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第77节:Java中的事务和数据库连接池和DBUtiles

前言

看哭你,字数:8803,承蒙关照,谢谢朋友点赞!

事务

Transaction事务,什么是事务,事务是包含一组操作,这组操作里面包含许多个单一的逻辑,只要有一个逻辑没有执行成功就算失败,导致回滚就是指所有的数据都会回到最初的状态.

有事务,是为了保证逻辑一定要成功,如银行转账.

回顾一下

什么是jsp,jsp的三大指令.

page: 定义当前页面的信息
include: 包含其他页面
taglib: 引入标签库
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三大动作标签:

<jsp:forward page="">:跳转
<jsp:param name="" value="">:跳转到具体页面或是某个页面被包含的时候,可以指定参数
<jsp:include page="">:包含
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九大内置对象:

// 四个作用域
pageContext 当前页
request 请求 一次请求 响应后就不行了
session 会话 一次会话
application 都可以 整个项目,直到关闭服务器// 5
response
out
exception
config -> ServletConfig
page -> this 翻译成java文件的类对象
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EL

${ 表达式 };
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取值

<% User user = new User(); %>
${user.ame}
从四个作用域里面找 
pageContext -> request -> session -> application
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<%User user = new User();pageContext.setAttribute("user",user);
%>
${sessionScope.user.name}强制用session找
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EL的11个隐式对象:

pageContext
// 作用域
pageScope
requestScope
sessionScope
applicationScope头相关
header
headerValues
参数
param
paramValues
cookie
initparam
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JSTL

导包哦,引入标签库是1.1的:

<c:set>: 存储到作用域
<c:set var="" value="" scope="">
<c: if>: 用来判断
<c:forEach items="" var="">:用于遍历
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数据库

数据库命令行:

关闭自动提交.

关闭了提交,再减100:

会到数据库查看:

值没改变!

添加改变代码:

package com.dashucoding.test;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;import org.junit.Test;import com.dashucoding.util.JDBCUtil;public class TestDemo { @Testpublic void testTransaction() {Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;try {conn = JDBCUtil.getConn();//查询数据/*String sql = "select * from account";ps = conn.prepareStatement(sql);*/String sql = "update account set money = money - ? where id = ?";ps = conn.prepareStatement(sql);// 扣钱ps.setInt(1, 100);ps.setInt(2, 1);ps.executeUpdate();/*ps.setInt(1, -100);ps.setInt(2, 1);ps.executeUpdate();*/// 查询数据 /*rs = ps.executeQuery();while(rs.next()) {System.out.println(rs.getString("name")+"=="+rs.getInt("money"));}*/} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}finally {JDBCUtil.release(conn, ps, rs);}}
}
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package com.dashucoding.util;import java.io.FileInputStream;
import java.io.InputStream;
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 {static String driverClass = null;static String url = null;static String name = null;static String password= null;static{try {//1. 创建一个属性配置对象Properties properties = new Properties();InputStream is = new FileInputStream("jdbc.properties");//使用类加载器，去读取src底下的资源文件。 后面在servlet
//			InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");//导入输入流。properties.load(is);//读取属性driverClass = properties.getProperty("driverClass");url = properties.getProperty("url");name = properties.getProperty("name");password = properties.getProperty("password");} catch (Exception e) {e.printStackTrace();}}/*** 获取连接对象* @return*/public static Connection getConn(){Connection conn = null;try {Class.forName(driverClass);//静态代码块 ---> 类加载了，就执行。 java.sql.DriverManager.registerDriver(new Driver());//DriverManager.registerDriver(new com.mysql.jdbc.Driver());//DriverManager.getConnection("jdbc:mysql://localhost/test?user=monty&password=greatsqldb");//2. 建立连接 参数一： 协议 + 访问的数据库 ， 参数二： 用户名 ， 参数三： 密码。conn = DriverManager.getConnection(url, name, password);} catch (Exception e) {e.printStackTrace();}return conn;}/*** 释放资源* @param conn* @param st* @param rs*/public static void release(Connection conn , Statement st , ResultSet rs){closeRs(rs);closeSt(st);closeConn(conn);}public static void release(Connection conn , Statement st){closeSt(st);closeConn(conn);}private static void closeRs(ResultSet rs){try {if(rs != null){rs.close();}} catch (SQLException e) {e.printStackTrace();}finally{rs = null;}}private static void closeSt(Statement st){try {if(st != null){st.close();}} catch (SQLException e) {e.printStackTrace();}finally{st = null;}}private static void closeConn(Connection conn){try {if(conn != null){conn.close();}} catch (SQLException e) {e.printStackTrace();}finally{conn = null;}}
}
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事务只针对连接.

package com.dashucoding.test;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;import org.junit.Test;import com.dashucoding.util.JDBCUtil;public class TestDemo { @Testpublic void test02(){Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;try {conn = JDBCUtil.getConn();String sql = "update account set money = money - ? where id = ?";ps = conn.prepareStatement(sql);//扣钱， 扣ID为1 的100块钱ps.setInt(1, 100);ps.setInt(2, 1);ps.executeUpdate();//int a = 10 /0 ;String s = null;s.length();//加钱， 给ID为2 加100块钱ps.setInt(1, -100);ps.setInt(2, 2);ps.executeUpdate();} catch (SQLException e) {e.printStackTrace();}finally {JDBCUtil.release(conn, ps, rs);}}@Testpublic void testTransaction() {Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;try {conn = JDBCUtil.getConn();// 连接conn.setAutoCommit(false);//查询数据/*String sql = "select * from account";ps = conn.prepareStatement(sql);*/String sql = "update account set money = money - ? where id = ?";ps = conn.prepareStatement(sql);// 扣钱ps.setInt(1, 100);ps.setInt(2, 1);ps.executeUpdate();int a = 10 /0 ;ps.setInt(1, -100);ps.setInt(2, 2);ps.executeUpdate();// 提交事务conn.commit();// 查询数据 /*rs = ps.executeQuery();while(rs.next()) {System.out.println(rs.getString("name")+"=="+rs.getInt("money"));}*/} catch (SQLException e) {// TODO Auto-generated catch block// 回滚事务try {conn.rollback();} catch (SQLException e1) {// TODO Auto-generated catch blocke1.printStackTrace();}e.printStackTrace();}finally {JDBCUtil.release(conn, ps, rs);}}
}
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事务

conn.setAutoCommit(false)来关闭自动提交的设置
conn.commit(); 提交事务
conn.rollback(); 回滚事务
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记住: 什么是事务,事务有什么用处,事务怎么用.

事务的特点:

1. 原子性: 指的是事务中包含的逻辑,不可以分割(事务中逻辑不可分)
2. 一致性: 事务执行前和执行后,保持数据的完整性一致(执行前后,数据保持一致)
3. 隔离性: 事务在执行期间不受到其他事务的影响(隔离不受影响)
4. 持久性: 事务执行结束,提交或回滚,数据都应该持久化到数据中(数据持久化在数据中)

安全问题

1. 读问题 脏读,不可重复读,幻读
2. 写问题 丢失更新,解决丢失更新的方法,一悲观锁和乐观锁

隔离级别

Read Uncommitted 读未提交
Read Committed 读已提交
Repeatable Read 重复读
Serializable 可串行化
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脏读:

一条连接:

另一条连接:

use bank;
start transaction;
select * from account;
select * from account;
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use bank;
start transaction;
update account set money = money + 300 where id = 1;
commit;
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读未提交

例子

这里查询,然后再看看数据库中的表:

命令提交:

不可重复读的问题

Repeatable Read重复读

可串化

读未提交,引发脏读,读已提交解决脏读,引发不可重复读, 可重复读解决脏读解决了脏读,不可重复读,

asss

小结

读: 脏读 不可重读读 幻读

脏读: 一个事务读到另外一个事务还未提交的数据

不可重复读: 一个事务读到另外一个事务提交的数据,导致前后两次查询结果不一致

幻读: 一个事务读到了另外一个事务已提交的插入的数据,导致多次查询结果不一致.

读未提交, 会导致丢失更新

读已提交, 能够屏蔽 脏读的现象,但是引发不可重复读

事务的安全隐患脏读

隔离级别:

read uncommitted 读未提交
read committed 读已提交
repeatable read 重复读
serializable 可串化
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mysql默认的是重复读.

设置A窗口的隔离级别为 读未提交

两个窗口都分别开启事务

读未提交是一个事务可以读取到另一个事务还没有提交的数据,会引发脏读现象,读取到的是数据库内存中的数据,并不是真正的磁盘上的数据.

还未提交时,数据库内存中的数据是不会改变的,只有到commit提交后,数据库中的数据才会提交,从而读取真正在磁盘上的数据.

Read Committed读已提交

在a发生了变化,屏蔽了脏读,引发不可重复读,读已提交.读已提交,在a窗口设置的是读已提交,两边开启事务.在b窗口更新操作.

在a窗口查询结果不一致,一次是在b窗口提交事务之前,一次的提交之后.

引发了不可重复读

不可重复读,一个事务读取到了另一个事务提交的数据,导致前后两次查询结果不一致.

会造成问题是前后读取到的结果不一样,发生了不可重复读,就是不可以 重复读取, 就是不能执行多次读取, 否则会导致结果不一致, 这下好了, 读取已提交导致了 重复读取, 结果还不一致, 就出现了叫 不可重复读 现象.

安全隐患_可重复读

Repeatable Read重复读, 重复读就是mysql默认的隔离级别,可以让食物在自己的会话中重复读取数据,并且不会出现结果不一致的现象, 就算其他事务提交了, 也还是会在窗口中出现以前的数据, 这就是可重复读了.

重复读, 就是让它可以重复查询, 结果还是和以前一样的效果出现.

设置重复读

安全隐患 _可串行化

幻读:什么是幻读呢? 就是一个事务读到另一个事务已提交的插入的数据,会导致多次查询结果不一致.就是幻读,是不是幻读理解为我幻想了, 事务已提交的插入数据, 导致幻想了,(幻读) 导致每次查询结果不一样.

事务已提交,多次查询结果不一致.

幻读->Serializable可串行化

该事务的级别是最高的事务级别,我是可串行化,是最高的.可以解决如下小弟的问题,如脏读,不可重复读,幻读,因为我是可串行化,是大佬,但作为大佬,还是会有缺点的.

是的,a提交才动.现在我们让b先开启事务.

可串行化, 谁先打开事务,就谁有权利,这个隔离级别,先打开就有权利让别人等着,等先打开事务的那个家伙,提交或者回滚后,才能进行,这种级别是用得比较少的,因为容易导致性能上效率低下.

隔离级别有四个哦

1. 读未提交
2. 读已提交
3. 可重复读
4. 可串行化

如果按照效率划分,从高到低,排个名次如下:

1. 读未提交 -> 脏读
2. 读已提交 -> 不可重复读
3. 可重复读 -> 解决重复读
4. 可串行化 -> 以上都是我小弟来着

按照拦截程度来划分,从高到底,排名如下:

1. 可串行化 -> 我是大哥
2. 可重复读 -> 我是二哥
3. 读已提交 -> 我是三弟
4. 读未提交 -> 我是小弟

事务_隔离级别小结

// 使用事务
conn.setAutoCommit(false);
// 提交
conn.commit();
// 回滚
conn.rollback();
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事务只是针对连接对象.事务是会自动提交的.

安全隐患和隔离级别

安全隐患: 读的安全隐患和写的安全隐患

读: 脏读,读到未提交的数据,一个事务读到了另一个事务未提交的数据; 不可重复读,就是一个事务读到了另一个事务已经提交的数据,导致前后两次查询的结果不一致; 幻读,就是一个事务读到了另一个事务添加的数据,导致前后查询结果不一致.

写: 丢失更新...

隔离级别

读未提交,导致脏读 读已提交,解决脏读,导致不可重复读 可重复读,解决脏读和不可重复读,导致幻读 可串行化,解决脏读,不可重复读,幻读

默认的mysql是可重复读,oracle默认是读已提交

写的问题_丢失更新

丢失更新

1. 乐观锁
2. 悲观锁

安全问题包含 读的问题和写的问题

事务的特性是什么? 原子性,一致性,隔离性,持久性

写的问题_丢失更新

b窗口没有提交.等待提交中:

案例控制面板,我的a:

哭了,这是设置默认的重复读啊!

丢失更新的问题

听说丢失更新

a事务和b事务同时查询一个表,a开始修改并提交name字段的名字,然后b事务开始修改该行的money的字段,如果b事务提交,那么之前a事务修改的名字没有了,变回去了哦,当然b事务回滚,也同样导致a事务更新没有了哦.回滚也会把之前b事务的最初的数据还原.

这里的情况处理序列化级别外,就是可串行化级别大佬哦!

解决丢失更新的方法

1. 悲观锁
2. 乐观锁

select * from account;
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悲观锁的态度,它是悲观的态度,它是一定会丢失更新,它的想法是我一定会出错.

而乐观锁,它的态度是我一定不会丢失更新.

悲观锁

数据库的锁机制,排他锁

select * from account for update;
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丢失更新的问题

不考虑隔离性,产生写入数据导致的问题为丢失更新的问题,两个事务同时对某一条记录做修改,然后会导致丢失更新的问题.

a,b两个事务同时获取一条数据,同时做了修改,a事务修改后,提交了事务,b事务修改后,不管是提交还是回滚,都会对数据发生影响.

悲观锁记住用了这句:

select * from account for update;
for update;
数据库锁机制,排他锁
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乐观锁

a事务先提交,数据库版本version变为1,b事务在提交的时候,比对数据库version和自己的version是不一样的,不允许提交,要先更新.

a提交的时候版本变为1,b提交的时候,发现版本不一致就无法提交,要进行更新后提交.

数据库连接池

什么是连接池,连接池的作用是什么,自定义连接池,开源的连接池?

那么什么是数据库连接池?

数据库连接池是Java程序和数据连接的中介媒介,以前一个Java程序对应一个连接,然后就可以连接到数据了,可以一旦多了呢?

就有人发明了数据库连接池,可以一下连接多个,但是是有限制的,一旦多了,就会扩容,额外增加3到5个,不会增幅太大,也有最大值的限制.

数据库的连接对象 创建工作 比较消耗性能 一开始在内存中会开辟一块空间, 用于是 这个数据库连接池的空间, 可以在池子里放置很多个连接对象, 数据库连接池里有很多个连接对象, 后面需要连接的话会直接从池子里面去, 就不用自己去创建连接了, 因为数据库的连接对象创建工作是比较耗时的, 使用完, 数据库连接池中的 连接对象 ,是要进行归还的, 确保连接对象可以循环连接使用.

创建数据库的连接池

// 简单使用数据库连接池
package com.dashucoding.util;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;import org.junit.Test;public class TestPool {@Testpublic void testPool() {Connection conn = null;PreparedStatement ps = null;MyDataSource dataSource = new MyDataSource();try {conn = dataSource.getConnection();String sql = "insert into account values (null, 'xilali', 10)";ps = conn.prepareStatement(sql);ps.executeUpdate();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}finally {try {ps.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}// 归还连接dataSource.addBack(conn);}}
}
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自定义数据库连接池

List <Connection> list = new ArrayList<Connection>();
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解决自定义数据库连接池问题

因为多了一个addBack方法,要记住这个方法,且不能用面向接口编程.修改close方法,改成不是关闭而是归还连接对象.

public class MyDataSource implements DataSource {// 创建连接池
List<Connection> list = new ArrayList<Connection>();public MyDataSource(){for(int i = 0; i < 10; i++){Connection conn = JDBCUtil.getConn();list.add(conn);}}@Overridepublic Connection getConnection() throws SQLException {if(list.size() == 0){for(int i=0; i<5; i++) {Connection conn = JDBCUtil.getConn();list.add(conn);}}Connection conn = list.remove(0);return conn;}// 用完后归还 public void addBack(Connection conn){list.add(conn);}
}
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public class TestPool{@Testpublic void testPool(){Connection conn = null;PreparedStatement ps = null;MyDataSource dataSource = new MyDataSource();try {conn = dataSource.getConnection();String sql = "insert into account values(null, 'dashu', 10)";ps = conn.prepareStatement(sql);ps.executeUpdate();}catch(SQLException e){e.printStackTrace();}finally{try{ps.close();}catch(SQLException e){e.printStackTrace();}// 归还连接dataSource.addBack(conn);}}
}
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如何扩展方法

装饰者模式

package com.dashucoding.test;public interface Waiter {void service();
}
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package com.dashucoding.test;public class Waitress implements Waiter {@Overridepublic void service() {System.out.println("在服务...");}
}
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package com.dashucoding.test;public class MainTest {public static void main(String[] args) {Waiter waiter = new Waitress();waiter.service();}
}
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装饰者模式:

package com.dashucoding.test;public class WaitressWrap implements Waiter {Waiter watier = null;public WaitressWrap(Waiter watier) {this.watier = watier;}@Overridepublic void service() {// TODO Auto-generated method stubSystem.out.println("微笑");watier.service();}}
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package com.dashucoding.test;public class MainTest {public static void main(String[] args) {/*Waiter waiter = new Waitress();waiter.service();*/WaitressWrap waitressWrap = new WaitressWrap(new Waitress());waitressWrap.service();}
}
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分析

Waiter -> service()Waitress -> service()WaitressWrap -> service()Waiter waiter;
public Waitress Wrap(Waiter waiter){this.waiter = watier;
}
void service(){sysowaiter.service();
}
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装饰者模式

package com.dashucoding.util;import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Logger;import javax.sql.DataSource;
// 这是一个数据库连接池
// 一开始 先往连接池放入10个连接
public class MyDataSource implements DataSource{// 创建连接池List<Connection> list = new ArrayList<Connection>();public MyDataSource() {// 10个连接for(int i = 0; i < 10; i++) {Connection conn = JDBCUtil.getConn();list.add(conn);}}// 该连接池对外公布的获取连接的方法@Overridepublic Connection getConnection() throws SQLException {// 来拿连接的时候,看看,池子里面有没有if(list.size() == 0) {for(int i = 0; i < 5; i++) {Connection  conn = JDBCUtil.getConn();list.add(conn);}}// TODO Auto-generated method stub// 那一个 给连接 如果有10个,0,1,2,3,->10 这样给// 确保给// 移除就给了嘛// remove(0) -> 移除第一个Connection conn = list.remove(0);// 把对象抛出去的时候,对这个对象进行包装Connection connection = new ConnectionWrap(conn,list);return connection;}// 用完后记得归还public void addBack(Connection conn) {list.add(conn);}@Overridepublic PrintWriter getLogWriter() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic int getLoginTimeout() throws SQLException {// TODO Auto-generated method stubreturn 0;}@Overridepublic Logger getParentLogger() throws SQLFeatureNotSupportedException {// TODO Auto-generated method stubreturn null;}@Overridepublic void setLogWriter(PrintWriter arg0) throws SQLException {// TODO Auto-generated method stub}@Overridepublic void setLoginTimeout(int arg0) throws SQLException {// TODO Auto-generated method stub}@Overridepublic boolean isWrapperFor(Class<?> arg0) throws SQLException {// TODO Auto-generated method stubreturn false;}@Overridepublic <T> T unwrap(Class<T> arg0) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic Connection getConnection(String arg0, String arg1) throws SQLException {// TODO Auto-generated method stubreturn null;}}
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package com.dashucoding.util;import java.sql.Array;
import java.sql.Blob;
import java.sql.CallableStatement;
import java.sql.Clob;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.NClob;
import java.sql.PreparedStatement;
import java.sql.SQLClientInfoException;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.SQLXML;
import java.sql.Savepoint;
import java.sql.Statement;
import java.sql.Struct;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.Executor;public class ConnectionWrap implements Connection{Connection connection = null;List<Connection> list;public ConnectionWrap(Connection connection,List<Connection> list) {super();this.connection = connection;this.list = list;}@Overridepublic void close() throws SQLException {// TODO Auto-generated method stub//connection.close();System.out.println("有人归还连接对象了,归还之前"+list.size());list.add(connection);System.out.println("有人归还连接对象了,归还之后"+list.size());}@Overridepublic PreparedStatement prepareStatement(String sql) throws SQLException {// TODO Auto-generated method stubreturn connection.prepareStatement(sql);}@Overridepublic boolean isWrapperFor(Class<?> iface) throws SQLException {// TODO Auto-generated method stubreturn false;}@Overridepublic <T> T unwrap(Class<T> iface) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic void abort(Executor executor) throws SQLException {// TODO Auto-generated method stub}@Overridepublic void clearWarnings() throws SQLException {// TODO Auto-generated method stub}@Overridepublic void commit() throws SQLException {// TODO Auto-generated method stub}@Overridepublic Array createArrayOf(String typeName, Object[] elements) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic Blob createBlob() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic Clob createClob() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic NClob createNClob() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic SQLXML createSQLXML() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic Statement createStatement() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability)throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic Struct createStruct(String typeName, Object[] attributes) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic boolean getAutoCommit() throws SQLException {// TODO Auto-generated method stubreturn false;}@Overridepublic String getCatalog() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic Properties getClientInfo() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic String getClientInfo(String name) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic int getHoldability() throws SQLException {// TODO Auto-generated method stubreturn 0;}@Overridepublic DatabaseMetaData getMetaData() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic int getNetworkTimeout() throws SQLException {// TODO Auto-generated method stubreturn 0;}@Overridepublic String getSchema() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic int getTransactionIsolation() throws SQLException {// TODO Auto-generated method stubreturn 0;}@Overridepublic Map<String, Class<?>> getTypeMap() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic SQLWarning getWarnings() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic boolean isClosed() throws SQLException {// TODO Auto-generated method stubreturn false;}@Overridepublic boolean isReadOnly() throws SQLException {// TODO Auto-generated method stubreturn false;}@Overridepublic boolean isValid(int timeout) throws SQLException {// TODO Auto-generated method stubreturn false;}@Overridepublic String nativeSQL(String sql) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic CallableStatement prepareCall(String sql) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency,int resultSetHoldability) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency)throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency,int resultSetHoldability) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic void releaseSavepoint(Savepoint savepoint) throws SQLException {// TODO Auto-generated method stub}@Overridepublic void rollback() throws SQLException {// TODO Auto-generated method stub}@Overridepublic void rollback(Savepoint savepoint) throws SQLException {// TODO Auto-generated method stub}@Overridepublic void setAutoCommit(boolean autoCommit) throws SQLException {// TODO Auto-generated method stub}@Overridepublic void setCatalog(String catalog) throws SQLException {// TODO Auto-generated method stub}@Overridepublic void setClientInfo(Properties properties) throws SQLClientInfoException {// TODO Auto-generated method stub}@Overridepublic void setClientInfo(String name, String value) throws SQLClientInfoException {// TODO Auto-generated method stub}@Overridepublic void setHoldability(int holdability) throws SQLException {// TODO Auto-generated method stub}@Overridepublic void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {// TODO Auto-generated method stub}@Overridepublic void setReadOnly(boolean readOnly) throws SQLException {// TODO Auto-generated method stub}@Overridepublic Savepoint setSavepoint() throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic Savepoint setSavepoint(String name) throws SQLException {// TODO Auto-generated method stubreturn null;}@Overridepublic void setSchema(String schema) throws SQLException {// TODO Auto-generated method stub}@Overridepublic void setTransactionIsolation(int level) throws SQLException {// TODO Auto-generated method stub}@Overridepublic void setTypeMap(Map<String, Class<?>> map) throws SQLException {// TODO Auto-generated method stub}}
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数据库连接池_DBCP

DBCP开源连接池 C3P0,什么是C3P0,怎么用

DBCP为数据库连接池,是java数据库连接池的一种是Apache开发的,通过数据库连接池可以让程序自动管理数据库的连接.

DataBase Connection Pool数据库连接池
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C3P0也是一种开源的连接池,实现了数据库和JNDI绑定,使用它的开源项目:

Spring, Hibernate
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怎么用DBCP

1. 导入jar包

commons-dbcp.jar
commons-pool.jar
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// 不使用配置文件
BasicDataSource dataSource = new BasicDataSource();
dataSource.setDriverClassName("com.mysql.jdbc.Driver");
dataSource.setUrl("jdbc:mysql://loclhost/users");
dataSource.setUsername("root");
dataSource.setPassword("root");conn = dataSource.getConnection();
String sql = "select * from user";
pstmt = conn.prepareStatement(sql);
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DBCP连接数据库使用

package com.dashucoding.dbcp;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;import org.apache.commons.dbcp.BasicDataSource;
import org.junit.Test;import com.dashucoding.util.JDBCUtil;// 这个连接池要连接数据库, 账号,密码
public class DBCPDemo {// ctrl + 2 fprivate Connection conn;private PreparedStatement ps;@Testpublic void testDBCP01(){// 数据库的连接池, 作用创建和连接try {// 构建数据源对象BasicDataSource dataSource = new BasicDataSource();// 连接什么数据库,用户名和密码dataSource.setDriverClassName("com.mysql.jdbc.Driver");dataSource.setUrl("jdbc:mysql://localhost/bank");dataSource.setUsername("你的账户");dataSource.setPassword("你的密码");// 得到连接对象conn = dataSource.getConnection();String sql = "insert into account values(null, ?, ?)";ps = conn.prepareStatement(sql);ps.setString(1, "dashucoding");ps.setInt(2, 10000);ps.executeUpdate();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}finally {JDBCUtil.release(conn, ps);}}
}
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以上是不使用配置文件的情况.

DBCP使用配置文件方式

package com.dashucoding.dbcp;import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
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;import com.dashucoding.util.JDBCUtil;public class DBCPDemo02 {@Testpublic void testDBCP02() {/*BasicDataSource dataSource = new BasicDataSource();dataSource.setConnectionProperties("dbcpconfig.properties");*/Connection conn = null;PreparedStatement ps = null;// 数据库的连接池, 作用创建和连接try {BasicDataSourceFactory factory = new BasicDataSourceFactory();Properties properties = new Properties();InputStream is = new FileInputStream("src//dbcpconfig.properties");properties.load(is);DataSource dataSource = factory.createDataSource(properties);// 得到连接对象conn = dataSource.getConnection();String sql = "insert into account values(null, ?, ?)";ps = conn.prepareStatement(sql);ps.setString(1, "liuliuliu");ps.setInt(2, 10000);ps.executeUpdate();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();} finally {JDBCUtil.release(conn, ps);}}}
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数据库连接池_C3P0

不使用配置方式

拷贝jar c3p0...jar
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 Just put the jar file [lib/c3p0-0.9.1.2.jar] in your application's effective CLASSPATH
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ComboPooledDataSource cpds = new ComboPooledDataSource();
cpds.setDriverClass( "org.postgresql.Driver" ); //loads the jdbc driver            
cpds.setJdbcUrl( "jdbc:postgresql://localhost/testdb" );
cpds.setUser("dbuser");                                  
cpds.setPassword("dbpassword");   
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package com.dashucoding.c3p0;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;import org.apache.commons.dbcp.BasicDataSource;
import org.junit.Test;import com.dashucoding.util.JDBCUtil;
import com.mchange.v2.c3p0.ComboPooledDataSource;public class C3P0Demo {@Testpublic void testC3P0() {Connection conn = null;PreparedStatement ps = null;try {// 创建dataSourceComboPooledDataSource dataSource = new ComboPooledDataSource();dataSource.setDriverClass("com.mysql.jdbc.Driver");        dataSource.setJdbcUrl( "jdbc:mysql://localhost/bank" );dataSource.setUser("root");                                  dataSource.setPassword("admin");  // 得到连接对象conn = dataSource.getConnection();String sql = "insert into account values(null, ?, ?)";ps = conn.prepareStatement(sql);ps.setString(1, "aaa");ps.setInt(2, 10000);ps.executeUpdate();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();} finally {JDBCUtil.release(conn, ps);}}}
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C3P0使用配置文件的方式

c3p0-config.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config><default-config><property name="driverClass">com.mysql.jdbc.Driver</property><property name="jdbcUrl">jdbc:mysql://localhost/bank</property><property name="user">你的账户</property><property name="password">你的密码</property><property name="initialPoolSize">10</property><property name="maxIdleTime">30</property><property name="maxPoolSize">100</property><property name="minPoolSize">10</property><property name="maxStatements">200</property></default-config></c3p0-config>
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package com.dashucoding.c3p0;import java.sql.Connection;
import java.sql.PreparedStatement;import org.junit.Test;import com.dashucoding.util.JDBCUtil;
import com.mchange.v2.c3p0.ComboPooledDataSource;
// 使用配置文件
public class C3P0Demo02 {@Testpublic void testC3P0() {Connection conn = null;PreparedStatement ps = null;try {// 配置文件 new了一个对象ComboPooledDataSource dataSource = new ComboPooledDataSource(); // 得到连接对象conn = dataSource.getConnection();String sql = "insert into account values(null, ?, ?)";ps = conn.prepareStatement(sql);ps.setString(1, "bbb");ps.setInt(2, 10000);ps.executeUpdate();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();} finally {JDBCUtil.release(conn, ps);}}
}
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可以弄oracle:

<!-- This app is massive! --><named-config name="oracle"> <property name="acquireIncrement">50</property><property name="initialPoolSize">100</property><property name="minPoolSize">50</property><property name="maxPoolSize">1000</property><!-- intergalactoApp adopts a different approach to configuring statement caching --><property name="maxStatements">0</property> <property name="maxStatementsPerConnection">5</property><!-- he's important, but there's only one of him --><user-overrides user="master-of-the-universe"> <property name="acquireIncrement">1</property><property name="initialPoolSize">1</property><property name="minPoolSize">1</property><property name="maxPoolSize">5</property><property name="maxStatementsPerConnection">50</property></user-overrides></named-config>
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oracle:

ComboPooledDataSource dataSource = new ComboPooledDataSource();
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DBUtils

什么是DBUtils呢?怎么用呢?

优化数据库连接,使用C3P0:

package com.dashucoding.util;import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;import com.mchange.v2.c3p0.ComboPooledDataSource;public class JDBCUtil02 {static ComboPooledDataSource dataSource = null;static {dataSource = new ComboPooledDataSource();}/*** 获取连接对象* @return* @throws SQLException */public static Connection getConn() throws SQLException{return dataSource.getConnection();}/*** 释放资源* @param conn* @param st* @param rs*/public static void release(Connection conn , Statement st , ResultSet rs){closeRs(rs);closeSt(st);closeConn(conn);}public static void release(Connection conn , Statement st){closeSt(st);closeConn(conn);}private static void closeRs(ResultSet rs){try {if(rs != null){rs.close();}} catch (SQLException e) {e.printStackTrace();}finally{rs = null;}}private static void closeSt(Statement st){try {if(st != null){st.close();}} catch (SQLException e) {e.printStackTrace();}finally{st = null;}}private static void closeConn(Connection conn){try {if(conn != null){conn.close();}} catch (SQLException e) {e.printStackTrace();}finally{conn = null;}}
}
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DBUtils优化增删改查方法

导包,两行代码交你增删改查,6666!

QueryRunner queryRunner = new QueryRunner(new ComboPooledDataSource());
queryRunner.update("insert into account values(null, ?, ?)", "bbb", 10000);
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两行.

package com.dashucoding.dbutils;import java.sql.SQLException;import org.apache.commons.dbutils.QueryRunner;
import org.junit.Test;import com.mchange.v2.c3p0.ComboPooledDataSource;public class TestDBUtils {@Testpublic void testInsert() throws SQLException {
//		ComboPooledDataSource dataSource = new ComboPooledDataSource(); // dbutils 简化了CRUD的代码QueryRunner queryRunner = new QueryRunner(new ComboPooledDataSource());/** queryRunner.update(sql);* 增删改* queryRunner.query(sql, rsh);* 查* */queryRunner.update("insert into account values(null, ?, ?)", "bbb", 10000);}}
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package com.dashucoding.dbutils;import java.sql.SQLException;import org.apache.commons.dbutils.QueryRunner;
import org.junit.Test;import com.mchange.v2.c3p0.ComboPooledDataSource;public class TestDBUtils {@Testpublic void testInsert() throws SQLException {
//		ComboPooledDataSource dataSource = new ComboPooledDataSource(); // dbutils 简化了CRUD的代码QueryRunner queryRunner = new QueryRunner(new ComboPooledDataSource());/** queryRunner.update(sql);* 增删改* queryRunner.query(sql, rsh);* 查* */queryRunner.update("insert into account values(null, ?, ?)", "bbb", 10000);queryRunner.update("delete from account where id = ?", 8);queryRunner.update("update account set money = ? where id = ?", 0, 10);}}
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查询

package com.dashucoding.dbutils;import java.sql.ResultSet;
import java.sql.SQLException;import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.junit.Test;import com.dashucoding.domain.Account;
import com.mchange.v2.c3p0.ComboPooledDataSource;public class TestDBUtils {@Testpublic void testInsert() throws SQLException {
//		ComboPooledDataSource dataSource = new ComboPooledDataSource(); // dbutils 简化了CRUD的代码QueryRunner queryRunner = new QueryRunner(new ComboPooledDataSource());// 查询的是一个Bean对象// new 匿名实现类->new接口的匿名实现类Account account = queryRunner.query("select * from account where id = ?", new ResultSetHandler<Account>() {// 去执行查询,查询到的数据在result里面,然后调用handle方法,用户手动去封装@Overridepublic Account handle(ResultSet rs) throws SQLException {// TODO Auto-generated method stubAccount account = new Account();while(rs.next()) {String name = rs.getString("name");int money = rs.getInt("money");account.setName(name);account.setMoney(money);}return account;}}, 1);System.out.println(account.toString());/** queryRunner.update(sql);* 增删改* queryRunner.query(sql, rsh);* 查* *//*queryRunner.update("insert into account values(null, ?, ?)", "bbb", 10000);queryRunner.update("delete from account where id = ?", 8);queryRunner.update("update account set money = ? where id = ?", 0, 10);*/}}
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查询优化

一个对象: BeanHandler

一个集合里面有很多对象: BeanListHandler

package com.dashucoding.domain;public class Account {private String name;private int money;public String getName() {return name;}public void setName(String name) {this.name = name;}public int getMoney() {return money;}public void setMoney(int money) {this.money = money;}@Overridepublic String toString() {return "Account [name=" + name + ", money=" + money + "]";}}
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package com.dashucoding.dbutils;import java.sql.SQLException;import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.junit.Test;import com.dashucoding.domain.Account;
import com.mchange.v2.c3p0.ComboPooledDataSource;public class TestDBUtils {@Testpublic void testInsert() throws SQLException {
//		ComboPooledDataSource dataSource = new ComboPooledDataSource(); // dbutils 简化了CRUD的代码QueryRunner queryRunner = new QueryRunner(new ComboPooledDataSource());// 查询的是一个Bean对象// new 匿名实现类->new接口的匿名实现类/*Account account = queryRunner.query("select * from account where id = ?", new ResultSetHandler<Account>() {// 去执行查询,查询到的数据在result里面,然后调用handle方法,用户手动去封装@Overridepublic Account handle(ResultSet rs) throws SQLException {// TODO Auto-generated method stubAccount account = new Account();while(rs.next()) {String name = rs.getString("name");int money = rs.getInt("money");account.setName(name);account.setMoney(money);}return account;}}, 1);System.out.println(account.toString());*/// 接口的实现类-> ResultSetHandler的实现类// Ctrl + t 实现类//ResultSetHandler// 一个对象查询一个对象使用BeanHandlerAccount account = queryRunner.query("select * from account where id = ?", new BeanHandler<Account>(Account.class), 1);System.out.println(account.toString());/** queryRunner.update(sql);* 增删改* queryRunner.query(sql, rsh);* 查* *//*queryRunner.update("insert into account values(null, ?, ?)", "bbb", 10000);queryRunner.update("delete from account where id = ?", 8);queryRunner.update("update account set money = ? where id = ?", 0, 10);*/}}
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优化成两行代码:

Account account = queryRunner.query("select * from account where id = ?", new BeanHandler<Account>(Account.class), 1);
System.out.println(account.toString());
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查询多个数据

// 查询多个对象
List<Account> list = queryRunner.query("select * from account",new BeanListHandler<Account>(Account.class));
for(Account account : list) {System.out.println(account.toString());
}
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package com.dashucoding.dbutils;import java.sql.SQLException;
import java.util.List;import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.junit.Test;import com.dashucoding.domain.Account;
import com.mchange.v2.c3p0.ComboPooledDataSource;public class TestDBUtils {@Testpublic void testInsert() throws SQLException {
//		ComboPooledDataSource dataSource = new ComboPooledDataSource(); // dbutils 简化了CRUD的代码QueryRunner queryRunner = new QueryRunner(new ComboPooledDataSource());// 查询的是一个Bean对象// new 匿名实现类->new接口的匿名实现类/*Account account = queryRunner.query("select * from account where id = ?", new ResultSetHandler<Account>() {// 去执行查询,查询到的数据在result里面,然后调用handle方法,用户手动去封装@Overridepublic Account handle(ResultSet rs) throws SQLException {// TODO Auto-generated method stubAccount account = new Account();while(rs.next()) {String name = rs.getString("name");int money = rs.getInt("money");account.setName(name);account.setMoney(money);}return account;}}, 1);System.out.println(account.toString());*/// 接口的实现类-> ResultSetHandler的实现类// Ctrl + t 实现类//ResultSetHandler// 一个对象查询一个对象使用BeanHandler/*Account account = queryRunner.query("select * from account where id = ?",new BeanHandler<Account>(Account.class), 1);System.out.println(account.toString());*//*List<Account> account = queryRunner.query("select * from account",new BeanListHandler<Account>(Account.class));*/// 查询多个对象List<Account> list = queryRunner.query("select * from account",new BeanListHandler<Account>(Account.class));for(Account account : list) {System.out.println(account.toString());}/** queryRunner.update(sql);* 增删改* queryRunner.query(sql, rsh);* 查* *//*queryRunner.update("insert into account values(null, ?, ?)", "bbb", 10000);queryRunner.update("delete from account where id = ?", 8);queryRunner.update("update account set money = ? where id = ?", 0, 10);*/}}
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小结

// 通过类的字节码,获得该类的实例:
Account a = new Account();Account a1 = Account.class.newInstance();new BeanHandler<Account>(Account.class)new BeanListHandler<Account>(Account.class)
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ResultSetHandler<T>

实现类:

总结

事务,连接池,DBUtils

查询:

QueryRunner queryRunner = new QueryRunner(new ComboPooledDataSource());queryRunner.update();
queryRunner.query
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1. 事务 脏读 不可重复读 幻读

丢失更新 写的问题 悲观锁 for update 乐观锁 ,添加字段版本级别

4个隔离级别 读未提交 读已提交 可重复读 可串行化

读未提交,引发脏读 读已提交,引发不可重复读,解决了脏读

可重复读,引发了幻读,解决了脏读,不可重复读 可串行化(序列化),解决了脏读,不可重复读,幻读,引发效率低下问题

数据库连接池

1. BCP -> 不使用配置 使用配置
2. C3P0 -> 不使用配置 使用配置
3. 自定义连接池 -> 饰者模式

结言

可在评论发表你的总结内容,做功课哦!

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