时间：2021-07-01 10:21:17 帮助过：20人阅读
create table account( id int primary key auto_increment, name varchar(20), money double ); insert into account values(null,‘aaa‘,1000); insert into account values(null,‘bbb‘,1000); insert into account values(null,‘ccc‘,1000);
测试方式二：
driverClass=com.mysql.jdbc.Driver url=jdbc:mysql:///mydb1 username=root password=root #driverClass=oracle.jdbc.driver.OracleDriver #url=jdbc:oracle:thin:@localhost:1521:XE #username=system #password=system
package cn.itcast.utils;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ResourceBundle;
//使用配置文件
public class JdbcUtils {
private static final String DRIVERCLASS;
private static final String URL;
private static final String USERNAME;
private static final String PASSWORD;
static {
DRIVERCLASS = ResourceBundle.getBundle("jdbc").getString("driverClass");
URL = ResourceBundle.getBundle("jdbc").getString("url");
USERNAME = ResourceBundle.getBundle("jdbc").getString("username");
PASSWORD = ResourceBundle.getBundle("jdbc").getString("password");
}
static {
try {
// 将加载驱动操作，放置在静态代码块中.这样就保证了只加载一次.
Class.forName(DRIVERCLASS);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
public static Connection getConnection() throws SQLException {
// 2.获取连接
Connection con = DriverManager.getConnection(URL, USERNAME, PASSWORD);
return con;
}
//关闭操作
public static void closeConnection(Connection con) throws SQLException{
if(con!=null){
con.close();
}
}
public static void closeStatement(Statement st) throws SQLException{
if(st!=null){
st.close();
}
}
public static void closeResultSet(ResultSet rs) throws SQLException{
if(rs!=null){
rs.close();
}
}
}
新建简单测试类TransactionTest1.java
package cn.itcast.transaction;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import cn.itcast.utils.JdbcUtils;
//jdbc中事务操作
public class TransactionTest1 {
public static void main(String[] args) throws SQLException {
// 修改id=2这个人的money=500;
String sql = "update account set money=500 where id=2";
Connection con = JdbcUtils.getConnection();
con.setAutoCommit(false); //开启事务，相当于 start transaction;
Statement st = con.createStatement();
st.executeUpdate(sql);
//事务回滚
//con.rollback();
con.commit(); //事务提交
st.close();
con.close();
}
}
package cn.itcast.transaction;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import cn.itcast.utils.JdbcUtils;
//jdbc中事务操作
public class TransactionTest2 {
public static void main(String[] args) {
// 修改id=2这个人的money=500;
String sql = "update account set money=500 where id=1";
Connection con = null;
Statement st = null;
try {
con = JdbcUtils.getConnection();
con.setAutoCommit(false); // 开启事务，相当于 start transaction;
st = con.createStatement();
st.executeUpdate(sql);
} catch (SQLException e) {
e.printStackTrace();
// 事务回滚
try {
con.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
} finally {
try {
con.commit(); // 事务提交
st.close();
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
package cn.itcast.dao;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import cn.itcast.exception.AccountException;
//没有使用ThreadLocal来获取Connection。
public class _AccountDaoImpl {
// 从accountOut账户转出money
public void accountOut(Connection con, String accountOut, double money)
throws SQLException, AccountException {
String sql = "update account set money=money-? where name=?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setDouble(1, money);
pst.setString(2, accountOut);
int row = pst.executeUpdate();
if (row == 0) {
throw new AccountException("转出失败");
}
pst.close();
}
// 向accountIn账户转入money
public void accountIn(Connection con, String accountIn, double money)
throws SQLException, AccountException {
String sql = "update account set money=money+? where name=?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setDouble(1, money);
pst.setString(2, accountIn);
int row = pst.executeUpdate();
if (row == 0) {
throw new AccountException("转入失败");
}
pst.close();
}
}
真实的实现类实现自别人设计的DAO接口，一般不会考虑到Connection
AccountDao接口如下：
package cn.itcast.dao;
import java.sql.Connection;
public interface AccountDao {
public void accountOut(String accountOut, double money) throws Exception;
public void accountIn(String accountIn, double money) throws Exception;
}
真实DAO实现类实现了AccountDao接口
package cn.itcast.dao;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import cn.itcast.exception.AccountException;
import cn.itcast.utils.JdbcUtils;
public class AccountDaoImpl implements AccountDao {
// 从accountOut账户转出money
public void accountOut(String accountOut, double money)
throws SQLException, AccountException {
String sql = "update account set money=money-? where name=?";
Connection con=JdbcUtils.getConnection();
PreparedStatement pst = con.prepareStatement(sql);
pst.setDouble(1, money);
pst.setString(2, accountOut);
int row = pst.executeUpdate();
if (row == 0) {
throw new AccountException("转出失败");
}
pst.close();
}
// 向accountIn账户转入money
public void accountIn( String accountIn, double money)
throws SQLException, AccountException {
String sql = "update account set money=money+? where name=?";
Connection con=JdbcUtils.getConnection();
PreparedStatement pst = con.prepareStatement(sql);
pst.setDouble(1, money);
pst.setString(2, accountIn);
int row = pst.executeUpdate();
if (row == 0) {
throw new AccountException("转入失败");
}
pst.close();
}
}
AccountException.java （自定义异常）
package cn.itcast.exception;
public class AccountException extends Exception {
public AccountException() {
super();
// TODO Auto-generated constructor stub
}
public AccountException(String message, Throwable cause) {
super(message, cause);
// TODO Auto-generated constructor stub
}
public AccountException(String message) {
super(message);
// TODO Auto-generated constructor stub
}
public AccountException(Throwable cause) {
super(cause);
// TODO Auto-generated constructor stub
}
}
JdbcUtils.java (封装Connection连接对象)
package cn.itcast.utils;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ResourceBundle;
public class JdbcUtils {
private static final String DRIVERCLASS;
private static final String URL;
private static final String USERNAME;
private static final String PASSWORD;
private static final ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
static {
DRIVERCLASS = ResourceBundle.getBundle("jdbc").getString("driverClass");
URL = ResourceBundle.getBundle("jdbc").getString("url");
USERNAME = ResourceBundle.getBundle("jdbc").getString("username");
PASSWORD = ResourceBundle.getBundle("jdbc").getString("password");
}
static {
try {
// 将加载驱动操作，放置在静态代码块中.这样就保证了只加载一次.
Class.forName(DRIVERCLASS);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
public static Connection getConnection() throws SQLException {
Connection con = tl.get();// 从ThreadLocal中获取Connection。第一次获取得到的是null.
if (con == null) {
// 2.获取连接
con = DriverManager.getConnection(URL, USERNAME, PASSWORD);
tl.set(con); // 将con装入到ThreadLocal中。
}
// tl.remove(); //解除
return con;
}
// 关闭操作
public static void closeConnection(Connection con) throws SQLException {
if (con != null) {
con.close();
}
}
public static void closeStatement(Statement st) throws SQLException {
if (st != null) {
st.close();
}
}
public static void closeResultSet(ResultSet rs) throws SQLException {
if (rs != null) {
rs.close();
}
}
}
AccountServlet.java
package cn.itcast.web.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import cn.itcast.exception.AccountException;
import cn.itcast.service.AccountService;
public class AccountServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
// 1.得到请求参数
String accountIn = request.getParameter("accountin");
String accountOut = request.getParameter("accountout");
double money = Double.parseDouble(request.getParameter("money"));
// 2.调用service,完成汇款操作
AccountService service = new AccountService();
try {
service.account(accountIn, accountOut, money);
response.getWriter().write("转账成功");
return;
} catch (AccountException e) {
e.printStackTrace();
response.getWriter().write(e.getMessage());
return;
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP ‘index.jsp‘ starting page</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/account" method="post">
转入账户:<input type="text" name="accountin"><br>
转出账户:<input type="text" name="accountout"><br>
金额:<input type="text" name="money"><br>
<input type="submit" value="提交">
</form>
</body>
</html>
看运行结果：
package cn.itcast.zq;
//使用继承增强
public class Demo1 {
public static void main(String[] args) {
Person1 p=new Student1();
p.eat();
}
}
class Person1{
public void eat(){
System.out.println("吃两个馒头");
}
}
class Student1 extends Person1{
@Override
public void eat(){
super.eat();
System.out.println("加两个鸡腿");
}
}
package cn.itcast.zq;
//使用装饰进行增强
public class Demo2 {
public static void main(String[] args) {
Car car=new Bmw();
//给车增强
CarDerector cd=new CarDerector(car);
cd.run();
}
}
interface Car {
void run();
}
class Bmw implements Car {
public void run() {
System.out.println("bmw run....");
}
}
class Benz implements Car {
public void run() {
System.out.println("benz run....");
}
}
// 使用装饰来完成
class CarDerector implements Car {
private Car car;
public CarDerector(Car car) {
this.car = car;
}
public void run() {
System.out.println("添加导航");
car.run();
}
}
package cn.itcast.zq;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import cn.itcast.utils.JdbcUtils;
public class Demo3 {
public static void main(String[] args) throws SQLException, ClassNotFoundException {
Class.forName("com.mysql.jdbc.Driver"); //注册驱动
final Connection con = DriverManager.getConnection("jdbc:mysql:///mydb1","root","root");
Connection proxy = (Connection) Proxy.newProxyInstance(con.getClass()
.getClassLoader(), con.getClass().getInterfaces(),
new InvocationHandler() {
public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable {
return method.invoke(con, args);
}
});
System.out.println(proxy);
}
}
运行发现出现了如下错误：
package cn.itcast.zq;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import cn.itcast.utils.JdbcUtils;
public class Demo3 {
public static void main(String[] args) throws SQLException, ClassNotFoundException {
Class.forName("com.mysql.jdbc.Driver"); //注册驱动
final Connection con = DriverManager.getConnection("jdbc:mysql:///mydb1","root","root");
Connection proxy = (Connection) Proxy.newProxyInstance(con.getClass()
.getClassLoader(), new Class[]{Connection.class},
new InvocationHandler() {
public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable {
return method.invoke(con, args);
}
});
System.out.println(proxy);
}
}
package cn.itcast.datasource;
import java.io.PrintWriter;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.LinkedList;
import java.util.logging.Logger;
import javax.sql.DataSource;
import cn.itcast.utils.JdbcUtils;
public class MyDataSource implements DataSource {
private LinkedList<Connection> ll; // 用于装Connection对象的容器。
public MyDataSource() throws SQLException {
ll = new LinkedList<Connection>();
// 当创建MyDateSource对象时，会向ll中装入5个Connection对象。
for (int i = 0; i < 5; i++) {
Connection con = JdbcUtils.getConnection();
ll.add(con);
}
}
// 获取连接方法
public Connection getConnection() throws SQLException {
if (ll.isEmpty()) {
for (int i = 0; i < 3; i++) {
Connection con = JdbcUtils.getConnection();
ll.add(con);
}
}
final Connection con = ll.removeFirst();
Connection proxyCon = (Connection) Proxy.newProxyInstance(con
.getClass().getClassLoader(), new Class[]{ Connection.class},
new InvocationHandler() {
public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable {
if ("close".equals(method.getName())) {
// 这代表是close方法，它要做的事情是将con对象重新装入到集合中.
ll.add(con);
System.out.println("重新将连接对象装入到集合中");
return null;
} else {
return method.invoke(con, args);// 其它方法执行原来操作
}
}
});
return proxyCon;
}
// 将Connection对象重新装入.
// public void readd(Connection con) {
//
// ll.addLast(con);
//
// }
// public int getSize() {
// return ll.size();
// }
public Connection getConnection(String username, String password)
throws SQLException {
return null;
}
public PrintWriter getLogWriter() throws SQLException {
return null;
}
public void setLogWriter(PrintWriter out) throws SQLException {
}
public void setLoginTimeout(int seconds) throws SQLException {
}
public int getLoginTimeout() throws SQLException {
return 0;
}
public <T> T unwrap(Class<T> iface) throws SQLException {
return null;
}
public boolean isWrapperFor(Class<?> iface) throws SQLException {
return false;
}
public Logger getParentLogger() throws SQLFeatureNotSupportedException {
// TODO Auto-generated method stub
return null;
}
}
新建测试类，测试刚才新建的数据库连接池
package cn.itcast.datasource;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.sql.DataSource;
//测试自己定义的连接池
public class MyDataSourceTest {
public static void main(String[] args) throws SQLException {
DataSource mds = new MyDataSource(); // 创建一个连接池
// 获取一个连接对象
Connection con = mds.getConnection();
// 操作
ResultSet rs = con.createStatement().executeQuery(
"select * from account");
while (rs.next()) {
System.out.println(rs.getInt("id") + " " + rs.getString("name"));
}
rs.close();
// 将连接对象重新装入到连接池
// mds.readd(con);
con.close(); // 原来作用是将Connection对象销毁，我们在使用连接池，获取Connection对象后，在调用close方法，就不在是销毁，而是将其重新放回到连接池。
// System.out.println(mds.getSize());
}
}
package cn.itcast.datasource;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
import javax.sql.DataSource;
import org.apache.commons.dbcp.BasicDataSource;
import org.apache.commons.dbcp.BasicDataSourceFactory;
import org.junit.Test;
public class DbcpTest {
// 1.手动配置
@Test
public void test1() throws SQLException {
BasicDataSource bds = new BasicDataSource();
// 需要设置连接数据库最基本四个条件
bds.setDriverClassName("com.mysql.jdbc.Driver");
bds.setUrl("jdbc:mysql:///mydb1");
bds.setUsername("root");
bds.setPassword("root");
// 得到一个Connection
Connection con = bds.getConnection();
ResultSet rs = con.createStatement().executeQuery(
"select * from account");
while (rs.next()) {
System.out.println(rs.getInt("id") + " " + rs.getString("name"));
}
rs.close();
con.close(); // 将Connection对象重新装入到连接池.
}
// 2.自动配置
@Test
public void test2() throws Exception {
Properties props = new Properties();
// props.setProperty("driverClassName", "com.mysql.jdbc.Driver");
// props.setProperty("url", "jdbc:mysql:///day18");
// props.setProperty("username", "root");
// props.setProperty("password", "abc");
InputStream fis = this.getClass().getResourceAsStream("/dbcp.properties");
props.load(fis);
DataSource ds = BasicDataSourceFactory.createDataSource(props);
// 得到一个Connection
Connection con = ds.getConnection();
ResultSet rs = con.createStatement().executeQuery(
"select * from account");
while (rs.next()) {
System.out.println(rs.getInt("id") + " " + rs.getString("name"));
}
rs.close();
con.close(); // 将Connection对象重新装入到连接池.
}
}
<?xml version="1.0" encoding="UTF-8"?> <c3p0-config> <default-config> <property name="driverClass">com.mysql.jdbc.Driver</property> <property name="jdbcUrl">jdbc:mysql:///mydb1</property> <property name="user">root</property> <property name="password">root</property> </default-config> </c3p0-config>测试类如下：
package cn.itcast.datasource;
import java.beans.PropertyVetoException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.sql.DataSource;
import org.apache.commons.dbcp.BasicDataSourceFactory;
import org.junit.Test;
import com.mchange.v2.c3p0.ComboPooledDataSource;
//c3p0连接池
public class C3p0Test {
//
@Test
public void test1() throws PropertyVetoException, SQLException {
ComboPooledDataSource cpds = new ComboPooledDataSource();
cpds.setDriverClass("com.mysql.jdbc.Driver");
cpds.setJdbcUrl("jdbc:mysql:///mydb1");
cpds.setUser("root");
cpds.setPassword("root");
// 得到一个Connection
Connection con = cpds.getConnection();
ResultSet rs = con.createStatement().executeQuery(
"select * from account");
while (rs.next()) {
System.out.println(rs.getInt("id") + " " + rs.getString("name"));
}
rs.close();
con.close(); // 将Connection对象重新装入到连接池.
}
@Test
public void test2() throws PropertyVetoException, SQLException {
ComboPooledDataSource cpds = new ComboPooledDataSource();
// 得到一个Connection
Connection con = cpds.getConnection();
ResultSet rs = con.createStatement().executeQuery(
"select * from account");
while (rs.next()) {
System.out.println(rs.getInt("id") + " " + rs.getString("name"));
}
rs.close();
con.close(); // 将Connection对象重新装入到连接池.
// String path = this.getClass().getResource("/").getPath();
// System.out.println(path);
}
}
<c3p0-config> <default-config> <!--当连接池中的连接耗尽的时候c3p0一次同时获取的连接数。Default: 3 --> <property name="acquireIncrement">3</property> <!--定义在从数据库获取新连接失败后重复尝试的次数。Default: 30 --> <property name="acquireRetryAttempts">30</property> <!--两次连接中间隔时间，单位毫秒。Default: 1000 --> <property name="acquireRetryDelay">1000</property> <!--连接关闭时默认将所有未提交的操作回滚。Default: false --> <property name="autoCommitOnClose">false</property> <!--c3p0将建一张名为Test的空表，并使用其自带的查询语句进行测试。如果定义了这个参数那么 属性preferredTestQuery将被忽略。你不能在这张Test表上进