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<H1>VM Bridge FAQ</H1>
This file contains answers to frequently asked questions. Please see <a href="http://php-java-bridge.sourceforge.net/pjb">http://php-java-bridge.sourceforge.net</a> for more information.
<H2>General questions</H2>
<H4>Which alternatives exist?</H4>
<p>There are at least 4 other php to java bridges which offer a similar API. One was distributed with PHP 4.0.0 and has been discontinued. Two other bridges are proprietary software, built into a vendor-specific framework from Zend or a J2EE application server from Caucho.
Furthermore IBM's Zero framework for Eclipse contains a PHP interpreter written in pure Java and a php to java bridge which can call Java methods in-process.</p>
<p>The only free alternatives are SOAP and XML-RPC, which are up to 50 times slower than the XML protocol implementation used by this VM Bridge.</p>
<H4>How do I enable the Java extension in my php.ini file?</H4>
<p>A Java extension does not exist, so you can't enable it.</p>
<p>The VM Bridge is a network protocol, it requires a running Java VM, for example the servlet container Apache/Tomcat. Or, if you want to call PHP libraries from Java, a running PHP container, e.g. Apache or IIS.</p>
<H4>What do I need to communicate with Java?</H4>
<p>Only the PHP code from <code>Java.inc</code> and a running Java application, for example <code>JavaBridge.jar</code>, or a running Java servlet, for example <code>JavaBridge.war</code>.</p>
<H4>What do I need to communicate with PHP?</H4>
<p>Only the PHP code from <code>JavaProxy.php</code> within your PHP web application and the Java libraries <code>JavaBridge.jar</code>, <code>php-script.jar</code> and <code>php-servlet.jar</code>.</p>
<H4>Which versions are supported?</H4>
<ul>
<li>PHP >= 5.1.2. PHP >= 5.3 recommended.</li>
<li>Java >= 1.4. Java >= 6 recommended.</li>
<li>J2EE >= 1.3. For J2EE 1.3 remove the <code>RequestListener</code> declaration from the WEB-INF/web.xml.</li>
<li>Mono >= 1.2.4 or .NET >= 2.</li>
</ul>
<H4>Do I need a Java Application Server or Servlet Engine?</H4>
<p>Java needs an execution environment.
</p>
<p>
You can also add PHP support to your standalone Java application by
adding the following line to its main class:
<blockquote>
<code>
static final php.java.bridge.JavaBridgeRunner runner = php.java.bridge.JavaBridgeRunner.getInstance(8087);
</code>
</blockquote>
The above code opens the port 8087, so that local PHP scripts can call
methods/procedures from your Java application, as long as your Java
application is running.
</p>
<p>The third option is the standard JSR 223 script interface, which
allows one to execute PHP code/scripts from Java applications.
</p>
<H4>Ho do I enable logging?</H4>
<p>
Copy <code>log4j.jar</code> into <code>java.ext.dirs</code>. Example for JDK 6:
<blockquote>
<code>
cp log4j.jar /usr/java/packages/lib/ext
</code>
</blockquote>
</p>
<p>
Start the log4j viewer. Example for JDK 6:
<blockquote>
<code>
/opt/jdk1.6/bin/java org.apache.log4j.chainsaw.Main
</code>
</blockquote>
</p>
<p>
Start the application server with the options <code>-Dphp.java.bridge.default_log_level=LEVEL</code>. Example for tomcat:
<blockquote>
<code>
JAVA_HOME=/opt/jdk1.6 JAVA_OPTS="-Dphp.java.bridge.default_log_level=5" bin/catalina.sh run
</code>
</blockquote>
Example for the standalone container:
<blockquote>
<code>
java -Dphp.java.bridge.default_log_level=5 -jar JavaBridge.jar SERVLET:8080
</code>
</blockquote>
</p>
<H4>How can I set Java options?</H4>
<p>
With the -D flag. See <code>java -jar JavaBridge.jar --help for details. If tomcat is being used, one can set these options as follows:
<blockquote>
<code>
JAVA_OPTS="-D... -D..." /opt/tomcat/bin/catalina.sh run
</code>
</blockquote>
</p>
<H4>How can I increase the memory available to Java?</H4>
<p>
Use a VM >= 1.6 and add more RAM to your computer. Older Java versions
support the <code>Xmx</code> flag:
<blockquote>
<code>
java -Xmx512M ... -jar JavaBridge.jar SERVLET:8080
</code>
</blockquote>
</p>
<H4>How can I set PHP options?</H4>
<p>
With a <code>define</code> before a PHP library is loaded. Global options can also be set in the <code>php.ini</code> file. Use phpinfo() to see the location of this file.
</p>
<H4>How can I configure the bridge?</H4>
<p>Useful options which can be set before the Java.inc/Mono.inc is loaded are:
<blockquote>
<code>
define ("JAVA_DEBUG", false);<br>
define ("JAVA_PREFER_VALUES", false);<br>
define ("JAVA_HOSTS", "127.0.0.1:8080");<br>
define ("JAVA_PIPE_DIR", null);<br>
require_once ("java/Java.inc");<br>
...
</code>
</blockquote>
Please see the Options.inc for details.
</p>
<p>Server-side options can be set in the
php.java.bridge.global.properties file, see the JavaBridge.jar zip
file (contained in the JavaBridge.war zip file) for details.
</p>
<H4>Can I use Java libraries without installing java?</H4> <p>Yes. On a GNU operating system (e.g.: GNU/Linux, GNU/windows (aka "cygwin"), ...) you can use the GCC compiler to compile Java classes to native code.
Simply compile the C based extension and omit the
<code>--with-java=</code> configure option. The bridge will use the
<code>libgcj</code> library, which is part of the GNU gcc compiler. This library also uses much less system
resources (memory, files) than a "real" Java VM.</p>
<H4>I can't load the resource or file from the current working directory!?!</H4>
<p>
The "current working directory" is not useful, as the Java back end may be running
on a different server or from a different working directory. Use a full path or a URL resource instead.
</p>
<H4>I get a blank page or some other error!?!</H4>
<p>
Check the PHP error log, see your <code>php.ini</code> file for details. If the command:
<blockquote>
<code>
echo '<?php require_once("http://localhost:8080/JavaBridge/java/Java.inc"); echo java("java.lang.System")->getProperties();?>' | php -n -d allow_url_include=On
</code>
</blockquote>
works in the shell but not within apache, then there's something wrong with your <code>php.ini</code> file.
</p>
<H4>Can I use Python instead of PHP?</H4>
<p>Yes, see the examples folder from the source download.</p>
<H4>Can I access Mono or .NET libraries using the pure PHP implementation?</H4>
<p>Yes, there's a PHP library "Mono.inc" generated from "Java.inc" and
a "MonoBridge.exe" generated from "JavaBridge.jar". If you want to
compile from source, use the configure
option <code>--with-mono</code>.</p>
<H4>What does a "protocol error ..." mean?</H4>
<p>That your Java or .NET VM has problems, for example an OutOfMemoryError. Check the back end (Tomcat/J2EE/.NET/...) log for details.</p>
<H4>Does it support PHP 4?</H4>
<p>No. Use VM Bridge version 4.3.2 or below instead.</p>
<H2>Class loading questions</H2>
<a name="java-require"></a>
<H4>How do I load Java libraries?</H4>
<p> During development simple libraries can be loaded dynamically with <code>java_require("myApplication.jar;myLib1.jar;myDriver1.jar;...");</code>. See the README for details.</p>
<H4>Where can I store my java libraries for the VM Bridge?</H4>
<p>Either within your web application <code>WEB-INF/lib</code> directory or in <code>php.java.bridge.base</code>/lib.</p>
<p> When the system property <code>php.java.bridge.base</code> is not set, libraries are loaded from <code>$HOME/lib</code> where <code>$HOME</code> denotes the home directory of the person or component which has started the java VM.</p>
<p> If libraries should be available globally, store them in <code>java.ext.dirs</code>, for example in <code>/usr/share/java/ext</code>.</p>
<p> If a library is not yet API-stable, store it into a sub directory of the <code>lib</code> directory and use the <code>java_require()</code> procedure. For example <code>java_require("myLibs0.2/foo.jar")</code> loads <code>foo.jar</code> from <code>php.java.bridge.base/lib/myLibs0.2</code>.</p>
<H4>Why can't Apache load my /foo/bar/baz.jar file?</H4>
<p>It probably doesn't have the permission to access it. Check if
baz.jar is a valid Java archive and if its main class is public. Try
to disable Security Enhanced Linux and store the jar file into a
folder accessible by the apache user and then extract the required
Security Enhanced Linux permissions from the audit log.</p>
<H4>Why do I get a ClassNotFoundException?</H4>
<p>You probably haven't required the relevant Java library. Or the
class doesn't exist or it is not public or it throws a java.lang.Error
during initialization. Check which library exports the feature and add
the library to the <code>java_require()</code> statement.</code></p>
<a name="java-dll-hell"></a>
<H4>Why do I get a NoClassDefFoundError?</H4>
<p>Because Java doesn't have a module system.</p>
<p>All libraries and their dependencies must be loaded by one, and only one class loader.</p>
<p>Please read the previous sentence until you understand what it means; for example a simple file system copy(!) operation may be the cause for a NoClassDefFoundError.</p>
<p><em>Please do not report NoClassDefFoundErrors to the mailing list or via the bug tracker. This is not a bug and we cannot help you any further!</em></p>
<H4>I cannot require my JDBC driver!?!</H4>
<p> Please re-read the <a href="#java-require">class loading section</a>. The following code loads all interconnected libraries using a single java_require() call:
<blockquote>
<code>
java_require("myApplication.jar;myJdbcDriver.jar");<br>
...<br>
$myApplication->callWithMyJdbcDriver();<br>
</code>
</blockquote>
</p>
<p>
The following incorrect code fails because the application (the "JavaBridge.jar" in this case) cannot be
accessed by the jdbc driver. This constraint is checked by the DriverManager:
<blockquote>
<code>
java_require("myJdbcDriver.jar"); // WRONG!<br>
new java("my.jdbc.Driver");<br>
java("java.sql.DriverManager")->getDriver("myJdbcURL"); // FAILS!<br>
</code>
</blockquote>
If you really need to access the driver directly from PHP code, either use the driver API directly or load "JavaBridge.jar" and "myJdbcDriver.jar" from the same class loader so that the DriverManager can link them together. Use the extra library directory (usually <code>~/lib/</code>) or the global repository (usually <code>/usr/java/packages/lib/ext</code>).
</p>
<H4>How do I load impure Java libraries?</H4>
<p>You can't. Java libraries must be pure Java.</p>
<p> Please read the
documentation of your J2EE server, Servlet engine or Java VM to see if and
how the environment can handle impure Java libraries. A common approach is to store the Java part in <code>java.ext.dirs</code> and the native part in <code>java.library.path</code>.</p>
<H2>J2EE/Servlet questions</H2>
<a name="load-balancing">
<H4>How do I set up a load balancer for the VM Bridge cluster?</H4>
<p>
Set up the VM Bridge cluster as <a href="#cluster">described below</a>. The example uses two nodes named "carlos" and "diego". The HTTP server front end runs on the web server "timon".
</p>
<p>Install Apache 2.2.0 or higher.</p>
<p>Enable <code>proxy_module</code> and <code>proxy_balancer_module</code>. The following example is for Linux (lines marked with "+" should be added to the <code>conf/httpd.conf</code> file):
<blockquote>
<code>
LoadModule rewrite_module modules/mod_rewrite.so<br>
+ LoadModule proxy_module modules/mod_proxy.so<br>
+ LoadModule proxy_balancer_module modules/mod_proxy_balancer.so<br>
LoadModule cache_module modules/mod_cache.so<br>
</code>
</blockquote>
</p>
<p>
Add the following code to the bottom of your <code>conf/httpd.conf</code> file:
<blockquote>
<code>
ProxyPass /JavaBridge balancer://mycluster maxattempts=2<br>
<Proxy balancer://mycluster><br>
BalancerMember http://diego:8080/JavaBridge<br>
BalancerMember http://carlos:8080/JavaBridge<br>
</Proxy><br>
<Location /balancer-manager><br>
SetHandler balancer-manager<br>
Deny from all<br>
Allow from 127.0.0.1<br>
</Location><br>
</code>
</blockquote>
</p>
<p>Start the cluster nodes on "carlos" and "diego".</p>
<p>Browse to <code>http://timon/JavaBridge/</code> (note the trailing slash) and click on the test.php. Click on refresh. Check if both nodes respond.</p>
<p>Browse to <code>http://timon/JavaBridge/sessionSharing.php</code> and click on refresh. Check the cookie value.</p>
<p>Browse to <code>http://timon/balancer-manager/</code>.
<p>Please see the <code>mod_rewrite</code> documentation for more information how to rewrite incoming URLs.</p>
</a>
<a name="cluster">
<H4>Ho do I set up a tomcat cluster?</H4>
<p>
Download tomcat 5 or higher, a Java JRE 5 or higher and the VM Bridge 4.1.6 or higher.
</p>
<p>
The following example uses two nodes running on two machines called
"carlos" and "diego".
</p>
<p>
On all nodes: Extract the tomcat distribution into a directory.
</p>
<p>On <strong>"diego"</strong> add the following to <code>conf/server.xml</code>:
<blockquote>
<code>
<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"<br>
channelSendOptions="8"><br>
<Manager className="org.apache.catalina.ha.session.DeltaManager"<br>
expireSessionsOnShutdown="false"<br>
notifyListenersOnReplication="true"/><br>
<Channel className="org.apache.catalina.tribes.group.GroupChannel"><br>
<Receiver className="org.apache.catalina.tribes.transport.nio.NioReceiver"<br>
address="<strong>diego</strong>"<br>
port="4000"<br>
autoBind="100"<br>
selectorTimeout="5000"<br>
maxThreads="6"/><br>
</Channel><br>
</Cluster><br>
</code>
</blockquote>
</p>
<p>On <strong>"carlos"</strong> add the following to <code>conf/server.xml</code>:
<blockquote>
<code>
<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"<br>
channelSendOptions="8"><br>
<Manager className="org.apache.catalina.ha.session.DeltaManager"<br>
expireSessionsOnShutdown="false"<br>
notifyListenersOnReplication="true"/><br>
<Channel className="org.apache.catalina.tribes.group.GroupChannel"><br>
<Receiver className="org.apache.catalina.tribes.transport.nio.NioReceiver"<br>
address="<strong>carlos</strong>"<br>
port="4000"<br>
autoBind="100"<br>
selectorTimeout="5000"<br>
maxThreads="6"/><br>
</Channel><br>
</Cluster><br>
</code>
</blockquote>
</p>
<p>Copy the "JavaBridge.war" into the "webapps" directory on "diego" and "carlos" and start both nodes. For example with the command:
<blockquote>
<code>
JAVA_OPTS="-Dphp.java.bridge.promiscuous=true" JAVA_HOME=/usr/java/default bin/catalina.sh run
</code>
</blockquote>
</p>
<p>
Please see your HTTP server documentation and <a href="#load-balancing">the description above</a> how to set it up as a load balancer.
</p>
</a>
<a name="global-servlet">
<H4>I want to use PHP for all tomcat applications. Apache and IIS are not available, but performance is important. How do I install it?</H4>
</a>
<ol>
<li>
Download and install the J2EE binary: copy <code>JavaBridge.war</code> into the tomcat <code>webapps</code> folder.<br>
<li>
Start tomcat, for example with:
<blockquote>
<code>
JAVA_HOME=/usr/java/default /opt/tomcat/bin/catalina.sh run
</code>
</blockquote>
<li>
Move(!) all libraries from the created webapps/JavaBridge/WEB-INF/lib folder to the tomcat lib folder and remove(!) webapps/JavaBridge/WEB-INF/web.xml.
The only reason to keep the JavaBridge directory is the WEB-INF/cgi/launcher* FastCGI launcher and the java/Java.inc files. Example:
<blockquote>
<code>
mv /opt/tomcat/webapps/JavaBridge/WEB-INF/lib/* /opt/tomcat/lib<br>
rm /opt/tomcat/webapps/JavaBridge/WEB-INF/web.xml
</code>
</blockquote>
<li>
Stop tomcat and remove webapps/JavaBridge.war. <em>Make sure that webapps/JavaBridge still exists, but without any libraries and web.xml!</em>
<blockquote></blockquote>
<li>
Add the lines marked with a <code>+</code> to the tomcat <code>conf/web.xml</code>:
<blockquote>
<code>
<br>
<!-- ================== Built In Servlet Definitions ==================== --><br>
<br>
+ <!-- PHP Servlet --><br>
+ <listener> <listener-class>php.java.servlet.ContextLoaderListener</listener-class> </listener><br>
+ <listener> <listener-class>php.java.servlet.RequestListener</listener-class> </listener><br>
+ <servlet><br>
+ <servlet-name>GlobalPhpJavaServlet</servlet-name><br>
+ <servlet-class>php.java.servlet.PhpJavaServlet</servlet-class><br>
+ </servlet><br>
+ <!-- PHP CGI Servlet --><br>
+ <servlet><br>
+ <servlet-name>GlobalPhpCGIServlet</servlet-name><br>
+ <servlet-class>php.java.servlet.PhpCGIServlet</servlet-class><br>
+ <init-param> <param-name>shared_fast_cgi_pool</param-name><param-value>On</param-value></init-param><br>
+ <init-param> <param-name>prefer_system_php_exec</param-name><param-value>On</param-value></init-param><br>
+ </servlet><br>
<br>
<!-- The default servlet for all web applications, that serves static --><br>
<!-- resources. It processes all requests that are not mapped to other --><br>
[...]<br>
<!-- ================ Built In Servlet Mappings ========================= --><br>
<br>
+ <!-- PHP Servlet Mapping --><br>
+ <servlet-mapping><br>
+ <servlet-name>GlobalPhpJavaServlet</servlet-name><br>
+ <url-pattern>*.phpjavabridge</url-pattern><br>
+ </servlet-mapping><br>
+ <!-- CGI Servlet Mapping --><br>
+ <servlet-mapping><br>
+ <servlet-name>GlobalPhpCGIServlet</servlet-name><br>
+ <url-pattern>*.php</url-pattern><br>
+ </servlet-mapping><br>
<br>
<!-- The servlet mappings for the built in servlets defined above. Note --><br>
<!-- that, by default, the CGI and SSI servlets are *not* mapped. You --><br>
<br>
</web-app><br>
</code>
</blockquote>
</p>
<li>
Start tomcat again.
</ol>
To test the above settings copy test.php to some other web context, for example "examples", adjust its require/include path and browse to
<code>http://yourHost.com:8080/examples/test.php</code>.
</p>
<a name="php-web-app">
<H4>How do I create a standalone PHP web application for distribution and how can users deploy it into tomcat?</H4>
</a>
<p>
Create a directory <code>myApplication</code>, create the directories <code>myApplication/WEB-INF/lib/</code> and <code>myApplication/WEB-INF/cgi/</code>.
Download the J2EE binary and copy the <code>JavaBridge.jar</code> and the <code>php-servlet.jar</code> from the JavaBridge.war to the <code>myApplication/WEB-INF/lib/</code> folder. Copy the contents of the <code>cgi</code> folder to <code>myApplication/WEB-INF/cgi/</code>. Create the file <code>myApplication/WEB-INF/web.xml</code> with the following content:
<blockquote>
<code>
<br>
<web-app><br>
<!-- PHP Servlet --><br>
<servlet><br>
<servlet-name>PhpJavaServlet</servlet-name><br>
<servlet-class>php.java.servlet.PhpJavaServlet</servlet-class><br>
</servlet><br>
<!-- PHP CGI processing servlet, used when Apache/IIS are not available --><br>
<servlet><br>
<servlet-name>PhpCGIServlet</servlet-name><br>
<servlet-class>php.java.servlet.PhpCGIServlet</servlet-class><br>
</servlet><br>
<br>
<!-- PHP Servlet Mapping --><br>
<servlet-mapping><br>
<servlet-name>PhpJavaServlet</servlet-name><br>
<url-pattern>*.phpjavabridge</url-pattern><br>
</servlet-mapping><br>
<!--PHP CGI Servlet Mapping --><br>
<servlet-mapping><br>
<servlet-name>PhpCGIServlet</servlet-name><br>
<url-pattern>*.php</url-pattern><br>
</servlet-mapping><br>
<br>
<!-- Welcome files --><br>
<welcome-file-list><br>
<welcome-file>index.php</welcome-file><br>
</welcome-file-list><br>
</web-app><br>
</code>
</blockquote>
</p>
<p>
To call Java code from PHP, copy the <code>java/Java.inc</code>
to some directory and require it as usual, e.g.: <code>require_once("java/Java.inc");</code>.
</p>
<p>
To call PHP code from Java, copy the <code>java/JavaProxy.php</code>
to some <em>web</em>directory and use the EngineFactory as usual, e.g.: <code>EngineFactory.getInvocablePhpScriptEngine(this, application, request, response);</code> or, if PHP is running somewhere else: <code>EngineFactory.getInvocablePhpScriptEngine(..., 80, "/phpApp/JavaProxy.php");</code>.
</p>
<p>
Copy the files <code>sessionSharing.jsp</code> and <code>sessionSharing.php</code> from the <code>JavaBridge.war</code> to <code>myApplication</code> and create <code>myApplication.war</code>, for example with the commands: <code>cd myApplication; jar cf ../myApplication.war *</code>. </p>
<p>The web archive can now be distributed, copy it to the tomcat <code>webapps</code> directory and re-start tomcat. Visit <code>http://localhost/myApplication/sessionSharing.php</code> and <code>http://localhost/myApplication/sessionSharing.jsp</code>.
</p>
<a name="tomcat-security">
<H4>I want to use Tomcat's security manager, how do I install the bridge?</H4>
</a>
<p>
Install the PHP/Java Bridge for all web application as described <a href="#global-servlet">here</a>.
</p>
<a name="php-jsp-session-sharing">
<H4>I want to use Apache/IIS as a front-end and tomcat as a back end. How do I enable PHP and JSP for all my applications?</H4>
</a>
<p> Set up Apache or IIS so that it forwards requests to the back
end. Please see <a href="#load-balancing">the description above</a>
for details.
</p>
<H4>Does the
bridge run native code within my servlet engine or application
server?</H4> <p>No. The bridge back end is written in pure java, it
doesn't use any native code. Native PHP runs within Apache, IIS, a
FCGI server or via CGI. If the PHP instance crashes, an error page is
returned to the client and the Apache, IIS, CGI container usually starts a new PHP instance for the next
request.</p>
<a name="ssl">
<H4>On Windows some PHP binaries do not support HTTPS/SSL</H4>
</a>
<p>
If you see the message:
<blockquote>
<code>
Warning: fsockopen() [function.fsockopen]: unable to connect to ssl://127.0.0.1:8443
(Unable to find the socket transport "ssl" - did you forget to enable it when you configured PHP?)
</code>
</blockquote>
this means that PHP cannot connect back to the official SSL port.
Please check the
"Registered Stream Socket Transports" from the <code>phpinfo()</code> (see the <code>test.php</code> page), it should display: <code>tcp, udp, ssl, sslv3, sslv2, tls</code>. If not, please recompile PHP with SSL enabled, use the flag <code>--with-openssl</code>.
<p>
A workaround is to use the official non-SSL port or to open a
dedicated local port for the PHP-Java communication. The following
example is for Tomcat:
<p>
<ol>
Disable <code>override_hosts</code> in the web application <code>WEB-INF/web.xml</code>:
<blockquote>
<code>
<context-param><br>
<param-name>override_hosts</param-name><br>
<param-value>Off</param-value><br>
</context-param><br>
</code>
</blockquote>
Either fetch the <code>Java.inc</code> directly from your back end (which also adjusts the <code>JAVA_HOSTS</code>) or change the <code>JAVA_HOSTS</code> option, for example:
<blockquote>
<code>
define("JAVA_HOSTS", "127.0.0.1:9090");
</code>
</blockquote>
</ol>
<p>
Restart the application server or servlet engine. Check the settings by running <code>phpinfo()</code> or by visiting the <code>test.php</code> page.
</p>
<H4>The EJB example works with the Sun J2EE server, but in JBoss I get a ClassCastException, what's wrong?</H4>
<p>It's a JBoss problem, although this problem may also appear in other application servers which do not strictly separate the application/bean domains. The JavaBridge.war already contains the <code>documentClient.jar</code> as a library, so JBoss references the library classes instead of the bean classes. Just remove the <code>documentClient.jar</code> from the <code>JavaBridge.war</code>, re-deploy <code>JavaBridge.war</code> and run the test again.
</p><p>
In JBoss' default setup the code:
<blockquote>
<code>
// access the home interface<br>
$DocumentHome = new JavaClass("DocumentHome");<br>
$PortableRemoteObject = new JavaClass("javax.rmi.PortableRemoteObject");<br>
$home=$PortableRemoteObject->narrow($objref, $DocumentHome);<br>
</code>
</blockquote>
refences the <code>DocumentHome</code> from the library, which is assignment-incompatible to <code>DocumentHome</code> from the enterprise bean (<code>DocumentHome@WebAppClassLoader</code> != <code>DocumentHome@BeanClassLoader</code>), so you get a ClassCastException in <code>narrow</code>.
</p>
<p>
In contrast the Sun J2EE server correctly separates the beans/applications; the <code>$objref</code> is a unique proxy generated by a parent of the <code>WebAppClassLoader</code>, so that <code>narrow</code> can always cast the proxy to <code>DocumentHome@WebAppClassLoader</code>, even if a class with the same name is already available from the <code>WebAppClassLoader</code>.</p>
<H4>How do I install PHP into the Nutch, Spring, JSF, ..., Framework?</H4>
<p>By providing JSR 223 based PHP beans and a description how to manage them, as usual. The code
<blockquote>
<code>
javax.script.ScriptEngine e = <br>
php.java.script.EngineFactory.getInvocablePhpScriptEngine (this, <br>
application, <br>
request, response);<br>
</code>
</blockquote>
can be used to access the JSR 223 ScriptEngine from the framework, provided that a listener has been configured in the WEB-INF/web.xml:
<blockquote>
<code>
<listener>
<listener-class>php.java.servlet.ContextLoaderListener</listener-class>
</listener>
</code>
</blockquote>
</p>
<H2>General runtime questions</H2>
<H4>How do I reference a class w/o creating an instance?</H4>
<p>
With the <code>java</code> function, for example: <code>java("java.lang.System")</code>.
</p>
<p>The function is defined in <code>http://localhost:8080/JavaBridge/java/Java.inc</code> as:
<blockquote>
<code>
function java($clazz) {<br>
static $classMap = array();<br>
if(array_key_exists($clazz, $classMap)) return $classMap[$clazz];<br>
return classMap[$clazz]=new JavaClass($clazz);<br>
}
</code>
</blockquote>
</p>
<H4>Why does java_context()->getHttpServletRequest()->getSession() return null?</H4>
<p>
PHP scripts must explicitly allocate a session with <code><a href="API/VM%20Bridge/_JavaProxy.inc.html#functionjava_session">java_session()</a></code>. For example:
<blockquote>
<code>
java_session(); <br>
// now the (Remote-)HttpServletRequest knows about the session: <br>
echo java_context()->getHttpServletRequest()->getSession(); <br>
</code>
</blockquote>
</p>
<H4>Where is my output?</H4> <p><code>System.out</code> and
<code>System.err</code> are redirected to the server log file(s). When
PHP scripts are invoked from a java framework (Java Server Faces for
example), even the PHP output is redirected. For the standalone back
end the output appears in the
<code>/var/log/php-java-bridge.log</code> or in VMBridge.log, see
.ini option <code>java.log_file</code>. For the j2ee back end the
location of the log file(s) depends on the j2ee server
configuration.</p>
<H4>How do I make my script state (objects or variables) persistent?</H4>
<p>If you must code it yourself: with
e.g. <code>java_session()->put("buf", $stringBuffer)</code></p>
<H4>How many threads does the bridge start?</H4>
<p>Request-handling threads are started
from a thread pool, which limits the number of user requests to 20
(default), see system property
<code>php.java.bridge.threads</code>. All further requests have to
wait until one of the worker threads returns to the pool. </p>
<p>When running in a servlet engine, a <a
href="server/documentation/API/php/java/bridge/http/ContextServer.html">ContextServer</a>
is started which handles the pipe or local socket communication
channel. </p> <p>When java invokes local scripts outside of a HTTP
environment, the bridge starts a <a
href="server/documentation/API/php/java/bridge/http/HttpServer.html">HttpServer</a>,
a <a
href="server/documentation/API/php/java/bridge/http/ContextServer.html">ContextServer</a>
and a <a
href="server/documentation/API/php/java/script/HttpProxy.html">HttpProxy</a>. The
HttpProxy represents the PHP continuation and the HttpServer the
request-handling java continuation associated with the JSR223 script.
</p>
<H4>How do I access enums or inner classes?</H4>
With the <code>classname$inner</code> syntax. For example <br><br>
<code>
public interface php {<br>
public class java {<br>
public enum bridge {JavaBridge, JavaBridgeRunner};<br>
}<br>
}<br>
</code><br>
can be accessed with:<br><br>
<code>
<?php<br>
java_require(getcwd()); // load php.class<br>
$bridge = new java('php$java$bridge');<br>
echo $bridge->JavaBridgeRunner;<br>
?><br>
</code><br>
The above code is not a good programming example but it demonstrates why a different syntax is used to access inner classes.
</p>
<H4>How do I create a primitive array?</H4>
<p>
Primitive types are wrapped by associated java classes.
The following example uses <code>reflect.Array</code> to create a new <code>byte</code> array:<br><br>
<code>
$Byte = new JavaClass("java.lang.Byte");<br>
$byte = $Byte->TYPE;<br>
$Array = new JavaClass("java.lang.reflect.Array");<br>
$byteArray = $Array->newInstance($byte, 255);<br>
$System = new JavaClass("java.lang.System");<br>
$length = $System->in->read($byteArray);<br>
$str = new Java("java.lang.String", $byteArray, 0, $length);<br>
echo "You have typed: $str\n";<br>
</code>
</p>
<H4>How fast is it?</H4> <p>
The following scripts were
executed on one 1.688 GHZ x86 cpu running RedHat Fedora Core 4 Linux and Sun jdk1.6.0_02:
</p>
The PHP 5.2.2 code<br>
<p>
<code>
<?php<br>
$buf=new java("java.lang.StringBuffer");<br>
<br>
$i=0;<br>
while($i<400000) {<br>
$i=$i+1;<br>
$buf->append($i);<br>
}<br>
<br>
print $buf->length() . "\n";<br>
?><br>
</code>
</p>
The ECMAScript ("Mozilla Rhino") code<br>
<p>
<code>
buf = new java.lang.StringBuffer();<br>
for(i=0; i<400000; i++) buf.append(new String(i));<br>
print (buf.toString().length());<br>
</code>
</p>
<p>
<center>
<TABLE
BORDER="1"
><COL><COL><COL><COL><THEAD
><TR
><TH
>Command</TH
><TH
>Script Engine</TH
><TH
>Communication Channel</TH
><TH
>Execution time (real, user, sys)</TH
></TR
></THEAD
<TBODY
><TR
><TD
>time jrunscript -l php t11.php</TD
><TD
>PHP5 + VM Bridge 4.3.3</TD
><TD
>named pipes</TD
><TD
>0m18.703s,<br>
0m16.209s,<br>
0m0.138s
</TD
></TR
>
<TBODY
><TR
><TD
>time jrunscript -l js t11.js</TD
><TD
>ECMA script</TD
><TD
>none (native code)</TD
><TD
>0m15.338s,<br>
0m14.996s,<br>
0m0.116s
</TD
></TR
>
</TABLE
>
</center>
</p>
<p>
</p>
<H4>How does the bridge handle OutOfMemoryErrors?</H4>
<p>
OutOfMemoryErrors may happen because a cached object cannot be released, either because <p>
<ol>
<li> the object is permanently referenced by a request-handling thread or</li>
<li> the object has been entered into the session or application store or
the object is referenced by a thread outside of the scope of the VM Bridge.</li>
</ol>
</p>
</p>
<p>When a <code>java.lang.OutOfMemoryError</code> reaches the request-handling thread, the VM Bridge thread pool removes the thread from its pool and writes a message <code>FATAL: OutOfMemoryError</code> to the VM Bridge log file. The session store is cleaned and all client connections are terminated without confirmation.
</p>
<p>
If the OutOfMemoryError persists, this means that a thread outside of the VM Bridge has caused this error condition.
</p>
<p>
OutOfMemory conditions can be debugged by running the back end with e.g.:<br><br>
<code>
java -agentlib:hprof=heap=sites -jar JavaBridge.jar<br>
</code>
</p>
<H4>How can PHP classes extend Java classes and Java methods?</H4>
<p>
By using <a href="API/VM%20Bridge/_JavaProxy.inc.html#functionjava_closure"><code>java_closure()</code></a> and the visitor pattern for example. The <code>tests.php5</code> folder contains a <code>script_api.php</code> example which shows how to implement <code>java.lang.Runnable</code> to run multiple PHP threads, concurrently accessing a shared resource.
</p>
<H4>How can I execute PHP code on the server?</H4>
<p>
With <code>java_begin_document()/java_end_document()</code>. For example:
<blockquote>
<code>
java_begin_document();<br>
$s = new Java("java.lang.StringBuffer");<br>
for($i=0; $i<10000; $i++) $s->append($i);<br>
java_end_document();<br>
</code>
</blockquote>
The above code sends the PHP code as an XML image to the server and executes it there.
</p>
<H4>How can I convert a Java object into a PHP value?</H4>
<p>
With <code>java_values()</code>. For example:
<blockquote>
<code>
$s = new Java("java.lang.String");<br>
$c = $chr = $s->toCharArray();<br>
print (java_values($s));<br>
print_r(java_values($c));<br>
</code>
</blockquote>
</p>
<H4> How can I convert a PHP object into a Java object?</H4>
<p>
With <code>java_closure()</code>. For example:
<blockquote>
<code>
class Foo {<br>
function toString() {return "php::foo";}<br>
}<br>
$foo = new Foo();<br>
$jObj = java_closure($foo);<br>
$String = new Java("java.lang.String");<br>
echo $String->valueOf($jObj);<br>
</code>
</blockquote>
</p>
<H4>How do I call JSP tags from PHP?</H4>
<p>
Example:
<blockquote>
<code>
require_once("http://localhost:8080/JavaBridge/java/Java.inc");<br>
java_require("myLibs/baz-taglib.jar");<br>
$tag = new Java("foo.bar.BazTag");<br>
<br>
$session = java_session();<br>
$ctx = java_context();<br>
$servlet = $ctx->getAttribute("php.java.servlet.Servlet");<br>
$response = $ctx->getAttribute("php.java.servlet.HttpServletResponse");<br>
$request = $ctx->getAttribute("php.java.servlet.HttpServletRequest");<br>
$factory = java("javax.servlet.jsp.JspFactory")->getDefaultFactory();<br>
$pc = $factory->getPageContext($servlet, $request, $response, null, true, 8192, false);<br>
<br>
$tag->setPageContext($pc);<br>
$value = $tag->doStartTag();<br>
if(($value != Java("javax.servlet.jsp.tagext.Tag")->SKIP_BODY) {<br>
if($value != Java("javax.servlet.jsp.tagext.Tag")->EVAL_BODY_INCLUDE)) {<br>
$tag->setBodyContent($pc->pushBody());<br>
$tag->doInitBody();<br>
}<br>
do {<br>
...<br>
} while($tag->doAfterBody() == Java("javax.servlet.jsp.tagext.BodyTag")->EVAL_BODY_AGAIN)<br>
}<br>
if($value != Java("javax.servlet.jsp.tagext.Tag")->EVAL_BODY_INCLUDE) $pc->popBody();<br>
$tag->doEndTag();<br>
</blockquote>
</code>
</p><p>
The generated content (if any) can be retrieved from the servlet output stream with:
<blockquote>
<code>
java_values($response->getBufferContents();
</code>
</blockquote>
</p>
<p>Please see the <code>php_java_lib/JspTag.php</code> and <code>tests.php5/tag.php</code> for details.</p>
<H4>How does the bridge support Java generics?</H4>
<p>
You can ignore the parameter type.
</p>
<p>
Java doesn't support real generics on byte-code level. The generics in JDK 1.5 and above are implemented as "erasures"; they are syntactic sugar, useful only for the Java compiler. The generated byte-code is the same as in JDK 1.4.
</p>
<H4>What about Java 5 varargs?</H4>
<p>
Pass them as a PHP array. Example:
</p>
<p>
<blockquote>
<code>
<?php require_once("http://localhost:8080/JavaBridge/java/Java.inc");<br>
$here=getcwd(); java_require("$here/varargs.jar");<br>
$t1 = new java('Varargs$Test', 1);<br>
$t2 = new java('Varargs$Test', 2);<br>
echo java("Varargs")->varargs(array($t1, $t2));<br>
?>
</code>
</blockquote>
</p>
<p>
<blockquote>
<code>
public class Varargs {<br>
public static class Test {<br>
public int i;<br>
public Test (int i) {<br>
this.i = i;<br>
}<br>
public String toString() {<br>
return String.valueOf(i);<br>
}<br>
}<br>
public static String varargs(Test ...tests) {<br>
StringBuffer buf = new StringBuffer();<br>
for (Test test : tests) {<br>
buf.append(test);<br>
}<br>
return buf.toString();<br>
}<br>
}<br>
</code>
</blockquote>
</p>
<H4>NULL tests</H4>
<p>
Use <code>java_is_null($value)</code> or <code>is_null (java_values ($value))</code> to test for a (Java-) NULL value.
</p>
<H4>How do I start the bridge back end when there's another Java VM listening on port 8080?</H4>
<p>Simply deploy the VM Bridge web archive into the servlet engine or application server listening on port 8080. Or use a different port.</p>
<H4>What's the difference between SERVLET_LOCAL:8080 and INET_LOCAL:8080?</H4>
<p>The standalone option SERVLET_LOCAL emulates a servlet engine and starts a HTTP server which can select the fastest channel supported on this operating system. On Linux this is a named pipe created in /dev/shm or INET_LOCAL as a fall back.</p>
<p>INET_LOCAL always uses local TCP socket communication.</p>
<H4>Whenever I reboot my computer I have to start the bridge back end again. How can I automate this?</H4>
<p>Download and install a servlet engine or J2EE server as a Windows
or Unix service.</p>
<H4>Do I have to require Java.inc in each of my scripts? Isn't that very slow?</H4>
<p>In order to communicate with Java, a PHP "Java" class definition is needed. Here's a simple PHP "Java" class definition which fits into one line:
<blockquote>
<code>
<?php<br>
// The following is the "Java" class definition, stripped down to fit into one line<br>
// To use this sample start Java with: java -jar JavaBridge.jar INET:9267<br>
// Or enable java.so or php_java.dll, which automatically start the above<br>
// process Then type: php sample.php<br>
//<br>
class P {const Pc="<C v=\"%s\" p=\"I\">", PC="</C>"; const Pi="<I v=\"%d\" m=\"%s\" p=\"I\">", PI="</I>"; const Ps="<S v=\"%s\"/>", Pl="<L v=\"%d\" p=\"%s\"/>", Po="<O v=\"%d\"/>"; private $c; function str($s){fwrite($this->c, sprintf(self::Ps, $s));} function obj($s){fwrite($this->c, sprintf(self::Po, $s->java));} function __construct(){$this->c=fsockopen("127.0.0.1",9267);} function cBeg($s){fwrite($this->c, sprintf(self::Pc, $s));} function cEnd(){fwrite($this->c, self::PC);} function iBeg($o, $m){fwrite($this->c, sprintf(self::Pi, $o, $m));} function iEnd(){fwrite($this->c, self::PI);} function val($s){if(is_object($s))$this->obj($s);else $this->str((string)$s);} function res(){$r=sscanf(fread($this->c, 8192),"%s v=\"%[^\"]\"");return $r[1];}} function gP() {static $p; if(!$p) $p=new P(); return $p;} class Java {var $java, $p; function __construct() {if(!func_num_args()) return; $this->p=gP(); $ar=func_get_args(); $this->p->cBeg(array_shift($ar)); foreach($ar as $arg) $this->p->val($arg); $this->p->cEnd(); $ar = sscanf($this->p->res(), "%d"); $this->java=$ar[0];} function __call($meth, $args) {$this->p->iBeg($this->java, $meth); foreach($args as $arg) $this->p->val($arg); $this->p->iEnd(); $proxy = new Java(); $ar = sscanf($this->p->res(), "%d"); $proxy->java=$ar[0]; $proxy->p=$this->p; return $proxy;} function toString() {$this->p->iBeg("", "castToString"); $this->p->val($this); $this->p->iEnd(); return base64_decode($this->p->res());}}<br>
<br>
// Test<br>
$i1 = new Java("java.math.BigInteger", "1");<br>
$i2 = new Java("java.math.BigInteger", "2");<br>
$i3 = $i1->add($i2);<br>
echo $i3->toString() . "\n";<br>
<br>
?><br>
</code>
</blockquote>
</p>
<p>The above simple "Java" class assumes that some Java VM has been
started on host "127.0.0.1", port "9267". And it cannot handle values
larger than 8192 bytes. Therefore the VM Bridge
library <code>Java.inc</code> should be used. Scripts should contain
the statement
<blockquote>
<code>
require_once("...java/Java.inc");
</code>
</blockquote>
at the beginning of each script. PHP compiles and caches PHP scripts, the <code>Java.inc</code> library is loaded only once.
</p>
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</HTML>
