The Community OpenORB - ConcurrencyControlService

If you have built the Persistent State Service with the build or sh build.sh command, the Persistent State Service examples are already built.

Otherwise, use the following command to build the PSS examples: build examples You will find the several jar files in the dist/examples directory, one for each example.

To launch the examples, you have to specify that you use the PSS profile with the flag -ORBProfile=persistent

For each example, set the classpath with the corresponding jar file and the openorb_pss-{version}.jar and check whether you have configured the OpenORB.xml file properly.

For example in Basic Session:

For examples in Transactional Session (except for Memory Persistence which does not support transactional sessions):

The PSDL (Persistent State Description Language) is a new description language to describe persistent data.

The PSDL is an extension of IDL. It means that you can use all IDL descriptions with PSDL.

There are two parts into a PSDL description:

The abstract description part is very important, because this is the part that provides portability! In this part, you describe persistent data and their home:

The abstract storage type defines local operations and states (persistent states).

For persistent state, the following syntax must be used: state state_type state_name; Example: state string name

Any kind of IDL type is valid for state type. The state access may be limited by the readonly key word. Example : readonly state float price; Local operations example: void print();

To describe an abstract storage type, you have to use a specific key word 'abstract storagetype'

			abstract storagetype Person
			{
				state string name
				state string address

				void print();
			};
			

Abstract storage types support multiple inheritances. They are managed by abstract storage homes. An abstract storage home contains:

Keys are additional structures to provide an easy way to find a storage type. Here is how to declare a key: key key_name ( states names ); The key member names must be a state name of the managed storage type.

A factory description provides a way to create new persistent data. Here is how to declare factories: factory factory_name ( states names );

An abstract storage home is declared by:

            abstract storagehome PersonHome of Person
            {
				key name;
                factory create ( name, address, age );
			};
			

Abstract storage homes support multiple inheritance. The second part of a PSDL description is a for concrete descriptions. There are two types of concrete descriptions:

A storage type implements one or several abstract storage types.

            storagetype PersonBase implements Person
			{ }
			

			storagehome PersonHomeBase of PersonBase implements PersonHome
			{ }
			

To develop portable applications and multi connector applications, it's better to use only abstract storage type and home to define states, local operations, keys and factories. This is the reason why, in the previous example the storage type and storage home content is empty!

A good way to understand PSDL is to study the examples provided with the OpenORB Persistent State Service distribution.

The OpenORB Persistent State Service provides a PSDL compiler. To start the compiler, enter the following command name: java org.openorb.pss.compiler.PsdlCompiler By default, the compiler generates file for the memory connector (in order to use the PSS API to develop transient applications). In addition to the PSDL option flags, all standard OpenORB IDL flag are available!

OpenORB provides an Ant task that eases the use of OpenORB PSDL compiler. The Ant task can be easily included in your projects by using the taskdef tag. The task does additionnal uptodate checks and only compiles idl files which are more recent than the target Java files. This is done using a cache (in a file called psdl2java.cache by default) which is updated every time the compiler is run.

             <project name="myproject">
               <taskdef resource="psdl2java.properties">
               ...
           

You only need to reference the openorb_tools-<version>.jar and openorb_pss-<version>.jar in the classpath of your build. The source files are set using a nested FileSet task which means that it possible to specify a whole tree of files to be compiled. It is possible to refine the set of files that are being compiled. This can be done with the includes, includesfile, excludes, and excludesfile attributes. With the includes or includesfile attribute, you specify the files you want to have included. The exclude or excludesfile attribute is used to specify the files you want to have excluded. In both cases, the list of files can be specified by either the filename, relative to the directory(s) specified in the srcdir attribute or nested <src> element(s), or by using wildcard patterns. See the section on Ant Manual,directory-based tasks, for information on how the inclusion/exclusion of files works, and how to write wildcard patterns.

Example:

<psdl2java destdir="${gensrc.dir}/main"
       srcdir="${psdl.dir}"
       generateapi="false"
       package="database"
       persistencetype="database"
       includes="Naming.psdl" />