JDBC - Esempio di oggetto CallableStatement
Di seguito è riportato l'esempio, che utilizza CallableStatement insieme a quanto segue getEmpName() Procedura memorizzata MySQL -
Assicurati di aver creato questa procedura memorizzata nel tuo database EMP. Puoi usare MySQL Query Browser per farlo.
DELIMITER $$
DROP PROCEDURE IF EXISTS `EMP`.`getEmpName` $$
CREATE PROCEDURE `EMP`.`getEmpName`
(IN EMP_ID INT, OUT EMP_FIRST VARCHAR(255))
BEGIN
SELECT first INTO EMP_FIRST
FROM Employees
WHERE ID = EMP_ID;
END $$
DELIMITER ;
Questo codice di esempio è stato scritto in base all'ambiente e alla configurazione del database eseguita nei capitoli precedenti.
Copia e incolla il seguente esempio in JDBCExample.java, compila ed esegui come segue:
//STEP 1. 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;
CallableStatement stmt = null;
try{
//STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
//STEP 3: Open a connection
System.out.println("Connecting to database...");
conn = DriverManager.getConnection(DB_URL,USER,PASS);
//STEP 4: Execute a query
System.out.println("Creating statement...");
String sql = "{call getEmpName (?, ?)}";
stmt = conn.prepareCall(sql);
//Bind IN parameter first, then bind OUT parameter
int empID = 102;
stmt.setInt(1, empID); // This would set ID as 102
// Because second parameter is OUT so register it
stmt.registerOutParameter(2, java.sql.Types.VARCHAR);
//Use execute method to run stored procedure.
System.out.println("Executing stored procedure..." );
stmt.execute();
//Retrieve employee name with getXXX method
String empName = stmt.getString(2);
System.out.println("Emp Name with ID:" +
empID + " is " + empName);
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
}//end JDBCExample
Ora compiliamo l'esempio sopra come segue:
C:\>javac JDBCExample.java
C:\>
Quando corri JDBCExample, produce il seguente risultato:
C:\>java JDBCExample
Connecting to database...
Creating statement...
Executing stored procedure...
Emp Name with ID:102 is Zaid
Goodbye!
C:\>
jdbc-statements.htm