Good work! How much is the size of the minimum OSGi-ed JRE? Thanks, xiaofeng
On Sun, Aug 16, 2009 at 3:22 PM, galaxy<tian.gal...@gmail.com> wrote: > Hi all > Now the code for OSGi-ed Runtime of Harmony is almost complete , I'd > like to give a review of > the work so far.The code and usage will be uploaded together soon > > Introduction To OSGi-ed JRE > > > > 1 : The main purpose > > OSGi has become one of the best ways to govern the jar files in a number of > applications Such as the power it exhibits in eclipse .And as we all know > ,the Harmony runtime is a modularized one and each module , with its > manifest file , is just like one bundle in the OSGi framework .So we are > think of governing the modules in Harmony runtime in a OSGi-ed way. > > > > 2 : Ways to meet the main purpose > > Naturally, there are two ways to meet this purpose: > > A Implementing the OSGi framework in VM in C/C++ to govern all the java > modules > > B Using one of the OSGi-ed framework implemented in java to implemented a > half OSGi-ed JRE. > > Finally I picked the plan B with the well known OSGi framework :Felix > .And the reasons are as follows > > First : Implementing a OSGi-ed framework from scratch in c/c++ in the vm is > difficult and time-consuming . > > Second : Plan A suffers from the facts that implementations differs huge > from VM to VM .Plan B won’t have this kind of problem as long as the modules > comply with the OSGi specifications and we have a adapted java.exe , the > rest is nearly the same. > > Third : Beside the framework ,each OSGi implementation has a lot of add-ons > .This will facilitate future development of new features and utilities .For > example : the could use the bundle fileinstall to install all the jar files > lies in a folder ,very helpful in certain circumstances.This could be done > rapidly if we choose plan B . > > > > 3 : Problems and fixes > > The difficulties ,or the main tasks ,of this project are as follows > > A Find the minimum working environment of OSGi-framework and modify the > rest modules in Harmony ,mainly the manifest file ,to resolve the coupling > > B Modify the classloading mechanism and booting of the jre to be able > run normal java applications > > And the fixes are > > For A: > > Harmony is a modularized runtime .So determine the minimum working > environment is no more than choose the right module to stay with the VM > .However ,although the coupling is little , it does exist . So a > modification of the module is necessary ,mainly the manifest file .And as I > want to remain the original structure of Harmony as largely as possible > ,more contents (classes ) will be included in the minimum environment other > than splitting the modules apart .The final jre include the following > component : > > > > luni.jar > > annotation.jar > > security.jar > > math.jar > > text.jar > > regex.jar > > noi_char.jar > > nio.jar > > logging.jar > > concurrent.jar > > archive.jar > > the ICU4J folder. > > > > The remaining jars are governed by the OSGi framework to handle. One more > thing to mention is the two classes > ,”java.beans.PropertyChangelinstener”,”java.beans.PropertyChangeEvent” has > to be moved out of beans.jar .This is because of the coupling of beans.jar > with other modules in the minimum runtime .Well the good thing is these two > classes havn’t imports any other classes in the modules governed by the OSGi > framework .I think we could include them in any modules lie in the minimum > runtime as long as the VM could find them . > > > > For B: > > I added one extra sphere between the VM and the main class to run > .org.apache.osgi.FelixStarter. , the following is done in this class > > First: Loading the configurations and Start Felix ,the OSGi framework we use > > Second: Initializing the class org.apache.osgi.OsgiClassLoader ,this class > will load the main class and subsequently all the classes used in the main > class > > Third: Transfer the arguments to the “real “ main class ,invoke the main > method . > > > > The sequence of class loading is as follows : > > > > First : Check the class name to determine whether it should be loaded by the > parent class loader .This work is done by specifying the > “org.osgi.framework.bootdelegation” property to include all the package > names in the modules stays in the VM . > > Second : load the classes in the bundle governed by the framework .I will > examine each bundle's export and import property to search for the class > name ; > > Third : the classes in the application’s class path . > > Finally : we could not find the class and a ClassNotFoundException will be > thrown . > > > > Both the OSGi framework and the Harmony do not allow the define , imports or > exports of java.* classes and packages ,so a lot of examines has been > removed to facilitate our purpose . > > > > > > > > > -- > regards > Tian > -- http://people.apache.org/~xli
