问题：安装失败，报如下错误：
An error occurred while collecting items to be installed
session context was:(profile=epp.package.jee, phase=org.eclipse.equinox.internal.p2.engine.phases.Collect, operand=, action=).
Unable to read repository at http://dist.springsource.com/release/TOOLS/update/3.8.4.RELEASE/e4.5/plugins/org.eclipse.m2e.core_1.7.0.20160603-1933.jar.
Read timed out
Unable to read repository at http://dist.springsource.com/release/TOOLS/update/3.8.4.RELEASE/e4.5/plugins/org.springframework.ide.eclipse.metadata_3.8.4.201703310634-RELEASE.jar.
Read timed out
Unable to read repository at http://dist.springsource.com/release/TOOLS/update/3.8.4.RELEASE/e4.5/plugins/org.springframework.ide.eclipse.quickfix_3.8.4.201703310634-RELEASE.jar.
Read timed out
解决办法：
在eclipse 安装目录，即eclipse .exe所在目录敲如下命令：
eclipse -application org.eclipse.equinox.p2.garbagecollector.application -profile epp.package.jee
问题分析：
出现错误的原因是Eclipse的更新管理P2出错了。
p2有它的一个垃圾回收机制，之前删除的JAR包在未被回收之前，再次重装，系统不会做重新download的动作，但是它又找不到那个JAR包了，故而报错。