你可以打开每个IDEA窗口只有一个IDEA项目。但Maven项目可以由多个模块组成，每个模块都有一个拥有自己的 pom.xml 。您还可以在同一个IDEA项目中导入多个Maven项目。

You can open only one IDEA project per IDEA window. But a Maven project can be made of multiple modules, each one having its own pom.xml. You can also import multiple Maven projects in the same IDEA project.

如果您有现有的Maven项目，只需打开根 pom.xml 使用文件>打开，IDEA将询问您是否应作为Maven项目开放（假设您已在IDEA中启用了Maven插件）。当您对 pom.xml 进行更改时，IDEA会建议您重新导入项目，从而添加/删除库以使IDEA项目与Maven项目同步。

If you have an existing Maven project, just open the root pom.xml using File > Open and IDEA will ask you if it should be opened as a Maven project (providing you have enabled the Maven plugin in IDEA). When you make changes to a pom.xml, IDEA will suggest you to reimport the project, thus adding/removing libraries to synchronize the IDEA project with the Maven project.

要向hibernate添加依赖项，请添加以下代码：

To add a dependency to hibernate, add this code:

<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-core</artifactId>
    <version>4.1.9.Final</version>
</dependency>
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-ehcache</artifactId>
    <version>4.1.9.Final</version>
</dependency>