blocks|key|305764|text|当然，这是可能的。您必须将ServletContextListener注册到您的web.xml，如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|305765|

<listener>
++++<listener-class>com.mycompany.servlets.ApplicationListener</listener-class>
</listener>|code-block|syntax|javascript|305766|com.mycompany.servlets.ApplicationListener的来源：|305767|package+com.mycompany.servlets;

public+class+ApplicationListener+implements+ServletContextListener+{

++++@Override
++++public+void+contextInitialized(ServletContextEvent+servletContextEvent)+{
++++++++//+this+method+is+invoked+once+when+web-application+is+deployed+(started)

++++++++//+reading+properties+file
++++++++FileInputStream+fis+=+null;
++++++++Properties+properties+=+new+Properties();
++++++++try+{
++++++++++++fis+=+new+FileInputStream("path/to/db.properties")++++
++++++++++++properties.load(fis);
++++++++}+catch(IOException+ex)+{
++++++++++++throw+new+RuntimeException(ex);
++++++++}+finally+{
++++++++++++try+{
++++++++++++++++if(fis+!=+null)+{
++++++++++++++++++++fis.close();
++++++++++++++++}
++++++++++++}+catch(IOException+e)+{
++++++++++++++++throw+new+RuntimeException(e);
++++++++++++}
++++++++}

++++++++//+creating+data+source+instance
++++++++SomeDataSourceImpl+dataSource+=+new+SomeDataSourceImpl();
++++++++dataSource.setJdbcUrl(properties.getProperty("db.url"));
++++++++dataSource.setUser(properties.getProperty("db.user"));
++++++++dataSource.setPassword(properties.getProperty("db.pwd"));

++++++++//+storing+reference+to+dataSource+in+ServletContext+attributes+map
++++++++//+there+is+only+one+instance+of+ServletContext+per+web-application,+which+can+be+accessed+from+almost+anywhere+in+web+application(servlets,+filters,+listeners+etc)
++++++++final+ServletContext+servletContext+=+servletContextEvent.getServletContext();
++++++++servletContext.setAttribute("some-data-source-alias",+dataSource);
++++}

++++@Override
++++public+void+contextDestroyed(ServletContextEvent+servletContextEvent)+{
++++++++//+this+method+is+invoked+once+when+web-application+is+undeployed+(stopped)+-+here+one+can+(should)+implement+resource+cleanup+etc
++++}

}|305768|然后，在web应用程序代码中的某处访问dataSource：|305769|ServletContext+servletContext+=+...;+//+as+mentioned+above,+it+should+be+accessible+from+almost+anywhere
DataSource+dataSource+=+(DataSource)+servletContext.getAttribute("some-data-source-alias");
//+use+dataSource|305770|SomeDataSourceImpl是javax.sql.DataSource的一些具体实现。如果您不使用特定的DataSource(如用于连接池的ComboPooledDataSource+)，并且不知道如何获得它，请告知-我将发布如何绕过它。|305771|some-data-source-alias+-只是DataSource属性映射中ServletContext实例的ServletContext别名(键)。较好的做法是在别名前面加上包名称，如com.mycompany.mywebapp.dataSource。|305772|希望这能帮到你。|305773|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javaee/6/api/javax/servlet/ServletContextListener.html|1|http://docs.oracle.com/javase/6/docs/api/javax/sql/DataSource.html|2|http://www.mchange.com/projects/c3p0/apidocs/com/mchange/v2/c3p0/ComboPooledDataSource.html^0|14|7|D|M|0|0|0|0|16|0|0|J|A|0|0|0|I|1K|A|J|K|1|22|L|2|0|0|M|Q|A|15|E|1M|E|2O|X|0|0^^$0|@$1|2|3|4|5|6|7|1A|8|@$9|1B|A|1C|B|C]]|D|@$9|1D|A|1E|1|1F]]|E|$]]|$1|F|3|G|5|H|7|1G|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1H|8|@$9|1I|A|1J|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|1K|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1L|8|@$9|1M|A|1N|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1O|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|1P|8|@$9|1Q|A|1R|B|C]|$9|1S|A|1T|B|C]]|D|@$9|1U|A|1V|1|1W]|$9|1X|A|1Y|1|1Z]]|E|$]]|$1|U|3|V|5|6|7|20|8|@$9|21|A|22|B|C]|$9|23|A|24|B|C]|$9|25|A|26|B|C]|$9|27|A|28|B|C]|$9|29|A|2A|B|C]]|D|@]|E|$]]|$1|W|3|X|5|6|7|2B|8|@]|D|@]|E|$]]|$1|Y|3|-4|5|6|7|2C|8|@]|D|@]|E|$]]]|Z|$10|$5|11|12|13|E|$14|15]]|16|$5|11|12|13|E|$14|17]]|18|$5|11|12|13|E|$14|19]]]]

Sure, this is possible. You have to register <a href="http://docs.oracle.com/javaee/6/api/javax/servlet/ServletContextListener.html" rel="nofollow">ServletContextListener</a> to your <code>web.xml</code> like this:


<pre><code>&lt;!-- at the beginning of web.xml --&gt;

&lt;listener&gt;
 &lt;listener-class&gt;com.mycompany.servlets.ApplicationListener&lt;/listener-class&gt;
&lt;/listener&gt;
</code></pre>

Source of <code>com.mycompany.servlets.ApplicationListener</code>:


<pre><code>package com.mycompany.servlets;

public class ApplicationListener implements ServletContextListener {

 @Override
 public void contextInitialized(ServletContextEvent servletContextEvent) {
 // this method is invoked once when web-application is deployed (started)

 // reading properties file
 FileInputStream fis = null;
 Properties properties = new Properties();
 try {
 fis = new FileInputStream("path/to/db.properties") 
 properties.load(fis);
 } catch(IOException ex) {
 throw new RuntimeException(ex);
 } finally {
 try {
 if(fis != null) {
 fis.close();
 }
 } catch(IOException e) {
 throw new RuntimeException(e);
 }
 }

 // creating data source instance
 SomeDataSourceImpl dataSource = new SomeDataSourceImpl();
 dataSource.setJdbcUrl(properties.getProperty("db.url"));
 dataSource.setUser(properties.getProperty("db.user"));
 dataSource.setPassword(properties.getProperty("db.pwd"));

 // storing reference to dataSource in ServletContext attributes map
 // there is only one instance of ServletContext per web-application, which can be accessed from almost anywhere in web application(servlets, filters, listeners etc)
 final ServletContext servletContext = servletContextEvent.getServletContext();
 servletContext.setAttribute("some-data-source-alias", dataSource);
 }

 @Override
 public void contextDestroyed(ServletContextEvent servletContextEvent) {
 // this method is invoked once when web-application is undeployed (stopped) - here one can (should) implement resource cleanup etc
 }

}
</code></pre>

And then, somewhere in web-application code to access <code>dataSource</code>:


<pre><code>ServletContext servletContext = ...; // as mentioned above, it should be accessible from almost anywhere
DataSource dataSource = (DataSource) servletContext.getAttribute("some-data-source-alias");
// use dataSource
</code></pre>

<code>SomeDataSourceImpl</code> is some concrete implementation of <a href="http://docs.oracle.com/javase/6/docs/api/javax/sql/DataSource.html" rel="nofollow">javax.sql.DataSource</a>. Please advise if you doesn't use specific <code>DataSource</code>s (like <a href="http://www.mchange.com/projects/c3p0/apidocs/com/mchange/v2/c3p0/ComboPooledDataSource.html" rel="nofollow">ComboPooledDataSource</a> for connection pooling) and don't know how to obtain it - I will post how to bypass this.

<code>some-data-source-alias</code> - is just <code>String</code> alias(key) for your <code>DataSource</code> instance in <code>ServletContext</code> attribute map. Good practice is to give aliases prepended with package name like <code>com.mycompany.mywebapp.dataSource</code>.

Hope this helps...

blocks|key|305833|text|如果这是Tomcat7，您可以在context.xml中编写自己的org.apache.tomcat.util.IntrospectionUtils.PropertySource实现读取变量，如"${...}“。您需要设置系统属性org.apache.tomcat.util.digester.PROPERTY_SOURCE以指向您的PropertySource实现。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|305834|entityMap^0|G|B|X|1K|37|1B|4N|E|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|G|$]]

If this is Tomcat 7, you can write your own <code>org.apache.tomcat.util.IntrospectionUtils.PropertySource</code> implementation read variables written like "${...}" in <code>context.xml</code>. You'll need to set the system property <code>org.apache.tomcat.util.digester.PROPERTY_SOURCE</code> to point to your <code>PropertySource</code> implementation.

I have a DataSource configuration in context.xml. Is it possible not to hard-code database parameters in that file? For example, use an external properties file, and load the parameters from it?

Something, like this:

context.xml:

<pre><code> &lt;Resource
 name="jdbc/myDS" auth="Container"
 type="javax.sql.DataSource"
 driverClassName="oracle.jdbc.OracleDriver"
 url="${db.url}"
 username="${db.user}"
 password="${db.pwd}"
 maxActive="2"
 maxIdle="2"
 maxWait="-1"/&gt;
</code></pre>

db.properties:

<pre><code>db.url=jdbc:oracle:thin:@server:1521:sid
db.user=test
db.pwd=test
</code></pre>

Externalize Tomcat configuration

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我在context.xml中有一个DataSource配置。是否可以不在该文件中对数据库参数进行硬编码？例如，使用外部属性文件，并从中加载参数？像这样的东西：context.xml： <Resource name="jdbc/myDS" auth="Container" type="javax.sql.DataS...

问外部化Tomcat配置
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