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| <h3>Build Path Computation</h3> |
| |
| <p>By default, PDE updates the build path of a plug-in project every time you |
| change the list of dependencies in the manifest editor. If you turn off |
| that feature on the Plug-in Development->Java Build Path Control preference |
| page, you will have to be responsible for updating the build path every time you |
| make a change to the list of dependencies.</p> |
| |
| <p>You are not required to use PDE's manifest editor to take advantage of PDE's |
| build path computation feature. You can always use the <b>Update Classpath...</b> |
| pop-up menu item available on all plugin.xml/fragment.xml files and Java plug-in |
| projects to explicitly update the build path of your plug-in. This will |
| cause a wizard to open:</p> |
| <p align="center"> |
| <img border="0" src="images/classpath-update.gif" alt=""Update class path" wizard" width="438" height="556"></p> |
| <p align="left">The checkbox list will contain all the plug-ins and fragments in |
| the workspace. Select the plug-ins/fragments whose build path you wish to update |
| and press 'Finish'.</p> |
| <p> Note that when computing the build path, PDE recreates it from scratch. |
| That means that you will lose any entries you have added manually to the build |
| path. The build path is updated from scratch because PDE builds it |
| recursively. Here's why:</p> |
| <p>If a Java class is referenced by a plug-in at run time, its libraries |
| will be searched first for the class, then the libraries of its required plug-ins, then the |
| libraries of their required plug-ins, and so on. In order to recreate a similar |
| lookup environment during design time, PDE updates the build path recursively. |
| It is possible for several different plug-ins to depend on the same library. If you delete one of |
| these plug-ins from your dependency list, it is not safe to remove libraries all |
| the way up the chain because some of the plug-ins you still have on the list may |
| be needing them. The only way to always maintain a valid build path is to create it |
| from scratch.</p> |
| <p>In order to provide for better sharing of projects on authoring servers, PDE |
| adds all external libraries to the build path relative to the run-time platform location |
| represented by 1 or more Java classpath variables whose suffix is <b>ECLIPSE_HOME</b>. This |
| way, you can have your code on the server and it will work regardless of the |
| location of your platform install. These variables are set and managed by PDE and you are not |
| supposed to modify their values.</p> |
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| <h3>Classpath containers</h3> |
| |
| <p>Since 2.1, PDE provides an alternative way of expressing and computing the |
| classpath. Instead of explicitly creating the entries for the dependent |
| plug-ins, it introduces a level of indirection using JDT classpath container. |
| The container replaces all the dependent plug-in entries and provides for a |
| stable and predictable classpath. When using classpath container, your classpath |
| will contain source folder(s), required plug-ins container, and JRE container |
| (uses identical mechanism to provide a proxy for the real JRE entries that are |
| computed on the fly). You can share this classpath on the server without worry |
| that it will cause problems on other developers' machines and/or operating |
| systems.</p> |
| |
| <p>In order to use classpath containers, all that is needed is to open |
| Preferences>Plug-in Development>Java build path control and select 'Use |
| classpath containers...' checkbox. You will need to update classpaths of your |
| project in order to see the changes applied. Once you switch to classpath |
| containers, you can use either external plug-ins or import binary plug-in |
| projects, or a mix of both. Whatever you do, classpath container will keep up |
| with the changes and adapt.</p> |
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