« Previous | 1 | 2 | 3 | Next »

Streaming Data


A PreparedStatement object has the ability to use input and output streams to supply parameter data. This enables you to place entire files into database columns that can hold large values, such as CLOB and BLOB data types.

There are following methods, which can be used to stream data:
  • setAsciiStream(): This method is used to supply large ASCII values.
  • setCharacterStream(): This method is used to supply large UNICODE values.
  • setBinaryStream(): This method is used to supply large binary values.
The setXXXStream() method requires an extra parameter, the file size, besides the parameter placeholder. This parameter informs the driver how much data should be sent to the database using the stream.

Example

Consider we want to upload an XML file XML_Data.xml into a database table. Here is the content of this XML file:

<?xml version="1.0"?>
<Employee>
<id>100</id>
<first>Zara</first>
<last>Ali</last>
<Salary>10000</Salary>
<Dob>18-08-1978</Dob>
<Employee>

Keep this XML file in the same directory where you are going to run this example.

This example would create a database table XML_Data and then file XML_Data.xml would be uploaded into this table.

Copy and past the following example in JDBCExample.java, compile and run as follows:

// Import required packages
import java.sql.*;
import java.io.*;
import java.util.*;
public class JDBCExample {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost/EMP";
// Database credentials
static final String USER = "username";
static final String PASS = "password";
public static void main(String[] args) {
Connection conn = null;
PreparedStatement pstmt = null;
Statement stmt = null;
ResultSet rs = null;
try{
// Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
// Open a connection
System.out.println("Connecting to database...");
conn = DriverManager.getConnection(DB_URL,USER,PASS);
//Create a Statement object and build table
stmt = conn.createStatement();
createXMLTable(stmt);
//Open a FileInputStream
File f = new File("XML_Data.xml");
long fileLength = f.length();
FileInputStream fis = new FileInputStream(f);
//Create PreparedStatement and stream data
String SQL = "INSERT INTO XML_Data VALUES (?,?)";
pstmt = conn.prepareStatement(SQL);
pstmt.setInt(1,100);
pstmt.setAsciiStream(2,fis,(int)fileLength);
pstmt.execute();
//Close input stream
fis.close();
// Do a query to get the row
SQL = "SELECT Data FROM XML_Data WHERE id=100";
rs = stmt.executeQuery (SQL);
// Get the first row
if (rs.next ()){
//Retrieve data from input stream
InputStream xmlInputStream = rs.getAsciiStream (1);
int c;
ByteArrayOutputStream bos = new ByteArrayOutputStream();
while (( c = xmlInputStream.read ()) != -1)
bos.write(c);
//Print results
System.out.println(bos.toString());
}
// Clean-up environment
rs.close();
stmt.close();
pstmt.close();
conn.close();
}catch(SQLException se){
//Handle errors for JDBC
se.printStackTrace();
}catch(Exception e){
//Handle errors for Class.forName
e.printStackTrace();
}finally{
//finally block used to close resources
try{
if(stmt!=null)
stmt.close();
}catch(SQLException se2){
}// nothing we can do
try{
if(pstmt!=null)
pstmt.close();
}catch(SQLException se2){
}// nothing we can do
try{
if(conn!=null)
conn.close();
}catch(SQLException se){
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}//end main
public static void createXMLTable(Statement stmt)
throws SQLException{
System.out.println("Creating XML_Data table..." );
//Create SQL Statement
String streamingDataSql = "CREATE TABLE XML_Data " +
"(id INTEGER, Data LONG)";
//Drop table first if it exists.
try{
stmt.executeUpdate("DROP TABLE XML_Data");
}catch(SQLException se){
}// do nothing
//Build table.
stmt.executeUpdate(streamingDataSql);
}//end createXMLTable
}//end JDBCExample

Now let us compile the above example as follows:

C:\>javac JDBCExample.java
C:\>

When you run JDBCExample, it produces the following result:

C:\>java JDBCExample
Connecting to database...
Creating XML_Data table...
<?xml version="1.0"?>
<Employee>
<id>100</id>
<first>Zara</first>
<last>Ali</last>
<Salary>10000</Salary>
<Dob>18-08-1978</Dob>
<Employee>
Goodbye!
C:\>
« Previous | 1 | 2 | 3 | Next »


copyright © 2014 - all rights riserved by javatechnologycenter.com