fcgi-java.htm

FastCGI,语言无关的、可伸缩架构的CGI开放扩展

         <I>fcgiapp</I> C library. To understand where these methods occur we need to look briefly at the FastCGI
         redefinition of standard I/O.
      </P>
      <P>
         Java defines standard I/O in the <I>java.System</I> class as follows:
      </P>
      <P>
         public static InputStream in = new BufferedInputStream(new FileInputStream(FileDescriptor.in), 128);<BR>
         public static PrintStream out = new PrintStream(new BufferedOutputStream(new
         FileOutputStream(FileDescriptor.out), 128), true);<BR>
         public static PrintStream err = new PrintStream(new BufferedOutputStream(new
         FileOutputStream(FileDescriptor.err), 128), true);
      </P>
      <P>
         The File Descriptors <I>in</I>, <I>out</I>, <I>err</I> are constants set to 0, 1 and 2 respectively.
      </P>
      <P>
         The FastCGI interface redefines <I>java.System in, out</I>, and <I>err</I> by replacing the File streams with
         Socket streams and inserting streams which know how to manage the FastCGI protocol between the Socket streams
         and the Buffered streams in the above definitions.
      </P>
      <P>
         For those cases where the FCGI application needs to bypass the standard I/O streams, it can directly access
         the methods of the FCGI input and output streams which roughly correspond to the functions in the C
         <I>fcgiapp</I> library. These streams can be accessed via the <I>request</I> class variable in FCGIInterface.
         Each Request object has instance variables that refer to an FCGIInputStream, and to two FCGIOutputStreams
         associated with that request.
      </P>
      <H3>
         <A NAME="S4">4. Environment Variables</A>
      </H3>
      <P>
         Java does not use the C <I>environ</I> list. Nor is there a <I>getenv</I> command that reads system
         environment variables. This is intentional for reasons of portability and security. Java has an internal
         dictionary of properties which belongs to the System class. These System properties are <I>name/value</I>
         associations that constitute the Java environment. When a Java application starts up, it reads in a file with
         default properties. As we have seen, additional System properties may be inserted by using the -D <I>Java</I>
         command argument.
      </P>
      <P>
         For CGI, where the Java application is invoked from a .cgi script that, in turn, invokes the Java interpreter,
         this script could read the environment and pass the variables to the Java application either by writing a file
         or by creating -D options on the fly. Both of these methods are somewhat awkward.
      </P>
      <P>
         For FastCGI Java applications, the environment variables are obtained from the FastCGI web server via
         <TT>FCGI_PARAMS</TT> records that are sent to the application at the start of each request. The FastCGI
         interface stores the original startup properties, combines these with the properties obtained from the server,
         and puts the new set of properties in the System properties dictionary. The only parameter that has to be
         specifically added at startup time is the FCGI_PORT parameter for the Socket creation. In the future, we
         expect that even this parameter won&#39;t be needed, since its use is due to an acknowledged rigidity in the
         JDK&#39;s implementation of sockets.
      </P>
      <P>
      </P>
      <H3>
         <A NAME="S4">5. Further examples: EchoFCGI and Echo2FCGI</A>
      </H3>
      <P>
         The next two examples illustrate the points made in the last two sections. EchoFCGI and Echo2FCGI both echo
         user input and display the application&#39;s environment variables. EchoFCGI reads the user input from
         System.in, while Echo2FCGI reads the user input directly from the intermediate FastCGI input stream.
      </P>
      <H4>
         A. EchoFCGI
      </H4>
<PRE>
import FCGIInterface;
import FCGIGlobalDefs;
import java.io.*;

class EchoFCGI {
 
 public static void main (String args[]) {
  int status = 0;
   while(new FCGIInterface().FCGIaccept()&gt;= 0) {
  System.out.println(&quot;Content-type: text/html\n\n&quot;);
   System.out.println(&quot;&lt;html&gt;&quot;);
   System.out.println(
    &quot;&lt;head%gt;&lt;TITLE&gt;FastCGI echo
                                      &lt;/TITLE&gt;&lt;/head&gt;&quot;);
   System.out.println(&quot;&lt;body&gt;&quot;); 
   System.out.println(
                                         &quot;&lt;H2&gt;FastCGI echo&lt;/H2&gt;&quot;);
   System.out.println(&quot;&lt;H3&gt;STDIN&lt;/H3&gt;&quot;);
   for ( int c = 0; c != -1; ) {
    try {
     c = System.in.read();
    } catch(IOException e) {
     System.out.println(
     &quot;&lt;br&gt;&lt;b&gt;SYSTEM EXCEPTION&quot;);
     Runtime rt = Runtime.getRuntime();
     rt.exit(status);
     }
    if (c != -1) { 
     System.out.print((char)c);
     }
    }
   System.out.println(
    &quot;&lt;H3&gt;Environment Variables:&lt;/H3&gt;&quot;);
 
   System.getProperties().list(System.out);
   System.out.println(&quot;&lt;/body&gt;&quot;);
   System.out.println(&quot;&lt;/html&gt;&quot;);
      }
  }
   }
</PRE>
      <H4>
         B. Echo2FCGI
      </H4>
<PRE>
import FCGIInterface;
import FCGIGlobalDefs;
import FCGIInputStream;
import FCGIOutputStream;
import FCGIMessage;
import FCGIRequest;
import java.io.*;

class Echo2FCGI {

 public static void main (String args[]) {
  int status = 0;
                FCGIInterface intf = new FCGIInterface();
   while(intf.FCGIaccept()&gt;= 0) {
  System.out.println(&quot;Content-type: text/html\n\n&quot;);
   System.out.println(&quot;&lt;html&gt;&quot;);
   System.out.println(
    &quot;&lt;head&gt;&lt;TITLE&gt;FastCGI echo
                                    &lt;/TITLE&gt;&lt;/head&gt;&quot;);
   System.out.println(&quot;&lt;body&gt;&quot;);   
   System.out.println(&quot;&lt;H2&gt;FastCGI echo&lt;/H2&gt;&quot;);
   System.out.println(&quot;&lt;H3&gt;STDIN:&lt;/H3&quot;&gt;);
   for ( int c = 0; c != -1; ) {
    try {
     c = intf.request.inStream.read();
    } catch(IOException e) {
     System.out.println(
     &quot;&lt;br&gt;&lt;b&gt;SYSTEM EXCEPTION&quot;);
     Runtime rt = Runtime.getRuntime();
     rt.exit(status);
     }
    if (c != -1) { 
     System.out.print((char)c);
     }
    }
   System.out.println(
    &quot;&lt;H3&gt;Environment Variables:&lt;/H3&gt;&quot;);
 
   System.getProperties().list(System.out);
   System.out.println(&lt;&quot;/body&gt;&quot;);
   System.out.println(&quot;&lt;/html&gt;&quot;);
      }
  }
   }
</PRE>
      <H4>
         C. Running these Examples
      </H4>
      <H5>
         Configuring
      </H5>
      <P>
         As with TinyFCGI, you need to configure the web server to recognize these two FastCGI applications. Your
         configuration now looks like this:
      </P>
      <P>
      </P>
<PRE>
ExternalAppClass java1 -host hostname:portNum
Responder java1 fcgi-devel-kit/examples/TinyFCGI
ExternalAppClass java2 -host hostname:portNumA
Responder java2 fcgi-devel-kit/examples/EchoFCGI
ExternalAppClass java3 -host hostname:porNumB
Responder java3 fcgi-devel-kit/examples/Echo2FCGI
</PRE>
      <P>
         Note that the application classes and port numbers are different for each application.
      </P>
      <H5>
         Running
      </H5>
      <P>
         As with TinyFCGI, you need to run these programs with the -D option using FCGI_PORT and the appropriate port
         number. To get some data for standard input we have created two html pages with forms that use a POST method.
         These are echo.html and echo2.html. You must edit these .html files to expand the path to
         <I>fcgi-devel-kit/examples</I> to a full path. Once the appropriate Java program is running, point your
         browser at the corresponding HTML page, enter some data and select the <I>go_find</I> button.
      </P>
      <H3>
         <A NAME="S6">6. FastCGI Java Classes</A>
      </H3>
      <P>
         The Java FastCGI classes are included in both source and byte code format in <I>fcgi-devel-kit/java/src</I>
         and :<I>fcgi-devel-kit/java/classes</I> respectively. The following is a brief description of these classes:
      </P>
      <P>
      </P>
      <DL>
         <DT CLASS="c4">
            FCGIInterface
         </DT>
         <DD>
            This class contains the FCGIaccept method called by the FastCGI user application. This method sets up the
            appropriate FastCGI environment for communication with the web server and manages FastCGI requests.<BR>
         </DD>
         <DT CLASS="c4">
            FCGIInputStream
         </DT>
         <DD>
            This input stream manages FastCGI internal buffers to ensure that the user gets all of the FastCGI messages
            associated with a request. It uses FCGIMessage objects to interpret these incoming messages.<BR>
         </DD>
         <DT CLASS="c4">
            FCGIOutputStream
         </DT>
         <DD>
            This output stream manages FastCGI internal buffers to send user data back to the web server and to notify
            the server of various FCGI protocol conditions. It uses FCGIMessage objects to format outgoing FastCGI
            messages.<BR>
         </DD>
         <DT CLASS="c4">
            FCGIMessage
         </DT>
         <DD>
            This is the only class that understands the actual structure of the FastCGI messages. It interprets
            incoming FastCGI records and constructs outgoing ones..<BR>
         </DD>
         <DT CLASS="c4">
            FCGIRequest
         </DT>
         <DD>
            This class currently contains data fields used by FastCGI to manage user requests. In a multi-threaded
            version of FastCGI, the role of this class will be expanded.<BR>
         </DD>
         <DT CLASS="c4">
            FCGIGlobalDefs
         </DT>
         <DD>
            This class contains definitions of FastCGI constants.
         </DD>
      </DL>
      <HR>
      <ADDRESS>
         <A HREF="mailto:[e-mail]">Steve Harris // [e-mail]</A>
      </ADDRESS>
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