maven2多模块集成

Question

我在集成的时候，在父工程文件夹下执行mvn clean 报错：project:null:App:jar:null 
Reason:Cannot find parent:com.demo:top for project: null:App:jar:null for project:null :App:jar:null 
其中top是父工程，App是应用项目，有一个web-app工程是web工程，web工程调用App的类来在web项目的jsp页面显示东西。我的父工程的pom.xml是：
<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>
  <groupId>com.top</groupId>
  <artifactId>top</artifactId>
  <packaging>pom</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>top</name>
  
  <modules>
   <module>App</module>
   <module>web-app</module>
  </modules>
  
  
   <build>
    <pluginManagement>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <source>1.6</source>
          <target>1.6</target>
        </configuration>
      </plugin>
    </plugins>
    </pluginManagement>
  </build>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>
App应用程序工程的pom.xml为：
<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>
  <parent>
   <groupId>com.dAemo</groupId>
   <artifactId>top</artifactId>
   <version>1.0-SNAPSHOT</version>
  </parent>
  
  <artifactId>App</artifactId>
  <packaging>jar</packaging>
  <name>App</name>
  <url>http://maven.apache.org</url>
  
  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-surefire-plugin</artifactId>
          <configuration>
            <testFailureIgnore>true</testFailureIgnore>
          </configuration>
        </plugin>
      </plugins>
    </pluginManagement> 
  </build>
  
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>
web项目的pom.xml为:
<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>
  <parent>
  <groupId>com.demo</groupId>
  <artifactId>top</artifactId>
  <version>1.0-SNAPSHOT</version>
  </parent>
  
  <artifactId>web-app</artifactId>
  <packaging>war</packaging>
  <name>web-app Maven Webapp</name>
  <url>http://maven.apache.org</url>
  
  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-surefire-plugin</artifactId>
          <configuration>
            <testFailureIgnore>true</testFailureIgnore>
          </configuration>
        </plugin>
      </plugins>
    </pluginManagement> 
  </build>  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
     <groupId>com.demo</groupId>
     <artifactId>App</artifactId>
     <version></version>
    </dependency>
  </dependencies>
  <build>
    <finalName>web-app</finalName>
  </build>
</project>