What is the VM Bridge?
----------------------

  The VM Bridge is a network protocol which can be used to
  connect a native script engine, for example PHP, with a Java or ECMA
  335 VM.

  Please read the http://php-java-bridge.sf.net for more information.


Overview
--------

  The generic VM Bridge implementation is distributed as an
  example web archive called "JavaBridge.war". It is a zip archive which
  contains the libraries "JavaBridge.jar", "php-script.jar" and
  "script-api.jar". Furthermore it contains some PHP examples which
  can be run in any pure Java J2EE server or servlet engine.

  The VM Bridge web application contains two servlets. The
  "PhpJavaServlet" handles requests from remote PHP clients running in
  Apache/IIS or from the command line:

    Apache/IIS/console::PHP <--> PhpJavaServlet

  The second servlet, PhpCGIServlet, can handle requests from internet
  clients directly. It can start PHP as a FastCGI or CGI sub component:

    internet browser <--> PhpCGIServlet <--> php-cgi <--> PhpJavaServlet


  Furthermore the bridge supports standalone Java applications through
  the JSR223 script API.


Build and execution instructions:
---------------------------------

  Type java -jar JavaBridge.war to test the download. This command
  extracts JavaBridge.jar from the archive.

  Double-click on JavaBridge.jar and select SERVLET_LOCAL:8080 to
  start a local HTTP server. Type java -jar JavaBridge.jar --help
  to see the list of available options.

  Use the following code to access Java from your PHP scripts:

    <?php require_once("http://localhost:8080/JavaBridge/java/Java.inc");
    $s = new Java("java.lang.String", "hello");
    ...
    ?>


------------------------------------
  Permanently activate the module
  -------------------------------

  Installation for the web:
  -------------------------

  Install a local J2EE server or servlet engine. For example Tomcat
  version 6. Copy the JavaBridge.war file into the autodeploy folder of
  the J2EE server or servlet engine.

  Example for Apache/Tomcat on Linux:

    cp JavaBridge.war /usr/share/tomcat5/webapps/

  Restart tomcat and wait until the directory webapps/JavaBridge
  appears.

  Then copy or symlink the JavaBridge folder to the document root
  of your HTTP server. Example for Linux:

    cp -r /usr/share/tomcat5/webapps/JavaBridge/ $HOME/public_html


  Installation for standalone Java J2SE applications:
  ---------------------------------------------------

  Copy the JavaBridge.jar to
  the java.ext.dirs. Example for JDK1.6 on Linux:

    cp JavaBridge.jar /usr/java/packages/lib/ext/

  Type

    /usr/java/default/bin/jrunscript -l php YOURSCRIPT.php

  to run PHP scripts from Java.

---------------------------------------------
  Starting the VM Bridge automatically
  ------------------------------------------

  For the web:
  ------------

  Install the J2EE server or servlet engine as a service. The
  Apache/Tomcat servlet engine automatically installs as a service on
  Windows and Linux.


  For standalone J2SE applications:
  ----------------------------------

  No installation necessary; the bridge starts automatically when the
  JSR 223 context is accessed. Example:

    jrunscript -cp JavaBridge.jar -l php

  automatically starts a "php-cgi" executable from the path. Please
  see the INSTALL.J2SE document for details how to access persistent
  script engines from a HTTP or FastCGI pool using the JSR 223
  interface.
  
---------------------------------------------
  AS/Servlet with PHP CGI/FastCGI
  -------------------------------

  Read the following instructions only if you don't want to use
  Apache or IIS.

  Deploy the JavaBridge.war into the Tomcat or J2EE server (please see 
  our FAQ section on http://php-java-bridge.sf.net), then visit 
  http://localhost:8080/JavaBridge and run the supplied JSP and PHP 
  examples.

  If the parameter name "use_fast_cgi" is set to "Autostart" in the
  web.xml, and a fcgi server does not listen on port 9667, and a fcgi
  binary can be found as either 

    /usr/bin/php-cgi 

  or 

    c:/Program Files/PHP/php-cgi.exe,

  then the back end automatically starts the Fast-CGI server on this
  computer. With the command:

    cd $HOME
    export REDIRECT_STATUS="200"
    export X_JAVABRIDGE_OVERRIDE_HOSTS="/"
    export PHP_FCGI_CHILDREN="5"
    export PHP_FCGI_MAX_REQUESTS="5000"
    /usr/bin/php-cgi -d allow_url_include=On -b 127.0.0.1:9667

  On Windows the command is:

    set REDIRECT_STATUS "200"
    set X_JAVABRIDGE_OVERRIDE_HOSTS "/"
    set PHP_FCGI_CHILDREN "5"
    set PHP_FCGI_MAX_REQUESTS "5000"
    launcher.exe php-cgi \\.\pipe\JavaBridge@9667 -d allow_url_include=On


  The PHP FastCGI server starts when the VM or the web context starts,
  it stops when the VM or web context terminates.


  If that failed, the bridge searches for a CGI binary called:
  
    php-cgi-<architecture>-<os>.exe or

    php-cgi-<architecture>-<os>.sh or

    php-cgi-<architecture>-<os>

  in the directory WEB-INF/cgi/. On Unix the binary must be executable. It
  is therefore recommended to always use a wrapper .sh script, for example:

  #!/bin/sh
  # This wrapper script reconstructs the executable permissions
  # which some zip or .war implementations do not preserve
  chmod +x ./php-cgi-i386-linux
  exec ./php-cgi-i386-linux

  Please see the README located in the directory WEB-INF/cgi/ for
  details.

  The <architecture> and <os> values are calculated as follows:

    System.getProperty("os.arch").toLowerCase();
    System.getProperty("os.name").toLowerCase();

  Please see the output of test.php for details.


  It is also possible to adjust the php_exec setting (see
  WEB-INF/web.xml), for example:

      <param-name>php_exec</param-name>
      <param-value>/usr/local/bin/php-cgi</param-value>

  or

      <param-name>php_exec</param-name>
      <param-value>c:/PHP/php-cgi.exe</param-value>

  In case your application server denies calling the CGI binary,
  either start apache or IIS or start a fast CGI server on port 9667
  as a separate process, for example from a service script. 

------------------------------------
  Log level
  ---------

  You can set the java.log_level to 7 values:

   0: Log nothing, not even fatal errors.

   1: Log fatal system errors such as "out of memory error".

   2: Log java exceptions.

   3: Log verbose, e.g.: "JavaBridge version x.y.z started"

   4: Log debug messages, including the c/s communication protocol.

   5: Log method invocations, including method selection.

   6: Reserved for internal use. Log messages which may be useful
      to debug certain parts of the bridge.

  The default log level is 3.  If java.log_level is missing, the
  back end uses the "default" log level supplied when the back end was
  started (the second argument after java -jar JavaBridge.jar ...).

   Example which starts tomcat with a full debug log:

   JAVA_HOME=/usr/java/default \
    JAVA_OPTS="-Dphp.java.bridge.default_log_level=6" \
    /opt/tomcat/bin/catalina.sh run

------------------------------------
  Security Enhanced Linux
  -----------------------

  SELinux is an implementation of a flexible and fine-grained
  mandatory access control architecture implemented in the Linux kernel.

  A system component running on a SELinux kernel must declare
  exactly a) which resources of the operating system it needs in order
  to function properly and b) what it provides to other components.

  The VM Bridge distribution contains two policy files,
  "php-java-bridge.te" and "php-java-bridge.fc". The
  "php-java-bridge.te" declares the javabridge_t domain and the
  resources it requires.  httpd and user domains are granted connect, 
  read and write to the VM Bridge server socket, which is
  "@var/run/.php-java-bridge_socket" in the Linux abstract name-space,
  and file create/read/write in the tmp_t.  Everything else (connections
  to other servers, file access, ...) is currently denied.

  The "php-java-bridge.fc" contains the file contexts for the PHP/Java
  Bridge and the log.

  Installation instructions for RHEL 5, Fedora Core 5 or above:
  -------------------------------------------------------------

  1. Create the binary policy with the command:

        cd security/module; make

  2. Inject the rules into the kernel, either the php-java-bridge-tomcat.pp 
     or the php-java-bridge.pp. For example:

        semodule -i php-java-bridge.pp 

  3. The rules apply to the javabridge_t domain. Another rule
     specifies that when an executable is called from the httpd_t domain
     and the executable is tagged as javabridge_exec_t, a domain transition
     to javabridge_t occurs. It is therefore important that RunJavaBridge
     is tagged with javabridge_exec_t and that it is called from the
     httpd_t domain. Furthermore the java executable must be a binary:

        chcon -t javabridge_exec_t /usr/lib/php/modules/RunJavaBridge
        chcon -t bin_t /usr/lib/php/modules/java

  4. The policy module can be removed with the command:
  
        semodule -r javabridge
  
  If the default policy is too restrictive and e.g. you want to use
  the VM Bridge to connect to your J2EE server, you can
  temporarily set the policy to "permissive", for example with the
  command "setenforce Permissive". Connect to the server, then extract
  the permissions from the audit log, for example with the command
  "audit2allow -l -i /var/log/audit/audit.log", then append them at the
  end of the "php-java-bridge.te" file and load the updated policy into
  the kernel. Don't forget to switch back, for example with "setenforce
  Enforcing".

  Please note that SEL security is orthogonal to the standard Unix 
  security. For example you could also put the java process into 
  a "jail"; set up a user account with restricted rights, change the 
  owner of RunJavaBridge and set the SUID bit:

        chown apache:apache /usr/lib/php/modules/RunJavaBridge
        chmod 6111 /usr/lib/php/modules/RunJavaBridge

  The java process would run with the limited rights of apache *and* be 
  protected by the SEL policy.

------------------------------------
  Security Issues
  ---------------

  If the JEE or servlet back end is used, the bridge opens a local TCP
  port on 9167 (MonoBridge.exe) or 9267 (JavaBridge.jar), 9567
  (JavaBridge.war) or 9667 (FastCGI). Please make sure that the ports
  in the range [9167, ..., 9667] cannot be accessed from the internet.

  If your application server denies socket listen/accept, add the
  following line to your AS policy file (for example
  ...\domains\domain1\config\server.policy or tomcat/conf/catalina.policy):

  grant {permission java.net.SocketPermission  "localhost:9267-","listen,accept";};


------------------------------------
  Loading user classes and libraries
  ----------------------------------

  Java libraries should be installed in one of the following
  directories: java.ext.dirs or, for the J2EE/servlet back end,
  WEB-INF/lib. Libraries in these directories are automatically loaded
  by a static loader whenever the JVM starts.

  Java libraries can be created with:

    javac -Djava.ext.dirs=. my/package/*.java
    jar cvf myLibrary-0.1.jar my/package/*.class 


------------------------------------
  Sun java platform issues
  ------------------------

  The sun java platform does not support java "modules". This causes
  certain problems when running java programs. When you compile a class
  foo which references a class bar and ship the class foo without
  providing bar, the sun java platform will not complain unless the user
  accidentally calls a method which references the non-existing class. If
  this happens, a "NoClassDefFound" error is thrown. This error may
  not(!) indicate which class is missing and it certainly does not
  indicate which external library is missing. The tests.php4 folder
  contains two tests, noClassDefFound.php and noClassDefFound2.php, which
  demonstrate this.

  To avoid this problem please document *exactly* (including the
  version number) which external libraries (.jar files) your software
  needs. If you have written software where certain methods require an
  optional library, please document this in the method header.

  If you receive this error when using a Java library, this may mean the
  following:

    * a jar file is stored at more than one location or the same
      location is accessed by more than one class loader. 
      
    * an old or different JDK than expected by the library is used,
      for example GNU Java instead of SUN or IBM Java.

    * the library is simply broken or it expects certain parameters in
      its environment (applet parameter or system property or property file).

    * the library may only work within a J2EE environment from a
      certain vendor, for example the WebSphere Application server or
      the Sun Java Application server.

------------------------------------
  UTF-8
  -----
  
  Since PHP does not support unicode, the VM Bridge uses UTF-8
  to convert characters into the host representation. All strings are
  created with new String(..., "UTF-8") and all internal String->byte[]
  conversions use getBytes("UTF-8").
  
  If you have old PHP files which are not UTF-8 encoded, you can
  change the default encoding with java_set_file_encoding().  For
  example:

    java_set_file_encoding("ISO-8859-1");

  For a list of available encodings please see the documentation of
  the JVM's file.encoding system property.

  The java_set_file_encoding() primitive only affects java.lang.String
  creation and internal conversions, it does not alter the JVM's
  file.encoding system property nor does it change the behaviour of
  methods which use the file.encoding property, getBytes() for
  example.  If you use:
  
    $str=new Java ("java.lang.String", "Cze????! -- ???????? -- Gr");
    echo $str->getBytes();

  the output conversion depends on the file.encoding system property
  which in turn depends on the process' LANG environment variable. You
  can check the file.encoding with the test.php script, see above.

  To be portable please do not use conversions which depend on the
  JVM's file.encoding. They are easy to avoid, the above example
  should be written as:

    $str=new Java ("java.lang.String", "Cze????! -- ???????? -- Gr");
    echo (string)$str;  // in PHP5 or higher
    echo $str->toString(); // in PHP4

------------------------------------
  Creating thread dumps in Java 6
  -------------------------------

  * Become "super user" or "admin user" and start the program jconsole
    located in the JDK 1.6 bin directory, for example with the following
    command:

      su -c "/opt/jdk1.6/bin/jconsole"

    On Windows make sure you have admin privileges before starting
    jconsole.
     
  * In the "Create new connection" dialog select "local process" and
    click on the "JavaBridge" entry. -- If the JavaBridge doesn't appear
    there, check if the JavaBridge is running within a Java 1.6 VM and if
    the jconsole has been started with sufficient permissions.

  * Click "connect".

  * Open the "Threads" tab and click on the thread you're interested in.


------------------------------------
  Performance tuning
  ------------------

  The VM Bridge protocol is very sensitive to network
  latency. If the Java server and PHP client do not run on the same
  computer, the objective is to minimize the number of network
  round-trips; java_values() can be used to obtain a Java array, Map
  or Collection in one round-trip.
  
  The call java_values($obj) evaluates $obj on the server-side and, if
  it is a Java array, Map or Collection, retrieves its values in one
  call.

  Example:

    $iter = $hits->iterator();                       // 1 round trip
    $resultList = new Java("java.util.LinkedList");  // 1 round trip
    $n = $hits->length()                             // 1 round trip

    while($n--) {
      $next = $iter->next();
      $resultList->add($next->get("name"));
    }
    $ar = java_values($resultList);                  // 1 round trip

  Assuming that a ping to the back-end reveals an average round-trip
  time of 6ms, the above code costs 6*6ms = 36ms (ignoring CPU and
  network bandwidth contraints).

  The more intuitive approach:

    $n = $hits->length();                            // $n = 30000
    while($iter->hasNext()) {                        // $n * 6ms
      $next = $iter->next();                         // $n * 6ms
      $a[$i++]=$next->get("name");                   // $n * 6ms
    }
 
  costs 30000*18ms + 6 ms = 9 min. It is 15000 times slower, 
  assuming that the client CPU can generate and send the XML document
  within 6ms and that the server CPU can generate/send the values of the
  resultList within 6ms, which usually isn't the case.

------------------------------------
  Mailing List
  ------------

  Please report bugs/problems to the mailing list:

    php-java-bridge-users@lists.sourceforge.net

