Maven is a Framework, Ant is a Toolbox

Maven is a pre-built road car, whereas Ant is a set of car parts. With Ant you have to build your own car, but at least if you need to do any off-road driving you can build the right type of car.

To put it another way, Maven is a framework whereas Ant is a toolbox. If you’re content with working within the bounds of the framework then Maven will do just fine. The problem for me was that I kept bumping into the bounds of the framework and it wouldn’t let me out.

XML Verbosity

tobrien is a guy who knows a lot about Maven and I think he provided a very good, honest comparison of the two products. He compared a simple Maven pom.xml with a simple Ant build file and he made mention of how Maven projects can become more complex. I think that its worth taking a look at a comparison of a couple of files that you are more likely to see in a simple real-world project. The files below represent a single module in a multi-module build.

First, the Maven file:

<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-4_0_0.xsd">

    <parent>
        <groupId>com.mycompany</groupId>
        <artifactId>app-parent</artifactId>
        <version>1.0</version>
    </parent>

    <modelVersion>4.0.0</modelVersion>
    <artifactId>persist</artifactId>
    <name>Persistence Layer</name>

    <dependencies>

        <dependency>
            <groupId>com.mycompany</groupId>
            <artifactId>common</artifactId>
            <scope>compile</scope>
            <version>${project.version}</version>
        </dependency>

        <dependency>
            <groupId>com.mycompany</groupId>
            <artifactId>domain</artifactId>
            <scope>provided</scope>
            <version>${project.version}</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate</artifactId>
            <version>${hibernate.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>commons-lang</groupId>
            <artifactId>commons-lang</artifactId>
            <version>${commons-lang.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring</artifactId>
            <version>${spring.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.dbunit</groupId>
            <artifactId>dbunit</artifactId>
            <version>2.2.3</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>${testng.version}</version>
            <scope>test</scope>
            <classifier>jdk15</classifier>
        </dependency>

        <dependency>
            <groupId>commons-dbcp</groupId>
            <artifactId>commons-dbcp</artifactId>
            <version>${commons-dbcp.version}</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>com.oracle</groupId>
            <artifactId>ojdbc</artifactId>
            <version>${oracle-jdbc.version}</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.easymock</groupId>
            <artifactId>easymock</artifactId>
            <version>${easymock.version}</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

</project>

And the equivalent Ant file:

<project name="persist" >

    <import file="../build/common-build.xml" />


    <path id="compile.classpath.main">
        <pathelement location="${common.jar}" />
        <pathelement location="${domain.jar}" />
        <pathelement location="${hibernate.jar}" />
        <pathelement location="${commons-lang.jar}" />
        <pathelement location="${spring.jar}" />
    </path>


    <path id="compile.classpath.test">
        <pathelement location="${classes.dir.main}" />
        <pathelement location="${testng.jar}" />
        <pathelement location="${dbunit.jar}" />
        <pathelement location="${easymock.jar}" />
        <pathelement location="${commons-dbcp.jar}" />
        <pathelement location="${oracle-jdbc.jar}" />
        <path refid="compile.classpath.main" />
    </path>


    <path id="runtime.classpath.test">
        <pathelement location="${classes.dir.test}" />
        <path refid="compile.classpath.test" />
    </path>


</project>

tobrien used his example to show that Maven has built-in conventions but that doesn’t necessarily mean that you end up writing less XML. I have found the opposite to be true. The pom.xml is 3 times longer than the build.xml and that is without straying from the conventions. In fact, my Maven example is shown without an extra 54 lines that were required to configure plugins. That pom.xml is for a simple project. The XML really starts to grow significantly when you start adding in extra requirements, which is not out of the ordinary for many projects.

But you have to tell Ant what to do

My Ant example above is not complete of course. We still have to define the targets used to clean, compile, test etc. These are defined in a common build file that is imported by all modules in the multi-module project. Which leads me to the point about how all this stuff has to be explicitly written in Ant whereas it is declarative in Maven.

Its true, it would save me time if I didn’t have to explicitly write these Ant targets. But how much time? The common build file I use now is one that I wrote 5 years ago with only slight refinements since then. After my 2 year experiment with Maven, I pulled the old Ant build file out of the closet, dusted it off and put it back to work. For me, the cost of having to explicitly tell Ant what to do has added up to less than a week over a period of 5 years.

Complexity

The next major difference I’d like to mention is that of complexity and the real-world effect it has. Maven was built with the intention of reducing the workload of developers tasked with creating and managing build processes. In order to do this it has to be complex. Unfortunately that complexity tends to negate their intended goal.

When compared with Ant, the build guy on a Maven project will spend more time:

  • Reading documentation: There is much more documentation on Maven, because there is so much more you need to learn.
  • Educating team members: They find it easier to ask someone who knows rather than trying to find answers themselves.
  • Troubleshooting the build: Maven is less reliable than Ant, especially the non-core plugins. Also, Maven builds are not repeatable. If you depend on a SNAPSHOT version of a plugin, which is very likely, your build can break without you having changed anything.
  • Writing Maven plugins: Plugins are usually written with a specific task in mind, e.g. create a webstart bundle, which makes it more difficult to reuse them for other tasks or to combine them to achieve a goal. So you may have to write one of your own to workaround gaps in the existing plugin set.

In contrast:

  • Ant documentation is concise, comprehensive and all in one place.
  • Ant is simple. A new developer trying to learn Ant only needs to understand a few simple concepts (targets, tasks, dependencies, properties) in order to be able to figure out the rest of what they need to know.
  • Ant is reliable. There haven’t been very many releases of Ant over the last few years because it already works.
  • Ant builds are repeatable because they are generally created without any external dependencies, such as online repositories, experimental third-party plugins etc.
  • Ant is comprehensive. Because it is a toolbox, you can combine the tools to perform almost any task you want. If you ever need to write your own custom task, it’s very simple to do.

Familiarity

Another difference is that of familiarity. New developers always require time to get up to speed. Familiarity with existing products helps in that regard and Maven supporters rightly claim that this is a benefit of Maven. Of course, the flexibility of Ant means that you can create whatever conventions you like. So the convention I use is to put my source files in a directory name src/main/java. My compiled classes go into a directory named target/classes. Sounds familiar doesn’t it.

I like the directory structure used by Maven. I think it makes sense. Also their build lifecycle. So I use the same conventions in my Ant builds. Not just because it makes sense but because it will be familiar to anyone who has used Maven before.