半翻译半整理的一点struts的东东，很浅显的，欢迎指正(二）-JSP教程,资料/其它

3．    struts plugins：
plugin从struts1.1开始介绍，它定义了一个org.apache.struts.action.plugin接口，它主要用来分配资源(allocating resources)或者建立数据库的连结或者jndi资源。这个接口提供了两个必须实现的方法：init()和destroy()。如果运用了plugin技术，那么在容器启动的时候，会调用plugin的init()方法。所以将应用系统的初始化信息写在这里。当容器停止struts应用系统的时候，会调用destroy()方法，destroy()方法主要是用来收回在init()方法中分配的资源信息。
◆    扩展plugin类
           ① 创建一个实现plugin接口的类
           ② 添加一个空的构造器
           ③ 实现init()及destroy()两个方法
           ④ 在struts-config.xml文件中对<plug-in />元素的配置
创建plugin必须继承org.apache.struts.action.plugin接口。并且实现init()及destroy()方法。例子：
package wiley;

import java.util.properties;
import java.io.file;
import java.io.fileinputstream;
import java.io.filenotfoundexception;
import java.io.ioexception;
import javax.servlet.servletexception;
import javax.servlet.servletcontext;
import org.apache.struts.action.plugin;
import org.apache.struts.config.moduleconfig;
import org.apache.struts.action.actionservlet;

public class wileyplugin implements plugin {
    
    public static final string properties = "properties";
    
    public wileyplugin() {}
    
    public void init(actionservlet servlet,
                 moduleconfig config)
          throws javax.servlet.servletexception {
        system.err.println("….>the plugin is starting<….");
        properties properties = new properties();
        string path = "c:\\applicationresources"+
        ".properties";
        try {
            // build a file object referening the properties file
            // to be loaded
            file file = new file(path);
            // create an input stream
            fileinputstream fis = new fileinputstream(file);
            // load the properties
            properties.load(fis);
            // get a reference to the servletcontext
            servletcontext context = servlet.getservletcontext();
            // add the loaded properties to the servletcontext
            // for retrieval throughout the rest of the application
            context.setattribute(properties, properties);
        }
        catch (filenotfoundexception fnfe) {
            throw new servletexception(fnfe.getmessage());
        }
        catch (ioexception ioe) {
            throw new servletexception(ioe.getmessage());
        }
    }
    
    public void destroy() {
        // we dont have anything to clean up, so
        // just log the fact that the plugin is shutting down
        system.err.println("….>the plugin is stopping<….");
    }
}
◆    配置plugin：
在struts-config.xml文件中配置<plug-in>元素。如下：
<plug-in classname=”wiley.wileyplugin” />
<plug-in />的详细配置信息见”struts-config.xml配置文件讲解”。