day12-功能实现11 - ToB企服应用市场:ToB评测及商务社交产业平台

package com.li.furns.utils;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import javax.sql.DataSource;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
/**
* 基于Druid数据库连接池的工具类
*/
public class JDBCUtilsByDruid {
private static DataSource ds;
//定义属性ThreadLocal，这里存放一个Connection
private static ThreadLocal<Connection> threadLocalConn = new ThreadLocal<>();
//在静态代码块完成ds的初始化
//静态代码块在加载类的时候只会执行一次，因此数据源也只会初始化一次
static {
Properties properties = new Properties();
try {
//因为我们是web项目，它的工作目录不在src下面，文件的加载需要使用类加载器
properties.load(JDBCUtilsByDruid.class.getClassLoader()
.getResourceAsStream("druid.properties"));
//properties.load(new FileInputStream("src\\druid.properties"));
ds = DruidDataSourceFactory.createDataSource(properties);
} catch (Exception e) {
e.printStackTrace();
}
}
// //编写getConnection方法
// public static Connection getConnection() throws SQLException {
// return ds.getConnection();
// }
/**
* 获取连接方法
* 从ThreadLocal中获取connection，
* 从而保证在同一个线程中获取的是同一个Connection
*
* @return
* @throws SQLException
*/
public static Connection getConnection() {
Connection connection = threadLocalConn.get();
if (connection == null) {//说明当前的threadLocalConn没有连接
//就从数据库连接池中获取一个连接，放到ThreadLocal中
try {
connection = ds.getConnection();
//设置为手动提交，即不要自动提交
connection.setAutoCommit(false);
} catch (SQLException e) {
e.printStackTrace();
}
threadLocalConn.set(connection);
}
return connection;
}
/**
* 提交事务
*/
public static void commit() {
Connection connection = threadLocalConn.get();
if (connection != null) {//确保该连接是有效的
try {
connection.commit();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
connection.close();//将连接释放回连接池
} catch (SQLException e) {
e.printStackTrace();
}
}
//1.当提交后，需要把connection从threadLocalConn中清除掉
//2.否则会造成ThreadLocalConn长时间持有该连接，会影响效率
//3.也因为我们Tomcat底层使用的是线程池技术
threadLocalConn.remove();
}
}
/**
* 回滚，回滚的是和connection相关的dml操作
*/
public static void rollback() {
Connection connection = threadLocalConn.get();
if (connection != null) {//保证当前的连接是有效的
try {
connection.rollback();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
threadLocalConn.remove();
}
//关闭连接（注意：在数据库连接池技术中，close不是真的关闭连接，而是将Connection对象放回连接池中）
public static void close(ResultSet resultSet, Statement statemenat, Connection connection) {
try {
if (resultSet != null) {
resultSet.close();
}
if (statemenat != null) {
statemenat.close();
}
if (connection != null) {
connection.close();
}
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}

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<filter>
<filter-name>TransactionFilter</filter-name>
<filter-class>com.li.furns.filter.TransactionFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>TransactionFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

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package com.li.furns.filter;
import com.li.furns.utils.JDBCUtilsByDruid;
import javax.servlet.*;
import java.io.IOException;
/**
* 管理事务
*
* @author 李
* @version 1.0
*/
public class TransactionFilter implements Filter {
public void init(FilterConfig config) throws ServletException {
}
public void destroy() {
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
try {
//先放行
chain.doFilter(request, response);
//统一提交
JDBCUtilsByDruid.commit();
} catch (Exception e) {
//只有在try{}中出现了异常，才会进行catch{}
//这里想要捕获异常，前提是底层的代码没有将抛出的异常捕获
JDBCUtilsByDruid.rollback();//回滚
e.printStackTrace();
}
}
}

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<error-page>
<error-code>404</error-code>
<location>/views/error/404.jsp</location>
</error-page>
<error-page>
<error-code>500</error-code>
<location>/views/error/500.jsp</location>
</error-page>

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