Calling Ant target from within custom task causes 'failed to create task or type import' error

I have created a custom Ant task as per one of my previous posts which calls an existing target in another xml file.

It seems to be doing what I want in terms of calling the build xml that I want, however, it now throws a very curious error:

build.xml:4: Problem: failed to create task or type import
Cause: The name is undefined.
Action: Check the spelling.
Action: Check that any custom tasks/types have been declared.
Action: Check that any <presetdef>/<macrodef> declarations have taken place.
    at org.apache.tools.ant.ProjectHelper.addLocationToBuildException(ProjectHelper.java:508)
    at org.apache.tools.ant.taskdefs.Ant.execute(Ant.java:369)
    at org.hardhat.task.HardHatTask.executeHardHat(HardHatTask.java:47)
    at org.hardhat.task.HardHatTask.execute(HardHatTask.java:23)
    at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:288)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)

The build xml that my custom Ant task is calling looks something like this:

<project name="myproject" default="all" basedir=".">
    <import file="includes.xml"/>

    <target name开发者_JAVA技巧="all" depends="doStuff" />
</project>

The error says the problem has to do with line 4 and the task 'import'. Any ideas as to why Ant doesn't seem to understand one of its own tasks?

---

Interestingly, it looks like the reason why it wasn't working was because my custom Ant task looked like this:

public void execute() {
    Ant ant = new Ant();
    Project project = new Project();
    project.setProperty("...", ...);
    ant.setProject(project);
    File directory = new File("...");
    ant.setDir(directory);
    ant.setAntfile("build.xml");
    ant.setTarget("all");
    ant.execute();
}

All I had to do was call getProject() instead of new Project() and the problem went away:

public void execute() {
    Ant ant = new Ant();
    Project project = getProject();
    project.setProperty("...", ...);
    ant.setProject(project);
    File directory = new File("...");
    ant.setDir(directory);
    ant.setAntfile("build.xml");
    ant.setTarget("all");
    ant.execute();
}