今天新建了个web项目，试了下buildPath来添加jar包，结果运行时提示找不到相关jar包；后来将jar包复制到WEB-INF/lib下，运行成功。然后在网上查了下，原来如此：

Build path jars are not a part of your web app.

On the other hand, the WEB-INF/lib jars are a part of your project.

The advantage of having WEB-INF/lib jars over build path jars is that they get bundled into your app when generating a WAR file.

This comes in handy when you want to deploy your app on some server where you don't have access to modify the jars in the build path.