spring-web导入失败

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
         http://maven.apache.org/maven-v4_0_0.xsd">

  <modelVersion>4.0.0</modelVersion>
  <packaging>war</packaging>

  <name>oa_web</name>
  <groupId>com.om</groupId>
  <artifactId>oa_web</artifactId>
  <version>1.0-SNAPSHOT</version>

  <properties>
    <spring.version>5.1.9.RELEASE</spring.version>
  </properties>

  <build>
    <plugins>
      <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>maven-jetty-plugin</artifactId>
        <version>6.1.7</version>
        <configuration>
          <connectors>
            <connector implementation="org.mortbay.jetty.nio.SelectChannelConnector">
              <port>8888</port>
              <maxIdleTime>30000</maxIdleTime>
            </connector>
          </connectors>
          <webAppSourceDirectory>${project.build.directory}/${pom.artifactId}-${pom.version}</webAppSourceDirectory>
          <contextPath>/</contextPath>
        </configuration>
      </plugin>
    </plugins>
  </build>

  <dependencies>

    <dependency>
      <groupId>com.om</groupId>
      <artifactId>oa_biz</artifactId>
      <version>1.0-SNAPSHOT</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>${spring.version}</version>
    </dependency>
  </dependencies>

</project>

不知道为什么我需要在oa_web重新定义一次spring.version,不知道是不是有什么代码屏蔽了oa的spring.version