What is Stub ?

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3.1 Stubs and Skeletons

RMI uses a standard mechanism (employed in RPC systems) for communicating with remote objects: stubs and skeletons. A stub for a remote object acts as a client’s local representative or proxy for the remote object. The caller invokes a method on the local stub which is responsible for carrying out the method call on the remote object. In RMI, a stub for a remote object implements the same set of remote interfaces that a remote object implements.

When a stub’s method is invoked, it does the following:

  •  initiates a connection with the remote JVM containing the remote object,
  •  marshals (writes and transmits) the parameters to the remote JVM,
  •  waits for the result of the method invocation,
  •  unmarshals (reads) the return value or exception returned, and
  •  returns the value to the caller.

The stub hides the serialization of parameters and the network-level communication in order to present a simple invocation mechanism to the caller.

In the remote JVM, each remote object may have a corresponding skeleton (in Java 2 platform-only environments, skeletons are not required). The skeleton is responsible for dispatching the call to the actual remote object implementation. When a skeleton receives an incoming method invocation it does the following:

  •  unmarshals (reads) the parameters for the remote method,
  •  invokes the method on the actual remote object implementation, and
  •  marshals (writes and transmits) the result (return value or exception) to the caller.

In the Java 2 SDK, Standard Edition, v1.2 an additional stub protocol was introduced that eliminates the need for skeletons in Java 2 platform-only environments. Instead, generic code is used to carry out the duties performed by skeletons in JDK1.1. Stubs and skeletons are generated by the rmic compiler.

XML file with Java DOM, SAX, JDOM (mkyong)

In Java JDK, two built-in XML parsers are available – DOM and SAX, both have their pros and cons. Here’s few examples to show how to create, modify and read a XML file with Java DOMSAXJDOM.

In addition, updated JAXB example to show you how to convert object to / from XML.

DOM XML Parser

The DOM is the easiest to use Java XML Parser. It parses an entire XML document and load it into memory, modeling it with Object for easy nodel traversal. DOM Parser is slow and consume a lot memory if it load a XML document which contains a lot of data.

SAX XML Parser

SAX parser is work differently with DOM parser, it does not load any XML document into memory and create some object representation of the XML document. Instead, the SAX parser use callback function (org.xml.sax.helpers.DefaultHandler) to informs clients of the XML document structure.

SAX Parser is faster and uses less memory than DOM parser.

JDOM XML Parser

JDOM provides a way to represent that document for easy and efficient reading, manipulation, and writing. It’s an alternative to DOM and SAX.

JAXB Example

JAXB, using annotation to convert Java object to / from XML file.

  • JAXB 2.0 hello world example
    A detail example to show you use JAXB to do XML Marshalling (convert object to XML) and XML Unmarshalling (Convert XML to object).

XML & Properties

The java.util.Properties class has build-in functionality to convert properties file into XML file or vice versse.

(original link : http://www.mkyong.com/tutorials/java-xml-tutorials/)