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String,StringBuilder,StringBuffer的區別

package 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 java.util.List;

import javabean.User;
import utils.JDBCUtils;

public class UsersDao {
    //增加資料
    public
boolean insert(User user){ Connection con=null; Statement state=null; try { con=JDBCUtils.getCon(); state=con.createStatement(); java.util.Date birthday=user.getBirthDay(); String sqlBirthday=String.format("%tF", birthday); String sql
="insert into user(id,username,password,email,birthday) " + "values('"+user.getId()+"','" +user.getUsername()+"','" +user.getPassword()+"','" +user.getEmail()+"','" +sqlBirthday+"')"; int row=state.executeUpdate(sql);
if(row>0){ return true; } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ JDBCUtils.realse(null,state,con); } return false; } //查詢全部資料 public List<User> findAllUser(){ Connection con=null; Statement state=null; ResultSet rs=null; try { con=JDBCUtils.getCon(); state=con.createStatement(); String sql="select * from user"; rs=state.executeQuery(sql); List<User> list=new ArrayList<User>(); while(rs.next()){ User user=new User(); user.setId(rs.getInt("id")); user.setUsername(rs.getString("username")); user.setPassword(rs.getString("password")); user.setEmail(rs.getString("email")); java.sql.Date birthDay=rs.getDate("birthday"); user.setBirthDay(birthDay); list.add(user); } return list; } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ JDBCUtils.realse(rs,state,con); } return null; } //根據ID查詢記錄 public User findById(int id){ Connection con=null; PreparedStatement prs=null; ResultSet rs=null; try { con=JDBCUtils.getCon(); String sql="select * from user where id=?"; prs=con.prepareStatement(sql); prs.setInt(1, id); rs=prs.executeQuery(); if(rs.next()){ User user=new User(); user.setId(rs.getInt("id")); user.setUsername(rs.getString("username")); user.setPassword(rs.getString("password")); user.setEmail(rs.getString("email")); java.sql.Date birthDay=rs.getDate("birthday"); user.setBirthDay(birthDay); return user; } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ JDBCUtils.realse(rs,prs,con); } return null; } //根據ID修改 public boolean update(User user){ Connection con=null; PreparedStatement prs=null; try { con=JDBCUtils.getCon(); String sql="update user set username=?,password=? where id=?"; prs=con.prepareStatement(sql); prs.setString(1, user.getUsername()); prs.setString(2, user.getPassword()); prs.setInt(3, user.getId()); int row=prs.executeUpdate(); if(row>0){ return true; } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ JDBCUtils.realse(null,prs,con); } return false; } //刪除根據Id public boolean deleteById(int id){ Connection con=null; PreparedStatement prs=null; try { con=JDBCUtils.getCon(); String sql="delete from user where id=?"; prs=con.prepareStatement(sql); prs.setInt(1, id); int row=prs.executeUpdate(); if(row>0){ return true; } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ JDBCUtils.realse(null,prs,con); } return false; } } 複製程式碼 複製程式碼 package javabean; import java.util.Date; public class User { private int id; private String username; private String password; private String email; private Date birthDay; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public Date getBirthDay() { return birthDay; } public void setBirthDay(Date birthDay) { this.birthDay = birthDay; } } 複製程式碼 複製程式碼 package utils; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; public class JDBCUtils { public static Connection getCon(){ try { Class.forName("com.mysql.jdbc.Driver"); Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbc","root","root"); return con; } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } return null; } //關閉連線 public static void realse(ResultSet rs,Statement state,Connection con){ try { if(rs !=null){ rs.close(); } if(state !=null){ state.close(); } if(con !=null){ con.close(); } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } } 複製程式碼 複製程式碼 package Test; import java.util.Date; import dao.UsersDao; import javabean.User; public class InsTest { public static void main(String[] args) { UsersDao dao=new UsersDao(); User user=new User(); user.setId(1); user.setUsername("zhaoqian"); user.setPassword("123456"); user.setEmail("[email protected]"); user.setBirthDay(new Date()); System.out.println(dao.insert(user)); } } 複製程式碼 複製程式碼 package Test; import java.util.ArrayList; import java.util.List; import dao.UsersDao; import javabean.User; public class ShowTest { public static void main(String[] args) { UsersDao dao=new UsersDao(); List<User> list=dao.findAllUser(); for(int i=0;i<list.size();i++){ System.out.println(list.get(i)); } } } 複製程式碼 複製程式碼 package Test; import dao.UsersDao; import javabean.User; public class ShowOneTest { public static void main(String[] args) { UsersDao dao=new UsersDao(); User u=dao.findById(1); System.out.println(u.getUsername()); } } 複製程式碼 複製程式碼 package Test; import dao.UsersDao; import javabean.User; public class UpdateTest { public static void main(String[] args) { UsersDao dao=new UsersDao(); User user=new User(); user.setId(1); user.setUsername("zhangsan"); user.setPassword("zhangsan123"); System.out.println(dao.update(user)); } } 複製程式碼 複製程式碼 package Test; import dao.UsersDao; public class DelectTest { public static void main(String[] args) { UsersDao dao=new UsersDao(); System.out.println(dao.deleteById(1)); } }