jdbc 編程
阿新 • • 發佈：2019-01-08
nal exe rda host connect rim strong .html prop
概念先參考：https://www.cnblogs.com/wuziyue/p/4827295.html
不要問為什麽，直接代碼搞起
1. com.domain 包 User 實體類
package com.domain;
public class User {
private String u_name;
private int u_age;
public String getU_name() {
return u_name;
}
public void setU_name(String u_name) {
this.u_name = u_name;
}
public int getU_age() {
return u_age;
}
public void setU_age(int u_age) {
this.u_age = u_age;
}
public User() {
}
public User(String u_name, int u_age) {
super();
this.u_name = u_name;
this.u_age = u_age;
}
@Override
public String toString() {
return "User [u_name=" + u_name + ", u_age=" + u_age + "]";
}
}
2. com.dao 包下的 IUserDao 接口
package com.dao;
import java.util.List;
import com.domain.User;
public interface IUserDao {
void addUserInfo(User user);
void deleteUserInfo(User user);
void updateUserAgeInfo(User user,int age);
User selectUserInfoByName(String name);
List<User> selectAllUserInfo();
}
3. com.dao.impl 包 UserDaoImpl 類
package com.dao.impl;
import org.junit.Test;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import com.Util.JDBCUtil;
import com.dao.IUserDao;
import com.domain.User;
public class UserDaoImpl implements IUserDao{
ResultSet rs = null;
Statement st = null;
User user = null;
/*常見的異常錯誤：No operations allowed after connection closed.
因為 當 數據庫的連接Connection是一個Static的，程序共享這一個Connection。
那麽第一次對數據庫操作沒問題，當把Connection關閉後，第二次還想操作數據庫時Connection肯定不存在了。
所以為了解決這個問題：我們最好把 創建Connection的實例寫到每個操作的方法中。
*/
/* 1. 增加用戶信息*/
@Test
public void addUserInfo(User user){
Connection conn = JDBCUtil.getInstance().getConnection();
try {
st = conn.createStatement();
int row = st.executeUpdate("insert into tb_user (id,`name`,age)values(null,‘"+user.getU_name()+"‘,"+user.getU_age()+")");
if(row > 0){
System.out.println("添加用戶成功");
}
} catch (SQLException e) {
e.printStackTrace();
}
JDBCUtil.getInstance().closeAll(rs,st,conn);
}
/*2. 刪除用戶信息*/
@Test
public void deleteUserInfo(User user) {
Connection conn = JDBCUtil.getInstance().getConnection();
try{
st = conn.createStatement();
int row = st.executeUpdate("delete from tb_user where name = ‘"+user.getU_name()+"‘");
if(row > 0){
System.out.println("刪除用戶成功");
}
}catch (Exception e) {
e.printStackTrace();
}
JDBCUtil.getInstance().closeAll(rs,st,conn);
}
/*3. 修改用戶信息*/
@Test
public void updateUserAgeInfo(User user,int age) {
Connection conn = JDBCUtil.getInstance().getConnection();
try{
st = conn.createStatement();
int row = st.executeUpdate("update tb_user set age = "+age+" where name = ‘"+user.getU_name()+"‘");
if(row > 0){
System.out.println("修改用戶信息成功");
}
}catch (Exception e) {
e.printStackTrace();
}
JDBCUtil.getInstance().closeAll(rs,st,conn);
}
/*4. 通過name查詢一個用戶信息*/
@Test
public User selectUserInfoByName(String name) {
Connection conn = JDBCUtil.getInstance().getConnection();
//這裏如果不寫，當方法3中調用次方法時，就會因為 Connection 關閉而報錯。
try{
st = conn.createStatement();
rs = st.executeQuery("select * from tb_user where `name` = ‘"+name+"‘");
while(rs.next()){
user = new User();
user.setU_name(rs.getString("name"));
user.setU_age(rs.getInt("age"));
}
}catch (Exception e) {
e.printStackTrace();
}
JDBCUtil.getInstance().closeAll(rs,st,conn);
return user;
}
/*5. 查詢所有用戶信息*/
@Override
public List<User> selectAllUserInfo() {
Connection conn = JDBCUtil.getInstance().getConnection();
List<User> userlist = new ArrayList();
try{
st = conn.createStatement();
rs = st.executeQuery("select * from tb_user");
while(rs.next()){
User user = new User();
user.setU_name(rs.getString("name"));
user.setU_age(rs.getInt("age"));
userlist.add(user);
}
}catch (Exception e) {
e.printStackTrace();
}
JDBCUtil.getInstance().closeAll(rs,st,conn);
return userlist;
}
}
4. com.Util 包 JDBCUtil 類 封裝共用的代碼
package com.Util;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class JDBCUtil {
/*// 1. 參數是硬編碼在代碼中
private static String driverName = "com.mysql.jdbc.Driver";
private static String url = "jdbc:mysql://localhost:3306/mysql001";
private static String userName = "root";
private static String passWorld = "root";
private static JDBCUtil instance = null;
Connection conn;
static{
try {
Class.forName(driverName);
instance = new JDBCUtil();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
//獲得鏈接對象
public Connection getConn(){
try {
return DriverManager.getConnection(url,userName,passWorld);
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
//關閉鏈接資源
public void close(ResultSet rs, Statement st, Connection conn){
try {
if(rs!=null) rs.close();
} catch (SQLException e) {
e.printStackTrace();
}finally {
try {
if(st!=null) st.close();
} catch (SQLException e) {
e.printStackTrace();
}finally {
try {
if(conn!=null) conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
*/
//2.把參數放到資源文件中
static Properties prop = new Properties();
//懶漢模式獲取 JDBCUtil類的一個實例
private JDBCUtil(){}
private static JDBCUtil instance = null;
public static JDBCUtil getInstance(){
if(instance == null){
instance = new JDBCUtil();
}
return instance;
}
static{
try {
prop.load(new FileInputStream("jdbc.properties"));
Class.forName(prop.getProperty("driverName"));
} catch (Exception e) {
e.printStackTrace();
}
}
//獲得鏈接對象
public Connection getConnection(){
Connection conn = null;
try {
conn = DriverManager.getConnection(prop.getProperty("url"),prop.getProperty("userName"),prop.getProperty("password"));
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
//關閉所有鏈接資源
public void closeAll(ResultSet rs, Statement st, Connection conn){
try {
if(rs!=null) rs.close();
} catch (SQLException e) {
e.printStackTrace();
}finally {
try {
if(st!=null) st.close();
} catch (SQLException e) {
e.printStackTrace();
}finally {
try {
if(conn!=null) conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
5. com.test 包 TestDao 測試類
package com.test;
import java.util.List;
import java.util.Scanner;
import org.junit.Test;
import com.dao.IUserDao;
import com.dao.impl.UserDaoImpl;
import com.domain.User;
public class TestDao {
IUserDao userdao = new UserDaoImpl();
@Test
public void addUserInfo(){
User user = new User("趙本本",75); //獲取數據
userdao.addUserInfo(user); //將數據傳到Dao層進行數據庫操作
}
@Test
public void deleteUserInfo(){
User user = new User("趙本本",75);
userdao.deleteUserInfo(user);;
}
/*修改用戶信息*/
@Test
public void updateUserAgeInfo(){
System.out.println("請輸入要修改的用戶姓名:");
String name = new Scanner(System.in).nextLine();
//將name傳到dao層驗證該用戶是否存在
User user = userdao.selectUserInfoByName(name);
if(user != null){
System.out.println("請輸入修改後的用戶年齡:");
int age = new Scanner(System.in).nextInt();
//將user對象和age傳到dao層進行修改數據操作
userdao.updateUserAgeInfo(user,age);;
}else{
System.out.println("不存在該用戶,gameover!!");
}
}
@Test
public void selectUserInfoByName(){
System.out.println("請輸入查詢的學生姓名");
String name = "李四";
System.out.println(userdao.selectUserInfoByName(name));
}
@Test
public void selectAllUserInfo(){
List<User> userlist = userdao.selectAllUserInfo();
for (User user : userlist) {
System.out.println(user);
}
}
}
6. 數據庫表：
CREATE TABLE `tb_user` ( `id` int(10) NOT NULL AUTO_INCREMENT, `name` varchar(20) DEFAULT NULL, `age` int(10) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;
7. jdbc.properties 配置文件
driverName = com.mysql.jdbc.Driver url = jdbc:mysql://localhost:3306/mysql001 userName = root password = root
待補充。。。。。。
jdbc 編程