Retrieving CLOB Values with getCharacterStream() Method

JDBC for SQL Server - Herong's Tutorial Examples

∟SQL Server CLOB (Character Large Object) - TEXT

∟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.

/* SqlServerClobGetCharacterStream.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
import java.io.*;
import java.sql.*;
public class SqlServerClobGetCharacterStream {
  public static void main(String [] args) {
    Connection con = null;
    try {
      com.microsoft.sqlserver.jdbc.SQLServerDataSource ds
        = new com.microsoft.sqlserver.jdbc.SQLServerDataSource();
      ds.setServerName("localhost");
//      ds.setPortNumber(60782);
      ds.setInstanceName("SQLEXPRESS");
      ds.setDatabaseName("AdventureWorks2019");
      ds.setUser("Herong");
      ds.setPassword("T0pSecret");
      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();
    }
  }
}

Surprisingly, the execution failed with newer versions of JDK, JDBC Driver and SQL Server:

herong> java -cp .;mssql-jdbc-9.4.1.jre16.jar \
  SqlServerClobGetCharacterStream

Record ID: 1
   Subject = Test on INSERT statement
java.io.IOException: Stream closed
  at java.io.BufferedReader.ensureOpen(BufferedReader.java:122)
  at java.io.BufferedReader.read(BufferedReader.java:179)
  at SqlServerClobGetCharacterStream.saveReader
     (SqlServerClobGetCharacterStream.java:47)
  at SqlServerClobGetCharacterStream.main
     (SqlServerClobGetCharacterStream.java:30)
   Body = (Saved in ClobOut_1.txt)

Record ID: 2
   (Same exception)

Record ID: 5
   (Same exception)

The same program was working with JDK 1.6, SQL Server 2005 and JDBC Driver 1.0:

herong> Progra~1\java\jdk1.6.0_2\bin\java \
   -cp .;sqljdbc.jar SqlServerClobGetCharacterStream

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: 7
   Subject = Test of setCharacterStream() methods
   Body = (Saved in ClobOut_7.txt)