JDBC-批处理与预备语句对象

下面是使用批处理和预备对象的典型步骤：

• 创建包含占位符的SQL语句。
• 创建预备语句对象，使用prepareStatement()方法。
• 使用setAutoCommit()设置自动上传为false。
• 添加任意SQL语句到批处理中，使用addBatch()创建语句对象。
• 使用executeBatch()执行全部的SQL语句。
• 最后，使用commit()方法上传修改。

示例代码基于之前设置的环境和数据库编写。

复制粘贴代码到JDBCExample.java，编译运行如下：

// 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

编译上述代码：

C:>javac JDBCExample.java
C:>

当你运行JDBCExample的时候，产生如下输出：

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:>