Java : Entity (XML) with Examples

Entity (Java SE 22 & JDK 22) with Examples.
You will find code examples on most Entity methods.

Summary

This interface represents a known entity, either parsed or unparsed, in an XML document. Note that this models the entity itself not the entity declaration.

Class diagram

Code examples on this page use the printDocument method below.

public void printDocument(Document document) throws TransformerException {
    final var transformer = TransformerFactory.newInstance().newTransformer();
    transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

    final var result = new StreamResult(new StringWriter());
    transformer.transform(new DOMSource(document), result);

    System.out.println(result.getWriter());
}

final var path = Path.of("R:", "java-work", "xxx");
System.out.println(path); // R:\java-work\xxx

Files.writeString(path, "yyy");

final var xml = """
        <!DOCTYPE root [
            <!ENTITY aaa "bbb">
            <!ENTITY xxx SYSTEM "file:///R:/java-work/xxx">
        ]>
        <root>
          &aaa;
          &xxx;
        </root>
        """;

final var factory = DocumentBuilderFactory.newInstance();
final var builder = factory.newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

//<root>
//  bbb
//  yyy
//</root>
printDocument(document);

final var entities = document.getDoctype().getEntities();

if (entities.getNamedItem("aaa") instanceof Entity entity) {
    System.out.println(entity); // [aaa: null]
    System.out.println(entity.getSystemId()); // null
}

if (entities.getNamedItem("xxx") instanceof Entity entity) {
    System.out.println(entity); // [xxx: null]
    System.out.println(entity.getSystemId()); // file:///R:/java-work/xxx
}

Fields declared in Node

ATTRIBUTE_NODE, CDATA_SECTION_NODE, COMMENT_NODE, DOCUMENT_FRAGMENT_NODE, DOCUMENT_NODE, DOCUMENT_POSITION_CONTAINED_BY, DOCUMENT_POSITION_CONTAINS, DOCUMENT_POSITION_DISCONNECTED, DOCUMENT_POSITION_FOLLOWING, DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC, DOCUMENT_POSITION_PRECEDING, DOCUMENT_TYPE_NODE, ELEMENT_NODE, ENTITY_NODE, ENTITY_REFERENCE_NODE, NOTATION_NODE, PROCESSING_INSTRUCTION_NODE, TEXT_NODE

Please see the link below.

Node with Examples

Methods

String getInputEncoding ()

An attribute specifying the encoding used for this entity at the time of parsing, when it is an external parsed entity.

final var path = Path.of("R:", "java-work", "xxx");
System.out.println(path); // R:\java-work\xxx

Files.writeString(path, "yyy");

final var xml = """
        <!DOCTYPE root [
            <!ENTITY aaa "bbb">
            <!ENTITY xxx SYSTEM "file:///R:/java-work/xxx">
        ]>
        <root>
          &aaa;
          &xxx;
        </root>
        """;

final var factory = DocumentBuilderFactory.newInstance();
final var builder = factory.newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

//<root>
//  bbb
//  yyy
//</root>
printDocument(document);

final var entities = document.getDoctype().getEntities();

if (entities.getNamedItem("aaa") instanceof Entity entity) {
    System.out.println(entity); // [aaa: null]
    System.out.println(entity.getInputEncoding()); // null
    System.out.println(entity.getSystemId()); // null
}

if (entities.getNamedItem("xxx") instanceof Entity entity) {
    System.out.println(entity); // [xxx: null]
    System.out.println(entity.getInputEncoding()); // UTF-8
    System.out.println(entity.getSystemId()); // file:///R:/java-work/xxx
}

String getNotationName ()

For unparsed entities, the name of the notation for the entity.

final var xml = """
        <!DOCTYPE root [
            <!ENTITY aaa SYSTEM "bbb" NDATA ccc>
        ]>
        <root/>
        """;

final var factory = DocumentBuilderFactory.newInstance();
final var builder = factory.newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

final var entities = document.getDoctype().getEntities();

if (entities.getNamedItem("aaa") instanceof Entity entity) {
    System.out.println(entity); // [aaa: null]
    System.out.println(entity.getSystemId()); // bbb
    System.out.println(entity.getNotationName()); // ccc
}

String getPublicId ()

The public identifier associated with the entity if specified, and null otherwise.

final var xml = """
        <!DOCTYPE root [
            <!ENTITY aaa PUBLIC "bbb" "ccc">
        ]>
        <root/>
        """;

final var factory = DocumentBuilderFactory.newInstance();
final var builder = factory.newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

final var entities = document.getDoctype().getEntities();

if (entities.getNamedItem("aaa") instanceof Entity entity) {
    System.out.println(entity); // [aaa: null]
    System.out.println(entity.getPublicId()); // bbb
    System.out.println(entity.getSystemId()); // ccc
}

String getSystemId ()

The system identifier associated with the entity if specified, and null otherwise.

final var path = Path.of("R:", "java-work", "xxx");
System.out.println(path); // R:\java-work\xxx

Files.writeString(path, "yyy");

final var xml = """
        <!DOCTYPE root [
            <!ENTITY aaa "bbb">
            <!ENTITY xxx SYSTEM "file:///R:/java-work/xxx">
        ]>
        <root>
          &aaa;
          &xxx;
        </root>
        """;

final var factory = DocumentBuilderFactory.newInstance();
final var builder = factory.newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

//<root>
//  bbb
//  yyy
//</root>
printDocument(document);

final var entities = document.getDoctype().getEntities();

if (entities.getNamedItem("aaa") instanceof Entity entity) {
    System.out.println(entity); // [aaa: null]
    System.out.println(entity.getInputEncoding()); // null
    System.out.println(entity.getSystemId()); // null
}

if (entities.getNamedItem("xxx") instanceof Entity entity) {
    System.out.println(entity); // [xxx: null]
    System.out.println(entity.getInputEncoding()); // UTF-8
    System.out.println(entity.getSystemId()); // file:///R:/java-work/xxx
}

String getXmlEncoding ()

An attribute specifying, as part of the text declaration, the encoding of this entity, when it is an external parsed entity.

final var path = Path.of("R:", "java-work", "xxx");
System.out.println(path); // R:\java-work\xxx

Files.writeString(path, """
        <?xml version="1.0" encoding="UTF-8"?>\
        yyy\
        """);

final var xml = """
        <!DOCTYPE root [
            <!ENTITY aaa "bbb">
            <!ENTITY xxx SYSTEM "file:///R:/java-work/xxx">
        ]>
        <root>
          &aaa;
          &xxx;
        </root>
        """;

final var factory = DocumentBuilderFactory.newInstance();
final var builder = factory.newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

//<root>
//  bbb
//  yyy
//</root>
printDocument(document);

final var entities = document.getDoctype().getEntities();

if (entities.getNamedItem("aaa") instanceof Entity entity) {
    System.out.println(entity); // [aaa: null]
    System.out.println(entity.getSystemId()); // null
    System.out.println(entity.getXmlVersion()); // null
    System.out.println(entity.getXmlEncoding()); // null
}

if (entities.getNamedItem("xxx") instanceof Entity entity) {
    System.out.println(entity); // [xxx: null]
    System.out.println(entity.getSystemId()); // file:///R:/java-work/xxx
    System.out.println(entity.getXmlVersion()); // 1.0
    System.out.println(entity.getXmlEncoding()); // UTF-8
}

final var path = Path.of("R:", "java-work", "aaa");
System.out.println(path); // R:\java-work\aaa

Files.writeString(path, """
        <?xml version="1.1" encoding="UTF-16"?>\
        bbb\
        """, StandardCharsets.UTF_16);

final var xml = """
        <?xml version="1.1" encoding="UTF-8"?>
        <!DOCTYPE root [
            <!ENTITY aaa SYSTEM "file:///R:/java-work/aaa">
        ]>
        <root>
          &aaa;
        </root>
        """;

final var factory = DocumentBuilderFactory.newInstance();
final var builder = factory.newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

//<root>
//  bbb
//</root>
printDocument(document);

final var entities = document.getDoctype().getEntities();

if (entities.getNamedItem("aaa") instanceof Entity entity) {
    System.out.println(entity); // [aaa: null]
    System.out.println(entity.getSystemId()); // file:///R:/java-work/aaa
    System.out.println(entity.getXmlVersion()); // 1.1
    System.out.println(entity.getXmlEncoding()); // UTF-16
}

String getXmlVersion ()

An attribute specifying, as part of the text declaration, the version number of this entity, when it is an external parsed entity.

final var path = Path.of("R:", "java-work", "xxx");
System.out.println(path); // R:\java-work\xxx

Files.writeString(path, """
        <?xml version="1.0" encoding="UTF-8"?>\
        yyy\
        """);

final var xml = """
        <!DOCTYPE root [
            <!ENTITY aaa "bbb">
            <!ENTITY xxx SYSTEM "file:///R:/java-work/xxx">
        ]>
        <root>
          &aaa;
          &xxx;
        </root>
        """;

final var factory = DocumentBuilderFactory.newInstance();
final var builder = factory.newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

//<root>
//  bbb
//  yyy
//</root>
printDocument(document);

final var entities = document.getDoctype().getEntities();

if (entities.getNamedItem("aaa") instanceof Entity entity) {
    System.out.println(entity); // [aaa: null]
    System.out.println(entity.getSystemId()); // null
    System.out.println(entity.getXmlVersion()); // null
    System.out.println(entity.getXmlEncoding()); // null
}

if (entities.getNamedItem("xxx") instanceof Entity entity) {
    System.out.println(entity); // [xxx: null]
    System.out.println(entity.getSystemId()); // file:///R:/java-work/xxx
    System.out.println(entity.getXmlVersion()); // 1.0
    System.out.println(entity.getXmlEncoding()); // UTF-8
}

final var path = Path.of("R:", "java-work", "aaa");
System.out.println(path); // R:\java-work\aaa

Files.writeString(path, """
        <?xml version="1.1" encoding="UTF-16"?>\
        bbb\
        """, StandardCharsets.UTF_16);

final var xml = """
        <?xml version="1.1" encoding="UTF-8"?>
        <!DOCTYPE root [
            <!ENTITY aaa SYSTEM "file:///R:/java-work/aaa">
        ]>
        <root>
          &aaa;
        </root>
        """;

final var factory = DocumentBuilderFactory.newInstance();
final var builder = factory.newDocumentBuilder();
final var document = builder.parse(new ByteArrayInputStream(xml.getBytes()));

//<root>
//  bbb
//</root>
printDocument(document);

final var entities = document.getDoctype().getEntities();

if (entities.getNamedItem("aaa") instanceof Entity entity) {
    System.out.println(entity); // [aaa: null]
    System.out.println(entity.getSystemId()); // file:///R:/java-work/aaa
    System.out.println(entity.getXmlVersion()); // 1.1
    System.out.println(entity.getXmlEncoding()); // UTF-16
}

Methods declared in Node

appendChild, cloneNode, compareDocumentPosition, getAttributes, getBaseURI, getChildNodes, getFeature, getFirstChild, getLastChild, getLocalName, getNamespaceURI, getNextSibling, getNodeName, getNodeType, getNodeValue, getOwnerDocument, getParentNode, getPrefix, getPreviousSibling, getTextContent, getUserData, hasAttributes, hasChildNodes, insertBefore, isDefaultNamespace, isEqualNode, isSameNode, isSupported, lookupNamespaceURI, lookupPrefix, normalize, removeChild, replaceChild, setNodeValue, setPrefix, setTextContent, setUserData