SyslogInitServlet


1   package com.protomatter.syslog.xml;
2   
3   /**
4    *  {{{ The Protomatter Software License, Version 1.0
5    *  derived from The Apache Software License, Version 1.1
6    *
7    *  Copyright (c) 1998-2002 Nate Sammons.  All rights reserved.
8    *
9    *  Redistribution and use in source and binary forms, with or without
10   *  modification, are permitted provided that the following conditions
11   *  are met:
12   *
13   *  1. Redistributions of source code must retain the above copyright
14   *     notice, this list of conditions and the following disclaimer.
15   *
16   *  2. Redistributions in binary form must reproduce the above copyright
17   *     notice, this list of conditions and the following disclaimer in
18   *     the documentation and/or other materials provided with the
19   *     distribution.
20   *
21   *  3. The end-user documentation included with the redistribution,
22   *     if any, must include the following acknowledgment:
23   *        "This product includes software developed for the
24   *         Protomatter Software Project
25   *         (http://protomatter.sourceforge.net/)."
26   *     Alternately, this acknowledgment may appear in the software itself,
27   *     if and wherever such third-party acknowledgments normally appear.
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29   *  4. The names "Protomatter" and "Protomatter Software Project" must
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34   *  5. Products derived from this software may not be called "Protomatter",
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51   */
52  
53  import java.io.*;
54  import java.net.*;
55  import java.util.*;
56  import java.text.MessageFormat  ;
57  import com.protomatter.syslog.*;
58  import javax.servlet.*;
59  import javax.servlet.http.*;
60  
61  /**
62   *  A servlet that configures Syslog when its <TT>init()</TT>
63   *  method is called.  It should be configured in a WebApp
64   *  by adding the following declaration to the <TT>web.xml</TT>
65   *  file for the WebApp:<P>
66   *
67   *  <PRE>
68   *    <B>&lt;servlet&gt;</B>
69   *      <B>&lt;servlet-name&gt;</B>SyslogInitServlet<B>&lt;/servlet-name&gt;</B>
70   *      <B>&lt;description&gt;</B>Syslog Initialization Servlet<B>&lt;/description&gt;</B>
71   *      <B>&lt;servlet-class&gt;</B>com.protomatter.syslog.xml.SyslogInitServlet<B>&lt;/servlet-class&gt;</B>
72   *      <B>&lt;init-param&gt;</B>
73   *        <B>&lt;param-name&gt;</B>config.xml<B>&lt;/param-name&gt;</B>
74   *        <B>&lt;param-value&gt;</B>/path/to/syslog.xml<B>&lt;/param-value&gt;</B>
75   *      <B>&lt;/init-param&gt;</B>
76   *      <B>&lt;init-param&gt;</B>
77   *        <B>&lt;param-name&gt;</B>show.config.on.get<B>&lt;/param-name&gt;</B>
78   *        <B>&lt;param-value&gt;</B>false<B>&lt;/param-value&gt;</B>
79   *      <B>&lt;/init-param&gt;</B>
80   *      <B>&lt;init-param&gt;</B>
81   *        <B>&lt;param-name&gt;</B>load.config.as.resource<B>&lt;/param-name&gt;</B>
82   *        <B>&lt;param-value&gt;</B>false<B>&lt;/param-value&gt;</B>
83   *      <B>&lt;/init-param&gt;</B>
84   *      <B>&lt;init-param&gt;</B>
85   *        <B>&lt;param-name&gt;</B>Syslog.xml.parser<B>&lt;/param-name&gt;</B>
86   *        <B>&lt;param-value&gt;</B>org.apache.xerces.parsers.SAXParser<B>&lt;/param-value&gt;</B>
87   *      <B>&lt;/init-param&gt;</B>
88   *      <B>&lt;init-param&gt;</B>
89   *        <B>&lt;param-name&gt;</B>Syslog.classloader.warning<B>&lt;/param-name&gt;</B>
90   *        <B>&lt;param-value&gt;</B>true<B>&lt;/param-value&gt;</B>
91   *      <B>&lt;/init-param&gt;</B>
92   *      <B>&lt;load-on-startup&gt;</B>1<B>&lt;/load-on-startup&gt;</B>
93   *    <B>&lt;/servlet&gt;</B>
94   *    <B>&lt;servlet-mapping&gt;</B>
95   *      <B>&lt;servlet-name&gt;</B>SyslogInitServlet<B>&lt;/servlet-name&gt;</B>
96   *      <B>&lt;url-pattern&gt;</B>/SyslogInitServlet<B>&lt;/url-pattern&gt;</B>
97   *    <B>&lt;/servlet-mapping&gt;</B>
98   *  </PRE><P>
99   *
100  *  The <TT>config.xml</TT> init param is requred and should point
101  *  to the XML configuration file for Syslog.<P>
102  *
103  *  If the optional <TT>show.config.on.get</TT> init param is set
104  *  to <TT>true</TT> (the default is <TT>false</TT>), then when
105  *  the servlet is hit with a <TT>GET</TT> request, it will return the
106  *  current Syslog configuration.  Care should be taken when using this
107  *  option since the syslog configuration file may contain database
108  *  passwords, etc.  It is a good idea to use declarative security
109  *  to protect this servlet if you are allowing it to display the
110  *  configuration file.<P>
111  *
112  *  If the optional <TT>load.config.as.resource</TT> init param is set
113  *  to <TT>true</TT> (the default is <TT>false</TT>), then when the
114  *  servlet initializes, it will try and find the configuration file
115  *  as a resource using the classloader that loaded the servlet.  This
116  *  is a useful option if you are using this servlet to allow you
117  *  to use a different Syslog instance for each EAR in a J2EE server.
118  *  For instance, if you set the value of the <TT>config.xml</TT>
119  *  parameter to "<TT>syslog-config.xml</TT>", and then set
120  *  <TT>load.config.as.resource</TT> to "<TT>true</TT>", then you
121  *  can put a file called "<TT>syslog-config.xml</TT>" in the base
122  *  of the EAR directory, and the servlet will find it.  This is
123  *  a nice option to use if you don't like to have hard-coded
124  *  paths in the <TT>web.xml</TT> file.<P>
125  *
126  *  The optional <TT>Syslog.xml.parser</TT> init param can be used
127  *  to set the class name of the XML parser used to read the XML
128  *  configuration file.  It is possible that a confused JAXP
129  *  registry can cause problems.  You should set this property
130  *  to "<TT>org.apache.xerces.parsers.SAXParser</TT>" or something
131  *  similar.  Note that this has the exact same effect as setting
132  *  the same property as a system property (using the "<TT>-D</TT>"
133  *  option to the JVM).  It is preferable to use that property
134  *  in the <TT>web.xml</TT> file instead of the system property
135  *  because you can then have the ability to use different
136  *  XML parsers for different EAR files.<P>
137  *
138  *  The optional <TT>Syslog.classloader.warning</TT> init param can be used
139  *  to turn off the classloader warning that is issued if Syslog is
140  *  loaded with a ClassLoader other than the system one.  The default
141  *  value for this property is <TT>true</TT>, meaning that the warning
142  *  <i>should</i> be displayed.  Note that this has the exact same effect as setting
143  *  the same property as a system property (using the "<TT>-D</TT>"
144  *  option to the JVM).  Some people prefer to use that property
145  *  in the <TT>web.xml</TT> file instead of the system property
146  *  because they don't like to have to set system properties.
147  *  Please read <a HREF="../classloader-warning.html">this document</a>
148  *  regarding classloader issues with Syslog.<P>
149  *
150  *  The <TT>&lt;servlet-mapping&gt;</TT> tag above is optional.  If
151  *  it is not specified, the servlet will still initialize syslog when
152  *  the WebApp comes up, but the servlet will not be visible to
153  *  web browsers.  This is generally a good thing.<P>
154  */
155 
156 public class SyslogInitServlet
157             extends HttpServlet
158 {
159     private boolean showConfigurationOnGet = false;
160     private boolean loadConfigAsResource = false;
161 
162     // By default, we show the classloader warning
163     private static final boolean WARNING_DEFAULT = true;
164 
165     private static final String   WARNING_OFF = "off";
166 
167     private static final String   TRUE = "true";
168 
169     private static final String   CONFIG_FILE_PARAM = "config.xml";
170 
171     private static final String   SHOW_CONFIG_ON_GET_PARAM = "show.config.on.get";
172 
173     private static final String   LOAD_CONFIG_AS_RESOURCE_PARAM = "load.config.as.resource";
174 
175     /**
176      *  Default constructor.
177      */
178     public SyslogInitServlet()
179     {
180         super();
181     }
182 
183     /**
184      *  Initialize syslog.
185      */
186     public void init(ServletConfig config)
187     throws ServletException
188     {
189         super.init(config);
190 
191         try
192         {
193             if (TRUE.equalsIgnoreCase(config.getInitParameter(SHOW_CONFIG_ON_GET_PARAM)))
194                 this.showConfigurationOnGet = true;
195 
196             if (TRUE.equalsIgnoreCase(config.getInitParameter(LOAD_CONFIG_AS_RESOURCE_PARAM)))
197                 this.loadConfigAsResource = true;
198 
199             boolean showClassloaderWarning = WARNING_DEFAULT;
200 
201             if (WARNING_OFF.equalsIgnoreCase(config.getInitParameter(Syslog.WARNING_PROPERTY)))
202                 showClassloaderWarning = false;
203 
204             String   filename = config.getInitParameter(CONFIG_FILE_PARAM);
205 
206             if (filename == null)
207                 throw new IllegalArgumentException  (MessageFormat.format(
208                                                        Syslog.getResourceString(MessageConstants.MUST_SPECIFY_INIT_PARAM_MESSAGE),
209                                                        new Object  [] { CONFIG_FILE_PARAM } ));
210 
211             String   xmlParserClass = System.getProperty(SyslogXML.XML_PARSER_PROPERTY);
212 
213             if (isValid(config.getInitParameter(SyslogXML.XML_PARSER_PROPERTY)))
214             {
215                 xmlParserClass = config.getInitParameter(SyslogXML.XML_PARSER_PROPERTY).trim();
216             }
217 
218             if (loadConfigAsResource)
219             {
220                 // try and find the file as a resource using the
221                 // ClassLoader that we were loaded with.
222                 ClassLoader   loader = this.getClass().getClassLoader();
223                 InputStream input = loader.getResourceAsStream(filename);
224 
225                 if (input != null)
226                 {
227                     SyslogXML.configure(input, xmlParserClass, showClassloaderWarning);
228                 }
229                 else
230                 {
231                     throw new SyslogInitException(MessageFormat.format(
232                                                       Syslog.getResourceString(MessageConstants.RESOURCE_NOT_FOUND),
233                                                       new Object  [] { filename }));
234                 }
235 
236             }
237             else
238             {
239                 File file = new File(filename);
240                 SyslogXML.configure(file, xmlParserClass, showClassloaderWarning);
241             }
242 
243         }
244         catch (SyslogInitException x)
245         {
246             throw new ServletException(Syslog.getResourceString(MessageConstants.CANNOT_CONFIGURE_MESSAGE), x);
247         }
248     }
249 
250     /**
251      *  Showdown syslog.
252      */
253     public void destroy()
254     {
255         Syslog.shutdown();
256     }
257 
258     private static boolean isValid(String   s)
259     {
260         if ((s == null) || (s.trim().length() == 0))
261             return false;
262 
263         return true;
264     }
265 
266     public void doGet(HttpServletRequest req, HttpServletResponse resp)
267     throws ServletException, IOException
268     {
269         if (this.showConfigurationOnGet)
270         {
271             resp.setContentType("text/plain");
272             OutputStream out = resp.getOutputStream();
273             SyslogXML.writeConfiguration(out);
274         }
275         else
276         {
277             resp.setContentType("text/html");
278             PrintWriter out = resp.getWriter();
279             out.println(Syslog.getResourceString(MessageConstants.SERVLET_SNIPPY_RESPONSE));
280         }
281     }
282 }
283
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