flex通过blazeds与java实现增删改查

用的是MySQL数据库。
1，建一个userdb库，再建userinfo表，字段：id(int),username(varchar),password(varchar)。
create database userdb;
use userdb;
create table userinfo(
id int(10) not null auto_increment,
username varchar(20),
password varchar(20),
primary key(id));
2，DBConnection.java
package com.datainfo;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class DBConnection {
public static Connection getConnection() throws ClassNotFoundException,
SQLException {
Connection conn = null;
String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost:3306/userdb";
String username = "root";
String password = "mysql";
Class.forName(driver);
conn = DriverManager.getConnection(url, username, password);
return conn;
}
}
3，User.java
package com.datainfo;
public class User {
private int id;
private String username;
private String password;
public User() {

}
/**
* @return the id
*/
public int getId() {
return id;
}
/**
* @param id
* the id to set
*/
public void setId(int id) {
this.id = id;
}
/**
* @return the username
*/
public String getUsername() {
return username;
}
/**
* @param username
* the username to set
*/
public void setUsername(String username) {
this.username = username;
}
/**
* @return the password
*/
public String getPassword() {
return password;
}
/**
* @param password
* the password to set
*/
public void setPassword(String password) {
this.password = password;
}
}

4，UserDAO.java
package com.datainfo;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import com.datainfo.DBConnection;
public class UserDAO {
public ArrayList getUserList() throws ClassNotFoundExcep