- 浏览: 1739344 次
- 性别:
- 来自: 北京
文章分类
- 全部博客 (723)
- IE 国际化 (1)
- java (310)
- python (52)
- Spring (101)
- eclipse (43)
- birt (10)
- exe4j (1)
- ActiveMQ (3)
- HornetQ (7)
- Ext (16)
- Linux (50)
- james (1)
- mail (3)
- 经验 (288)
- tomcat (5)
- Netty (3)
- ant (6)
- rsync (2)
- MD5 (3)
- 正则表达式 (3)
- 非技术 (59)
- mysql (28)
- sftp (1)
- Commons (2)
- oracle (3)
- vsftp (1)
- jdoc (1)
- socket (3)
- SEDA (2)
- UUID (1)
- quartz (7)
- javascript (50)
- sql (5)
- array (3)
- POI (3)
- redis (2)
- junit (4)
- 二维码 (1)
- jdk (8)
- h2 (6)
- maven (37)
- JVM (5)
- html (4)
- css (1)
- excel (4)
- myeclipse (2)
- scala (0)
- jQuery (5)
- log (10)
- slf4j (2)
- log4j (9)
- REST (15)
- guava (18)
- Joda-Time (7)
- ini4j (1)
- 配置文件 (2)
- lucene (1)
- database (3)
- curator (2)
- zookeeper (3)
- 并发 (2)
- jetty (6)
- ehcache (5)
- windows (1)
- protobuf (1)
- select2 (2)
- easyui (10)
- Freemarker (1)
- Filter (1)
- twisted (1)
- DateTime (11)
- mockrunner (1)
- DataSource (4)
- ajax (1)
- shell (18)
- powermockito (5)
- json (5)
- lombok (1)
- jointjs (1)
- cookie (1)
- mybatis (11)
- 加密解密 (2)
- 安全 (2)
- web (1)
- notepad++ (3)
- mac (48)
- sublime (14)
- git (7)
- docker (10)
- jar (1)
- gson (5)
- ubuntu (3)
- 模式 (1)
- neo4j (2)
- elasticsearch (1)
- OmniGranffle (1)
- ASCII (1)
- jdbc (3)
- kafka (1)
- MQ (1)
- chrome (3)
- 华为 (1)
- 路由器 (1)
- api (2)
- 架构 (1)
- 设计模式 (1)
- pip (4)
- springboot (48)
- 数据库 (4)
- thread (1)
- java.thread (1)
- sqlite (1)
- postman (1)
- springboot-actuator (2)
- jwt (1)
- token (1)
- brew (9)
- vim (1)
- virtualbox (1)
- Swagger (1)
- spring-retry (3)
- 调度 (1)
- item2 (5)
- graph (12)
- jgrapht (12)
- tuple (1)
- hadoop (5)
- curl (1)
- 算法 (3)
- Jekyll (1)
- github (1)
- ssh-keygen (1)
- zip (2)
- http (2)
- RestTemplate (8)
- 文件处理 (2)
- XStream (1)
- XML (3)
- JAXB (1)
- 笛卡尔积 (2)
- hive (1)
- 搜狗输入法 (1)
- 常用java类 (2)
- nginx (1)
- log4j2 (1)
- drawio (2)
- 安卓 (1)
- 小米 (1)
- okhttp (1)
- requests (1)
- 格式化 (2)
- MySQL Workbench (1)
- 分布式 (1)
- zip4j (1)
- hbase (5)
- hikari (1)
- javers (1)
- pydatetime (4)
- pyassert (1)
- pylog (2)
- tree (2)
- download (1)
- zeppelin (1)
- utils (2)
- wget (1)
- 鼠标 (1)
- 位运算 (2)
- open api (1)
- 域名 (1)
最新评论
-
youngcoder:
haohaohao~
Spring cache 注解功能不起作用的解决方案 -
kanpiaoxue:
lixz 写道有具体实例demo吗好多年前写的了。你还是去官网 ...
spring batch(一):基础部分 -
lixz:
有具体实例demo吗
spring batch(一):基础部分 -
BuDongOrz:
...
Spring MVC controller 读取配置文件 -
hvang1988:
理解错了,原来还是计数,不是时间
spring batch(二):核心部分(1):配置Spring batch
我使用DBCP连接池的时候,发生异常:nested exception is java.sql.SQLRecoverableException: IO Error: Broken pipe
开始怀疑网络有问题,后来同事说这个是连接池里面的链接都是长连接,一直保持与数据库的链接。我用的是Oracle数据库。出于某种原因,Oracle数据库会把很长时间的链接kill掉。这样,连接池里面的长连接,并不知道自身在服务器端已经被kill了,再次发生向数据库的请求连接时,发生上面的异常。
没有办法,我只能写了个方法,来解决这个问题:代码如下:
/** * <pre> * Date:2011-12-29 * 防止发生异常:nested exception is java.sql.SQLRecoverableException: IO Error: Broken pipe * 原因:连接池链接一段时间之后,会被oracle在服务器端中断,而连接池并不知道自己的链接被中断,照旧进行连接操作,发生异常 * @param dataSource * @param oldConn * @return * @throws SQLException * </pre> */ private static Connection getValidConnection(DataSource dataSource,Connection oldConn) throws SQLException { //get the connection from the datasource Connection conn = oldConn; int commonTimeout = 150; //check the connection, if the connection is not suitable, then get the new connection and check it again while(null == conn || conn.isClosed() || !conn.isValid(commonTimeout)) { try { if(null != conn && !conn.isClosed()) { //close the connection conn.close(); } } catch (SQLException e) { logger.error("Can not close connection :\t"+e.getMessage(),e); } //get the new connection conn = dataSource.getConnection(); } //return the valid connection return conn; }
我用的是Spring3.1的框架,使用的是JdbcTemplate来执行存储过程。所以我修改了spring的源码 org.springframework.jdbc.datasource.DataSourceUtils 类里面的 public static Connection getConnection(DataSource dataSource) throws CannotGetJdbcConnectionException 方法,如下:
/* * Copyright 2002-2010 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.jdbc.datasource; import java.sql.Connection; import java.sql.SQLException; import java.sql.Statement; import javax.sql.DataSource; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.springframework.jdbc.CannotGetJdbcConnectionException; import org.springframework.transaction.TransactionDefinition; import org.springframework.transaction.support.TransactionSynchronizationAdapter; import org.springframework.transaction.support.TransactionSynchronizationManager; import org.springframework.util.Assert; /** * Helper class that provides static methods for obtaining JDBC Connections from * a {@link javax.sql.DataSource}. Includes special support for Spring-managed * transactional Connections, e.g. managed by {@link DataSourceTransactionManager} * or {@link org.springframework.transaction.jta.JtaTransactionManager}. * * <p>Used internally by Spring's {@link org.springframework.jdbc.core.JdbcTemplate}, * Spring's JDBC operation objects and the JDBC {@link DataSourceTransactionManager}. * Can also be used directly in application code. * * @author Rod Johnson * @author Juergen Hoeller * @see #getConnection * @see #releaseConnection * @see DataSourceTransactionManager * @see org.springframework.transaction.jta.JtaTransactionManager * @see org.springframework.transaction.support.TransactionSynchronizationManager */ public abstract class DataSourceUtils { /** * Order value for TransactionSynchronization objects that clean up JDBC Connections. */ public static final int CONNECTION_SYNCHRONIZATION_ORDER = 1000; private static final Log logger = LogFactory.getLog(DataSourceUtils.class); /** * Obtain a Connection from the given DataSource. Translates SQLExceptions into * the Spring hierarchy of unchecked generic data access exceptions, simplifying * calling code and making any exception that is thrown more meaningful. * <p>Is aware of a corresponding Connection bound to the current thread, for example * when using {@link DataSourceTransactionManager}. Will bind a Connection to the * thread if transaction synchronization is active, e.g. when running within a * {@link org.springframework.transaction.jta.JtaTransactionManager JTA} transaction). * @param dataSource the DataSource to obtain Connections from * @return a JDBC Connection from the given DataSource * @throws org.springframework.jdbc.CannotGetJdbcConnectionException * if the attempt to get a Connection failed * @see #releaseConnection */ public static Connection getConnection(DataSource dataSource) throws CannotGetJdbcConnectionException { try { //return doGetConnection(dataSource); //modified here Connection oldConn = doGetConnection(dataSource); return getValidConnection(dataSource, oldConn); } catch (SQLException ex) { throw new CannotGetJdbcConnectionException("Could not get JDBC Connection", ex); } } /** * <pre> * Date:2011-12-29 * 防止发生异常:nested exception is java.sql.SQLRecoverableException: IO Error: Broken pipe * 原因:连接池链接一段时间之后,会被oracle在服务器端中断,而连接池并不知道自己的链接被中断,照旧进行连接操作,发生异常 * @param dataSource * @param oldConn * @return * @throws SQLException * </pre> */ private static Connection getValidConnection(DataSource dataSource,Connection oldConn) throws SQLException { //get the connection from the datasource Connection conn = oldConn; int commonTimeout = 150; //check the connection, if the connection is not suitable, then get the new connection and check it again while(null == conn || conn.isClosed() || !conn.isValid(commonTimeout)) { try { if(null != conn && !conn.isClosed()) { //close the connection conn.close(); } } catch (SQLException e) { logger.error("Can not close connection :\t"+e.getMessage(),e); } //get the new connection conn = dataSource.getConnection(); } //return the valid connection return conn; } /** * Actually obtain a JDBC Connection from the given DataSource. * Same as {@link #getConnection}, but throwing the original SQLException. * <p>Is aware of a corresponding Connection bound to the current thread, for example * when using {@link DataSourceTransactionManager}. Will bind a Connection to the thread * if transaction synchronization is active (e.g. if in a JTA transaction). * <p>Directly accessed by {@link TransactionAwareDataSourceProxy}. * @param dataSource the DataSource to obtain Connections from * @return a JDBC Connection from the given DataSource * @throws SQLException if thrown by JDBC methods * @see #doReleaseConnection */ public static Connection doGetConnection(DataSource dataSource) throws SQLException { Assert.notNull(dataSource, "No DataSource specified"); ConnectionHolder conHolder = (ConnectionHolder) TransactionSynchronizationManager.getResource(dataSource); if (conHolder != null && (conHolder.hasConnection() || conHolder.isSynchronizedWithTransaction())) { conHolder.requested(); if (!conHolder.hasConnection()) { logger.debug("Fetching resumed JDBC Connection from DataSource"); conHolder.setConnection(dataSource.getConnection()); } return conHolder.getConnection(); } // Else we either got no holder or an empty thread-bound holder here. logger.debug("Fetching JDBC Connection from DataSource"); Connection con = dataSource.getConnection(); if (TransactionSynchronizationManager.isSynchronizationActive()) { logger.debug("Registering transaction synchronization for JDBC Connection"); // Use same Connection for further JDBC actions within the transaction. // Thread-bound object will get removed by synchronization at transaction completion. ConnectionHolder holderToUse = conHolder; if (holderToUse == null) { holderToUse = new ConnectionHolder(con); } else { holderToUse.setConnection(con); } holderToUse.requested(); TransactionSynchronizationManager.registerSynchronization( new ConnectionSynchronization(holderToUse, dataSource)); holderToUse.setSynchronizedWithTransaction(true); if (holderToUse != conHolder) { TransactionSynchronizationManager.bindResource(dataSource, holderToUse); } } return con; } /** * Prepare the given Connection with the given transaction semantics. * @param con the Connection to prepare * @param definition the transaction definition to apply * @return the previous isolation level, if any * @throws SQLException if thrown by JDBC methods * @see #resetConnectionAfterTransaction */ public static Integer prepareConnectionForTransaction(Connection con, TransactionDefinition definition) throws SQLException { Assert.notNull(con, "No Connection specified"); // Set read-only flag. if (definition != null && definition.isReadOnly()) { try { if (logger.isDebugEnabled()) { logger.debug("Setting JDBC Connection [" + con + "] read-only"); } con.setReadOnly(true); } catch (SQLException ex) { Throwable exToCheck = ex; while (exToCheck != null) { if (exToCheck.getClass().getSimpleName().contains("Timeout")) { // Assume it's a connection timeout that would otherwise get lost: e.g. from JDBC 4.0 throw ex; } exToCheck = exToCheck.getCause(); } // "read-only not supported" SQLException -> ignore, it's just a hint anyway logger.debug("Could not set JDBC Connection read-only", ex); } catch (RuntimeException ex) { Throwable exToCheck = ex; while (exToCheck != null) { if (exToCheck.getClass().getSimpleName().contains("Timeout")) { // Assume it's a connection timeout that would otherwise get lost: e.g. from Hibernate throw ex; } exToCheck = exToCheck.getCause(); } // "read-only not supported" UnsupportedOperationException -> ignore, it's just a hint anyway logger.debug("Could not set JDBC Connection read-only", ex); } } // Apply specific isolation level, if any. Integer previousIsolationLevel = null; if (definition != null && definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT) { if (logger.isDebugEnabled()) { logger.debug("Changing isolation level of JDBC Connection [" + con + "] to " + definition.getIsolationLevel()); } int currentIsolation = con.getTransactionIsolation(); if (currentIsolation != definition.getIsolationLevel()) { previousIsolationLevel = currentIsolation; con.setTransactionIsolation(definition.getIsolationLevel()); } } return previousIsolationLevel; } /** * Reset the given Connection after a transaction, * regarding read-only flag and isolation level. * @param con the Connection to reset * @param previousIsolationLevel the isolation level to restore, if any * @see #prepareConnectionForTransaction */ public static void resetConnectionAfterTransaction(Connection con, Integer previousIsolationLevel) { Assert.notNull(con, "No Connection specified"); try { // Reset transaction isolation to previous value, if changed for the transaction. if (previousIsolationLevel != null) { if (logger.isDebugEnabled()) { logger.debug("Resetting isolation level of JDBC Connection [" + con + "] to " + previousIsolationLevel); } con.setTransactionIsolation(previousIsolationLevel); } // Reset read-only flag. if (con.isReadOnly()) { if (logger.isDebugEnabled()) { logger.debug("Resetting read-only flag of JDBC Connection [" + con + "]"); } con.setReadOnly(false); } } catch (Throwable ex) { logger.debug("Could not reset JDBC Connection after transaction", ex); } } /** * Determine whether the given JDBC Connection is transactional, that is, * bound to the current thread by Spring's transaction facilities. * @param con the Connection to check * @param dataSource the DataSource that the Connection was obtained from * (may be <code>null</code>) * @return whether the Connection is transactional */ public static boolean isConnectionTransactional(Connection con, DataSource dataSource) { if (dataSource == null) { return false; } ConnectionHolder conHolder = (ConnectionHolder) TransactionSynchronizationManager.getResource(dataSource); return (conHolder != null && connectionEquals(conHolder, con)); } /** * Apply the current transaction timeout, if any, * to the given JDBC Statement object. * @param stmt the JDBC Statement object * @param dataSource the DataSource that the Connection was obtained from * @throws SQLException if thrown by JDBC methods * @see java.sql.Statement#setQueryTimeout */ public static void applyTransactionTimeout(Statement stmt, DataSource dataSource) throws SQLException { applyTimeout(stmt, dataSource, 0); } /** * Apply the specified timeout - overridden by the current transaction timeout, * if any - to the given JDBC Statement object. * @param stmt the JDBC Statement object * @param dataSource the DataSource that the Connection was obtained from * @param timeout the timeout to apply (or 0 for no timeout outside of a transaction) * @throws SQLException if thrown by JDBC methods * @see java.sql.Statement#setQueryTimeout */ public static void applyTimeout(Statement stmt, DataSource dataSource, int timeout) throws SQLException { Assert.notNull(stmt, "No Statement specified"); Assert.notNull(dataSource, "No DataSource specified"); ConnectionHolder holder = (ConnectionHolder) TransactionSynchronizationManager.getResource(dataSource); if (holder != null && holder.hasTimeout()) { // Remaining transaction timeout overrides specified value. stmt.setQueryTimeout(holder.getTimeToLiveInSeconds()); } else if (timeout > 0) { // No current transaction timeout -> apply specified value. stmt.setQueryTimeout(timeout); } } /** * Close the given Connection, obtained from the given DataSource, * if it is not managed externally (that is, not bound to the thread). * @param con the Connection to close if necessary * (if this is <code>null</code>, the call will be ignored) * @param dataSource the DataSource that the Connection was obtained from * (may be <code>null</code>) * @see #getConnection */ public static void releaseConnection(Connection con, DataSource dataSource) { try { doReleaseConnection(con, dataSource); } catch (SQLException ex) { logger.debug("Could not close JDBC Connection", ex); } catch (Throwable ex) { logger.debug("Unexpected exception on closing JDBC Connection", ex); } } /** * Actually close the given Connection, obtained from the given DataSource. * Same as {@link #releaseConnection}, but throwing the original SQLException. * <p>Directly accessed by {@link TransactionAwareDataSourceProxy}. * @param con the Connection to close if necessary * (if this is <code>null</code>, the call will be ignored) * @param dataSource the DataSource that the Connection was obtained from * (may be <code>null</code>) * @throws SQLException if thrown by JDBC methods * @see #doGetConnection */ public static void doReleaseConnection(Connection con, DataSource dataSource) throws SQLException { if (con == null) { return; } if (dataSource != null) { ConnectionHolder conHolder = (ConnectionHolder) TransactionSynchronizationManager.getResource(dataSource); if (conHolder != null && connectionEquals(conHolder, con)) { // It's the transactional Connection: Don't close it. conHolder.released(); return; } } // Leave the Connection open only if the DataSource is our // special SmartDataSoruce and it wants the Connection left open. if (!(dataSource instanceof SmartDataSource) || ((SmartDataSource) dataSource).shouldClose(con)) { logger.debug("Returning JDBC Connection to DataSource"); con.close(); } } /** * Determine whether the given two Connections are equal, asking the target * Connection in case of a proxy. Used to detect equality even if the * user passed in a raw target Connection while the held one is a proxy. * @param conHolder the ConnectionHolder for the held Connection (potentially a proxy) * @param passedInCon the Connection passed-in by the user * (potentially a target Connection without proxy) * @return whether the given Connections are equal * @see #getTargetConnection */ private static boolean connectionEquals(ConnectionHolder conHolder, Connection passedInCon) { if (!conHolder.hasConnection()) { return false; } Connection heldCon = conHolder.getConnection(); // Explicitly check for identity too: for Connection handles that do not implement // "equals" properly, such as the ones Commons DBCP exposes). return (heldCon == passedInCon || heldCon.equals(passedInCon) || getTargetConnection(heldCon).equals(passedInCon)); } /** * Return the innermost target Connection of the given Connection. If the given * Connection is a proxy, it will be unwrapped until a non-proxy Connection is * found. Otherwise, the passed-in Connection will be returned as-is. * @param con the Connection proxy to unwrap * @return the innermost target Connection, or the passed-in one if no proxy * @see ConnectionProxy#getTargetConnection() */ public static Connection getTargetConnection(Connection con) { Connection conToUse = con; while (conToUse instanceof ConnectionProxy) { conToUse = ((ConnectionProxy) conToUse).getTargetConnection(); } return conToUse; } /** * Determine the connection synchronization order to use for the given * DataSource. Decreased for every level of nesting that a DataSource * has, checked through the level of DelegatingDataSource nesting. * @param dataSource the DataSource to check * @return the connection synchronization order to use * @see #CONNECTION_SYNCHRONIZATION_ORDER */ private static int getConnectionSynchronizationOrder(DataSource dataSource) { int order = CONNECTION_SYNCHRONIZATION_ORDER; DataSource currDs = dataSource; while (currDs instanceof DelegatingDataSource) { order--; currDs = ((DelegatingDataSource) currDs).getTargetDataSource(); } return order; } /** * Callback for resource cleanup at the end of a non-native JDBC transaction * (e.g. when participating in a JtaTransactionManager transaction). * @see org.springframework.transaction.jta.JtaTransactionManager */ private static class ConnectionSynchronization extends TransactionSynchronizationAdapter { private final ConnectionHolder connectionHolder; private final DataSource dataSource; private int order; private boolean holderActive = true; public ConnectionSynchronization(ConnectionHolder connectionHolder, DataSource dataSource) { this.connectionHolder = connectionHolder; this.dataSource = dataSource; this.order = getConnectionSynchronizationOrder(dataSource); } @Override public int getOrder() { return this.order; } @Override public void suspend() { if (this.holderActive) { TransactionSynchronizationManager.unbindResource(this.dataSource); if (this.connectionHolder.hasConnection() && !this.connectionHolder.isOpen()) { // Release Connection on suspend if the application doesn't keep // a handle to it anymore. We will fetch a fresh Connection if the // application accesses the ConnectionHolder again after resume, // assuming that it will participate in the same transaction. releaseConnection(this.connectionHolder.getConnection(), this.dataSource); this.connectionHolder.setConnection(null); } } } @Override public void resume() { if (this.holderActive) { TransactionSynchronizationManager.bindResource(this.dataSource, this.connectionHolder); } } @Override public void beforeCompletion() { // Release Connection early if the holder is not open anymore // (that is, not used by another resource like a Hibernate Session // that has its own cleanup via transaction synchronization), // to avoid issues with strict JTA implementations that expect // the close call before transaction completion. if (!this.connectionHolder.isOpen()) { TransactionSynchronizationManager.unbindResource(this.dataSource); this.holderActive = false; if (this.connectionHolder.hasConnection()) { releaseConnection(this.connectionHolder.getConnection(), this.dataSource); } } } @Override public void afterCompletion(int status) { // If we haven't closed the Connection in beforeCompletion, // close it now. The holder might have been used for other // cleanup in the meantime, for example by a Hibernate Session. if (this.holderActive) { // The thread-bound ConnectionHolder might not be available anymore, // since afterCompletion might get called from a different thread. TransactionSynchronizationManager.unbindResourceIfPossible(this.dataSource); this.holderActive = false; if (this.connectionHolder.hasConnection()) { releaseConnection(this.connectionHolder.getConnection(), this.dataSource); // Reset the ConnectionHolder: It might remain bound to the thread. this.connectionHolder.setConnection(null); } } this.connectionHolder.reset(); } } }
发表评论
-
swagger生成javaAPI的server&client代码
2021-03-25 11:05 841文章原文: 《Spring Boot: API ... -
springboot 返回JSON日期格式问题
2021-03-24 16:36 1058springboot返回的时间格式,根据版本的不同,可能返回 ... -
在其他项目中如何依赖一个springboot的jar?
2021-03-17 16:08 579资料:How to add a dependency ... -
指定java stream中并行处理的线程池大小
2021-03-04 11:38 1455Java8实战:并行线程池 写道 并行流内部使用了默认的F ... -
Can we disable the default web server in the Spring Boot application?
2021-02-22 11:07 242The major strong point in S ... -
Java 8 Comparator: How to Sort a List
2021-02-22 10:54 302文章地址: https://dzone.com/art ... -
Java Getter and Setter: Basics, Common Mistakes, and Best Practices
2021-02-22 10:19 447文章地址: https://dzone.com/ar ... -
Java String Format Examples
2021-02-22 10:14 268参考资料地址: 文章地址: https://dzo ... -
位运算&位掩码示例(权限)
2021-02-10 14:26 415参考资料地址: 1、https://juejin. ... -
Java 位移运算符
2021-02-08 16:21 357参考文章: 1、【 ... -
java中tree的应用示例:javax.swing.tree.DefaultMutableTreeNode
2021-02-03 15:03 454package org.kanpiaoxue. ... -
数据分页逻辑
2021-01-20 17:48 259//当前页 int intPage = I ... -
eclipse导入导出Snippets
2021-01-20 10:45 321导出: Display the snippets v ... -
eclipse迁移配置、插件(导出/导入快捷键、代码风格等等)
2021-01-20 10:28 678有的时候需要从一个eclipse导出它的所有配置,比如 ... -
eclipse需要的jdk版本查询
2021-01-18 11:38 444现在jdk的版本升级太快,eclipse的升级也 ... -
mac查看JAVA_HOME
2021-01-17 00:37 684在mac里面安装好java之后需要设置JAVA_HOM ... -
单例模式
2021-01-14 10:03 231参考资料: https://dzone.com/art ... -
计算工作日期的java工具类
2020-12-31 10:55 273import org.apache.common ... -
java的四舍五入
2020-12-30 11:59 426参考文章: https://www.cnblogs.c ... -
存储单位工具类(来自于hadoop)
2020-12-25 17:30 178/** * 存储单位工具类 * @ClassN ...
相关推荐
在linux上通过JDBC连接ORACLE 时总是出现 java.sql.SQLRecoverableException: IO Error: Connection reset 的问题
关于 SQL Server ErrorLog 错误日志说明学习sqlserver的朋友可以参考下。
本资源为一个java工程文件,实现了MyBatis连接Oracle数据库并进行简单的查询操作。
asp代码ASP家教信息管理系统(源代码+论文)本资源系百度网盘分享地址
基于ssm高校毕业选题管理系统.zip
人工智能毕业设计&课程设计
Python库是一组预先编写的代码模块,旨在帮助开发者实现特定的编程任务,无需从零开始编写代码。这些库可以包括各种功能,如数学运算、文件操作、数据分析和网络编程等。Python社区提供了大量的第三方库,如NumPy、Pandas和Requests,极大地丰富了Python的应用领域,从数据科学到Web开发。Python库的丰富性是Python成为最受欢迎的编程语言之一的关键原因之一。这些库不仅为初学者提供了快速入门的途径,而且为经验丰富的开发者提供了强大的工具,以高效率、高质量地完成复杂任务。例如,Matplotlib和Seaborn库在数据可视化领域内非常受欢迎,它们提供了广泛的工具和技术,可以创建高度定制化的图表和图形,帮助数据科学家和分析师在数据探索和结果展示中更有效地传达信息。
Python库是一组预先编写的代码模块,旨在帮助开发者实现特定的编程任务,无需从零开始编写代码。这些库可以包括各种功能,如数学运算、文件操作、数据分析和网络编程等。Python社区提供了大量的第三方库,如NumPy、Pandas和Requests,极大地丰富了Python的应用领域,从数据科学到Web开发。Python库的丰富性是Python成为最受欢迎的编程语言之一的关键原因之一。这些库不仅为初学者提供了快速入门的途径,而且为经验丰富的开发者提供了强大的工具,以高效率、高质量地完成复杂任务。例如,Matplotlib和Seaborn库在数据可视化领域内非常受欢迎,它们提供了广泛的工具和技术,可以创建高度定制化的图表和图形,帮助数据科学家和分析师在数据探索和结果展示中更有效地传达信息。
粒子群算法 粒子群算法(Particle Swarm Optimization,PSO)是一种优化算法,受到鸟群或鱼群等群体行为的启发。该算法通过模拟群体中个体之间的合作和竞争来搜索最优解。粒子群算法通常用于解决连续优化问题。 ### 工作原理: 1. **初始化**:随机生成一群粒子(也称为个体),每个粒子代表搜索空间中的一个解,并随机初始化其位置和速度。 2. **评估**:根据每个粒子的位置,计算其对应的适应度值(目标函数值)。 3. **更新**:根据个体最优和全局最优的情况,更新每个粒子的速度和位置。粒子会根据自己历史最好的位置以及整个群体历史最好的位置进行调整,以期望更好的搜索方向。 4. **迭代**:重复评估和更新步骤,直到满足停止条件(如达到最大迭代次数、目标函数值足够接近最优解等)。 ### 主要参数: - 粒子数量(Population Size):群体中粒子的数量,通常越大越容易找到全局最优解,但计算成本也会增加。 - 惯性权重(Inertia Weight):控制粒子运动的惯性,平衡局部搜索和全局搜索能力。通常随着迭代次数增加而逐渐减小。
20210327 AI-for-Drug-Discovery-2020
Python库是一组预先编写的代码模块,旨在帮助开发者实现特定的编程任务,无需从零开始编写代码。这些库可以包括各种功能,如数学运算、文件操作、数据分析和网络编程等。Python社区提供了大量的第三方库,如NumPy、Pandas和Requests,极大地丰富了Python的应用领域,从数据科学到Web开发。Python库的丰富性是Python成为最受欢迎的编程语言之一的关键原因之一。这些库不仅为初学者提供了快速入门的途径,而且为经验丰富的开发者提供了强大的工具,以高效率、高质量地完成复杂任务。例如,Matplotlib和Seaborn库在数据可视化领域内非常受欢迎,它们提供了广泛的工具和技术,可以创建高度定制化的图表和图形,帮助数据科学家和分析师在数据探索和结果展示中更有效地传达信息。
Linux创建虚拟机的步骤
这是一个基于SpringBoot开发的校园二手书交易管理系统,使用Java语言,包含102个文件。主要文件类型包括39个Java源文件、23个HTML文件、10个PNG图片文件、9个XML文件、9个JavaScript文件、4个CSS文件、2个Markdown文档、2个JPG图片文件、1个gitignore文件和1个SVG文件。该项目简洁易用,采用的技术经典,非常适合Java项目入门学习和企业级Java开发熟悉,提供了二手书交易管理、用户认证、数据统计等功能,旨在为校园内的二手书交易提供一个便捷、安全的平台。
基于SSM的旅游管理系统.zip
基于ssm框架网络财务设计与实现.zip
三菱PLC例程源码PLC同变频器通讯程序3本资源系百度网盘分享地址
基于ssm+jsp网上茶叶销售平台.zip
随着网络和科学技术的飞速发展,网络建设作为信息化建设的基础,也越来越受到企业的重视,网络结构和网络信息安全都是企业信息化建设中需要解决的重要问题。 本设计出于对众宇通讯公司长期稳定发展的考虑,针对公司的现状和发展需求,为公司设计了一个稳定的、相对安全的、可扩展并且可以支撑必要的网络应用的网络结构。在此次设计中,主要的运用到的技术与实现功能有:(1)汇聚交换机上使用DHCP技术,使各个接入层设备可自动获取相应的IP地址,也避免了IP地址的冲突;(2)运用VRRP技术,增强网络的连续性和稳定性,实现多链路备份冗余和网关备份冗余;(3)运用MSTP技术,将不同的VLAN与相应实例捆绑,避免了网络环路和广播风暴的产生;(4)通过防火墙技术,实现了企业内部与外部网络之间的信息交互安全。除此之外,还进行了VLAN的划分,端口安全设置,ACL访问限制,NAT地址转换,使用OSPF协议、静态路由等网络配置。 本论文基于华为ENSP仿真模拟软件,充分考虑到了整个公司网络今后的实用性、安全性以及可扩展性。利用所学的相关知识和网络技术,对众宇通讯公司的网络进行模拟设计。此设计根据三层网络结构来搭建网络拓扑,
Gromacs中文手册5.0.2
三菱PLC例程源码八层以下货梯通用程序(奥菱达)本资源系百度网盘分享地址