nu.xom

## Class Serializer

- Object
- - nu.xom.Serializer

-     public class Serializer
      extends Object

  Outputs a `Document` object in a specific encoding using various options for controlling white space, normalization, indenting, line breaking, and base URIs. However, in general these options do affect the document's infoset. In particular, if you set either the maximum line length or the indent size to a positive value, then the serializer will not respect input white space. It may trim leading and trailing space, condense runs of white space to a single space, convert carriage returns and linefeeds to spaces, add extra space where none was present before, and otherwise muck with the document's white space. The defaults, however, preserve all significant white space including ignorable white space and boundary white space.

  Version:
    1.2d1
  Author:
    Elliotte Rusty Harold

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `Serializer(OutputStream out)` Create a new serializer that uses the UTF-8 encoding.
    `Serializer(OutputStream out, String encoding)` Create a new serializer that uses the specified encoding.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected void` | `breakLine()` Writes the current line break string onto the underlying output stream and indents as specified by the current level and the indent property.
    `void` | `flush()` Flushes the data onto the output stream.
    `protected int` | `getColumnNumber()` Returns the current column number of the output stream.
    `String` | `getEncoding()` Returns the name of the character encoding used by this serializer.
    `int` | `getIndent()` Returns the number of spaces this serializer indents.
    `String` | `getLineSeparator()` Returns the string used as a line separator.
    `int` | `getMaxLength()` Returns the preferred maximum line length.
    `boolean` | `getPreserveBaseURI()` Returns true if this serializer preserves the original base URIs by inserting extra `xml:base` attributes.
    `boolean` | `getUnicodeNormalizationFormC()` Indicates whether serialization will perform Unicode normalization on all data using normalization form C (NFC).
    `void` | `setIndent(int indent)` Sets the number of additional spaces to add to each successive level in the hierarchy.
    `void` | `setLineSeparator(String lineSeparator)` Sets the line separator.
    `void` | `setMaxLength(int maxLength)` Sets the suggested maximum line length for this serializer.
    `void` | `setOutputStream(OutputStream out)` Flushes the previous output stream and redirects further output to the new output stream.
    `void` | `setPreserveBaseURI(boolean preserve)` Determines whether this serializer inserts extra `xml:base` attributes to attempt to preserve base URI information from the document.
    `void` | `setUnicodeNormalizationFormC(boolean normalize)` If true, this property indicates serialization will perform Unicode normalization on all data using normalization form C (NFC).
    `protected void` | `write(Attribute attribute)` Writes an attribute in the form `name="value"`.
    `protected void` | `write(Comment comment)` Writes a comment onto the output stream using the current options.
    `protected void` | `write(DocType doctype)` Writes a `DocType` object onto the output stream using the current options.
    `void` | `write(Document doc)` Serializes a document onto the output stream using the current options.
    `protected void` | `write(Element element)` Serializes an element onto the output stream using the current options.
    `protected void` | `write(ProcessingInstruction instruction)` Writes a processing instruction onto the output stream using the current options.
    `protected void` | `write(Text text)` Writes a `Text` object onto the output stream using the current options.
    `protected void` | `writeAttributes(Element element)` Writes all the attributes of the specified element onto the output stream, one at a time, separated by white space.
    `protected void` | `writeAttributeValue(String value)` Writes a string onto the underlying output stream.
    `protected void` | `writeChild(Node node)` Writes a child node onto the output stream using the current options.
    `protected void` | `writeEmptyElementTag(Element element)` Writes an empty-element tag for the element including all its namespace declarations and attributes.
    `protected void` | `writeEndTag(Element element)` Writes the end-tag for an element in the form `</name>`.
    `protected void` | `writeEscaped(String text)` Writes a string onto the underlying output stream.
    `protected void` | `writeNamespaceDeclaration(String prefix, String uri)` Writes a namespace declaration in the form `xmlns:prefix="uri"` or `xmlns="uri"`.
    `protected void` | `writeNamespaceDeclarations(Element element)` Writes all the namespace declaration attributes of the specified element onto the output stream, one at a time, separated by white space.
    `protected void` | `writeRaw(String text)` Writes a string onto the underlying output stream.
    `protected void` | `writeStartTag(Element element)` Writes the start-tag for the element including all its namespace declarations and attributes.
    `protected void` | `writeXMLDeclaration()` Writes the XML declaration onto the output stream, followed by a line break.

    - ### Methods inherited from class Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### Serializer

          public Serializer(OutputStream out)

      Create a new serializer that uses the UTF-8 encoding.

      Parameters:
        `out` - the output stream to write the document on
      Throws:
        `NullPointerException` - if `out` is null

    - #### Serializer

          public Serializer(OutputStream out,
                            String encoding)
                     throws UnsupportedEncodingException

      Create a new serializer that uses the specified encoding. The encoding must be recognized by the Java virtual machine. If you attempt to use an encoding that the local Java virtual machine does not support, the constructor will throw an `UnsupportedEncodingException`. Currently the following encodings are recognized by XOM:

      - UTF-8
      - UTF-16
      - UTF-16BE
      - UTF-16LE
      - ISO-10646-UCS-2
      - ISO-8859-1
      - ISO-8859-2
      - ISO-8859-3
      - ISO-8859-4
      - ISO-8859-5
      - ISO-8859-6
      - ISO-8859-7
      - ISO-8859-8
      - ISO-8859-9
      - ISO-8859-10
      - ISO-8859-11 (a.k.a. TIS-620)
      - ISO-8859-13
      - ISO-8859-14
      - ISO-8859-15
      - ISO-8859-16
      - IBM037 (a.k.a. CP037, EBCDIC-CP-US, EBCDIC-CP-CA, EBCDIC-CP-WA, EBCDIC-CP-NL, and CSIBM037)
      - GB18030

      You can use encodings not in this list if the virtual machine supports them. However, they may be significantly slower than the encodings in this list.

      I've noticed Java has significant bugs in its handling of some of these encodings. In some cases such as 0x80 in Big5, XOM will escape a character that should not need to be escaped because Java can't output that character in the specified encoding, even though the output character set does contain it. :-(

      Parameters:
        `out` - the output stream to write the document on
        `encoding` - the character encoding for the serialization
      Throws:
        `NullPointerException` - if `out` or `encoding` is null
        `UnsupportedEncodingException` - if the VM does not support the requested encoding

  - ### Method Detail

    - #### setOutputStream

          public void setOutputStream(OutputStream out)
                               throws IOException

      Flushes the previous output stream and redirects further output to the new output stream.

      Parameters:
        `out` - the output stream to write the document on
      Throws:
        `NullPointerException` - if `out` is null
        `IOException` - if the previous output stream encounters an I/O error when flushed

    - #### write

          public void write(Document doc)
                     throws IOException

      Serializes a document onto the output stream using the current options.

      Parameters:
        `doc` - the `Document` to serialize
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `NullPointerException` - if `doc` is null
        `UnavailableCharacterException` - if the document contains an unescapable character (e.g. in an element name) that is not available in the current encoding

    - #### writeXMLDeclaration

          protected void writeXMLDeclaration()
                                      throws IOException

      Writes the XML declaration onto the output stream, followed by a line break.

      Throws:
        `IOException` - if the underlying output stream encounters an I/O error

    - #### write

          protected void write(Element element)
                        throws IOException

      Serializes an element onto the output stream using the current options. The result is guaranteed to be well-formed.

      If the element is empty, this method invokes `writeEmptyElementTag`. If the element is not empty, then:

      1. It calls `writeStartTag`.
      2. It passes each of the element's children to `writeChild` in order.
      3. It calls `writeEndTag`.

      It may break lines or add white space if the serializer has been configured to indent or use a maximum line length.

      Parameters:
        `element` - the `Element` to serialize
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `UnavailableCharacterException` - if the element name contains a character that is not available in the current encoding

    - #### writeEndTag

          protected void writeEndTag(Element element)
                              throws IOException

      Writes the end-tag for an element in the form `</name>`.

      Parameters:
        `element` - the element whose end-tag is written
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error

    - #### writeStartTag

          protected void writeStartTag(Element element)
                                throws IOException

      Writes the start-tag for the element including all its namespace declarations and attributes.

      The `writeAttributes` method is called to write all the non-namespace-declaration attributes. The `writeNamespaceDeclarations` method is called to write all the namespace declaration attributes.

      Parameters:
        `element` - the element whose start-tag is written
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `UnavailableCharacterException` - if the name of the element or the name of any of its attributes contains a character that is not available in the current encoding

    - #### writeEmptyElementTag

          protected void writeEmptyElementTag(Element element)
                                       throws IOException

      Writes an empty-element tag for the element including all its namespace declarations and attributes.

      The `writeAttributes` method is called to write all the non-namespace-declaration attributes. The `writeNamespaceDeclarations` method is called to write all the namespace declaration attributes.

      If subclasses don't wish empty-element tags to be used, they can override this method to simply invoke `writeStartTag` followed by `writeEndTag`.

      Parameters:
        `element` - the element whose empty-element tag is written
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `UnavailableCharacterException` - if the name of the element or the name of any of its attributes contains a character that is not available in the current encoding

    - #### writeAttributes

          protected void writeAttributes(Element element)
                                  throws IOException

      Writes all the attributes of the specified element onto the output stream, one at a time, separated by white space. If preserveBaseURI is true, and it is necessary to add an `xml:base` attribute to the element in order to preserve the base URI, then that attribute is also written here. Each individual attribute is written by invoking `write(Attribute)`.

      Parameters:
        `element` - the `Element` whose attributes are written
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `UnavailableCharacterException` - if the name of any of the element's attributes contains a character that is not available in the current encoding

    - #### writeNamespaceDeclarations

          protected void writeNamespaceDeclarations(Element element)
                                             throws IOException

      Writes all the namespace declaration attributes of the specified element onto the output stream, one at a time, separated by white space. Each individual declaration is written by invoking `writeNamespaceDeclaration`.

      Parameters:
        `element` - the `Element` whose namespace declarations are written
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `UnavailableCharacterException` - if any of the element's namespace prefixes contains a character that is not available in the current encoding

    - #### writeNamespaceDeclaration

          protected void writeNamespaceDeclaration(String prefix,
                                                   String uri)
                                            throws IOException

      Writes a namespace declaration in the form `xmlns:prefix="uri"` or `xmlns="uri"`. It does not write the spaces on either side of the namespace declaration. These are written by `writeNamespaceDeclarations`.

      Parameters:
        `prefix` - the namespace prefix; the empty string for the default namespace
        `uri` - the namespace URI
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `UnavailableCharacterException` - if the namespace prefix contains a character that is not available in the current encoding

    - #### write

          protected void write(Attribute attribute)
                        throws IOException

      Writes an attribute in the form `name="value"`. Characters in the attribute value are escaped as necessary.

      Parameters:
        `attribute` - the `Attribute` to write
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `UnavailableCharacterException` - if the attribute name contains a character that is not available in the current encoding

    - #### write

          protected void write(Comment comment)
                        throws IOException

      Writes a comment onto the output stream using the current options. Since character and entity references are not resolved in comments, comments can only be serialized when all characters they contain are available in the current encoding.

      Parameters:
        `comment` - the `Comment` to serialize
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `UnavailableCharacterException` - if the comment contains a character that is not available in the current encoding

    - #### write

          protected void write(ProcessingInstruction instruction)
                        throws IOException

      Writes a processing instruction onto the output stream using the current options. Since character and entity references are not resolved in processing instructions, processing instructions can only be serialized when all characters they contain are available in the current encoding.

      Parameters:
        `instruction` - the `ProcessingInstruction` to serialize
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `UnavailableCharacterException` - if the comment contains a character that is not available in the current encoding

    - #### write

          protected void write(Text text)
                        throws IOException

      Writes a `Text` object onto the output stream using the current options. Reserved characters such as <, > and " are escaped using the standard entity references such as `&lt;`, `&gt;`, and `&quot;`.

      Characters which cannot be encoded in the current character set (for example, Ω in ISO-8859-1) are encoded using character references.

      Parameters:
        `text` - the `Text` to serialize
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error

    - #### write

          protected void write(DocType doctype)
                        throws IOException

      Writes a `DocType` object onto the output stream using the current options.

      Parameters:
        `doctype` - the document type declaration to serialize
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `UnavailableCharacterException` - if the document type declaration contains a character that is not available in the current encoding

    - #### writeChild

          protected void writeChild(Node node)
                             throws IOException

      Writes a child node onto the output stream using the current options. It is invoked when walking the tree to serialize the entire document. It is not called, and indeed should not be called, for either the `Document` node or for attributes.

      Parameters:
        `node` - the `Node` to serialize
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error
        `XMLException` - if an `Attribute`, a `Document`, or `Namespace` is passed to this method

    - #### writeEscaped

          protected final void writeEscaped(String text)
                                     throws IOException

      Writes a string onto the underlying output stream. Non-ASCII characters that are not available in the current character set are encoded with numeric character references. The three reserved characters <, >, and & are escaped using the standard entity references `&lt;`, `&gt;`, and `&amp;`. Double and single quotes are not escaped.

      Parameters:
        `text` - the parsed character data to serialize
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error

    - #### writeAttributeValue

          protected final void writeAttributeValue(String value)
                                            throws IOException

      Writes a string onto the underlying output stream. Non-ASCII characters that are not available in the current character set are escaped using hexadecimal numeric character references. Carriage returns, line feeds, and tabs are also escaped using hexadecimal numeric character references in order to ensure their preservation on a round trip. The four reserved characters <, >, &, and " are escaped using the standard entity references `&lt;`, `&gt;`, `&amp;`, and `&quot;`. The single quote is not escaped.

      Parameters:
        `value` - the attribute value to serialize
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error

    - #### writeRaw

          protected final void writeRaw(String text)
                                 throws IOException

      Writes a string onto the underlying output stream. without escaping any characters. Non-ASCII characters that are not available in the current character set cause an `IOException`.

      Parameters:
        `text` - the `String` to serialize
      Throws:
        `IOException` - if the underlying output stream encounters an I/O error or `text` contains characters not available in the current character set

    - #### breakLine

          protected final void breakLine()
                                  throws IOException

      Writes the current line break string onto the underlying output stream and indents as specified by the current level and the indent property.

      Throws:
        `IOException` - if the underlying output stream encounters an I/O error

    - #### flush

          public void flush()
                     throws IOException

      Flushes the data onto the output stream. It is not enough to flush the output stream. You must flush the serializer object itself because it uses some internal buffering. The serializer will flush the underlying output stream.

      Throws:
        `IOException` - if the underlying output stream encounters an I/O error

    - #### getIndent

          public int getIndent()

      Returns the number of spaces this serializer indents.

      Returns:
        the number of spaces this serializer indents each successive level beyond the previous one

    - #### setIndent

          public void setIndent(int indent)

      Sets the number of additional spaces to add to each successive level in the hierarchy. Use 0 for no extra indenting. The maximum indentation is in limited to approximately half the maximum line length. The serializer will not indent further than that no matter how many levels deep the hierarchy is.

      When this variable is set to a value greater than 0, the serializer does not preserve white space. Spaces, tabs, carriage returns, and line feeds can all be interchanged at the serializer's discretion, and additional white space may be added before and after tags. Carriage returns, line feeds, and tabs will not be escaped with numeric character references.

      Inside elements with an `xml:space="preserve"` attribute, white space is preserved and no indenting takes place, regardless of the setting of the indent property, unless, of course, an `xml:space="default"` attribute overrides the `xml:space="preserve"` attribute.

      The default value for indent is 0; that is, the default is not to add or subtract any white space from the source document.

      Parameters:
        `indent` - the number of spaces to indent each successive level of the hierarchy
      Throws:
        `IllegalArgumentException` - if indent is less than zero

    - #### getLineSeparator

          public String getLineSeparator()

      Returns the string used as a line separator. This is always `"\n"`, `"\r"`, or `"\r\n"`.

      Returns:
        the line separator

    - #### setLineSeparator

          public void setLineSeparator(String lineSeparator)

      Sets the line separator. This can only be one of the three strings `"\n"`, `"\r"`, or `"\r\n"`. All other values are forbidden. If this method is invoked, then line separators in the character data will be changed to this string. Line separators in attribute values will be changed to the hexadecimal numeric character references corresponding to this string.

      The default line separator is `"\r\n"`. However, line separators in character data and attribute values are not changed to this string, unless this method is called first.

      Parameters:
        `lineSeparator` - the line separator to set
      Throws:
        `IllegalArgumentException` - if you attempt to use any line separator other than `"\n"`, `"\r"`, or `"\r\n"`.

    - #### getMaxLength

          public int getMaxLength()

      Returns the preferred maximum line length.

      Returns:
        the preferred maximum line length.

    - #### setMaxLength

          public void setMaxLength(int maxLength)

      Sets the suggested maximum line length for this serializer. Setting this to 0 indicates that no automatic wrapping is to be performed. When a line approaches this length, the serializer begins looking for opportunities to break the line. Generally it will break on any ASCII white space character (tab, carriage return, linefeed, and space). In some circumstances the serializer may not be able to break the line before the maximum length is reached. For instance, if an element name is longer than the maximum line length the only way to correctly serialize it is to exceed the maximum line length. In this case, the serializer will exceed the maximum line length.

      The default value for maximum line length is 0, which is interpreted as no maximum line length. Setting this to a negative value just sets it to 0.

      When this variable is set to a value greater than 0, the serializer does not preserve white space. Spaces, tabs, carriage returns, and line feeds can all be interchanged at the serializer's discretion. Carriage returns, line feeds, and tabs will not be escaped with numeric character references.

      Inside elements with an `xml:space="preserve"` attribute, the maximum line length is not enforced, regardless of the setting of the this property, unless, of course, an `xml:space="default"` attribute overrides the `xml:space="preserve"` attribute.

      Parameters:
        `maxLength` - the preferred maximum line length

    - #### getPreserveBaseURI

          public boolean getPreserveBaseURI()

      Returns true if this serializer preserves the original base URIs by inserting extra `xml:base` attributes.

      Returns:
        true if this `Serializer` inserts extra `xml:base` attributes to attempt to preserve base URI information from the document.

    - #### setPreserveBaseURI

          public void setPreserveBaseURI(boolean preserve)

      Determines whether this serializer inserts extra `xml:base` attributes to attempt to preserve base URI information from the document. The default is false, do not preserve base URI information. `xml:base` attributes that have been explicitly added to an element are always output. This property only determines whether or not extra `xml:base` attributes are added.

      Parameters:
        `preserve` - true if `xml:base` attributes should be added as necessary to preserve base URI information

    - #### getEncoding

          public String getEncoding()

      Returns the name of the character encoding used by this serializer.

      Returns:
        the encoding used for the output document

    - #### setUnicodeNormalizationFormC

          public void setUnicodeNormalizationFormC(boolean normalize)

      If true, this property indicates serialization will perform Unicode normalization on all data using normalization form C (NFC). Performing Unicode normalization may change the document's infoset. The default is false; do not normalize. This version is based on Unicode 4.0.

      This feature has not yet been benchmarked or optimized. It may result in substantially slower code.

      If all your data is in the first 256 code points of Unicode (i.e. the ISO-8859-1, Latin-1 character set), then it's already in normalization form C and normalizing won't change anything.

      Parameters:
        `normalize` - true if normalization is performed; false if it isn't

    - #### getUnicodeNormalizationFormC

          public boolean getUnicodeNormalizationFormC()

      Indicates whether serialization will perform Unicode normalization on all data using normalization form C (NFC). The default is false; do not normalize.

      Returns:
        true if this serializer performs Unicode normalization; false if it doesn't

    - #### getColumnNumber

          protected final int getColumnNumber()

      Returns the current column number of the output stream. This method useful for subclasses that implement their own pretty printing strategies by inserting white space and line breaks at appropriate points.

      Columns are counted based on Unicode characters, not Java chars. A surrogate pair counts as one character in this context, not two. However, a character followed by a combining character (e.g. e followed by combining accent acute) counts as two characters. This latter choice (treating combining characters like regular characters) is under review, and may change in the future if it's not too big a performance hit.

      Returns:
        the current column number

Copyright 2002-2026 Elliotte Rusty Harold
elharo@ibiblio.org