derby) - PreparedStatement
MySQL JDBC Driver (MySQL Connector/J)
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 - Reference Implementation of JdbcRowSet
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 Express Edition
Microsoft JDBC Driver for SQL Server
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