JDBC - Lote com objeto de instrução

Aqui está uma sequência típica de etapas para usar o processamento em lote com objeto de declaração -

Crie um objeto Statement usando os métodos createStatement () .
Defina a confirmação automática como false usando setAutoCommit () .
Adicione quantas instruções SQL desejar em lote usando o método addBatch () no objeto de instrução criado.
Execute todas as instruções SQL usando o método executeBatch () no objeto de instrução criado.
Finalmente, comprometa todas as mudanças usando o método commit () .

Este código de amostra foi escrito com base na configuração do ambiente e do banco de dados feita nos capítulos anteriores.

Copie e cole o seguinte exemplo em JDBCExample.java, compile e execute da seguinte forma -

// 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

Agora vamos compilar o exemplo acima da seguinte maneira -

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

Quando você corre JDBCExample, ele produz o seguinte resultado -

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:\>

jdbc-batch-processing.htm

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