CODEWITHSUNDEEP
javamaven
mahesh
mahesh

Reputation: 1633

Why modelVersion of pom.xml is necessary and always set to 4.0.0?

I have noticed that Maven's <modelVersion></modelVersion> of pom.xml is always set to 4.0.0.

Can you please help me understand what is the importance of this tag and why it should be set to 4.0.0?

Upvotes: 125

Views: 59511

Answers (4)

Boj
Boj

Reputation: 4053

It is always set to 4.0.0 in Maven 2 and 3, because, at present, there is no other model.

Notice that modelVersion contains 4.0.0. That is currently the only supported POM version, and is always required. [source]

But it wouldn't necessarily need to always be set to 4.0.0 if there was another version of the model. A POM has to comply with a model. Let's say Maven 4 comes up with model 4.1. If you write your pom to comply with 4.1, it wouldn't be compatible with Maven 3 and model 4.0.0.

It's defined as a mandatory, possibly to enforce a specific XML model in case new models are defined.

Upvotes: 113

Nilotpal
Nilotpal

Reputation: 3588

modelVersion - containing the model version of the POM. Maven 1.x used a model which contained a 3.0.0 element as an immediate child of the root. Maven 2.x / 3.x has used a 4.0.0 element.

version - containing the version of the project. If this attribute is missing then the parent element must be present and the version will be inherited from the parent project.

Upvotes: 7

Asanke
Asanke

Reputation: 601

The Correct answer should be the combination of the answers by @Toumi and @Boj. Also have a look at https://cwiki.apache.org/confluence/display/MAVEN/POM+Model+Version+5.0.0 for more background of this.

Upvotes: 7

Toumi
Toumi

Reputation: 3155

model version is the version of project descriptor your POM conforms to. It needs to be included and is set. The value 4.0.0 just indicated that it is compatible Maven 3.

Upvotes: 13

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