Ordinary project into a maven project, there are two solutions. See below
The first:
The first step: Check whether the project pom.xml file, if not create one, fill out the content (that is, its dependencies)
Step Two: Right pom.xml file, click on the Add as Maven Project, wait maven download jar package, complete.
Figure:
The second:
The first step: check whether the project for the pom file, not first create and then fill in the content.
Step Two: Right-click on the item and then select Add Framework Support, shown below:
The third step: find maven checked, click ok, wait for the project to build.
Step four: Complete.