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reflect.java |
What is PHP4 ext/java? PHP4 ext/java provides a simple and effective means for creating and invoking methods on Java objects from PHP. The JVM is created using JNI, and everything runs in-process. Two examples are provided, jver and jawt, to illustrate usage of this extension. A few things to note: 1) new Java() will create an instance of a class if a suitable constructor is available. If no parameters are passed and the default constructor is useful as it provides access to classes like "java.lang.System" which expose most of their functionallity through static methods. 2) Accessing a member of an instance will first look for bean properties then public fields. In other words, "print $date.time" will first attempt to be resolved as "$date.getTime()", then as "$date.time"; 3) Both static and instance members can be accessed on an object with the same syntax. Furthermore, if the java object is of type "java.lang.Class", then static members of the class (fields and methods) can be accessed. 4) Exceptions raised result in PHP warnings, and null results. The warnings may be eliminated by prefixing the method call with an "@" sign. The following APIs may be used to retrieve and reset the last error: java_last_exception_get() java_last_exception_clear() 5) Overload resolution is in general a hard problem given the differences in types between the two languages. The PHP Java extension employs a simple, but fairly effective, metric for determining which overload is the best match. Additionally, method names in PHP are not case sensitive, potentially increasing the number of overloads to select from. Once a method is selected, the parameters are cooerced if necessary, possibly with a loss of data (example: double precision floating point numbers will be converted to boolean). 6) In the tradition of PHP, arrays and hashtables may pretty much be used interchangably. Note that hashtables in PHP may only be indexed by integers or strings; and that arrays of primitive types in Java can not be sparse. Also note that these constructs are passed by value, so may be expensive in terms of memory and time. Build and execution instructions: Given the number of platforms and providers of JVMs, no single set of instructions will be able to cover all cases. So in place of hard and fast instructions, below are a working examples for a number of free and commercial implementations and platforms. Please adjust the paths to suit your installation. Also, if you happen to get this to work on another JVM/platform combination, please let me know, particularly if a unique build or execution setup was required. Note for Windows users: semi-colons (";") mark the beginning of comments in php.ini files, so if you wish to add to the classpath, make sure that the entire string is in quotes. See the JDK 1.1.8 instructions below for an example. This function has been tested in both CGI and Apache (apxs) modes. As the current design requires shared libraries, this support can not be linked statically into Apache. With ext/java, no Java Virtual Machines are created until the first Java call is made. This not only eliminates unnecessary overhead if the extension is never used, it also provides error messages directly back to the user instead of being burried in a log some place. For people interested in robustness, performance, and more complete integration with Java, consider using the sapi/servlet interface which is built upon the Java extension. Running PHP as a servlet enables PHP to utilize the existing JVM and threads from the servlet engine, and provides direct access to the servlet request and response objects. Finally, the bottom of this readme contains some guidance for how to approach situations in which these instructions don't work on your machine. ======================================================================== === JVM=Kaffe 1.0.4 (as delivered with OS), OS=Redhat Linux 6.1 === ======================================================================== build instructions: ./configure --with-java php.ini: [java] java.library.path=/usr/lib/kaffe:/home/rubys/php4/modules java.class.path=/usr/share/kaffe/Klasses.jar:/home/rubys/php4/modules/php_java.jar extension_dir=/home/rubys/php4/modules extension=java.so ======================================================================== === JVM=Kaffe 1.0.5 (built from source), OS=Redhat Linux 6.1 === ======================================================================== build instructions: ./configure --with-java php.ini: [java] java.library.path=/usr/local/lib/kaffe:/home/rubys/php4/modules java.class.path=/usr/local/share/kaffe/Klasses.jar:/home/rubys/php4/modules/php_java.jar extension_dir=/home/rubys/php4/modules extension=java.so ======================================================================== === JVM=IBM 1.1.8, OS=Redhat Linux 6.1 === ======================================================================== build instructions: ./configure --with-java php.ini: [java] java.class.path=/home/jdk118/lib/classes.zip:/home/rubys/php4/modules/php_java.jar extension_dir=/home/rubys/php4/modules extension=java.so ======================================================================== === JVM=Blackdown 1.2.2 RC4, OS=Redhat Linux 6.1 === ======================================================================== build instructions: ./configure --with-java php.ini: [java] java.class.path=/home/rubys/php4/lib/php_java.jar extension_dir=/home/rubys/php4/modules extension=java.so ======================================================================== === JVM=Sun JDK 1.2.2, OS=Linux === ======================================================================== build instructions: ./configure --with-java php.ini: [java] java.class.path=/home/rubys/php4/lib/php_java.jar java.library.path=/home/rubys/php4/modules extension_dir=/home/rubys/php4/modules extension=java.so ======================================================================== === JVM=Sun JDK 1.1.8, OS=Windows NT 4 === ======================================================================== build instructions: SET JAVA_HOME=D:\jdk1.1.8 msdev ext\java\java.dsp /MAKE "java - Win32 Debug_TS" php.ini: [java] java.class.path="D:\jdk1.1.8\lib\classes.zip;F:\PHP4\Debug_TS\php_java.jar" extension=php_java.dll ======================================================================== === JVM=Sun JDK 1.2.2, OS=Windows NT 4 === ======================================================================== build instructions: SET JAVA_HOME=D:\jdk1.2.2 msdev ext\java\java.dsp /MAKE "java - Win32 Debug_TS" php.ini: [java] java.class.path=F:\PHP4\Debug_TS\php_java.jar extension=php_java.dll ========================================================================= Guidance for when these instructions don't work. JDK vendors don't typically document their internal workings, and are typically very reliant on code inside of the JAVA main program and the installation directory structure. For this reason, running PHP as a servlet is typically much easier to get working. But if for some reason this is not appropriate for you, and the instructions above don't work, then read on. The first thing to realize is that the directory structure of the JDK is very important. Some users (particularly on Windows) get a message about a DLL or shared library not being available and proceed to find that file and copy it into a system directory. This typically just gets you to the next problem - for example, it appears that many JDKs attempt to locate the runtime Java classes (rt.jar) in a directory relative to these system libraries. So unless you are inclined to copy your entire Java installation, you are much better adjusting your PATHs. Not documented above, but useful for many JDK's is ability to specify the library path via java.library.path in the php.ini. On many Unix machines, determining the initial value for this can be done by changing directory to where you find a shared library that can't be loaded (example: libjava.so), and executing "ld libjava.so". If you see some modules listed as "not found", add the necessary directories to LD_LIBRARY_PATH and repeat until successful. On my system, I require the following two directories. /home/jdk1.2.2/jre/lib/i386/native_threads /home/jdk1.2.2/jre/lib/i386/classic Note: this only determines the statically loaded libraries. Additional libraries (such as libzip.so) may be loaded dynamically. On my system, libzip.so is located in /home/jdk1.2.2/jre/lib/i386 Another php.ini variable which may be helpful is java.home. If java.library.path doesn't work for you (it won't on any JDK 1.1 implementations, for example), then try setting the system PATH or the LD_LIBRARY_PATH before starting your web server. For Apache on Linux systems, this can be accomplished by editing the Root's .bashrc and adding the necessary export LD_LIBRARY_PATH statement. If that doesn't work, try dividing an (hopefully) conquering by temporarily eliminating items such as Apache from the process by adjusting the arguments passed to the ./configure command (i.e., removing --with-apxs). If all else fails, "man dlopen" on Unix systems will give more insight on what the system is trying to do internally.