https://ant.apache.org/: master POM (The Apache Software Foundation) 
/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package org.apache.tools.ant.types;

import java.util.Stack;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.ComponentHelper;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.ProjectComponent;
import org.apache.tools.ant.util.IdentityStack;


Base class for those classes that can appear inside the build file
as stand alone data types.

This class handles the common description attribute and provides
a default implementation for reference handling and checking for
circular references that is appropriate for types that can not be
nested inside elements of the same type (i.e. <patternset>
but not <path>).


/**
 * Base class for those classes that can appear inside the build file
 * as stand alone data types.
 *
 * <p>This class handles the common description attribute and provides
 * a default implementation for reference handling and checking for
 * circular references that is appropriate for types that can not be
 * nested inside elements of the same type (i.e. &lt;patternset&gt;
 * but not &lt;path&gt;).</p>
 *
 */
public abstract class DataType extends ProjectComponent implements Cloneable {
    // CheckStyle:VisibilityModifier OFF

    
Value to the refid attribute.

Deprecated:since 1.7. The user should not be directly referencing variable. Please use getRefid instead.
/**
     * Value to the refid attribute.
     *
     * @deprecated since 1.7.
     *             The user should not be directly referencing
     *             variable. Please use {@link #getRefid} instead.
     */
    @Deprecated
    protected Reference ref;

    
Are we sure we don't hold circular references?

Subclasses are responsible for setting this value to false
if we'd need to investigate this condition (usually because a
child element has been added that is a subclass of
DataType).


Deprecated:since 1.7. The user should not be directly referencing variable. Please use setChecked or isChecked instead.
/**
     * Are we sure we don't hold circular references?
     *
     * <p>Subclasses are responsible for setting this value to false
     * if we'd need to investigate this condition (usually because a
     * child element has been added that is a subclass of
     * DataType).</p>
     *
     * @deprecated since 1.7.
     *             The user should not be directly referencing
     *             variable. Please use {@link #setChecked} or
     *             {@link #isChecked} instead.
     */
    @Deprecated
    protected boolean checked = true;
    // CheckStyle:VisibilityModifier ON

    
Has the refid attribute of this element been set?

Returns:true if the refid attribute has been set
/**
     * Has the refid attribute of this element been set?
     * @return true if the refid attribute has been set
     */
    public boolean isReference() {
        return ref != null;
    }

    
Set the value of the refid attribute.

Subclasses may need to check whether any other attributes
have been set as well or child elements have been created and
thus override this method. if they do the must call
super.setRefid.


Params:
  • ref – the reference to use
/**
     * Set the value of the refid attribute.
     *
     * <p>Subclasses may need to check whether any other attributes
     * have been set as well or child elements have been created and
     * thus override this method. if they do the must call
     * <code>super.setRefid</code>.</p>
     * @param ref the reference to use
     */
    public void setRefid(final Reference ref) {
        this.ref = ref;
        checked = false;
    }

    
Gets as descriptive as possible a name used for this datatype instance.

Returns:String name.
/**
     * Gets as descriptive as possible a name used for this datatype instance.
     * @return <code>String</code> name.
     */
    protected String getDataTypeName() {
        return ComponentHelper.getElementName(getProject(), this, true);
    }

    
Convenience method.

Since:Ant 1.7
/**
     * Convenience method.
     * @since Ant 1.7
     */
    protected void dieOnCircularReference() {
        dieOnCircularReference(getProject());
    }

    
Convenience method.

Params:
  • p – the Ant Project instance against which to resolve references.
Since:Ant 1.7
/**
     * Convenience method.
     * @param p the Ant Project instance against which to resolve references.
     * @since Ant 1.7
     */
    protected void dieOnCircularReference(Project p) {
        if (checked || !isReference()) {
            return;
        }
        dieOnCircularReference(new IdentityStack<>(this), p);
    }

    
Check to see whether any DataType we hold references to is
included in the Stack (which holds all DataType instances that
directly or indirectly reference this instance, including this
instance itself).

If one is included, throw a BuildException created by circularReference.


This implementation is appropriate only for a DataType that
cannot hold other DataTypes as children.


The general contract of this method is that it shouldn't do anything if checked is true and set it to true on exit.


Params:
  • stack – the stack of references to check.
  • project – the project to use to dereference the references.
Throws:
/**
     * Check to see whether any DataType we hold references to is
     * included in the Stack (which holds all DataType instances that
     * directly or indirectly reference this instance, including this
     * instance itself).
     *
     * <p>If one is included, throw a BuildException created by {@link
     * #circularReference circularReference}.</p>
     *
     * <p>This implementation is appropriate only for a DataType that
     * cannot hold other DataTypes as children.</p>
     *
     * <p>The general contract of this method is that it shouldn't do
     * anything if {@link #checked} is true and
     * set it to true on exit.</p>
     * @param stack the stack of references to check.
     * @param project the project to use to dereference the references.
     * @throws BuildException on error.
     */
    protected void dieOnCircularReference(final Stack<Object> stack,
                                          final Project project)
        throws BuildException {

        if (checked || !isReference()) {
            return;
        }
        Object o = ref.getReferencedObject(project);

        if (o instanceof DataType) {
            IdentityStack<Object> id = IdentityStack.getInstance(stack);

            if (id.contains(o)) {
                throw circularReference();
            } else {
                id.push(o);
                ((DataType) o).dieOnCircularReference(id, project);
                id.pop();
            }
        }
        checked = true;
    }

    
Allow DataTypes outside org.apache.tools.ant.types to indirectly call
dieOnCircularReference on nested DataTypes.

Params:
  • dt – the DataType to check.
  • stk – the stack of references to check.
  • p – the project to use to dereference the references.
Throws:
Since:Ant 1.7
/**
     * Allow DataTypes outside org.apache.tools.ant.types to indirectly call
     * dieOnCircularReference on nested DataTypes.
     * @param dt the DataType to check.
     * @param stk the stack of references to check.
     * @param p the project to use to dereference the references.
     * @throws BuildException on error.
     * @since Ant 1.7
     */
    public static void invokeCircularReferenceCheck(DataType dt, Stack<Object> stk,
                                                    Project p) {
        dt.dieOnCircularReference(stk, p);
    }

    
Allow DataTypes outside org.apache.tools.ant.types to indirectly call
dieOnCircularReference on nested DataTypes.

Pushes dt on the stack, runs dieOnCircularReference and pops
it again.


Params:
  • dt – the DataType to check.
  • stk – the stack of references to check.
  • p – the project to use to dereference the references.
Throws:
Since:Ant 1.8.0
/**
     * Allow DataTypes outside org.apache.tools.ant.types to indirectly call
     * dieOnCircularReference on nested DataTypes.
     *
     * <p>Pushes dt on the stack, runs dieOnCircularReference and pops
     * it again.</p>
     * @param dt the DataType to check.
     * @param stk the stack of references to check.
     * @param p the project to use to dereference the references.
     * @throws BuildException on error.
     * @since Ant 1.8.0
     */
    public static void pushAndInvokeCircularReferenceCheck(DataType dt,
                                                           Stack<Object> stk,
                                                           Project p) {
        stk.push(dt);
        dt.dieOnCircularReference(stk, p);
        stk.pop();
    }

    
Performs the check for circular references and returns the
referenced object.

Type parameters:
  • <T> – required reference type
Throws:
  • BuildException – if the reference is invalid (circular ref, wrong class, etc).
Returns:the dereferenced object.
Since:Ant 1.7
Deprecated:use getCheckedRef(Class)
/**
     * Performs the check for circular references and returns the
     * referenced object.
     * @param <T> required reference type
     * @return the dereferenced object.
     * @throws BuildException if the reference is invalid (circular ref, wrong class, etc).
     * @since Ant 1.7
     * @deprecated use getCheckedRef(Class)
     */
    @Deprecated
    protected <T> T getCheckedRef() {
        return getCheckedRef(getProject());
    }

    
Performs the check for circular references and returns the
referenced object.

Params:
  • requiredClass – the class that this reference should be a subclass of.
Type parameters:
  • <T> – required reference type
Throws:
  • BuildException – if the reference is invalid (circular ref, wrong class, etc).
Returns:the dereferenced object.
Since:Ant 1.10.6
/**
     * Performs the check for circular references and returns the
     * referenced object.
     * @param <T> required reference type
     * @param requiredClass the class that this reference should be a subclass of.
     * @return the dereferenced object.
     * @throws BuildException if the reference is invalid (circular ref, wrong class, etc).
     * @since Ant 1.10.6
     */
    protected <T> T getCheckedRef(final Class<T> requiredClass) {
        return getCheckedRef(requiredClass, getDataTypeName(), getProject());
    }

    
Performs the check for circular references and returns the
referenced object.

Params:
  • p – the Ant Project instance against which to resolve references.
Type parameters:
  • <T> – required reference type
Throws:
  • BuildException – if the reference is invalid (circular ref, wrong class, etc).
Returns:the dereferenced object.
Since:Ant 1.7
Deprecated:use getCheckedRef(Class)
/**
     * Performs the check for circular references and returns the
     * referenced object.
     * @param <T> required reference type
     * @param p the Ant Project instance against which to resolve references.
     * @return the dereferenced object.
     * @throws BuildException if the reference is invalid (circular ref, wrong class, etc).
     * @since Ant 1.7
     * @deprecated use getCheckedRef(Class)
     */
    @Deprecated
    @SuppressWarnings("unchecked")
    protected <T> T getCheckedRef(Project p) {
        return getCheckedRef((Class<T>) getClass(), getDataTypeName(), p);
    }

    
Performs the check for circular references and returns the
referenced object.

Params:
  • requiredClass – the class that this reference should be a subclass of.
  • dataTypeName –  the name of the datatype that the reference should be
                     (error message use only).
Type parameters:
  • <T> – required reference type
Throws:
  • BuildException – if the reference is invalid (circular ref, wrong class, etc).
Returns:the dereferenced object.
/**
     * Performs the check for circular references and returns the
     * referenced object.
     * @param <T> required reference type
     * @param requiredClass the class that this reference should be a subclass of.
     * @param dataTypeName  the name of the datatype that the reference should be
     *                      (error message use only).
     * @return the dereferenced object.
     * @throws BuildException if the reference is invalid (circular ref, wrong class, etc).
     */
    protected <T> T getCheckedRef(final Class<T> requiredClass,
                                   final String dataTypeName) {
        return getCheckedRef(requiredClass, dataTypeName, getProject());
    }

    
Performs the check for circular references and returns the
referenced object.  This version allows the fallback Project instance to be specified.

Params:
  • requiredClass – the class that this reference should be a subclass of.
  • dataTypeName –  the name of the datatype that the reference should be
                     (error message use only).
  • project –       the fallback Project instance for dereferencing.
Type parameters:
  • <T> – required reference type
Throws:
  • BuildException – if the reference is invalid (circular ref, wrong class, etc),
                       or if project is null.
Returns:the dereferenced object.
Since:Ant 1.7
/**
     * Performs the check for circular references and returns the
     * referenced object.  This version allows the fallback Project instance to be specified.
     * @param <T> required reference type
     * @param requiredClass the class that this reference should be a subclass of.
     * @param dataTypeName  the name of the datatype that the reference should be
     *                      (error message use only).
     * @param project       the fallback Project instance for dereferencing.
     * @return the dereferenced object.
     * @throws BuildException if the reference is invalid (circular ref, wrong class, etc),
     *                        or if <code>project</code> is <code>null</code>.
     * @since Ant 1.7
     */
    protected <T> T getCheckedRef(final Class<T> requiredClass,
                                  final String dataTypeName, final Project project) {
        if (project == null) {
            throw new BuildException("No Project specified");
        }
        dieOnCircularReference(project);
        T o = ref.getReferencedObject(project);
        if (requiredClass.isAssignableFrom(o.getClass())) {
            return o;
        }
        log("Class " + displayName(o.getClass())
                        + " is not a subclass of "
                        + displayName(requiredClass),
                Project.MSG_VERBOSE);
        throw new BuildException(ref.getRefId() + " doesn\'t denote a " + dataTypeName);
    }

    
Creates an exception that indicates that refid has to be the
only attribute if it is set.

Returns:the exception to throw
/**
     * Creates an exception that indicates that refid has to be the
     * only attribute if it is set.
     * @return the exception to throw
     */
    protected BuildException tooManyAttributes() {
        return new BuildException("You must not specify more than one "
            + "attribute when using refid");
    }

    
Creates an exception that indicates that this XML element must
not have child elements if the refid attribute is set.

Returns:the exception to throw
/**
     * Creates an exception that indicates that this XML element must
     * not have child elements if the refid attribute is set.
     * @return the exception to throw
     */
    protected BuildException noChildrenAllowed() {
        return new BuildException("You must not specify nested elements "
            + "when using refid");
    }

    
Creates an exception that indicates the user has generated a
loop of data types referencing each other.

Returns:the exception to throw
/**
     * Creates an exception that indicates the user has generated a
     * loop of data types referencing each other.
     * @return the exception to throw
     */
    protected BuildException circularReference() {
        return new BuildException("This data type contains a circular "
            + "reference.");
    }

    
The flag that is used to indicate that circular references have been checked.

Returns:true if circular references have been checked
/**
     * The flag that is used to indicate that circular references have been checked.
     * @return true if circular references have been checked
     */
    protected boolean isChecked() {
        return checked;
    }

    
Set the flag that is used to indicate that circular references have been checked.

Params:
  • checked – if true, if circular references have been checked
/**
     * Set the flag that is used to indicate that circular references have been checked.
     * @param checked if true, if circular references have been checked
     */
    protected void setChecked(final boolean checked) {
        this.checked = checked;
    }

    
get the reference set on this object

Returns:the reference or null
/**
     * get the reference set on this object
     * @return the reference or null
     */
    public Reference getRefid() {
        return ref;
    }

    
check that it is ok to set attributes, i.e that no reference is defined

Throws:
Since:Ant 1.6
/**
     * check that it is ok to set attributes, i.e that no reference is defined
     * @since Ant 1.6
     * @throws BuildException if not allowed
     */
    protected void checkAttributesAllowed() {
        if (isReference()) {
            throw tooManyAttributes();
        }
    }

    
check that it is ok to add children, i.e that no reference is defined

Throws:
Since:Ant 1.6
/**
     * check that it is ok to add children, i.e that no reference is defined
     * @since Ant 1.6
     * @throws BuildException if not allowed
     */
    protected void checkChildrenAllowed() {
        if (isReference()) {
            throw noChildrenAllowed();
        }
    }

    
Basic DataType toString().

Returns:this DataType formatted as a String.
/**
     * Basic DataType toString().
     * @return this DataType formatted as a String.
     */
    @Override
    public String toString() {
        String d = getDescription();
        return d == null ? getDataTypeName() : getDataTypeName() + " " + d;
    }

    
Throws:
Since:Ant 1.7
Returns:a shallow copy of this DataType.
/**
     * @since Ant 1.7
     * @return a shallow copy of this DataType.
     * @throws CloneNotSupportedException if there is a problem.
     */
    @Override
    public Object clone() throws CloneNotSupportedException {
        DataType dt = (DataType) super.clone();
        dt.setDescription(getDescription());
        if (getRefid() != null) {
            dt.setRefid(getRefid());
        }
        dt.setChecked(isChecked());
        return dt;
    }

    private String displayName(Class<?> clazz) {
        return clazz.getName() + " (loaded via " + clazz.getClassLoader() + ")";
    }
}