MySQL_(Java)使用JDBC向数据库发起查询请求 传送门
MySQL_(Java)使用JDBC向数据库中插入(insert)数据 传送门
MySQL_(Java)使用JDBC向数据库中删除(delete)数据 传送门
MySQL_(Java)使用JDBC向数据库中修改(update)数据 传送门
MySQL_(Java)【连接池】简单在JDBCUtils.java中创建连接池 传送门
数据库中事务：
我们之前分享数据库的数据操作，无外乎对数据库的数据进行增、删、改、查。就比如我们去买东西，一般都是先付钱，卖家收到钱再发货。这个用数据库来表示就是，第一步：从用户的账户中减去一部分金额。第二步，再把减去的金额添加到商家的账户上。
但是万一遇到特殊的情况，你成功的完成了第一步，从用户的数据库中扣除了钱，这时候突然停电，系统出现了故障，没有完成第二步。这就尴尬了，用户的钱少了，商家也没收到钱。
为了应对这种情况的发生，数据库就出现了一个功能事务，事务就是一组由 SQL 语句组成的业务逻辑，当事务内的所有 SQL语句都成功的执行，整个事务才算成功，否则就是失败。失败意味着整个的数据操作没有意义，就要把数据恢复到执行事务操作之前的状态。
Learn
一、未添加事务且普通转账正常
二、在扣款和收款操作之间添加一个隐式异常
三、添加事物
数据库表结构:
一、未添加事务且普通转账正常
由a向b转账1000元
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) throws SQLException {
Connection con = null;
PreparedStatement stmt1 = null;
PreparedStatement stmt2 = null;
ResultSet rs = null;
try {
con = JDBCUtils.getConnection(); 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 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！！");
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(rs, stmt1, con);
}
} }
JDBC01.java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement; public class JDBCUtils { 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 = "123"; //创建数据库的连接
public static Connection getConnection() {
try {
Class.forName("com.mysql.jdbc.Driver");
return DriverManager.getConnection(connectionURL,username,password);
} catch (Exception e) { e.printStackTrace();
}
return null;
} //关闭数据库的连接
public static void close(ResultSet rs,Statement stmt,Connection con) throws SQLException {
if(rs!=null)
rs.close();
if(stmt!=null)
stmt.close();
if(con!=null)
con.close();
}
}
JDBCUtils.java
转账资源操作【资源关闭】优化版
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) throws SQLException {
Connection con = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
con = JDBCUtils.getConnection(); String sql = "update garytb set balance = balance - ? where username = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username1);
stmt.executeUpdate();// 返回值代表收到影响的行数 sql = "update garytb set balance = balance + ? where username = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username2);
stmt.executeUpdate();// 返回值代表收到影响的行数
System.out.println("操作成功！！");
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(rs, stmt, con);
}
} }
JDBC01.java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList; public class JDBCUtils { 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 = "123"; private static ArrayList<Connection> conList = new ArrayList<Connection>(); static {
for(int i =0;i<5;i++) {
Connection con = createConnection();
conList.add(con);
}
} public static Connection getConnection() {
if(conList.isEmpty()==false) {
Connection con = conList.get(0);
conList.remove(con);
return con;
}else {
return createConnection();
}
} private static Connection createConnection() {
try {
Class.forName("com.mysql.jdbc.Driver"); return DriverManager.getConnection(connectionURL, username, password);
} catch (Exception 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();
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
conList.add(con);
}
}
JDBCUtils.java
//由username1向username2转账金额
public static void transferAccount(String username1,String username2,int money) throws SQLException {
Connection con = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
con = JDBCUtils.getConnection(); String sql = "update garytb set balance = balance - ? where username = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username1);
stmt.executeUpdate();// 返回值代表收到影响的行数 sql = "update garytb set balance = balance + ? where username = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username2);
stmt.executeUpdate();// 返回值代表收到影响的行数
System.out.println("操作成功！！");
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(rs, stmt, con);
}
}
二、在扣款和收款操作之间添加一个隐式异常
当程序运行到异常代码块时，程序不会往下继续执行,因此a方1000元已扣除但b方未收到1000元款项
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 stmt = null;
ResultSet rs = null;
try {
con = JDBCUtils.getConnection(); String sql = "update garytb set balance = balance - ? where username = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username1);
stmt.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 = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username2);
stmt.executeUpdate();// 返回值代表收到影响的行数
System.out.println("操作成功！！");
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(rs, stmt, con);
}
} }
JDBC01.java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList; public class JDBCUtils { 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 = "123"; private static ArrayList<Connection> conList = new ArrayList<Connection>(); static {
for(int i =0;i<5;i++) {
Connection con = createConnection();
conList.add(con);
}
} public static Connection getConnection() {
if(conList.isEmpty()==false) {
Connection con = conList.get(0);
conList.remove(con);
return con;
}else {
return createConnection();
}
} private static Connection createConnection() {
try {
Class.forName("com.mysql.jdbc.Driver"); return DriverManager.getConnection(connectionURL, username, password);
} catch (Exception 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();
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
conList.add(con);
}
}
JDBCUtils.java
//由username1向username2转账金额
public static void transferAccount(String username1,String username2,int money) {
Connection con = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
con = JDBCUtils.getConnection(); String sql = "update garytb set balance = balance - ? where username = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username1);
stmt.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 = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username2);
stmt.executeUpdate();// 返回值代表收到影响的行数
System.out.println("操作成功！！");
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(rs, stmt, con);
}
}
三、添加事物
一旦事物之间出现异常，则不会提交事物给数据库
//开启事物 是否自动提交
con.setAutoCommit(false); //当事物中所有事物都完成了才会提交
con.commit();
当a向b转账1000元后出现异常，b未收到1000元，这一系列操作处于同一事物中，此事物有异常不会提交给程序
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 stmt = null;
ResultSet rs = null;
try {
con = JDBCUtils.getConnection(); //开启事物 是否自动提交
con.setAutoCommit(false); String sql = "update garytb set balance = balance - ? where username = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username1);
stmt.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 sql = "update garytb set balance = balance + ? where username = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username2);
stmt.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 {
JDBCUtils.close(rs, stmt, con);
}
} }
JDBC01.java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList; public class JDBCUtils { 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 = "123"; private static ArrayList<Connection> conList = new ArrayList<Connection>(); static {
for(int i =0;i<5;i++) {
Connection con = createConnection();
conList.add(con);
}
} public static Connection getConnection() {
if(conList.isEmpty()==false) {
Connection con = conList.get(0);
conList.remove(con);
return con;
}else {
return createConnection();
}
} private static Connection createConnection() {
try {
Class.forName("com.mysql.jdbc.Driver"); return DriverManager.getConnection(connectionURL, username, password);
} catch (Exception 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();
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
conList.add(con);
}
}
JDBCUtils.java
//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 stmt = null;
ResultSet rs = null;
try {
con = JDBCUtils.getConnection(); //开启事物 是否自动提交
con.setAutoCommit(false); String sql = "update garytb set balance = balance - ? where username = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username1);
stmt.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 sql = "update garytb set balance = balance + ? where username = ?";
stmt = con.prepareStatement(sql);
stmt.setInt(1, money);
stmt.setString(2, username2);
stmt.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 {
JDBCUtils.close(rs, stmt, con);
}
}
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