用于客户端/服务器通信的Java标准

Question

What is the "official" Java API for client/server or P2P communication? Java RMI? Some other networking API??

Is this official networking API the standard for both SE and EE?

I'm sure the answer is very context-specific, so let's take a look at a few instances:

1. You have 2 swing clients installed on 2 machines and connected to the same network (or the Internet), and you want either of them to send the other a primitive, such as the integer 4, or some POJO, like a "Widget" object
2. Same as #1 above, but between a Swing client and a fully-compliant Java EE back-end (implementing managed beans, app servers, the whole nine yards)

I don't have a specific application in mind, I'm just wondering what are the "norms" for client-client and client-server communication in the world of Java.

Answer 1

If being bound by Java isn't a problem, RMI is a pretty abstracted solution when it comes to the client and server solution "exchanging" data (especially when the data is Java classes which might be difficult/too much effort to represent as textual data). Just make sure your object implements Serializable and almost anything can be transmitted over the wire.

If this doesn't fit your bill and you want to drop down the raw networking stuff, the client-server socket framework Netty is a pretty good choice.

Answer 2

There's no such thing as the most official networking API in J2SE, all J2SE APIs are official in the sense they are supported by Sun (now Oracle).
That said, you should choose your API based on following criteria:

• Do you (or your team) know how to use particular API;
• How simple/complex is this API to use;
• What throughput are you aiming for? For performance-sensitive applications you may be forced to use binary protocol. For the rest of cases, you can use text-based protocol.

For example, between two clients simple text-based protocol will suffice for passing POJOs, for example using Apache MINA or Google protocol buffers.
This will work between client and server as well.

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Response to Zac's questions in comment:

1. Binary protocols performance gain comes from the fact you don't need to convert everything to text form and back -- you just can pass binary presentation of you application memory with minimal changes, like, in case of BSD Sockets API, converting from host byte-order to network byte-order. Unfortunately, I don't know details about how RMI/Java serialization processes objects, but I'm sure, it still much faster than passing all data in readable form;
2. Yes, MINA and protocol buffers have Java APIs. They just not part of Java SE bundle, you have to download them separately. By the way, MINA can use both binary and readable serialization, depending on how you use it.
3. You should define notion of 'good' somehow, for example, answering to questions I mentioned above. If you want to use objects over network, use RMI. If you don't, Netty or MINA will suffice, whatever you'll find easier to master.

Answer 3

For P2P, Sun at one point pushed JXTA pretty hard.

I wouldn't dare to use RMI for P2P communication.

Answer 4

rmi is pretty much the standard java to java protocol. it's built in and very simple to use. most j2ee backends also communicate using rmi, although that's not the only possibility.

Answer 5

J2SE the most common is probably RMI or raw sockets.

J2EE uses a messaging bus that everyone (servers and clients) subscribes to which is quite different from rmi style solutions (although at the lowest level an implementation may still rely on RMI). It helps automate redundancy and failover. If you need this functionality I believe it can be used in SE as well.

I haven't used J2EE for quite a while now, so this may have changed, but I doubt it. The messaging system was a core component of J2EE.