如何在Eclipse中从Maven创建项目

Question

I've installed the m2e plugin in Eclipse. I'm trying to download the source and dependencies of MG4J and use it in my project. In the upper-right corner there's a Maven link. However, I don't know what to do with it! I downloaded the source and opened a file and found the SCM location. I entered it in the "Checkout Maven Projects from SCM" project type, but when I click finish, nothing happened. How can I achieve this?

Update:

I'm new to the world of Java. What I'm trying to do is this: I wanted to use MG4J in my project. I think I might have to change its code. First I downloaded the source and dependencies archives and extracted them, added .jar files to the build path and everything compiled. But it failed to run on some occasions. I contacted the MG4J people. They said that I have to use Maven to resolve dependencies. Now, here I am with all the archives and after 1 day, I still can't run a simple program.

In short I want to do this:

project 1: MG4J (automatically resolves dependencies, etc)

project 2: MyProject (relies on MG4J)

Answer 1

MG4J uses Ant with Ivy (not Maven) as a build tool and dependency manager. So, if you want to be able to modify the source and build it you are going to have to use the same tools.

1. Install Apache Ant, make a note of the installation directory (ANT_HOME)
2. Download an Apache Ivy binary distribution
3. Unpack the Apache Ivy binary distribution to a folder, then copy ivy-2.xxjar to ANT_HOME/lib
4. Download the source for MG4J . It comes as a JAR which you need to extract to a folder (MG4J_SRC).
5. In the MG4J_SRC folder execute the command ant ivy-setupjars jar . If the build is successful, it will create a binary distribution for MG4J, as a JAR called mg4j-xxjar.

So, now you have a locally built version of the library, but you still can't use it (easily) in Maven. To make it accessible to your Mavenised project, you should install the library into your local Maven repo.

mvn install:install-file  -Dfile={MG4J_SRC}/mg4j-x.x.jar
                          -DgroupId=your.groupId
                          -DartifactId=your.artifactId
                          -Dversion=your.version
                          -Dpackaging=jar
                          -DlocalRepositoryPath=path-to-specific-local-repo

Replace the your.groupId, your.artifactId, your.version and localRepositoryPath variables with values that make sense for your environment

You can then add a dependency to the other project's POM:

<dependency>
  <groupId>your.groupId</groupId>
  <artifactId>your-artifactId</artifactId>
  <version>your.version</version>
</dependency>

Now, as a final step, you want to make working with the MG4J source possible (and easy) from within Eclipse. In your IDE, open File->New->Project and select 'Java Project from Existing Ant Buildfile' (type Ant in your Filter to narrow down the list).

Click through the wizard and Finish. Now you have an Ant-based project in Eclipse, where you can easily modify the source and execute builds. As a last step, you can change the deploy target in the MG4J build.xml file to install the MG4J into your local repository (as opposed to pushing it to Maven Central).

Answer 2

You have to add the MG4j dependency in your project pom file

<dependencies>
  [...]
  <dependency>
    <groupId>it.unimi.di</groupId>
    <artifactId>mg4j</artifactId>
    <version>5.2</version>
  </dependency>
</dependencies>

Answer 3

Try download the source code into your workspace directory, then in eclipse try Import->Maven->"Existing Maven Project" and point to source code directory of the project. Let me know if this works.

Answer 4

mvn eclipse:eclipse将创建eclipse需要的垫片，然后创建项目，您应该会很高兴。