这个问题必须记录一下。
现象：Eclipse Helios 启动时 hung 在 Initial Web Service Dom...查看log之后发现：
!ENTRY org.eclipse.osgi 4 0 2011-06-02 07:06:16.296
!MESSAGE Application error
!STACK 1
java.lang.IllegalStateException: Unable to acquire application service. Ensure that the org.eclipse.core.runtime bundle is resolved and started (see config.ini).
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:74)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:369)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:619)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:574)
at org.eclipse.equinox.launcher.Main.run(Main.java:1407)
重现：在使用向导创建 Web Project 的时候，使用的 Dynamic web module version 默认为2.5。重启 Eclipse之后，加载 project的时候可能会出现。
原因：jst.web facet of 2.5 which is obviously a conflict with the 2.4 servlet api
解决方法：修改${project}/.settings/org.eclipse.wst.common.project.facet.core.xml - 将 <installed facet="jst.web" version="2.5"/> 改为 <installed facet="jst.web" version="2.4"/>
参考：
https://bugs.eclipse.org/bugs/show_bug.cgi?id=335423
http://www.xgap.org/ticket/419
Helios
本文出自 “雨寒” 博客，请务必保留此出处http://august.blog.51cto.com/59588/579542