Read Me

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 -classpath JavaBridge.war TestInstallation to extract the
  JavaBridge.jar from the web archive. The command extracts
  ext/JavaBridge.jar and java/Java.inc from the web archive.

  Double-click on JavaBridge.jar and select SERVLET_LOCAL:8080 to
  start a local HTTP server. Type java -jar ext/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, php-script.jar and script-api.jar to
  the java.ext.dirs. Example for JDK1.6 on Linux:

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

  Type

    /usr/java/default/bin/jrunscript -l php-interactive

  to start an interactive PHP session.

---------------------------------------------
  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 -classpath JavaBridge.jar -l php-interactive 

  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. 

  If the directory "/dev/shm" exists, or if the Java.inc option 
  JAVA_PIPE_DIR points to an existing directory, the bridge uses 
  named pipes. On Windows, where standard named pipes are not available, 
  the bridge uses TCP sockets. If your application server denies socket 
  accept/resolve, please either run the AS on a Unix operating system or 
  add the following lines to your AS policy file (for 
  example ...\domains\domain1\config\server.policy):

    grant {
      permission java.net.SocketPermission  "*", "accept,resolve";
    };

------------------------------------
  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 2.  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 ...).

  The log4j viewer "Chainsaw" can be used to automatically capture the
  log from the bridge, regardless in which environment it is
  running. log4j.jar must be in the Java VM's java.ext.dirs (usually
  jre/lib/ext), Chainsaw must be running and the back end must have
  been started without a log file argument or with the .ini option
  java.log_file="@127.0.0.1:4445". Chainsaw can be started with e.g.:

   /opt/jdk1.5/bin/java -cp /opt/jdk1.5/jre/lib/ext/log4j.jar \
                                               org.apache.log4j.chainsaw.Main

   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 4 and Fedora Core 4:
  -------------------------------------------------------

   1. Install selinux-policy-targeted-sources-*.rpm, for example with
      the command:

        rpm -i selinux-policy-targeted-sources-1.17.30-2.19.noarch.rpm

   2. Update the policy files with the VM Bridge policy:

        su -c "sh security/update_policy.sh /etc/selinux/targeted/src/policy"

  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
  ---------------

  The bridge uses abstract local sockets, named pipes (located in
  /dev/shm/) or local TCP sockets as communication channels.

  It is recommended to use the local back end on a Unix machine which
  supports abstract local ("unix domain") sockets or "/dev/shm".
  On these systems the communication channel is not visible and cannot be
  attacked. If you are running a Security Enhanced Linux kernel, which
  is standard since RHEL4 or FC3, the back end is also protected by the
  SEL policy. The servlet back end uses a HTTP tunnel to execute one
  statement and then switches to named pipes for the rest of the
  communication.

  On other systems, such as Windows and Mac OSX, 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 the directory "/dev/shm" exists, or if the Java.inc option 
  JAVA_PIPE_DIR points to an existing directory, the bridge uses 
  named pipes. On Windows, where standard named pipes are not available, 
  the bridge uses TCP sockets. If your application server denies socket 
  accept/resolve, please either run the AS on a Unix operating system or 
  add the following lines to your AS policy file (for 
  example ...\domains\domain1\config\server.policy):

    grant {
      permission java.net.SocketPermission  "*", "accept,resolve";
    };

------------------------------------
  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.

  The location of a "php.java.bridge.base" depends on the Java system
  property -Dphp.java.bridge.base. It defaults to user.home. When
  the standalone component is invoked as a sub component of Apache or
  IIS, php.java.bridge.base is initialized with the PHP .ini
  extension_dir setting, which is usually /usr/lib/php/modules or
  c:\php.
  
  Java libraries can also be loaded or re-loaded on demand by a
  dynamic loader. They should have the following file name:
  <name>-<version>.jar and be stored in a sub directory of the
  php.java.bridge.base/lib/ directory or in a sub directory of the
  /usr/share/java directory. For example:

    /usr/share/java/batStore/batStore-1.0.jar.

  Java libraries can be created from .class files with the following
  command:

    jar cvf myLibrary-0.1.jar my/package/*.class 

  The dynamic loader can link java libraries into PHP files at
  run-time if the PHP files contain the command:

    java_require("<library1>;<libraryN>");

  Note that <library> can also be a directory containing .jar files.

  For example:

    <?php
      // process order
      java_require("j2ee.jar;myProject/myLibrary-0.1.jar");

      $proc = new Java("my.package.InputProcessor", ...);
      $proc->doSomething($_POST);
      ...
    ?>

  Minor upgrades of dynamic-loaded libraries can be installed at
  run-time. When the dynamic loader detects that the time stamp or the
  version number of the .jar file has changed, it automatically loads
  the new version.

  Disadvantages of the dynamic loader:

  * An attempt to load an impure java library immediately throws an
    UnsatisfiedLinkError.

  * Class loading via the dynamic loader is slower, because it
    cannot use the global VM class cache.

  * Libraries must be explicitly required by using the php
    java_require() procedure.

  Disadvantages of the static loader:

  * All java libraries are loaded when the Java- or Mono VM
    starts. For the PHP CLI component, which usually starts a new VM for
    each PHP invocation (unless java.hosts or java.socketname is set),
    this may cause a noticeable delay (a few 100 ms).

  * The static loader can only load libraries which are stored in the
    /usr/share/java/ext directory. Hot deployment is not possible
    because all classes are loaded when the VM starts.

  * The standard directories /usr/share/java/ext or
    /usr/java/packages/lib/ext/ don't exist on Windows so that users must
    check the windows registry to find the "standard" java extension dir.

  It is recommended to store Java libraries which are API stable or
  use the java native interface into java.ext.dirs. All other
  libraries can go into a project specific directory within
  php.java.bridge.base/lib/ or /usr/share/java/ and be loaded
  on-demand.

  Note that classes loaded from two different class loader instances
  cannot access each other. This means that, e.g., neither

    java_require("foo.jar");
    ...
    Class.forName("foo");  // wrong!

  nor 

    java_require("foo.jar"); java_require("bar.jar");
    $foo = new Java("foo");
    $foo->callWithBar(); // error!

  nor
 
    java_require("foo.jar;system-library.jar");
    $foo = new Java("foo");
    $foo->callWithSystemLibrary(); // fail if system-library has been loaded

  nor

    java_require("myJdbcDriver.jar");
    java("java.sql.DriverManager")->doSomethingWith(myJdbcDriver);

  work as expected.

  In the first example the class was loaded from the bootstrap class
  loader, which cannot access foo.jar's class loader. In the second
  example foo and bar depend on each other, so that the call fails
  because bar cannot be accessed from foo.jar's class loader, and the
  remaining examples try to inject new dependencies for already loaded
  classes, the "system library" and the "DriverManager".

------------------------------------
  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.

    * java_require("foo.jar"); java_require("bar.jar"); was used instead of
      java_require("foo.jar;bar.jar"); to load two interconnected libraries.

    * 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.

---------------------------------------------
  FreeBSD issues
  --------------
 
  FreeBSD is not directly supported. Please use the FreeBSD
  PHP/Java Bridge port instead. 

  In order to use unix domain sockets on FreeBSD, compile java.so,
  libnatcJavaBridge.so and start JavaBridge.jar with the argument
  LOCAL:/path/to/your/socket/file.

------------------------------------
  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 and java_begin_document(),
  java_end_document() can be used to execute PHP code on the server.
  
  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.

  The java_begin_document()/java_end_document() pair encapsulates PHP
  code, sends an image of it (as a streamed XML document) to the server
  and executes it there. This works for all PHP statements.

  Example:

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

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