If you have a SQL statement that needs to be executed multiple times, it is more efficient to use a JDBC PreparedStatement object to run it. JDBC PreparedStatement class supports the following main features:
- ????SQL statements PreparedStatement objects are pre-compiled on the database server side.
- ????IN parameters are supported in SQL statements in PreparedStatement objects.
- ????Batch execution mode is supported to run the run SQL statement multiple times in a single transaction.
您可以使用Connection的prepareStatement()方法建立好一個(gè)預(yù)先編譯（precompile）的SQL語句，當(dāng)中參數(shù)會(huì)變動(dòng)的部份，先指定"?"這個(gè)佔(zhàn)位字元，例如：
PreparedStatement stmt = conn.prepareStatement(
??? "INSERT INTO message VALUES(?, ?, ?, ?, ?)");
使用PreparedStatement也可以進(jìn)行批次處理，直接來看個(gè)例子就知道如何使用：
PreparedStatement stmt = conn.prepareStatement(
??? "INSERT INTO Users VALUES(?,?, ?)");
?
User[] users = ...;
for(int i=0; i<users.length; i++) {
???? stmt.setInt(1, users[i].getID());
???? stmt.setString(2, users[i].getName());
???? stmt.setString(3, users[i].getPassword());
???? stmt.addBatch( );
}
?
stmt.executeBatch();?
A PreparedStatement object should be created from a Connection object with the prepareStatement() method and executed like a regular Statement object as shown in the following program:
import java.util.*;
import java.sql.*;
import javax.sql.*;
import javax.naming.*;
public class MySqlPreparedSelect {
? public static void main(String [] args) {
??? Connection con = null;
??? try {
????? com.mysql.jdbc.jdbc2.optional.MysqlDataSource ds
??????? = new com.mysql.jdbc.jdbc2.optional.MysqlDataSource();
????? ds.setServerName("localhost");
????? ds.setPortNumber(3306);
????? ds.setDatabaseName("HerongDB");
????? ds.setUser("Herong");
????? ds.setPassword("TopSecret");
????? con = ds.getConnection();
// PreparedStatement for SELECT statement
????? PreparedStatement sta = con.prepareStatement(
"SELECT * FROM Profile WHERE ID = 2");
// Execute the PreparedStatement as a query
????? ResultSet res = sta.executeQuery();
// Get values out of the ResultSet
????? res.next();
????? String firstName = res.getString("FirstName");
????? String lastName = res.getString("LastName");
????? System.out.println("User ID 2: "+firstName+' '+lastName);
// Close ResultSet and PreparedStatement
????? res.close();
????? sta.close();
????? con.close();???????
??? } catch (Exception e) {
????? System.err.println("Exception: "+e.getMessage());
????? e.printStackTrace();
??? }
? }
}