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Batch Processing


Batch Processing allows you to group related SQL statements into a batch and submit them with one call to the database.

When you send several SQL statements to the database at once, you reduce the amount of communication overhead, thereby improving performance.
  • JDBC drivers are not required to support this feature. You should use the DatabaseMetaData.supportsBatchUpdates() method to determine if the target database supports batch update processing. The method returns true if your JDBC driver supports this feature.
  • The addBatch() method of Statement, PreparedStatement, and CallableStatement is used to add individual statements to the batch. The executeBatch() is used to start the execution of all the statements grouped together.
  • The executeBatch() returns an array of integers, and each element of the array represents the update count for the respective update statement.
  • Just as you can add statements to a batch for processing, you can remove them with the clearBatch() method. This method removes all the statements you added with the addBatch() method. However, you cannot selectively choose which statement to remove.
Batching with Statement Object

Here is a typical sequence of steps to use Batch Processing with Statment Object:
  • Create a Statement object using either createStatement() methods.
  • Set auto-commit to false using setAutoCommit().
  • Add as many as SQL statements you like into batch using addBatch() method on created statement object.
  • Execute all the SQL statements using executeBatch() method on created statement object.
  • Finally, commit all the changes using commit() method.
Example

The following code snippet provides an example of a batch update using Statement object:

// Create statement object
Statement stmt = conn.createStatement();
// Set auto-commit to false
conn.setAutoCommit(false);
// Create SQL statement
String SQL = "INSERT INTO Employees (id, first, last, age) " +
"VALUES(200,'Zia', 'Ali', 30)";
// Add above SQL statement in the batch.
stmt.addBatch(SQL);
// Create one more SQL statement
String SQL = "INSERT INTO Employees (id, first, last, age) " +
"VALUES(201,'Raj', 'Kumar', 35)";
// Add above SQL statement in the batch.
stmt.addBatch(SQL);
// Create one more SQL statement
String SQL = "UPDATE Employees SET age = 35 " +
"WHERE id = 100";
// Add above SQL statement in the batch.
stmt.addBatch(SQL);
// Create an int[] to hold returned values
int[] count = stmt.executeBatch();
//Explicitly commit statements to apply changes
conn.commit();

For a better understanding, let us study the Batching - Example Code as discussed below.

Batching - Example Code

Here is a typical sequence of steps to use Batch Processing with Statement Object:
  1. Create a Statement object using either createStatement() methods.
  2. Set auto-commit to false using setAutoCommit().
  3. Add as many as SQL statements you like into batch using addBatch() method on created statement object.
  4. Execute all the SQL statements using executeBatch() method on created statement object.
  5. Finally, commit all the changes using commit() method.
This sample code has been written based on the environment and database setup done in the previous chapters.

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

// Import required packages
import java.sql.*;
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;
Statement stmt = 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 statement
System.out.println("Creating statement...");
stmt = conn.createStatement();
// Set auto-commit to false
conn.setAutoCommit(false);
// First, let us select all the records and display them.
printRows( stmt );
// Create SQL statement
String SQL = "INSERT INTO Employees (id, first, last, age) " +
"VALUES(200,'Zia', 'Ali', 30)";
// Add above SQL statement in the batch.
stmt.addBatch(SQL);
// Create one more SQL statement
SQL = "INSERT INTO Employees (id, first, last, age) " +
"VALUES(201,'Raj', 'Kumar', 35)";
// Add above SQL statement in the batch.
stmt.addBatch(SQL);
// Create one more SQL statement
SQL = "UPDATE Employees SET age = 35 " +
"WHERE id = 100";
// Add above SQL statement in the batch.
stmt.addBatch(SQL);
// Create an int[] to hold returned values
int[] count = stmt.executeBatch();
//Explicitly commit statements to apply changes
conn.commit();
// Again, let us select all the records and display them.
printRows( stmt );
// Clean-up environment
stmt.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(conn!=null)
conn.close();
}catch(SQLException se){
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}//end main
public static void printRows(Statement stmt) throws SQLException{
System.out.println("Displaying available rows...");
// Let us select all the records and display them.
String sql = "SELECT id, first, last, age FROM Employees";
ResultSet rs = stmt.executeQuery(sql);
while(rs.next()){
//Retrieve by column name
int id = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");
//Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
}
System.out.println();
rs.close();
}//end printRows()
}//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 statement...
Displaying available rows...
ID: 95, Age: 20, First: Sima, Last: Chug
ID: 100, Age: 18, First: Zara, Last: Ali
ID: 101, Age: 25, First: Mahnaz, Last: Fatma
ID: 102, Age: 30, First: Zaid, Last: Khan
ID: 103, Age: 30, First: Sumit, Last: Mittal
ID: 110, Age: 20, First: Sima, Last: Chug
Displaying available rows...
ID: 95, Age: 20, First: Sima, Last: Chug
ID: 100, Age: 35, First: Zara, Last: Ali
ID: 101, Age: 25, First: Mahnaz, Last: Fatma
ID: 102, Age: 30, First: Zaid, Last: Khan
ID: 103, Age: 30, First: Sumit, Last: Mittal
ID: 110, Age: 20, First: Sima, Last: Chug
ID: 200, Age: 30, First: Zia, Last: Ali
ID: 201, Age: 35, First: Raj, Last: Kumar
Goodbye!
C:\>

Batching with PrepareStatement Object

Here is a typical sequence of steps to use Batch Processing with PrepareStatement Object:

1. Create SQL statements with placeholders.
2. Create PrepareStatement object using either prepareStatement() methods.
3. Set auto-commit to false using setAutoCommit().
4. Add as many as SQL statements you like into batch using addBatch() method on created statement object.
5. Execute all the SQL statements using executeBatch() method on created statement object.
6. Finally, commit all the changes using commit() method.

The following code snippet provides an example of a batch update using PrepareStatement object:

// Create SQL statement
String SQL = "INSERT INTO Employees (id, first, last, age) " +
"VALUES(?, ?, ?, ?)";
// Create PrepareStatement object
PreparedStatemen pstmt = conn.prepareStatement(SQL);
//Set auto-commit to false
conn.setAutoCommit(false);
// Set the variables
pstmt.setInt( 1, 400 );
pstmt.setString( 2, "Pappu" );
pstmt.setString( 3, "Singh" );
pstmt.setInt( 4, 33 );
// Add it to the batch
pstmt.addBatch();
// Set the variables
pstmt.setInt( 1, 401 );
pstmt.setString( 2, "Pawan" );
pstmt.setString( 3, "Singh" );
pstmt.setInt( 4, 31 );
// Add it to the batch
pstmt.addBatch();
//add more batches
.
.
.
.
//Create an int[] to hold returned values
int[] count = stmt.executeBatch();
//Explicitly commit statements to apply changes
conn.commit();

For a better understanding, let us to study the Batching - Example Code with PrepareStatement object as discussed below.

Batching - Example Code

Here is a typical sequence of steps to use Batch Processing with PrepareStatement Object:
  • Create SQL statements with placeholders.
  • Create PrepareStatement object using either prepareStatement() methods.
  • Set auto-commit to false using setAutoCommit().
  • Add as many as SQL statements you like into batch using addBatch() method on created statement object.
  • Execute all the SQL statements using executeBatch() method on created statement object.
  • Finally, commit all the changes using commit() method.
This sample code has been written based on the environment and database setup done in the previous chapters.

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

// Import required packages
import java.sql.*;
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 stmt = 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 SQL statement
String SQL = "INSERT INTO Employees(id,first,last,age) " +
"VALUES(?, ?, ?, ?)";
// Create preparedStatemen
System.out.println("Creating statement...");
stmt = conn.prepareStatement(SQL);
// Set auto-commit to false
conn.setAutoCommit(false);
// First, let us select all the records and display them.
printRows( stmt );
// Set the variables
stmt.setInt( 1, 400 );
stmt.setString( 2, "Pappu" );
stmt.setString( 3, "Singh" );
stmt.setInt( 4, 33 );
// Add it to the batch
stmt.addBatch();
// Set the variables
stmt.setInt( 1, 401 );
stmt.setString( 2, "Pawan" );
stmt.setString( 3, "Singh" );
stmt.setInt( 4, 31 );
// Add it to the batch
stmt.addBatch();
// Create an int[] to hold returned values
int[] count = stmt.executeBatch();
//Explicitly commit statements to apply changes
conn.commit();
// Again, let us select all the records and display them.
printRows( stmt );
// Clean-up environment
stmt.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(conn!=null)
conn.close();
}catch(SQLException se){
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}//end main
public static void printRows(Statement stmt) throws SQLException{
System.out.println("Displaying available rows...");
// Let us select all the records and display them.
String sql = "SELECT id, first, last, age FROM Employees";
ResultSet rs = stmt.executeQuery(sql);
while(rs.next()){
//Retrieve by column name
int id = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");
//Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
}
System.out.println();
rs.close();
}//end printRows()
}//end JDBCExample

Now let us compile above example as follows:

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

When you run JDBCExample, it produces following result:

C:\>java JDBCExample
Connecting to database...
Creating statement...
Displaying available rows...
ID: 95, Age: 20, First: Sima, Last: Chug
ID: 100, Age: 35, First: Zara, Last: Ali
ID: 101, Age: 25, First: Mahnaz, Last: Fatma
ID: 102, Age: 30, First: Zaid, Last: Khan
ID: 103, Age: 30, First: Sumit, Last: Mittal
ID: 110, Age: 20, First: Sima, Last: Chug
ID: 200, Age: 30, First: Zia, Last: Ali
ID: 201, Age: 35, First: Raj, Last: Kumar
Displaying available rows...
ID: 95, Age: 20, First: Sima, Last: Chug
ID: 100, Age: 35, First: Zara, Last: Ali
ID: 101, Age: 25, First: Mahnaz, Last: Fatma
ID: 102, Age: 30, First: Zaid, Last: Khan
ID: 103, Age: 30, First: Sumit, Last: Mittal
ID: 110, Age: 20, First: Sima, Last: Chug
ID: 200, Age: 30, First: Zia, Last: Ali
ID: 201, Age: 35, First: Raj, Last: Kumar
ID: 400, Age: 33, First: Pappu, Last: Singh
ID: 401, Age: 31, First: Pawan, Last: Singh
Goodbye!
C:\>
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