JDBC Tutorials - Herong's Tutorial Examples - 3.10, by Dr. Herong Yang
Closing InputStream Too Early on setCharacterStream()
This section describes an error condition where executeUpdate() gives an exception if the Reader is closed too early.
The program in the previous tutorial worked nicely. But if you make a mistake by placing the bodyIn.close() statement before ps.executeUpdate(), you may get an IOException when ps.executeUpdate() is called. The reason is simple, reading of data from the Reader is done at the time of executeUpdate() call, not before. Here is a test program:
/* OracleClobSetCharacterStreamError.java * Copyright (c) HerongYang.com. All Rights Reserved. */ import java.io.*; import java.sql.*; public class OracleClobSetCharacterStreamError { 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(); // Deleting the record for re-testing String subject = "Error test of setCharacterStream()"; Statement sta = con.createStatement(); sta.executeUpdate("DELETE FROM Article WHERE Subject = '" +subject+"'"); // Inserting CLOB value with a PreparedStatement PreparedStatement ps = con.prepareStatement( "INSERT INTO Article (ID, Subject, Body) VALUES (4,?,?)"); ps.setString(1, subject); Reader bodyIn = new FileReader("OracleClobSetCharacterStreamError.java"); File fileIn = new File( "OracleClobSetCharacterStreamError.java"); ps.setCharacterStream(2, bodyIn, (int) fileIn.length()); // Error - Closing the Reader too early. bodyIn.close(); int count = ps.executeUpdate(); ps.close(); // Retrieving CLOB value with getString() sta = con.createStatement(); ResultSet res = sta.executeQuery("SELECT * FROM Article" +" WHERE Subject = '"+subject+"'"); res.next(); System.out.println("The inserted record: "); System.out.println(" Subject = "+res.getString("Subject")); System.out.println(" Body = " +res.getString("Body").substring(0,256)); res.close(); sta.close(); con.close(); } catch (Exception e) { e.printStackTrace(); } } }
Surprisingly, I did not get any I/O exceptions. May be the Oracle JDBC driver reads data at the time of setCharacterStream() call. The program executed correctly:
herong> Progra~1\java\jdk1.8.0_45\bin\java -cp .;\local\lib\ojdbc14.jar OracleClobSetCharacterStreamError The inserted record: Subject = Error test of setCharacterStream() Subject = Error test of setCharacterStream() Body = /* OracleClobSetCharacterStreamError.java * Copyright (c) HerongYang.com. All Rights Reserved. */ import java.io.*; import java.sql.*; public class OracleClobSetCharacterStreamError { public static void main(String [] args) { Connection con =
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