import com.sun.org.apache.xerces.internal.impl.xs.XSImplementationImpl; //导入依赖的package包/类
/**
 * A method to request a DOM implementation.
 * @param features A string that specifies which features are required.
 *   This is a space separated list in which each feature is specified
 *   by its name optionally followed by a space and a version number.
 *   This is something like: "XML 1.0 Traversal Events 2.0"
 * @return An implementation that has the desired features, or
 *   <code>null</code> if this source has none.
 */
public DOMImplementation getDOMImplementation(String features) {
    DOMImplementation impl = super.getDOMImplementation(features);
    if (impl != null){
        return impl;
    }
    // if not try the PSVIDOMImplementation
    impl = PSVIDOMImplementationImpl.getDOMImplementation();
    if (testImpl(impl, features)) {
        return impl;
    }
    // if not try the XSImplementation
    impl = XSImplementationImpl.getDOMImplementation();
    if (testImpl(impl, features)) {
        return impl;
    }

    return null;
}
 

import com.sun.org.apache.xerces.internal.impl.xs.XSImplementationImpl; //导入依赖的package包/类
/**
 * A method to request a list of DOM implementations that support the
 * specified features and versions, as specified in .
 * @param features A string that specifies which features and versions
 *   are required. This is a space separated list in which each feature
 *   is specified by its name optionally followed by a space and a
 *   version number. This is something like: "XML 3.0 Traversal +Events
 *   2.0"
 * @return A list of DOM implementations that support the desired
 *   features.
 */
public DOMImplementationList getDOMImplementationList(String features) {
    final Vector implementations = new Vector();

    // first check whether the CoreDOMImplementation would do
    DOMImplementationList list = super.getDOMImplementationList(features);
    //Add core DOMImplementations
    for (int i=0; i < list.getLength(); i++ ) {
        implementations.addElement(list.item(i));
    }

    DOMImplementation impl = PSVIDOMImplementationImpl.getDOMImplementation();
    if (testImpl(impl, features)) {
        implementations.addElement(impl);
    }

    impl = XSImplementationImpl.getDOMImplementation();
    if (testImpl(impl, features)) {
        implementations.addElement(impl);
    }
    return new DOMImplementationListImpl(implementations);
}