Mercurial API for Java?

Question

Is there a plain API to access Mercurial repositories from Java?

There are plugins for Netbeans and Eclipse, but unlike their Subversion counterparts, they do not us

Answer 1

A new option is JavaHg, which gives you a high-level Java API. The unit tests give a good example of how it is to program with it (as of JavaHg 0.1):

public void commitTest() throws IOException {
    Repository repo = getTestRepository();
    writeFile("x", "abc");

    CommitCommand commit = CommitCommand.on(repo);
    StatusCommand status = StatusCommand.on(repo);

    List statusLines = status.lines();
    Assert.assertEquals(1, statusLines.size());
    Assert.assertEquals(StatusLine.Type.UNKNOWN, statusLines.get(0).getType());

    AddCommand.on(repo).execute();
    statusLines = status.lines();
    Assert.assertEquals(1, statusLines.size());
    Assert.assertEquals(StatusLine.Type.ADDED, statusLines.get(0).getType());

    commit.message("Add a file").user("Martin Geisler");
    Changeset cset = commit.execute();
    Assert.assertEquals("Martin Geisler", cset.getUser());
    statusLines = status.lines();
    Assert.assertEquals(0, statusLines.size());
}

It interacts with the Mercurial command server present in version 1.9 and later. This means that there will be a persistent Mercurial process around that accepts multiple commands and so you avoid the startup overhead normally associated with launching Mercurial. We expect that it will be used in a coming version of MercurialEclipse. (I'm one of the authors of JavaHg.)