1.可以添加Junit,用于程序单元测试

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

2.可以添加log4j,用于添加程序运行日志信息

Let‘s add another dependency to our project. Let‘s say we‘ve added some logging to the code and need to add log4j as a dependency. First, we need to know what the groupId, artifactId, and version are for log4j. We can browse ibiblio and look for it, or use Google to help by searching for "site:www.ibiblio.org maven2 log4j". The search shows a directory called /maven2/log4j/log4j (or /pub/packages/maven2/log4j/log4j). In that directory is a file called maven-metadata.xml. Here‘s what the maven-metadata.xml for log4j looks like:

<metadata>
  <groupId>log4j</groupId>
  <artifactId>log4j</artifactId>
  <version>1.1.3</version>
  <versioning>
    <versions>
      <version>1.1.3</version>
      <version>1.2.4</version>
      <version>1.2.5</version>
      <version>1.2.6</version>
      <version>1.2.7</version>
      <version>1.2.8</version>
      <version>1.2.11</version>
      <version>1.2.9</version>
      <version>1.2.12</version>
    </versions>
  </versioning>
</metadata>

From this file, we can see that the groupId we want is "log4j" and the artifactId is "log4j". We see lots of different version values to choose from; for now, we‘ll just use the latest version, 1.2.12 (some maven-metadata.xml files may also specify which version is the current release version). Alongside the maven-metadata.xml file, we can see a directory corresponding to each version of the log4j library. Inside each of these, we‘ll find the actual jar file (e.g. log4j-1.2.12.jar) as well as a pom file (this is the pom.xml for the dependency, indicating any further dependencies it might have and other information) and another maven-metadata.xml file. There‘s also an md5 file corresponding to each of these, which contains an MD5 hash for these files. You can use this to authenticate the library or to figure out which version of a particular library you may be using already.

Now that we know the information we need, we can add the dependency to our pom.xml:

<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/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.mycompany.app</groupId>
  <artifactId>my-app</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>Maven Quick Start Archetype</name>
  <url>http://maven.apache.org</url>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>1.2.12</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>
</project>

Now, when we compile the project (mvn compile), we‘ll see Maven download the log4j dependency for us.