blocks|key|307685|text|不要重复发明轮子。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|307686|尝试以下现成的第三方组件之一：|307687|307688|Apache+DBCP+-+Tomcat和您的truly.|unordered-list-item|offset|length|307689|c3p0|307690|都在内部使用它|307691|Apache+DBCP提供了关于如何设置池化javax.sql.DataSource的不同示例。这里有一个sample可以帮助您入门。|307692|entityMap|0|LINK|mutability|MUTABLE|url|http://commons.apache.org/dbcp/|1|http://sourceforge.net/projects/c3p0/|2|http://java.sun.com/javase/6/docs/api/javax/sql/DataSource.html|3|https://github.com/apache/commons-dbcp/blob/master/doc/PoolingDataSourceExample.java^0|0|0|0|0|B|0|0|0|4|1|0|0|M|K|2|1H|6|3|0^^$0|@$1|2|3|4|5|6|7|13|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|14|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|15|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|16|8|@]|9|@$H|17|I|18|1|19]]|A|$]]|$1|J|3|K|5|G|7|1A|8|@]|9|@$H|1B|I|1C|1|1D]]|A|$]]|$1|L|3|M|5|6|7|1E|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|1F|8|@]|9|@$H|1G|I|1H|1|1I]|$H|1J|I|1K|1|1L]]|A|$]]|$1|P|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]]|Q|$R|$5|S|T|U|A|$V|W]]|X|$5|S|T|U|A|$V|Y]]|Z|$5|S|T|U|A|$V|10]]|11|$5|S|T|U|A|$V|12]]]]

Don't reinvent the wheel.

Try one of the readily available 3rd party components:

<ul>
<li><a href="http://commons.apache.org/dbcp/" rel="nofollow noreferrer">Apache DBCP</a> - This one is
used internally by Tomcat, and by
yours truly.</li>
<li><a href="http://sourceforge.net/projects/c3p0/" rel="nofollow noreferrer">c3p0</a></li>
</ul>

Apache DBCP comes with different example on how to setup a pooling <a href="http://java.sun.com/javase/6/docs/api/javax/sql/DataSource.html" rel="nofollow noreferrer">javax.sql.DataSource</a>. Here is one <a href="https://github.com/apache/commons-dbcp/blob/master/doc/PoolingDataSourceExample.java" rel="nofollow noreferrer">sample</a> that can help you get started.

blocks|key|305699|text|Apache+Commons有一个用于此目的的库：DBCP。除非你对你的池有奇怪的需求，否则我会使用一个库，因为它一定会比你所希望的更加棘手和微妙。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|305700|entityMap|0|LINK|mutability|MUTABLE|url|http://commons.apache.org/dbcp/^0|P|4|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Apache Commons has a library for that purpose: <a href="http://commons.apache.org/dbcp/" rel="nofollow noreferrer">DBCP</a>. Unless you have strange requirements around your pools, I'd use a library as it's bound to be trickier and more subtle than you would hope.

blocks|key|308710|text|我推荐使用commons-dbcp库。这里列出了许多关于如何使用它的examples，这里是move+simple+one的链接。用法非常简单：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|308711|+BasicDataSource+ds+=+new+BasicDataSource();
+ds.setDriverClassName("oracle.jdbc.driver.OracleDriver")
+ds.setUsername("scott");
+ds.setPassword("tiger");
+ds.setUrl(connectURI);
+...
+Connection+conn+=+ds.getConnection();|code-block|syntax|javascript|308712|您只需要创建一次数据源，因此如果您不知道如何创建数据源，请务必阅读文档。如果您不知道如何正确编写JDBC语句，从而不会泄漏资源，那么您可能还需要阅读此Wikipedia页面。|308713|entityMap|0|LINK|mutability|MUTABLE|url|http://commons.apache.org/dbcp/|1|http://svn.apache.org/viewvc/commons/proper/dbcp/trunk/doc/|2|http://svn.apache.org/viewvc/commons/proper/dbcp/trunk/doc/BasicDataSourceExample.java?view=markup|3|http://en.wikipedia.org/wiki/Java_Database_Connectivity^0|5|C|0|Y|8|1|1F|A|2|0|0|23|9|3|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]|$A|12|B|13|1|14]|$A|15|B|16|1|17]]|C|$]]|$1|D|3|E|5|F|7|18|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|19|8|@]|9|@$A|1A|B|1B|1|1C]]|C|$]]|$1|K|3|-4|5|6|7|1D|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]|U|$5|N|O|P|C|$Q|V]]|W|$5|N|O|P|C|$Q|X]]]]

I would recommend using the <a href="http://commons.apache.org/dbcp/" rel="noreferrer">commons-dbcp</a> library. There are numerous <a href="http://svn.apache.org/viewvc/commons/proper/dbcp/trunk/doc/" rel="noreferrer">examples</a> listed on how to use it, here is the link to the move <a href="http://svn.apache.org/viewvc/commons/proper/dbcp/trunk/doc/BasicDataSourceExample.java?view=markup" rel="noreferrer">simple one</a>. The usage is very simple:

<pre><code> BasicDataSource ds = new BasicDataSource();
 ds.setDriverClassName("oracle.jdbc.driver.OracleDriver")
 ds.setUsername("scott");
 ds.setPassword("tiger");
 ds.setUrl(connectURI);
 ...
 Connection conn = ds.getConnection();
</code></pre>

You only need to create the data source once, so make sure you read the documentation if you do not know how to do that. If you are not aware of how to properly write JDBC statements so you do not leak resources, you also might want to read this <a href="http://en.wikipedia.org/wiki/Java_Database_Connectivity" rel="noreferrer">Wikipedia</a> page.

blocks|key|3044551|text|通常，如果您需要一个连接池，那么您正在编写一个在某些托管环境中运行的应用程序，也就是说，您正在应用程序服务器内部运行。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3044552|开箱即用的解决方案将是与其他应用程序服务器设施最好的集成。但是，如果您没有在应用程序服务器内部运行，我建议您使用。它被广泛使用，并提供了大多数应用程序所需的所有基本池化功能。|3044553|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Usually if you need a connection pool you are writing an application that runs in some managed environment, that is you are running inside an application server. If this is the case be sure to <a href="http://docs.jboss.org/jbossas/jboss4guide/r4/html/cluster.chapt.html" rel="noreferrer">check what connection pooling facilities your application server provides</a>before trying any other options. 

The out-of-the box solution will be the best integrated with the rest of the application servers facilities. If however you are not running inside an application server I would recommend the <a href="http://commons.apache.org/dbcp/" rel="noreferrer">Apache Commons DBCP Component</a>. It is widely used and provides all the basic pooling functionality most applications require.

blocks|key|305850|text|正如其他人回答的那样，您可能会对Apache+Dbcp或c3p0感到满意。两者都很受欢迎，而且都运行得很好。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|305851|关于你的疑虑|305852|305853|没有javax.sql或java.sql的池化连接实现吗？为什么使用这些不是最好的呢？|blockquote|305854|305855|305856|它们不提供实现，而是提供接口和一些支持类，只与实现第三方库(池或驱动程序)的程序员相关。通常你甚至都不会去看它。您的代码应该以透明的方式处理来自池的连接，就像它们是“普通”连接一样。|305857|entityMap|0|LINK|mutability|MUTABLE|url|http://commons.apache.org/dbcp/|1|http://sourceforge.net/projects/c3p0/^0|G|B|0|S|4|1|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@$A|Y|B|Z|1|10]|$A|11|B|12|1|13]]|C|$]]|$1|D|3|E|5|6|7|14|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|15|8|@]|9|@]|C|$]]|$1|G|3|H|5|I|7|16|8|@]|9|@]|C|$]]|$1|J|3|-4|5|6|7|17|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|18|8|@]|9|@]|C|$]]|$1|L|3|M|5|6|7|19|8|@]|9|@]|C|$]]|$1|N|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]]|O|$P|$5|Q|R|S|C|$T|U]]|V|$5|Q|R|S|C|$T|W]]]]

As answered by others, you will probably be happy with <a href="http://commons.apache.org/dbcp/" rel="nofollow noreferrer">Apache Dbcp</a> or <a href="http://sourceforge.net/projects/c3p0/" rel="nofollow noreferrer">c3p0</a>. Both are popular, and work fine.

Regarding your doubt

<blockquote>
 Doesn't javax.sql or java.sql have
 pooled connection implementations? Why
 wouldn't it be best to use these?
</blockquote>

They don't provide implementations, rather interfaces and some support classes, only revelant to the programmers that implement third party libraries (pools or drivers). Normally you don't even look at that. Your code should deal with the connections from your pool just as they were "plain" connections, in a transparent way.

blocks|key|3258552|text|在我工作的地方(我记得是Oracle+Application+server+10g+)使用的应用服务器中，池化是由应用服务器处理的。我们使用带有javax.sql.InitialContext的JNDI查找来检索javax.sql.DataSource。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3258553|它做了类似这样的事情|3258554|try+{+++++
+++context+=+new+InitialContext();
+++jdbcURL+=+(DataSource)+context.lookup("jdbc/CachedDS");
+++System.out.println("Obtained+Cached+Data+Source+");
}
catch(NamingException+e)+++
{++
++++System.err.println("Error+looking+up+Data+Source+from+Factory:+"%2Be.getMessage());
}|code-block|syntax|javascript|3258555|(这段代码不是我们写的，它是从this+documentation复制过来的。)|3258556|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/javase/6/docs/api/javax/naming/InitialContext.html|1|http://java.sun.com/javase/6/docs/api/javax/sql/DataSource.html|2|http://www.oracle.com/technology/oramag/code/tips2003/092103.html?_template=/ocom/print^0|20|O|2Y|K|20|O|0|2Y|K|1|0|0|0|F|I|2|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@$9|15|A|16|1|17]|$9|18|A|19|1|1A]]|E|$]]|$1|F|3|G|5|6|7|1B|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|1C|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1D|8|@]|D|@$9|1E|A|1F|1|1G]]|E|$]]|$1|O|3|-4|5|6|7|1H|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]|W|$5|R|S|T|E|$U|X]]|Y|$5|R|S|T|E|$U|Z]]]]

In the app server we use where I work (Oracle Application Server 10g, as I recall), pooling is handled by the app server. We retrieve a <a href="http://java.sun.com/javase/6/docs/api/javax/sql/DataSource.html" rel="noreferrer"><code>javax.sql.DataSource</code></a> using a JNDI lookup with a <a href="http://java.sun.com/javase/6/docs/api/javax/naming/InitialContext.html" rel="noreferrer"><code>javax.sql.InitialContext</code></a>.

it's done something like this

<pre><code>try { 
 context = new InitialContext();
 jdbcURL = (DataSource) context.lookup("jdbc/CachedDS");
 System.out.println("Obtained Cached Data Source ");
}
catch(NamingException e) 
{ 
 System.err.println("Error looking up Data Source from Factory: "+e.getMessage());
}
</code></pre>

(We didn't write this code, it's copied from <a href="http://www.oracle.com/technology/oramag/code/tips2003/092103.html?_template=/ocom/print" rel="noreferrer">this documentation</a>.)

blocks|key|308819|text|如果你需要一个独立的连接池，我更喜欢C3P0而不是DBCP+(我在这篇previous+answer中提到过)，我只是在重负载下使用DBCP遇到了太多问题。使用C3P0非常简单。从documentation|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|308820|ComboPooledDataSource+cpds+=+new+ComboPooledDataSource();
cpds.setDriverClass(+"org.postgresql.Driver"+);+//loads+the+jdbc+driver
cpds.setJdbcUrl(+"jdbc:postgresql://localhost/testdb"+);
cpds.setUser("swaldman");
cpds.setPassword("test-password");

//+the+settings+below+are+optional+--+c3p0+can+work+with+defaults
cpds.setMinPoolSize(5);
cpds.setAcquireIncrement(5);
cpds.setMaxPoolSize(20);

//+The+DataSource+cpds+is+now+a+fully+configured+and+usable+pooled+DataSource+|code-block|syntax|javascript|308821|但是，如果您在应用程序服务器内部运行，我建议您使用它提供的内置连接池。在这种情况下，您将需要对其进行配置(请参阅应用服务器的文档)，并通过JNDI检索DataSource：|308822|DataSource+ds+=+(DataSource)+new+InitialContext().lookup("jdbc/myDS");|308823|entityMap|0|LINK|mutability|MUTABLE|url|http://www.mchange.com/projects/c3p0/index.html|1|http://commons.apache.org/dbcp/|2|https://stackoverflow.com/questions/2826212/need-code-to-create-connection-pool-in-java/2826295#2826295|3|http://www.mchange.com/projects/c3p0/index.html#using_combopooleddatasource^0|I|4|0|P|4|1|Z|F|2|2I|D|3|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]|$A|14|B|15|1|16]|$A|17|B|18|1|19]|$A|1A|B|1B|1|1C]]|C|$]]|$1|D|3|E|5|F|7|1D|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|1E|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|1F|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|1G|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]|W|$5|P|Q|R|C|$S|X]]|Y|$5|P|Q|R|C|$S|Z]]]]

If you need a standalone connection pool, my preference goes to <a href="http://www.mchange.com/projects/c3p0/index.html" rel="noreferrer">C3P0</a> over <a href="http://commons.apache.org/dbcp/" rel="noreferrer">DBCP</a> (that I've mentioned in this <a href="https://stackoverflow.com/questions/2826212/need-code-to-create-connection-pool-in-java/2826295#2826295">previous answer</a>), I just had too much problems with DBCP under heavy load. Using C3P0 is dead simple. From the <a href="http://www.mchange.com/projects/c3p0/index.html#using_combopooleddatasource" rel="noreferrer">documentation</a>:

<pre><code>ComboPooledDataSource cpds = new ComboPooledDataSource();
cpds.setDriverClass( "org.postgresql.Driver" ); //loads the jdbc driver
cpds.setJdbcUrl( "jdbc:postgresql://localhost/testdb" );
cpds.setUser("swaldman");
cpds.setPassword("test-password");

// the settings below are optional -- c3p0 can work with defaults
cpds.setMinPoolSize(5);
cpds.setAcquireIncrement(5);
cpds.setMaxPoolSize(20);

// The DataSource cpds is now a fully configured and usable pooled DataSource 
</code></pre>

But if you are running inside an application server, I would recommend to use the built-in connection pool it provides. In that case, you'll need to configure it (refer to the documentation of your application server) and to retrieve a DataSource via JNDI:

<pre><code>DataSource ds = (DataSource) new InitialContext().lookup("jdbc/myDS");
</code></pre>

blocks|key|310901|text|Vibur+DBCP是另一个用于此目的的库。可以在它的网站上找到几个示例，这些示例展示了如何将其配置为与Hibernate、Spring%2BHibernate或编程一起使用：http://www.vibur.org/|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|310902|另请参阅免责声明here。|310903|entityMap|0|LINK|mutability|MUTABLE|url|http://www.vibur.org/|1|https://stackoverflow.com/a/19729373/1682918^0|0|A|2E|L|0|0|8|4|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@$9|U|A|V|1|W]]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@$9|Y|A|Z|1|10]]|E|$]]|$1|H|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]|P|$5|K|L|M|E|$N|Q]]]]

Vibur DBCP is another library for that purpose. Several examples showing how to configure it for use with Hibernate, Spring+Hibernate, or programatically, can be found on its website: <a href="http://www.vibur.org/" rel="nofollow noreferrer">http://www.vibur.org/</a>

Also, see the disclaimer <a href="https://stackoverflow.com/a/19729373/1682918">here</a>.

blocks|key|3044703|text|HikariCP|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3044704|它很现代，很快，很简单。我在每个新项目中都使用它。与C3P0相比，我更喜欢它，我不太了解其他池。|3044705|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/brettwooldridge/HikariCP/^0|0|8|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

<h2><a href="https://github.com/brettwooldridge/HikariCP/" rel="noreferrer">HikariCP</a></h2>

It's modern, it's fast, it's simple. I use it for every new project.
I prefer it a lot over C3P0, don't know the other pools too well.

blocks|key|310944|text|如果您正在寻找一个可嵌入的解决方案，并且不太关心性能(尽管我还没有在这方面对其进行测试)，那么MiniConnectionPoolManager是一个java文件实现。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|310945|它是多许可的EPL、LGPL和MPL。|310946|它的文档还提供了值得检查的替代方案(在DBCP和C3P0之上)：|310947|310948|Proxool|unordered-list-item|310949|BoneCP|310950|Tomcat+JDBC+Connection+Pool|310951|310952|entityMap|0|LINK|mutability|MUTABLE|url|http://www.source-code.biz/miniconnectionpoolmanager/|1|http://www.eclipse.org/legal|2|http://www.gnu.org/licenses/lgpl.html|3|http://www.mozilla.org/MPL|4|http://proxool.sourceforge.net/|5|http://jolbox.com/|6|http://people.apache.org/~fhanik/jdbc-pool/jdbc-pool.html^0|1B|P|1B|P|0|0|6|3|1|A|4|2|F|3|3|0|0|0|0|7|4|0|0|6|5|0|0|R|6|0|0^^$0|@$1|2|3|4|5|6|7|1C|8|@$9|1D|A|1E|B|C]]|D|@$9|1F|A|1G|1|1H]]|E|$]]|$1|F|3|G|5|6|7|1I|8|@]|D|@$9|1J|A|1K|1|1L]|$9|1M|A|1N|1|1O]|$9|1P|A|1Q|1|1R]]|E|$]]|$1|H|3|I|5|6|7|1S|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|1T|8|@]|D|@]|E|$]]|$1|K|3|L|5|M|7|1U|8|@]|D|@$9|1V|A|1W|1|1X]]|E|$]]|$1|N|3|O|5|M|7|1Y|8|@]|D|@$9|1Z|A|20|1|21]]|E|$]]|$1|P|3|Q|5|M|7|22|8|@]|D|@$9|23|A|24|1|25]]|E|$]]|$1|R|3|-4|5|6|7|26|8|@]|D|@]|E|$]]|$1|S|3|-4|5|6|7|27|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]|10|$5|V|W|X|E|$Y|11]]|12|$5|V|W|X|E|$Y|13]]|14|$5|V|W|X|E|$Y|15]]|16|$5|V|W|X|E|$Y|17]]|18|$5|V|W|X|E|$Y|19]]|1A|$5|V|W|X|E|$Y|1B]]]]

<a href="http://www.source-code.biz/miniconnectionpoolmanager/" rel="nofollow"><code>MiniConnectionPoolManager</code></a> is a one-java-file implementation, if you're looking for an embeddable solution and are not too concerned about performances (though I haven't tested it in that regard).

It is multi-licensed <a href="http://www.eclipse.org/legal" rel="nofollow">EPL</a>, <a href="http://www.gnu.org/licenses/lgpl.html" rel="nofollow">LGPL</a> and <a href="http://www.mozilla.org/MPL" rel="nofollow">MPL</a>.

Its documentation also gives alternatives worth checking (on top of DBCP and C3P0):

<ul>
<li><a href="http://proxool.sourceforge.net/" rel="nofollow">Proxool</a></li>
<li><a href="http://jolbox.com/" rel="nofollow">BoneCP</a></li>
<li><a href="http://people.apache.org/~fhanik/jdbc-pool/jdbc-pool.html" rel="nofollow">Tomcat JDBC Connection Pool</a></li>
</ul>

blocks|key|3258690|text|池|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|3258691|3258692|池化机制是一种预先创建对象的方式。当一个类被加载时，它通过重新使用相同的对象来对对象数据执行任何操作来提高应用程序的performance+&+memory分配和释放许多对象创建了大量的内存管理overhead.|unordered-list-item|CODE|3258693|Object清理不需要，因为我们正在使用相同的对象，从而减少了垃圾收集负载。|3258694|3258695|«池化[+Object池，String常量池，Thread池，连接池]|3258696|String常量池|3258697|3258698|字符串字面池仅维护每个不同字符串值的一个副本。调用intern方法时，它使用immutable.|3258699|When方法检查池中相同内容的对象可用性。«如果池中有String-copy可用，则返回引用。«否则，String对象将添加到池中并返回引用。|3258700|3258701|示例:用于验证池中Unique+Object的字符串。|3258702|public+class+StringPoolTest+{
++++public+static+void+main(String[]+args)+{+//+Integer.valueOf(),+String.equals()
++++++++String+eol+=+System.getProperty("line.separator");+//java7+System.lineSeparator();

++++++++String+s1+=+"Yash".intern();
++++++++System.out.format("Val:%25s+Hash:%25s+SYS:%25s+"%2Beol,+s1,+s1.hashCode(),+System.identityHashCode(s1));
++++++++String+s2+=+"Yas"%2B"h".intern();
++++++++System.out.format("Val:%25s+Hash:%25s+SYS:%25s+"%2Beol,+s2,+s2.hashCode(),+System.identityHashCode(s2));
++++++++String+s3+=+"Yas".intern()%2B"h".intern();
++++++++System.out.format("Val:%25s+Hash:%25s+SYS:%25s+"%2Beol,+s3,+s3.hashCode(),+System.identityHashCode(s3));
++++++++String+s4+=+"Yas"%2B"h";
++++++++System.out.format("Val:%25s+Hash:%25s+SYS:%25s+"%2Beol,+s4,+s4.hashCode(),+System.identityHashCode(s4));
++++}
}|code-block|syntax|javascript|3258703|使用使用第三方库的类型4+的连接池[+、、]|3258704|Type+4+-+The+Thin+driver+converts+JDBC+calls+directly+into+the+vendor-specific+database+protocol+Ex[Oracle+-+Thick,+MySQL+-+Quora].+wiki|3258705|在连接池机制中，当类被加载时，它获取对象，并向用户提供一个包装的物理连接对象。是实际连接的包装器。|3258706|3258707|getConnection()从连接池中选择一个空闲的包装连接并返回it.|3258708|close()，而不是关闭它，将包装连接返回objectpool。|3258709|3258710|示例:在Java7中使用~+DBCP2连接池[try-with-resources]|3258711|public+class+ConnectionPool+{
++++static+final+BasicDataSource+ds_dbcp2+=+new+BasicDataSource();
++++static+final+ComboPooledDataSource+ds_c3p0+=+new+ComboPooledDataSource();
++++static+final+DataSource+ds_JDBC+=+new+DataSource();

++++static+Properties+prop+=+new+Properties();
++++static+{
++++++++try+{
++++++++++++prop.load(ConnectionPool.class.getClassLoader().getResourceAsStream("connectionpool.properties"));

++++++++++++ds_dbcp2.setDriverClassName(+prop.getProperty("DriverClass")+);
++++++++++++ds_dbcp2.setUrl(+prop.getProperty("URL")+);
++++++++++++ds_dbcp2.setUsername(+prop.getProperty("UserName")+);
++++++++++++ds_dbcp2.setPassword(+prop.getProperty("Password")+);
++++++++++++ds_dbcp2.setInitialSize(+5+);

++++++++++++ds_c3p0.setDriverClass(+prop.getProperty("DriverClass")+);
++++++++++++ds_c3p0.setJdbcUrl(+prop.getProperty("URL")+);
++++++++++++ds_c3p0.setUser(+prop.getProperty("UserName")+);
++++++++++++ds_c3p0.setPassword(+prop.getProperty("Password")+);
++++++++++++ds_c3p0.setMinPoolSize(5);
++++++++++++ds_c3p0.setAcquireIncrement(5);
++++++++++++ds_c3p0.setMaxPoolSize(20);

++++++++++++PoolProperties+pool+=+new+PoolProperties();
++++++++++++pool.setUrl(+prop.getProperty("URL")+);
++++++++++++pool.setDriverClassName(+prop.getProperty("DriverClass")+);
++++++++++++pool.setUsername(+prop.getProperty("UserName")+);
++++++++++++pool.setPassword(+prop.getProperty("Password")+);
++++++++++++pool.setValidationQuery("SELECT+1");//+SELECT+1(mysql)+select+1+from+dual(oracle)

++++++++++++pool.setInitialSize(5);
++++++++++++pool.setMaxActive(3);
++++++++++++ds_JDBC.setPoolProperties(+pool+);
++++++++}+catch+(IOException+e)+{+++e.printStackTrace();
++++++++}+catch+(PropertyVetoException+e)+{+e.printStackTrace();+}
++++}

++++public+static+Connection+getDBCP2Connection()+throws+SQLException+{
++++++++return+ds_dbcp2.getConnection();
++++}

++++public+static+Connection+getc3p0Connection()+throws+SQLException+{
++++++++return+ds_c3p0.getConnection();
++++}

++++public+static+Connection+getJDBCConnection()+throws+SQLException+{
++++++++return+ds_JDBC.getConnection();
++++}
}
public+static+boolean+exists(String+UserName,+String+Password+)+throws+SQLException+{
++++boolean+exist+=+false;
++++String+SQL_EXIST+=+"SELECT+*+FROM+users+WHERE+username=?+AND+password=?";
++++try+(+Connection+connection+=+ConnectionPool.getDBCP2Connection();
++++++++++PreparedStatement+pstmt+=+connection.prepareStatement(SQL_EXIST);+)+{
++++++++pstmt.setString(1,+UserName+);
++++++++pstmt.setString(2,+Password+);

++++++++try+(ResultSet+resultSet+=+pstmt.executeQuery())+{
++++++++++++exist+=+resultSet.next();+//+Note+that+you+should+not+return+a+ResultSet+here.
++++++++}
++++}
++++System.out.println("User+:+"%2Bexist);
++++return+exist;
}|3258712|jdbc:<DB>:<drivertype>:<HOST>:<TCP/IP+PORT>:<dataBaseName>+jdbc:oracle:thin:@localhost:1521:myDBName+jdbc:mysql://localhost:3306/myDBName|3258713|connectionpool.properties|3258714|URL+++++++++:+jdbc:mysql://localhost:3306/myDBName
DriverClass+:+com.mysql.jdbc.Driver
UserName++++:+root
Password++++:|3258715|Web应用程序:当所有连接都是closedMySQL+"wait_timeout“时，为了避免连接问题，默认8小时，以便重新打开与底层数据库的连接。|3258716|您可以通过设置testOnBorrow+=+true和validationQuery=+"SELECT+1“来测试每个连接，并且不要将autoReconnect用于MySQL服务器，因为它已被弃用。|3258717|=====+=====+context.xml+=====+=====
<?xml+version="1.0"+encoding="UTF-8"?>

<Context>
++++<Resource+name="jdbc/MyAppDB"+auth="Container"+
++++++++factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"+
++++++++type="javax.sql.DataSource"+

++++++++initialSize="5"+minIdle="5"+maxActive="15"+maxIdle="10"

++++++++testWhileIdle="true"
++++++++++++timeBetweenEvictionRunsMillis="30000"

++++++++testOnBorrow="true"
++++++++++++validationQuery="SELECT+1"
++++++++++++validationInterval="30000"


++++++++driverClassName="com.mysql.jdbc.Driver"+
++++++++url="jdbc:mysql://localhost:3306/myDBName"+
++++++++username="yash"+password="777"
++++/>
</Context>

=====+=====+web.xml+=====+=====
<resource-ref>
++++<description>DB+Connection</description>
++++<res-ref-name>jdbc/MyAppDB</res-ref-name>
++++<res-type>javax.sql.DataSource</res-type>
++++<res-auth>Container</res-auth>
</resource-ref>
=====+=====+DBOperations+=====+=====
servlet+«+++init()+{}
Normal+call+used+by+sevlet++«+static+{}

static+DataSource+ds;
static+{
++++try+{
++++++++Context+ctx=new+InitialContext();
++++++++Context+envContext+=+(Context)ctx.lookup("java:comp/env");
++++++++ds++=+++(DataSource)+envContext.lookup("jdbc/MyAppDB");
++++}+catch+(NamingException+e)+{+++e.printStackTrace();++++}
}|3258718|另请参阅以下内容：|3258719|3258720|am-i-using-jdbc-connection-pooling|3258721|configuring-jdbc-pool-high-concurrency|3258722|3258723|entityMap|0|LINK|mutability|MUTABLE|url|http://www.javaranch.com/journal/200601/JDBCConnectionPooling.html|1|https://stackoverflow.com/questions/10224476/what-if-size-of-string-pool-exceeds/10225508#10225508|2|https://docs.oracle.com/javase/tutorial/essential/concurrency/pools.html|3|https://stackoverflow.com/questions/4930781/how-do-hashcode-and-identityhashcode-work-at-the-back-end/4933258#4933258|4|https://en.wikipedia.org/wiki/JDBC_driver|5|http://commons.apache.org/proper/commons-pool/api-2.2/org/apache/commons/pool2/ObjectPool.html?is-external=true|6|https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html|7|https://docs.oracle.com/cd/E11882_01/appdev.112/e13995/oracle/jdbc/OracleDriver.html|8|http://dev.mysql.com/doc/connector-j/5.1/en/connector-j-reference-configuration-properties.html|9|http://viralpatel.net/blogs/database-connection-pooling-tomcat-eclipse-db/|10|https://stackoverflow.com/questions/7592056/am-i-using-jdbc-connection-pooling|11|http://www.tomcatexpert.com/blog/2010/04/01/configuring-jdbc-pool-high-concurrency^0|0|1|0|0|1M|B|20|6|1M|B|20|6|0|0|0|5|6|D|6|N|6|5|6|0|D|6|1|N|6|2|0|0|9|0|0|0|0|0|9|D|3|0|0|E|8|0|0|3N|3O|4|0|3N|3O|4|4|0|0|1D|0|0|0|11|0|F|0|0|X|0|7|M|A|5|0|0|0|16|N|I|N|I|6|0|0|0|1M|1N|15|2T|10|0|1M|1N|15|2T|10|1S|6|7|2Y|5|8|0|0|P|0|0|0|22|0|3|9|0|0|2R|0|0|0|9|0|0|0|Y|0|Y|A|0|0|12|0|12|B|0|0^^$0|@$1|2|3|4|5|6|7|2Y|8|@$9|2Z|A|30|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|31|8|@]|D|@]|E|$]]|$1|G|3|H|5|I|7|32|8|@$9|33|A|34|B|C]|$9|35|A|36|B|C]|$9|37|A|38|B|J]|$9|39|A|3A|B|J]]|D|@]|E|$]]|$1|K|3|L|5|I|7|3B|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|3C|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|3D|8|@$9|3E|A|3F|B|J]|$9|3G|A|3H|B|J]|$9|3I|A|3J|B|J]]|D|@$9|3K|A|3L|1|3M]|$9|3N|A|3O|1|3P]|$9|3Q|A|3R|1|3S]]|E|$]]|$1|P|3|Q|5|6|7|3T|8|@$9|3U|A|3V|B|C]]|D|@]|E|$]]|$1|R|3|-4|5|6|7|3W|8|@]|D|@]|E|$]]|$1|S|3|T|5|I|7|3X|8|@]|D|@]|E|$]]|$1|U|3|V|5|I|7|3Y|8|@]|D|@]|E|$]]|$1|W|3|-4|5|6|7|3Z|8|@]|D|@]|E|$]]|$1|X|3|Y|5|6|7|40|8|@]|D|@$9|41|A|42|1|43]]|E|$]]|$1|Z|3|10|5|11|7|44|8|@]|D|@]|E|$12|13]]|$1|14|3|15|5|6|7|45|8|@$9|46|A|47|B|C]]|D|@]|E|$]]|$1|16|3|17|5|6|7|48|8|@$9|49|A|4A|B|C]|$9|4B|A|4C|B|C]|$9|4D|A|4E|B|J]]|D|@$9|4F|A|4G|1|4H]]|E|$]]|$1|18|3|19|5|6|7|4I|8|@$9|4J|A|4K|B|C]]|D|@]|E|$]]|$1|1A|3|-4|5|6|7|4L|8|@]|D|@]|E|$]]|$1|1B|3|1C|5|I|7|4M|8|@$9|4N|A|4O|B|C]|$9|4P|A|4Q|B|J]]|D|@]|E|$]]|$1|1D|3|1E|5|I|7|4R|8|@$9|4S|A|4T|B|C]|$9|4U|A|4V|B|J]]|D|@$9|4W|A|4X|1|4Y]]|E|$]]|$1|1F|3|-4|5|6|7|4Z|8|@]|D|@]|E|$]]|$1|1G|3|1H|5|6|7|50|8|@$9|51|A|52|B|C]|$9|53|A|54|B|J]]|D|@$9|55|A|56|1|57]]|E|$]]|$1|1I|3|1J|5|11|7|58|8|@]|D|@]|E|$12|13]]|$1|1K|3|1L|5|6|7|59|8|@$9|5A|A|5B|B|C]|$9|5C|A|5D|B|C]|$9|5E|A|5F|B|C]|$9|5G|A|5H|B|J]|$9|5I|A|5J|B|J]|$9|5K|A|5L|B|J]]|D|@$9|5M|A|5N|1|5O]|$9|5P|A|5Q|1|5R]]|E|$]]|$1|1M|3|1N|5|6|7|5S|8|@$9|5T|A|5U|B|C]]|D|@]|E|$]]|$1|1O|3|1P|5|11|7|5V|8|@]|D|@]|E|$12|13]]|$1|1Q|3|1R|5|6|7|5W|8|@$9|5X|A|5Y|B|C]]|D|@$9|5Z|A|60|1|61]]|E|$]]|$1|1S|3|1T|5|6|7|62|8|@$9|63|A|64|B|C]]|D|@]|E|$]]|$1|1U|3|1V|5|11|7|65|8|@]|D|@]|E|$12|13]]|$1|1W|3|1X|5|6|7|66|8|@$9|67|A|68|B|C]]|D|@]|E|$]]|$1|1Y|3|-4|5|6|7|69|8|@]|D|@]|E|$]]|$1|1Z|3|20|5|I|7|6A|8|@$9|6B|A|6C|B|C]]|D|@$9|6D|A|6E|1|6F]]|E|$]]|$1|21|3|22|5|I|7|6G|8|@$9|6H|A|6I|B|C]]|D|@$9|6J|A|6K|1|6L]]|E|$]]|$1|23|3|-4|5|6|7|6M|8|@]|D|@]|E|$]]|$1|24|3|-4|5|6|7|6N|8|@]|D|@]|E|$]]]|25|$26|$5|27|28|29|E|$2A|2B]]|2C|$5|27|28|29|E|$2A|2D]]|2E|$5|27|28|29|E|$2A|2F]]|2G|$5|27|28|29|E|$2A|2H]]|2I|$5|27|28|29|E|$2A|2J]]|2K|$5|27|28|29|E|$2A|2L]]|2M|$5|27|28|29|E|$2A|2N]]|2O|$5|27|28|29|E|$2A|2P]]|2Q|$5|27|28|29|E|$2A|2R]]|2S|$5|27|28|29|E|$2A|2T]]|2U|$5|27|28|29|E|$2A|2V]]|2W|$5|27|28|29|E|$2A|2X]]]]

Pool

<ul>
<li>Pooling Mechanism is the way of creating the Objects in advance. When a class is loaded.</li>
<li>It improves the application <code>performance</code> [By re using same object's to perform any action on Object-Data] &amp; <code>memory</code> [allocating and de-allocating many objects creates a significant memory management overhead].</li>
<li>Object clean-up is not required as we are using same Object, reducing the Garbage collection load.</li>
</ul>

« Pooling [ <a href="http://www.javaranch.com/journal/200601/JDBCConnectionPooling.html" rel="nofollow noreferrer"><code>Object</code></a> pool, <a href="https://stackoverflow.com/questions/10224476/what-if-size-of-string-pool-exceeds/10225508#10225508"><code>String</code></a> Constant Pool, <a href="https://docs.oracle.com/javase/tutorial/essential/concurrency/pools.html" rel="nofollow noreferrer"><code>Thread</code></a> Pool, Connection pool]

String Constant pool

<ul>
<li>String literal pool maintains only one copy of each distinct string value. which must be immutable.</li>
<li>When the intern method is invoked, it check object availability with same content in pool using equals method.
« If String-copy is available in the Pool then returns the reference.
« Otherwise, String object is added to the pool and returns the reference.</li>
</ul>

Example: String to verify <a href="https://stackoverflow.com/questions/4930781/how-do-hashcode-and-identityhashcode-work-at-the-back-end/4933258#4933258">Unique Object</a> from pool.

<pre><code>public class StringPoolTest {
 public static void main(String[] args) { // Integer.valueOf(), String.equals()
 String eol = System.getProperty("line.separator"); //java7 System.lineSeparator();

 String s1 = "Yash".intern();
 System.out.format("Val:%s Hash:%s SYS:%s "+eol, s1, s1.hashCode(), System.identityHashCode(s1));
 String s2 = "Yas"+"h".intern();
 System.out.format("Val:%s Hash:%s SYS:%s "+eol, s2, s2.hashCode(), System.identityHashCode(s2));
 String s3 = "Yas".intern()+"h".intern();
 System.out.format("Val:%s Hash:%s SYS:%s "+eol, s3, s3.hashCode(), System.identityHashCode(s3));
 String s4 = "Yas"+"h";
 System.out.format("Val:%s Hash:%s SYS:%s "+eol, s4, s4.hashCode(), System.identityHashCode(s4));
 }
}
</code></pre>

Connection pool using Type-4 <a href="http://www.oracle.com/technetwork/topics/jdbc-faq-090281.html#02_01" rel="nofollow noreferrer">Driver</a> using 3rd party libraries[ <a href="https://commons.apache.org/proper/commons-dbcp/configuration.html" rel="nofollow noreferrer"><code>DBCP2</code></a>, <a href="http://www.mchange.com/projects/c3p0/index.html#quickstart" rel="nofollow noreferrer"><code>c3p0</code></a>, <a href="https://tomcat.apache.org/tomcat-8.0-doc/jdbc-pool.html" rel="nofollow noreferrer"><code>Tomcat JDBC</code></a>]

<code>Type 4 - The Thin driver converts JDBC calls directly into the vendor-specific database protocol Ex[Oracle - Thick, MySQL - Quora].</code> <a href="https://en.wikipedia.org/wiki/JDBC_driver" rel="nofollow noreferrer">wiki</a>

In Connection pool mechanism, when the class is loaded it get's the <a href="https://docs.oracle.com/cd/E29542_01/web.1111/e13726/phys_conr.htm#JDBCP1037" rel="nofollow noreferrer"><code>physical JDBC connection</code></a> objects and provides a wrapped physical connection object to user. <a href="https://commons.apache.org/proper/commons-dbcp/jacoco/org.apache.commons.dbcp2/PoolableConnection.java.html" rel="nofollow noreferrer"><code>PoolableConnection</code></a> is a wrapper around the actual connection. 

<ul>
<li><code>getConnection()</code> pick one of the free wrapped-connection form the connection <a href="http://commons.apache.org/proper/commons-pool/api-2.2/org/apache/commons/pool2/ObjectPool.html?is-external=true" rel="nofollow noreferrer">objectpool</a> and returns it.</li>
<li><code>close()</code> instead of closing it returns the wrapped-connection back to pool.</li>
</ul>

Example: Using ~ DBCP2 Connection Pool with Java 7[<a href="https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html" rel="nofollow noreferrer"><code>try-with-resources</code></a>]

<pre><code>public class ConnectionPool {
 static final BasicDataSource ds_dbcp2 = new BasicDataSource();
 static final ComboPooledDataSource ds_c3p0 = new ComboPooledDataSource();
 static final DataSource ds_JDBC = new DataSource();

 static Properties prop = new Properties();
 static {
 try {
 prop.load(ConnectionPool.class.getClassLoader().getResourceAsStream("connectionpool.properties"));

 ds_dbcp2.setDriverClassName( prop.getProperty("DriverClass") );
 ds_dbcp2.setUrl( prop.getProperty("URL") );
 ds_dbcp2.setUsername( prop.getProperty("UserName") );
 ds_dbcp2.setPassword( prop.getProperty("Password") );
 ds_dbcp2.setInitialSize( 5 );

 ds_c3p0.setDriverClass( prop.getProperty("DriverClass") );
 ds_c3p0.setJdbcUrl( prop.getProperty("URL") );
 ds_c3p0.setUser( prop.getProperty("UserName") );
 ds_c3p0.setPassword( prop.getProperty("Password") );
 ds_c3p0.setMinPoolSize(5);
 ds_c3p0.setAcquireIncrement(5);
 ds_c3p0.setMaxPoolSize(20);

 PoolProperties pool = new PoolProperties();
 pool.setUrl( prop.getProperty("URL") );
 pool.setDriverClassName( prop.getProperty("DriverClass") );
 pool.setUsername( prop.getProperty("UserName") );
 pool.setPassword( prop.getProperty("Password") );
 pool.setValidationQuery("SELECT 1");// SELECT 1(mysql) select 1 from dual(oracle)

 pool.setInitialSize(5);
 pool.setMaxActive(3);
 ds_JDBC.setPoolProperties( pool );
 } catch (IOException e) { e.printStackTrace();
 } catch (PropertyVetoException e) { e.printStackTrace(); }
 }

 public static Connection getDBCP2Connection() throws SQLException {
 return ds_dbcp2.getConnection();
 }

 public static Connection getc3p0Connection() throws SQLException {
 return ds_c3p0.getConnection();
 }

 public static Connection getJDBCConnection() throws SQLException {
 return ds_JDBC.getConnection();
 }
}
public static boolean exists(String UserName, String Password ) throws SQLException {
 boolean exist = false;
 String SQL_EXIST = "SELECT * FROM users WHERE username=? AND password=?";
 try ( Connection connection = ConnectionPool.getDBCP2Connection();
 PreparedStatement pstmt = connection.prepareStatement(SQL_EXIST); ) {
 pstmt.setString(1, UserName );
 pstmt.setString(2, Password );

 try (ResultSet resultSet = pstmt.executeQuery()) {
 exist = resultSet.next(); // Note that you should not return a ResultSet here.
 }
 }
 System.out.println("User : "+exist);
 return exist;
}
</code></pre>

<code>jdbc:&lt;DB&gt;:&lt;drivertype&gt;:&lt;HOST&gt;:&lt;TCP/IP PORT&gt;:&lt;dataBaseName&gt;</code>
<code>jdbc:</code><a href="https://docs.oracle.com/cd/E11882_01/appdev.112/e13995/oracle/jdbc/OracleDriver.html" rel="nofollow noreferrer"><code>oracle</code></a><code>:thin:@localhost:1521:myDBName</code>
<code>jdbc:</code><a href="http://dev.mysql.com/doc/connector-j/5.1/en/connector-j-reference-configuration-properties.html" rel="nofollow noreferrer"><code>mysql</code></a><code>://localhost:3306/myDBName</code>

connectionpool.properties

<pre><code>URL : jdbc:mysql://localhost:3306/myDBName
DriverClass : com.mysql.jdbc.Driver
UserName : root
Password :
</code></pre>

<a href="http://viralpatel.net/blogs/database-connection-pooling-tomcat-eclipse-db/" rel="nofollow noreferrer">Web</a> Application: To avoid connection problem when all the connection's are closed[MySQL "wait_timeout" default 8 hours] in-order to reopen the connection with underlying DB.

You can do this to Test Every Connection by setting testOnBorrow = true and validationQuery= "SELECT 1" and donot use autoReconnect for MySQL server as it is deprecated. <a href="http://dev.mysql.com/doc/connector-j/5.1/en/connector-j-reference-configuration-properties.html" rel="nofollow noreferrer">issue</a>

<pre><code>===== ===== context.xml ===== =====
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!-- The contents of this file will be loaded for a web application --&gt;
&lt;Context&gt;
 &lt;Resource name="jdbc/MyAppDB" auth="Container" 
 factory="org.apache.tomcat.jdbc.pool.DataSourceFactory" 
 type="javax.sql.DataSource" 

 initialSize="5" minIdle="5" maxActive="15" maxIdle="10"

 testWhileIdle="true"
 timeBetweenEvictionRunsMillis="30000"

 testOnBorrow="true"
 validationQuery="SELECT 1"
 validationInterval="30000"


 driverClassName="com.mysql.jdbc.Driver" 
 url="jdbc:mysql://localhost:3306/myDBName" 
 username="yash" password="777"
 /&gt;
&lt;/Context&gt;

===== ===== web.xml ===== =====
&lt;resource-ref&gt;
 &lt;description&gt;DB Connection&lt;/description&gt;
 &lt;res-ref-name&gt;jdbc/MyAppDB&lt;/res-ref-name&gt;
 &lt;res-type&gt;javax.sql.DataSource&lt;/res-type&gt;
 &lt;res-auth&gt;Container&lt;/res-auth&gt;
&lt;/resource-ref&gt;
===== ===== DBOperations ===== =====
servlet « init() {}
Normal call used by sevlet « static {}

static DataSource ds;
static {
 try {
 Context ctx=new InitialContext();
 Context envContext = (Context)ctx.lookup("java:comp/env");
 ds = (DataSource) envContext.lookup("jdbc/MyAppDB");
 } catch (NamingException e) { e.printStackTrace(); }
}
</code></pre>

See these also:

<ul>
<li><a href="https://stackoverflow.com/questions/7592056/am-i-using-jdbc-connection-pooling">am-i-using-jdbc-connection-pooling</a></li>
<li><a href="http://www.tomcatexpert.com/blog/2010/04/01/configuring-jdbc-pool-high-concurrency" rel="nofollow noreferrer">configuring-jdbc-pool-high-concurrency</a></li>
</ul>

blocks|key|3258739|text|您应该考虑使用UCP。Universal+Connection+Pool+(UCP)是一个Java连接池。它是一个功能丰富的连接池，与Oracle的Real+Application+Clusters+(RAC)、ADG、DG数据库紧密集成。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3258740|有关UCP的更多详细信息，请参阅此page。|3258741|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/database/121/JJUCP/toc.htm|1|http://www.oracle.com/technetwork/database/application-development/index-099369.html^0|B|V|0|0|H|4|1|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|F|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]]]

You should consider using UCP. 
<a href="https://docs.oracle.com/database/121/JJUCP/toc.htm" rel="nofollow">Universal Connection Pool (UCP)</a> is a Java connection pool. It is a features rich connection pool and tightly integrated with Oracle's Real Application Clusters (RAC), ADG, DG databases. 

Refer to this <a href="http://www.oracle.com/technetwork/database/application-development/index-099369.html" rel="nofollow">page</a> for more details about UCP.

blocks|key|305980|text|在2017年末，Proxool，BoneCP，C3P0，DBCP在这个时候大部分都不存在了。HikariCP+(创建于2012年)看起来很有前途，打破了我所知道的一切。http://www.baeldung.com/hikaricp|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|305981|Proxool有许多问题：|305982|305983|项目具有未完成的代码(已定义但未执行操作的属性)|unordered-list-item|305984|
|305985|默认的最大连接寿命(如果未定义)为4小时(excessive)|305986|305987|HouseKeeper线程每池每5秒运行一次(超出)|305988|305989|您可以修改代码并进行这些改进。但由于它创建于2003年，并于2008年更新，它缺少像hikaricp这样的解决方案所利用的近10年的java改进。|305990|entityMap|0|LINK|mutability|MUTABLE|url|http://www.baeldung.com/hikaricp^0|2C|W|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@$A|12|B|13|1|14]]|C|$]]|$1|D|3|E|5|6|7|15|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|16|8|@]|9|@]|C|$]]|$1|G|3|H|5|I|7|17|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|18|8|@]|9|@]|C|$]]|$1|L|3|M|5|I|7|19|8|@]|9|@]|C|$]]|$1|N|3|K|5|6|7|1A|8|@]|9|@]|C|$]]|$1|O|3|P|5|I|7|1B|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|1C|8|@]|9|@]|C|$]]|$1|R|3|S|5|6|7|1D|8|@]|9|@]|C|$]]|$1|T|3|-4|5|6|7|1E|8|@]|9|@]|C|$]]]|U|$V|$5|W|X|Y|C|$Z|10]]]]

In late 2017 Proxool, BoneCP, C3P0, DBCP are mostly defunct at this time. HikariCP (created in 2012) seems promising, blows the doors off anything else I know of.
<a href="http://www.baeldung.com/hikaricp" rel="nofollow noreferrer">http://www.baeldung.com/hikaricp</a>

Proxool has a number of issues: 
- Under heavy load can exceed max number of connections and not return below max 
- Can manage to not return to min connections even after connections expire 
- Can lock up the entire pool (and all server/client threads) if it has trouble connecting to the database during HouseKeeper thread (does not use .setQueryTimeout) 
- HouseKeeper thread, while having connection pool lock for its process, requests the Prototyper thread to recreate connections (sweep) which can result in race condition/lockup. In these method calls the last parameter should always be sweep:false during the loop, only sweep:true below it. 
- HouseKeeper only needs the single PrototypeController sweep at the end and has more [mentioned above] 
- HouseKeeper thread checks for testing of connections before seeing what connections may be expired [some risk of testing expired connection that may be broken/terminated through other timeouts to DB in firewall, etc.] 
- The project has unfinished code (properties that are defined but not acted upon) 
- The Default max connection life if not defined is 4 hours (excessive) 
- HouseKeeper thread runs every five seconds per pool (excessive) 
 
You can modify the code and make these improvements. But as it was created in 2003, and updated in 2008, its lacking nearly 10 years of java improvements that solutions like hikaricp utilize.

Can anybody provide examples or links on how to establish a JDBC connection pool?

From searching google I see many different ways of doing this and it is rather confusing.

Ultimately I need the code to return a <code>java.sql.Connection</code> object, but I am having trouble getting started..any suggestions welcome.

Update: Doesn't <code>javax.sql</code> or <code>java.sql</code> have pooled connection implementations? Why wouldn't it be best to use these?

How to establish a connection pool in JDBC?

内存管理

数据库

服务器

MySQL

Java

有人能提供关于如何建立JDBC连接池的示例或链接吗？通过搜索google，我看到了许多不同的方法，这是相当令人困惑的。最终，我需要返回java.sql.Connection对象的代码，但我很难获得欢迎的started..any建议。更新：没有javax.sql或java.sql的池连接实现吗？为什么使用这些不是最好的呢...

问如何在JDBC中建立连接池？
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