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MySQL_(Java)【事物操作】使用JDBC模拟银行转账向数据库发起修改请求 传送门
MySQL_(Java)【连接池】简单在JDBCUtils.java中创建连接池 传送门
DBCP（DataBase Connection Pool）：数据库连接池，是Java数据库连接池的一种，通过数据库连接池，可以让程序自动管理数据库连接的释放和断开【百度百科】
模拟银行由a向b转账1000元操作，使用事物+DBCP连接池
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class JDBC01 {
public static void main(String[] args) throws SQLException {
transferAccount("a","b",1000);
}
public static void selectAll() throws SQLException {
//注册驱动 使用驱动连接数据库
Connection con = null;
Statement stmt = null;
ResultSet rs = null;
try {
//数据库的连接
con = JDBCUtils.getConnection();
//数据库的增删改查
stmt = con.createStatement();
//返回一个结果集
rs =stmt.executeQuery("select * from garytb");
while(rs.next()) {
//System.out.println(rs.getString(1)+","+rs.getString(2)+","+rs.getString(3));
System.out.println(rs.getString("id")+","+rs.getString("username")+","+rs.getString("password"));
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
JDBCUtils.close(rs, stmt, con);
}
}
//校验用户
public static boolean selectByUernamePassword(String username,String password) throws SQLException {
Connection con=null;
Statement stmt = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
String url ="jdbc:mysql://localhost:3306/garysql?useUnicode=true&characterEncoding=UTF8&useSSL=false";
con = DriverManager.getConnection(url,"root","123456");
stmt =con.createStatement();
String sql = "select * from garytb where username = '"+username+"' and password = '"+password+"'";
//System.out.println(sql);
rs = stmt.executeQuery(sql);
if(rs.next()) {
return true;
}else {
return false;
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
if(rs!=null)
rs.close();
if(stmt!=null)
stmt.close();
if(con!=null)
con.close();
}
return false;
}
public static boolean selectByUP2(String username,String password) throws SQLException{
Connection con=null;
Statement stmt = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
String url ="jdbc:mysql://localhost:3306/garysql?useUnicode=true&characterEncoding=UTF8&useSSL=false";
con = DriverManager.getConnection(url,"root","123456");
String sql = "select * from garytb where username = ? and password = ?";
PreparedStatement pstmt = con.prepareStatement(sql);
//添加参数
pstmt.setString(1, username);
pstmt.setString(2, password);
//进行查询
rs = pstmt.executeQuery();
if(rs.next()) {
return true;
}else {
return false;
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
if(rs!=null)
rs.close();
if(stmt!=null)
stmt.close();
if(con!=null)
con.close();
}
return false;
}
//pageNumber是页数，第几页，pageCount是每页显示多少个数据
public static void selectUserByPage(int pageNumber,int pageCount) throws SQLException {
//注册驱动 使用驱动连接数据库
Connection con = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
//String url ="jdbc:mysql://localhost:3306/garysql";
//指定编码查询数据库
String url ="jdbc:mysql://localhost:3306/garysql?useUnicode=true&characterEncoding=UTF8&useSSL=false";
String user = "root";
String password = "123456";
//建立和数据库的连接
con = DriverManager.getConnection(url,user,password);
stmt = con.prepareStatement("select * from garytb limit ?,?");
stmt.setInt(1, (pageNumber-1)*pageCount );
stmt.setInt(2, pageCount);
rs = stmt.executeQuery();
while(rs.next()) {
//System.out.println(rs.getString(1)+","+rs.getString(2)+","+rs.getString(3));
System.out.println(rs.getString("id")+","+rs.getString("username")+","+rs.getString("password"));
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
if(rs!=null)
rs.close();
if(stmt!=null)
stmt.close();
if(con!=null)
con.close();
}
}
//crud: create read update delete
//插入语句
public static void insert(String username,String password) throws SQLException {
//注册驱动 使用驱动连接数据库
Connection con = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
con = JDBCUtils.getConnection();
String sql = "insert into garytb(username,password) values(?,?)";
stmt = con.prepareStatement(sql);
stmt.setString(1, username);
stmt.setString(2, password);
int result =stmt.executeUpdate();// 返回值代表收到影响的行数
System.out.println("插入成功"+username);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
JDBCUtils.close(rs, stmt, con);
}
}
//删除语句
public static void delete(int id) throws SQLException {
//注册驱动 使用驱动连接数据库
Connection con = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
con = JDBCUtils.getConnection();
String sql = "delete from garytb where id = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, id);
int result =stmt.executeUpdate();// 返回值代表收到影响的行数
if(result>0) {
System.out.println("删除成功");
}else {
System.out.println("删除失败");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(rs, stmt, con);
}
}
//修改语句
public static void update(int id,String newPassword) throws SQLException {
Connection con = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
con = JDBCUtils.getConnection();
String sql = "update garytb set password = ? where id = ?";
stmt = con.prepareStatement(sql);
stmt.setString(1, newPassword);
stmt.setInt(2, id);
int result =stmt.executeUpdate();// 返回值代表收到影响的行数
if(result>0) {
System.out.println("修改成功");
}else {
System.out.println("修改失败");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(rs, stmt, con);
}
}
//事物操作
//由username1向username2转账金额
public static void transferAccount(String username1,String username2,int money) {
Connection con = null;
PreparedStatement stmt1 = null;
PreparedStatement stmt2 = null;
ResultSet rs = null;
try {
con = DBCPDataSource.getConnection();
//开启事物 是否自动提交
con.setAutoCommit(false);
String sql = "update garytb set balance = balance - ? where username = ?";
stmt1 = con.prepareStatement(sql);
stmt1.setInt(1, money);
stmt1.setString(2, username1);
stmt1.executeUpdate();// 返回值代表收到影响的行数
//显示异常throw new Exception("出现错误");
//隐示异常 空指针异常
//String s = null;
//s.charAt(2);
sql = "update garytb set balance = balance + ? where username = ?";
stmt2 = con.prepareStatement(sql);
stmt2.setInt(1, money);
stmt2.setString(2, username2);
stmt2.executeUpdate();// 返回值代表收到影响的行数
System.out.println("操作成功！！");
//提交事务
//当事物中所有事物都完成了才会提交
con.commit();
} catch (Exception e) {
e.printStackTrace();
} finally {
DBCPDataSource.close(stmt2, stmt1, con);
}
}
}
JDBC01.java
import java.sql.Connection;
import java.sql.SQLException;
import org.apache.commons.dbcp2.BasicDataSource;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DBCPDataSource {
private static final String connectionURL = "jdbc:mysql://localhost:3306/garysql?useUnicode=true&characterEncoding=UTF8&useSSL=false";
private static final String username = "root";
private static final String password = "123456";
private static BasicDataSource ds;
//静态代码块：当整个程序执行的时候，优先加载静态代码块
static {
//初始化dbcp数据源
ds = new BasicDataSource();
ds.setDriverClassName("com.mysql.jdbc.Driver");
ds.setUrl(connectionURL);
ds.setUsername(username);
ds.setPassword(password);
//初始化连接池5个
ds.setInitialSize(5);
//连接池最多个数20个
ds.setMaxTotal(20);
//最小的空闲连接
ds.setMinIdle(3);
}
public static Connection getConnection() {
try {
//通过dbcp得到的连接，不需要归还，直接close就可以
return ds.getConnection();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
public static void close(ResultSet rs,Statement stmt,Connection con) {
closeResultSet(rs);
closeStatement(stmt);
closeConnection(con);
}
public static void close(Statement stmt1,Statement stmt2,Connection con) {
closeStatement(stmt1);
closeStatement(stmt2);
closeConnection(con);
}
private static void closeResultSet(ResultSet rs ) {
try {
if(rs!=null)rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private static void closeStatement(Statement stmt) {
try {
if(stmt!=null)
stmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private static void closeConnection(Connection con) {
try {
if(con!=null)con.close();//这里会把链接归还给dbcp连接池，并不是真正的断开链接
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
DBCPDataSource.java
a向b转账事物方法
//事物操作
//由username1向username2转账金额
public static void transferAccount(String username1,String username2,int money) {
Connection con = null;
PreparedStatement stmt1 = null;
PreparedStatement stmt2 = null;
ResultSet rs = null;
try {
con = DBCPDataSource.getConnection();
//开启事物 是否自动提交
con.setAutoCommit(false);
String sql = "update garytb set balance = balance - ? where username = ?";
stmt1 = con.prepareStatement(sql);
stmt1.setInt(1, money);
stmt1.setString(2, username1);
stmt1.executeUpdate();// 返回值代表收到影响的行数
//显示异常throw new Exception("出现错误");
//隐示异常 空指针异常
//String s = null;
//s.charAt(2);
sql = "update garytb set balance = balance + ? where username = ?";
stmt2 = con.prepareStatement(sql);
stmt2.setInt(1, money);
stmt2.setString(2, username2);
stmt2.executeUpdate();// 返回值代表收到影响的行数
System.out.println("操作成功！！");
//提交事务
//当事物中所有事物都完成了才会提交
con.commit();
} catch (Exception e) {
e.printStackTrace();
} finally {
DBCPDataSource.close(stmt2, stmt1, con);
}
}