大家好,又见面了,我是你们的朋友全栈君。
最近在做项目的时候,对java连接到数据库小有体会,特此来写一篇博客给大家讲解在java中如何连接使用数据库。来展示下效果图:
首先,我们来编写关于数据库里的数据操作,包括基本的增删查改以及增加的功能。我在数据库里定义了一个info库,并在库里添加了player表。player表内容如下:
可以看到,表里定义了三个变量int型scores,char类型的name与password。我写了一个 MyDBConnection类,来连接数据库,代码如下:
package dates;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
public class MyDBConnection{//连接类
private String DBDriver;
private String DBURL;
private String DBUser;
private String DBPass;
private Connection conn=null;
private Statement stmt=null;
public MyDBConnection(){
DBDriver="com.mysql.jdbc.Driver";
DBURL="jdbc:mysql://localhost:3306/info";
DBUser="root";//用户名
DBPass="473721601";//数据库密码
try{
Class.forName(DBDriver);//加载驱动程序
//System.out.println("数据库驱动程序加载成功");
}catch(Exception e){
e.printStackTrace();
}
try{
conn=DriverManager.getConnection(DBURL,DBUser,DBPass);//取得连接对象
stmt=conn.createStatement();//取得SQL语句对象
System.out.print("连接数据库成功");
}catch(Exception e){
e.printStackTrace();
}
}
public Connection getMyConnection(){
return conn;
}
public Statement getMyStatement(){
return stmt;
}
public void closeMyConnection(){//关闭数据库连接
try{
stmt.close();
conn.close();
}catch(SQLException e){
e.printStackTrace();
}
}
public String toString(){
return "数据库驱动程序"+DBDriver+",链接地址"+DBURL+",用户名"+DBUser+",密码"+DBPass;
}
}
//连接类
private String DBDriver;
private String DBURL;
private String DBUser;
private String DBPass;
private Connection conn=null;
private Statement stmt=null;
public MyDBConnection(){
DBDriver="com.mysql.jdbc.Driver";
DBURL="jdbc:mysql://localhost:3306/info";
DBUser="root";//用户名
DBPass="473721601";//数据库密码
try{
Class.forName(DBDriver);//加载驱动程序
//System.out.println("数据库驱动程序加载成功");
}catch(Exception e){
e.printStackTrace();
}
try{
conn=DriverManager.getConnection(DBURL,DBUser,DBPass);//取得连接对象
stmt=conn.createStatement();//取得SQL语句对象
System.out.print("连接数据库成功");
}catch(Exception e){
e.printStackTrace();
}
}
public Connection getMyConnection(){
return conn;
}
public Statement getMyStatement(){
return stmt;
}
public void closeMyConnection(){//关闭数据库连接
try{
stmt.close();
conn.close();
}catch(SQLException e){
e.printStackTrace();
}
}
public String toString(){
return "数据库驱动程序"+DBDriver+",链接地址"+DBURL+",用户名"+DBUser+",密码"+DBPass;
}
}
数据库连接成功后会显式数据库已连接成功。
再来看看怎么样对数据库中的数据进行操作的:
public void insertData(String name,String password,int scores){//插入操作
try{
String newType1=new String(name.getBytes(),"GBK");//字节转码
String newType2=new String(password.getBytes(),"GBK");
String sql="INSERT INTO player(scores,name,password)VALUES("+scores+",'"+newType1+"','"+newType2+"')";
stmt.executeUpdate(sql);//更新语句
}catch(Exception e1){
e1.printStackTrace();
}
}
getBytes()让String对象转换为“GBK”的字节码,并可以插入到数据库中,而看sql这一句:
"INSERT INTO player(scores,name,password)VALUES("+scores+",'"+newType1+"','"+newType2+"')";
这是数据库插入操作的标准语句,意思为将scores,name,password三个数据插入到player表中,而后执行数据库的更新语句,完成插入。
删除:
public void deleteData(int mscores){
String sql="DELETE FROM player WHERE scores="+mscores+"";
System.out.print(sql);
try{
stmt.executeUpdate(sql);
//System.out.println("一条记录被删除");
}catch(SQLException e){
e.printStackTrace();
}
}
"DELETE FROM player WHERE scores="+mscores+"";
这句意思为从表里删除所有scores等于mscores的数据,在这里我删除判断条件的只有数据库里的scores是否有等于mscores的,如果还需要加条件,比如要加name判断,则代码如下:
public void deleteData(int mscores,String mname){
String sql="DELETE FROM player WHERE scores="+mscores+"&&name='"+mname+"'";
System.out.print(sql);
try{
stmt.executeUpdate(sql);
//System.out.println("一条记录被删除");
}catch(SQLException e){
e.printStackTrace();
}
}
从而语句变为从player表里删除scores等于mscores且name等于mname的所有数据。
修改;
public void updateData(int mscores,int scores,String name,String password){//修改
String sql="UPDATE player SET scores="+scores+",name='"+name+"',password='"+password+"'where scores="+mscores+"&&name='"+name+"'&&password='"+password+"'";
try{
stmt.executeUpdate(sql);
}catch(SQLException e){
e.printStackTrace();
}
}
修改了scores的数据。
查询:
public void selectPassword(){
String sql="SELECT scores,name,password FROM player";
try{
ResultSet rs=stmt.executeQuery(sql);//返回结果集
while(rs.next()){//指针向后移动
String mpassword=rs.getString("password");
System.out.print(mpassword);}}catch(Exception e){e.printStackTrace();}}
查询操作多了个结果集,来获取每组数据,并用next方法来进行“指针”后移,并用getString方法将password数据读取出来。如果要读取scores的数据。则可修改代码如下:
String mscores=rs.getShort("scores");
不同的数据类型从数据库中获取的方法不同。
说完了基本操作,来看看整个的操作类:
package dates;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class DBOperation{
private MyDBConnection myDB=null;
private Connection conn=null;
private Statement stmt=null;
private int scores;
private int number1=0;
private int number2=0;
private String name;
private String password;
public DBOperation(MyDBConnection myDB){
conn=myDB.getMyConnection();//取得对象
stmt=myDB.getMyStatement();//取得sql语句
}
public void insertData(String name,String password,int scores){
try{
String newType1=new String(name.getBytes(),"GBK");//字节转码
String newType2=new String(password.getBytes(),"GBK");
String sql="INSERT INTO player(scores,name,password)VALUES("+scores+",'"+newType1+"','"+newType2+"')";
stmt.executeUpdate(sql);//更新语句
}catch(Exception e1){
e1.printStackTrace();
}
}
public void deleteData(int scores){
String sql="DELETE FROM player WHERE scores="+scores+"";
System.out.print(sql);
try{
stmt.executeUpdate(sql);
//System.out.println("一条记录被删除");
}catch(SQLException e){
e.printStackTrace();
}
}
public void updateData(int mscores,int scores,String name,String password){//修改
String sql="UPDATE player SET scores="+scores+",name='"+name+"',password='"+password+"'where scores="+mscores+"&&name='"+name+"'&&password='"+password+"'";
try{
stmt.executeUpdate(sql);
}catch(SQLException e){
e.printStackTrace();
}
}
public boolean selectPassword(String mpassword){//查询密码
String sql="SELECT scores,name,password FROM player";
try{
ResultSet rs=stmt.executeQuery(sql);//返回结果集
while(rs.next()){//指针向后移动
password=rs.getString("password");
number2++;
//System.out.print(rs.getString("password")+" ");
if(password.equals(mpassword)&&(number2==number1)){
//System.out.print("number2:"+number2);
return true;
}
}
}catch(Exception e){
e.printStackTrace();
}
return false;
}
public boolean selectName(String mname){//查询id
String sql="SELECT scores,name,password FROM player";
try{
ResultSet rs=stmt.executeQuery(sql);//返回结果集
while(rs.next()){//指针向后移动
name=rs.getString("name");
number1++;
if(name.equals(mname)){
//System.out.print("number1:"+number1);
return true;
}
}
}catch(Exception e){
e.printStackTrace();
}
return false;
}
public int getScores(){
return scores;
}
public String getName(){
return name;
}
public String getPassword(){
return password;
}
public void setNumber1(){
number1=0;
}
public void setNumber2(){
number2=0;
}
}
代码中写了bool类型的selectName与selectPassword方法,并用number1与number2记录name与password在数据库的位置,登录操作实际的思路是在先在数据库中查找用户id,如果查到了就记录此id在第几个位置,并将位置传入selectPassword方法,进行查询密码匹配,判断密码和用户输入的密码是否相同且该密码的位置是否和id的位置相同。如果没找到该id,则提示用户注册,注册其实就是在数据库中插入数据。
下面来看看,一个简单的界面窗口类:
package ui;
import java.awt.Button;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.*;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
import dates.DBOperation;
import dates.MyDBConnection;
public class Window implements MouseListener {
public JFrame frame = new JFrame("登录窗口");
private JLabel label1=new JLabel("游戏id:");
private JTextField txt1=new JTextField();
private JLabel label2=new JLabel("密 码:");
private JTextField txt2=new JTextField();
private JButton btn1=new JButton("登陆");
private JButton btn2=new JButton("注册");
private JButton btn3=new JButton("退出");
private String text1;
private String text2;
private int distinguish;//用来记录鼠标悬停在哪个位置
MyDBConnection myDB=new MyDBConnection();
public DBOperation myOpr=new DBOperation(myDB);
public Window(){
}
public void show(){
frame.setLayout(null);//定义空布局
frame.setSize(470,300);
frame.setLocation(400, 200);
Font font=new Font("华文行楷",Font.BOLD,20);
label1.setFont(font);
label1.setForeground(Color.gray);//设置字体颜色
label2.setFont(font);
label2.setForeground(Color.gray);
txt1.setOpaque(false);//设置文本框透明
txt2.setOpaque(false);
btn1.setContentAreaFilled(false);//设置button组件透明
btn1.setFont(font);
btn1.setForeground(Color.gray);
btn1.setBorder(BorderFactory.createRaisedBevelBorder());//设置突出button组件
btn2.setContentAreaFilled(false);
btn2.setFont(font);
btn2.setBorder(BorderFactory.createRaisedBevelBorder());
btn2.setForeground(Color.gray);
btn3.setContentAreaFilled(false);
btn3.setFont(font);
btn3.setBorder(BorderFactory.createRaisedBevelBorder());
btn3.setForeground(Color.gray);
JPanel bj = new JPanel() {//设置背景
protected void paintComponent(Graphics g) {
Image bg;
try {
bg = ImageIO.read(new File("src/image/开始背景.PNG"));
g.drawImage(bg, 0, 0, getWidth(), getHeight(), null);
} catch (IOException e) {
e.printStackTrace();
}
}
};
label1.setBounds(100,50,100,100);
txt1.setBounds(180,90, 150, 20);
label2.setBounds(100,80,100,100);
txt2.setBounds(180,120, 150, 20);
btn1.setBounds(100,200,80,20);
btn2.setBounds(190,200,80,20);
btn3.setBounds(280,200,80,20);
frame.setContentPane(bj);
frame.setLayout(null);
frame.add(label1);
frame.add(txt1);
frame.add(label2);
frame.add(txt2);
frame.add(btn1);
frame.add(btn2);
frame.add(btn3);
btn1.addMouseListener(this);//添加鼠标监听
btn2.addMouseListener(this);
btn3.addMouseListener(this);
frame.setVisible(true);
}
public void mouseClicked(MouseEvent arg0) {
text1=txt1.getText();//获取用户输入数据
text2=txt2.getText();
if(distinguish==1){
if(myOpr.selectName(text1)){//登录判断
if(myOpr.selectPassword(text2)){
JOptionPane.showMessageDialog(null, "登陆成功","提示",2);
txt1.setText("");
txt2.setText("");
distinguish=4;
frame.setVisible(false);//登录成功则关闭界面
}else{
JOptionPane.showMessageDialog(null, "密码错误","提示",2);
txt2.setText("");
myOpr.setNumber1();//密码错误将number置0
myOpr.setNumber2();
}
}else{
JOptionPane.showMessageDialog(null, "此id不存在,请注册","提示",2);
txt1.setText("");
txt2.setText("");
}
}
if(distinguish==2){
String logi=(String) JOptionPane.showInputDialog(null,"请输入你的id:\n","注册",JOptionPane.PLAIN_MESSAGE,null,null,"在这输入");
String pas=(String) JOptionPane.showInputDialog(null,"请输入你的密码:\n","注册",JOptionPane.PLAIN_MESSAGE,null,null,"在这输入");
myOpr.insertData(logi,pas,0);
JOptionPane.showMessageDialog(null, "注册成功","提示",2);
}
if(distinguish==3){
int n = JOptionPane.showConfirmDialog(null, "是否退出?", "游戏结束",JOptionPane.YES_NO_OPTION);
myDB.closeMyConnection();
if(n==JOptionPane.YES_OPTION){
System.exit(1);
}
}
}
public void mouseEntered(MouseEvent arg0) {
if (arg0.getSource() == btn1) {
distinguish=1;//鼠标悬停在btn1处则把distinguish置1
btn1.setForeground(Color.red);//改变颜色
btn1.setBorder(BorderFactory.createLoweredBevelBorder());//组件凹陷
btn2.setForeground(Color.gray);
btn2.setBorder(BorderFactory.createRaisedBevelBorder());
btn3.setForeground(Color.gray);
btn3.setBorder(BorderFactory.createRaisedBevelBorder());
}
if (arg0.getSource() == btn2) {
distinguish=2;
btn1.setForeground(Color.gray);
btn1.setBorder(BorderFactory.createRaisedBevelBorder());
btn2.setForeground(Color.red);
btn2.setBorder(BorderFactory.createLoweredBevelBorder());
btn3.setForeground(Color.gray);
btn3.setBorder(BorderFactory.createRaisedBevelBorder());
}
if (arg0.getSource() == btn3) {
distinguish=3;
btn1.setForeground(Color.gray);
btn1.setBorder(BorderFactory.createRaisedBevelBorder());
btn2.setForeground(Color.gray);
btn2.setBorder(BorderFactory.createRaisedBevelBorder());
btn3.setForeground(Color.red);
btn3.setBorder(BorderFactory.createLoweredBevelBorder());
}
}
public void mouseExited(MouseEvent arg0) {//鼠标退出三个button组件后恢复
distinguish=0;
label1.setForeground(Color.gray);
label2.setForeground(Color.gray);
txt1.setOpaque(false);
txt2.setOpaque(false);
btn1.setContentAreaFilled(false);
btn1.setForeground(Color.gray);
btn1.setBorder(BorderFactory.createRaisedBevelBorder());
btn2.setContentAreaFilled(false);
btn2.setBorder(BorderFactory.createRaisedBevelBorder());
btn2.setForeground(Color.gray);
btn3.setContentAreaFilled(false);
btn3.setBorder(BorderFactory.createRaisedBevelBorder());
btn3.setForeground(Color.gray);
}
public void mousePressed(MouseEvent arg0) {
}
public void mouseReleased(MouseEvent arg0) {
}
public String getText1(){
return text1;
}
public String getText2(){
return text2;
}
public int getDistinguish(){
return distinguish;
}
}
到此为止,所有的登录界面的介绍已完成,下面是登录的背景材料和完整的代码。
代码链接:https://pan.baidu.com/s/1_AFdIFe01WKSUa0lEPD3-Q
具体的代码在这个练手的项目里:…,https://github.com/suyeq/java-fly-fight,一个飞机大战小项目
发布者:全栈程序员-用户IM,转载请注明出处:https://javaforall.cn/128659.html原文链接:https://javaforall.cn
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