blocks|key|874701|text|一种方法是读取xml文件并对其进行解析。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|874702|在ServletContextListener中解析后，您可以将其放在中的某个静态映射上|offset|length|style|CODE|874703|entityMap^0|0|1|M|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

One way is to read xml file and parse it.

You can put it on some static map in after parsing in <code>ServletContextListener</code>

blocks|key|874796|text|您需要将所需的参数放入web.xml文件的env-entry条目中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|874797|<env-entry>+
++++<env-entry-name>dbhost</env-entry-name>
++++<env-entry-type>java.lang.String</env-entry-type>
++++<env-entry-value>localhost</env-entry-value>+
</env-entry>|code-block|syntax|javascript|874798|然后通过jndi上下文访问它们。|874799|import+javax.naming.Context;
import+javax.naming.InitialContext;
...
//+Get+the+base+naming+context
Context+env+=+(Context)new+InitialContext().lookup("java:comp/env");

//+Get+a+single+value
String+dbhost+=+(String)env.lookup("dbhost");|874800|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You need to put the required parameters in env-entry entries of your web.xml file:

<pre><code>&lt;env-entry&gt; 
 &lt;env-entry-name&gt;dbhost&lt;/env-entry-name&gt;
 &lt;env-entry-type&gt;java.lang.String&lt;/env-entry-type&gt;
 &lt;env-entry-value&gt;localhost&lt;/env-entry-value&gt; 
&lt;/env-entry&gt;
</code></pre>

and then access them via the jndi context 

<pre><code>import javax.naming.Context;
import javax.naming.InitialContext;
...
// Get the base naming context
Context env = (Context)new InitialContext().lookup("java:comp/env");

// Get a single value
String dbhost = (String)env.lookup("dbhost");
</code></pre>

blocks|key|1089442|text|您可以在web.xml和javax.servlet.ServletContextListener中使用上下文参数来填充一些静态字段。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1089443|在普通的java类中，你会读到这个静态字段。|1089444|<?xml+version="1.0"+encoding="UTF-8"?>
<web-app+version="2.5"+xmlns="http://java.sun.com/xml/ns/javaee"
++++xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
++++xsi:schemaLocation="http://java.sun.com/xml/ns/javaee+http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
...
<context-param>
++++<description>Prameter</description>
++++<param-name>myParam</param-name>
++++<param-value>123456790</param-value>
</context-param>
...
</web-app>|code-block|syntax|javascript|1089445|您可以使用ServletContext.getInitParameter访问此上下文参数|offset|length|style|CODE|1089446|entityMap^0|0|0|0|5|V|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|T|8|@$K|U|L|V|M|N]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

You could use context-parameters in your web.xml and a javax.servlet.ServletContextListener to populate some static fields.

In you normal java class you read this this static fields.

<pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"&gt;
...
&lt;context-param&gt;
 &lt;description&gt;Prameter&lt;/description&gt;
 &lt;param-name&gt;myParam&lt;/param-name&gt;
 &lt;param-value&gt;123456790&lt;/param-value&gt;
&lt;/context-param&gt;
...
&lt;/web-app&gt;
</code></pre>

You can access this context parameter with <code>ServletContext.getInitParameter</code>

blocks|key|874907|text|创建一个可以从其中一个servlets+init初始化的静态类。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|874908|entityMap|0|LINK|mutability|MUTABLE|url|http://download.oracle.com/javaee/1.3/api/javax/servlet/Servlet.html#init%2528javax.servlet.ServletConfig%2529^0|B|D|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]]]]

Create a static class that would be initialized from one of the <a href="http://download.oracle.com/javaee/1.3/api/javax/servlet/Servlet.html#init%28javax.servlet.ServletConfig%29" rel="nofollow">servlets init</a>.

blocks|key|874950|text|实现ServletContextListener|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|874951|package+util;

import+javax.servlet.ServletContext;
import+javax.servlet.ServletContextEvent;
import+javax.servlet.ServletContextListener;

public+class+MyConfigListener+implements+ServletContextListener+{
++++@Override
++++public+void+contextInitialized(ServletContextEvent+sce)+{
++++++++ServletContext+ctx+=+sce.getServletContext();

++++++++String+hostname+=+ctx.getInitParameter("my.config.hostname");

++++++++//+now+go+and+do+something+with+that
++++}

++++@Override
++++public+void+contextDestroyed(ServletContextEvent+sce)+{}

}|code-block|syntax|javascript|874952|别忘了在web.xml中注册它|874953|<context-param>
++<param-value>somewhere.example.org</param-value>
++<param-name>my.config.hostname</param-name>
</context-param>
<listener>
++<listener-class>util.MyConfigListener</listener-class>
</listener>|874954|entityMap^0|2|M|0|0|4|7|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

Implement a <code>ServletContextListener</code>:

<pre><code>package util;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class MyConfigListener implements ServletContextListener {
 @Override
 public void contextInitialized(ServletContextEvent sce) {
 ServletContext ctx = sce.getServletContext();

 String hostname = ctx.getInitParameter("my.config.hostname");

 // now go and do something with that
 }

 @Override
 public void contextDestroyed(ServletContextEvent sce) {}

}
</code></pre>

And don't forget to register it in <code>web.xml</code>:

<pre><code>&lt;context-param&gt;
 &lt;param-value&gt;somewhere.example.org&lt;/param-value&gt;
 &lt;param-name&gt;my.config.hostname&lt;/param-name&gt;
&lt;/context-param&gt;
&lt;listener&gt;
 &lt;listener-class&gt;util.MyConfigListener&lt;/listener-class&gt;
&lt;/listener&gt;
</code></pre>

I've got a regular java file that I use to update and query a mysql database but I need to take configurable options in that file (like host name, password, etc) and put it in the web.xml file (or perhaps another file if that's an option, but ideally in web.xml).

But I don't know how to get access to web.xml values from a regular non-servlet java file.

Or would I need to read the xml (like any other xml file... or is there a shortcut route to this...)

How can I read context parameter/web.xml values in a non-servlet java file?

数据库

我有一个常规的java文件，用于更新和查询mysql数据库，但我需要获取该文件中的可配置选项(如主机名、密码等)，并将其放入web.xml文件(如果可以，也可以放入另一个文件，但最好是在web.xml中)。但是我不知道如何从常规的非servlet java文件访问web.xml值。或者我是否需要读取xml (就像任何其...

问如何读取非servlet java文件中的上下文参数/web.xml值？
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