Connect PHP code to Java backend

Question

I am implementing a website using PHP for the front end and a Java service as the back end. The two parts are as follows:

1. PHP front end listens to http requests and interacts with the database.

2. The Java back end run continuously and responds to calls from the front end.

More specifically, the back end is a daemon that connects and maintain the link to several IM services (AOL, MSN, Yahoo, Jabber...).

Both of the layers will be deployed on the same system (a CentOS box, I suppose) and introducing a middle layer (for instance: using XML-RPC) will reduce the performance (the resource is also rather limited).

Question: Is there a way to link the two layers directly? (no more web services in between)

Solution 1

Since this is communication between two separate running processes, a "direct" call (as in JNI) is not possible. The easiest ways to do such interprocess communcation are probably named pipes and network sockets. In both cases, you'll have to define a communication protocol and implement it on both sides. Using a standard protocol such as XML-RPC makes this easier, but is not strictly necessary.

Solution 2

There are generally four patterns for application integration:

1. via Filesystem, ie. one producers writes data to a directory monitored by the consumer
2. via Database, ie. two applications share a schema or table and use it to swap data
3. via RMI/RPC/web service/any blocking, sync call from one app to another. For PHP to Java you can pick from the various integration libraries listed above, or use some web services standards like SOAP.
4. via messaging/any non-blocking, async operation where one app sends a message to another app.

Each of these patterns has pros and cons, but a good rule of thumb is to pick the one with the loosest coupling that you can get away with. For example, if you selected #4 your Java app could crash without also taking down your PHP app.

I'd suggest before looking at specific libraries or technologies listed in the answers here that you pick the right pattern for you, then investigate your specific options.

Solution 3

I have tried PHP-Java bridge(php-java-bridge.sourceforge.net/pjb/) and it works quite well. Basically, we need to run a jar file (JavaBridge.jar) which listens on port(there are several options available like Local socket, 8080 port and so on). Your java class files must be availabe to the JavaBridge in the classpath. You need to include a file Java.inc in your php and you can access the Java classes.

Solution 4

Sure, there are lots of ways, but you said about the limited resource...

IMHO define your own lightweight RPC-like protocol and use sockets on TCP/IP to communicate. Actually in this case there's no need to use full advantages of RPC etc... You need only to define API for this particular case and implement it on both sides. In this case you can serialize your packets to quite small. You can even assign a kind of GUIDs to your remote methods and use them to save the traffic and speed-up your intercommunication.

The advantage of sockets usage is that your solution will be pretty scalable.

Solution 5

You could try the PHP/Java integration.

Also, if the communication is one-way (something like "sendmail for IM"), you could write out the PHP requests to a file and monitor that in your Java app.

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Comments

[David Rabinowitz]

From the Introduction: "Warning: This extension is EXPERIMENTAL. The behaviour of this extension including the names of its functions and any other documentation surrounding this extension may change without notice in a future release of PHP. This extension should be used at your own risk."

[Michael Borgwardt]

You should edit your question rather than answering it. And as I wrote, it's not possible for two separate processes to communicate without SOME sort of intermediate layer. As for access from the outside, that's what firewalls are for, but a named pipe would not exhibit this problem.

[ThoaiOnline]

I want something really minimal. For a VPS with limited resources (around 256MB of RAM), it's ok to use ws for 10 connections, but 1000 connections will make it a big problem. Thinking about scalability at minimum cost.

[Kdeveloper]

When Java generates you're PHP code, the resulting PHP code will be different each time it run's. Thus depending how PHP opcode caching exactly works, this solution has a high change of disables PHP caching (APC, eAccelerator, etc) and thus degrading performance for all scripts that include this java generated PHP code.