dependencyManagement管理依赖

dependencyManagement的作用：Maven使用dependencyManagement元素来提供了一种管理依赖版本号的方式

<dependencyManagement>
  <dependencies>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.0.1</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>java.servlet.jsp</groupId>
        <artifactId>jsp-api</artifactId>
        <version>2.0</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.11</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.21</version>
        <scope>provided</scope>
    </dependency>
  </dependencies>
</dependencyManagement>