JDBC
public class DBUtil {
private static Connection conn;
public static Connection getConnection(){
try {
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/fidelity";
String name = "root";
String pwd = "root";
conn = DriverManager.getConnection(url, name, pwd);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
package com.fidelity.dao;
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.fidelity.util.DBUtil;
import com.fidelity.vo.User;
//实现对表t_user的增删改查的所有代码
public class UserDAO {
public boolean save() {
return true;
}
public User findById() {
return null;
}
public ArrayList<User> findAll() {
ArrayList<User> users = new ArrayList<User>();
try {
// 连接数据库的事交给DBUtil
Connection conn = DBUtil.getConnection();
Statement stmt = conn.createStatement();
String sql = "SELECT * FROM t_user";
ResultSet rs = stmt.executeQuery(sql);
// 把查询到的数据一个一个放入到ArrayList里,准备回传
while (rs.next()) {
int id = rs.getInt(1);
String uname = rs.getString("uname");
String upwd = rs.getString(3);
User u = new User();
u.setId(id);
u.setUname(uname);
u.setUpwd(upwd);
users.add(u);
System.out.println(id + "-" + uname + "-" + upwd);
}
rs.close();
stmt.close();
// 关闭数据库的连接
DBUtil.close();
} catch (SQLException e) {
e.printStackTrace();
}
return users;
}
// public boolean isExists(User user) {
// boolean result = false;
// // 连接数据库,执行sql,获得结果,返回
// try {
// Connection conn = DBUtil.getConnection();
// Statement stmt = conn.createStatement();
// String sql = "SELECT * FROM t_user WHERE uname='"+user.getUname()+"' AND UPWD='"+user.getUpwd()+"'";
//
// System.out.println(sql);
//
//
// ResultSet rs = stmt.executeQuery(sql);
// // 判断是否存在
// if(rs.next()){
// result = true;
// }
// // close
// DBUtil.close();
//
// } catch (Exception e) {
// e.printStackTrace();
// }
// return result;
// }
public boolean isExists(User user) {
boolean result = false;
// 连接数据库,执行sql,获得结果,返回
try {
Connection conn = DBUtil.getConnection();
// 语句对象
// Statement stmt = conn.createStatement();
String sql = "SELECT * FROM t_user WHERE uname=? AND UPWD=?";
// 预编译语句对象
PreparedStatement pstmt = conn.prepareStatement(sql);
// 赋值
pstmt.setString(1, user.getUname());
pstmt.setString(2, user.getUpwd());
System.out.println(sql);
ResultSet rs = pstmt.executeQuery();
// 判断是否存在
if(rs.next()){
result = true;
}
// close
DBUtil.close();
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
public boolean insertToDb(String uname, String upwd) {
boolean result = false;
try{
Connection conn= DBUtil.getConnection();
//String sql="INSERT INTO t_user(uname,upwd) VALUES('aa','bb')";
String sql = "INSERT INTO t_user(uname,upwd) VALUES (?,?)";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, uname);
pstmt.setString(2, upwd);
int i=pstmt.executeUpdate();
if(i==1){
result=true;
}
}catch(SQLException e){
e.printStackTrace();
}
return result;
}
}