Makes writing XML much much easier
/*
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*
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*
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* distribution.
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* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org /)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
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import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.util.Stack;
/**
* Makes writing XML much much easier.
* Improved from
* <a href="http://builder.com.com/article.jhtml?id=u00220020318yan01.htm&page=1&vf=tt">article</a>
*
* @author <a href="mailto:bayard@apache.org">Henri Yandell</a>
* @author <a href="mailto:pete@fingertipsoft.com">Peter Cassetta</a>
* @author Last changed by: $Author: gommma $
* @version $Revision: 859 $ $Date: 2008-11-02 12:50:23 +0100 (dom, 02 nov 2008) $
* @since 1.0
*/
public class XmlWriter
{
/**
* CDATA start tag: {@value}
*/
public static final String CDATA_START = "<![CDATA[";
/**
* CDATA end tag: {@value}
*/
public static final String CDATA_END = "]]>";
/**
* Default encoding value which is {@value}
*/
public static final String DEFAULT_ENCODING = "UTF-8";
/**
* Logger for this class
*/
private Writer out; // underlying writer
private String encoding; // the encoding to be written into the XML header/metatag
private Stack stack = new Stack(); // of xml element names
private StringBuffer attrs; // current attribute string
private boolean empty; // is the current node empty
private boolean closed = true; // is the current node closed...
private boolean pretty = true; // is pretty printing enabled?
/**
* was text the last thing output?
*/
private boolean wroteText = false;
/**
* output this to indent one level when pretty printing
*/
private String indent = " ";
/**
* output this to end a line when pretty printing
*/
private String newline = "\n";
/**
* Create an XmlWriter on top of an existing java.io.Writer.
*/
public XmlWriter(Writer writer)
{
this(writer, null);
}
/**
* Create an XmlWriter on top of an existing java.io.Writer.
*/
public XmlWriter(Writer writer, String encoding)
{
setWriter(writer, encoding);
}
/**
* Create an XmlWriter on top of an existing {@link java.io.OutputStream}.
* @param outputStream
* @param encoding The encoding to be used for writing to the given output
* stream. Can be null. If it is null the
* {@link #DEFAULT_ENCODING} is used.
* @throws UnsupportedEncodingException
* @since 2.4
*/
public XmlWriter(OutputStream outputStream, String encoding)
throws UnsupportedEncodingException
{
if(encoding==null)
{
encoding = DEFAULT_ENCODING;
}
OutputStreamWriter writer = new OutputStreamWriter(outputStream, encoding);
setWriter(writer, encoding);
}
/**
* Turn pretty printing on or off.
* Pretty printing is enabled by default, but it can be turned off
* to generate more compact XML.
*
* @param enable true to enable, false to disable pretty printing.
*/
public void enablePrettyPrint(boolean enable)
{
this.pretty = enable;
}
/**
* Specify the string to prepend to a line for each level of indent.
* It is 2 spaces (" ") by default. Some may prefer a single tab ("\t")
* or a different number of spaces. Specifying an empty string will turn
* off indentation when pretty printing.
*
* @param indent representing one level of indentation while pretty printing.
*/
public void setIndent(String indent)
{
this.indent = indent;
}
/**
* Specify the string used to terminate each line when pretty printing.
* It is a single newline ("\n") by default. Users who need to read
* generated XML documents in Windows editors like Notepad may wish to
* set this to a carriage return/newline sequence ("\r\n"). Specifying
* an empty string will turn off generation of line breaks when pretty
* printing.
*
* @param newline representing the newline sequence when pretty printing.
*/
public void setNewline(String newline)
{
this.newline = newline;
}
/**
* A helper method. It writes out an element which contains only text.
*
* @param name String name of tag
* @param text String of text to go inside the tag
*/
public XmlWriter writeElementWithText(String name, String text) throws IOException
{
writeElement(name);
writeText(text);
return endElement();
}
/**
* A helper method. It writes out empty entities.
*
* @param name String name of tag
*/
public XmlWriter writeEmptyElement(String name) throws IOException
{
writeElement(name);
return endElement();
}
/**
* Begin to write out an element. Unlike the helper tags, this tag
* will need to be ended with the endElement method.
*
* @param name String name of tag
*/
public XmlWriter writeElement(String name) throws IOException
{
return openElement(name);
}
/**
* Begin to output an element.
*
* @param name name of element.
*/
private XmlWriter openElement(String name) throws IOException
{
boolean wasClosed = this.closed;
closeOpeningTag();
this.closed = false;
if (this.pretty)
{
// ! wasClosed separates adjacent opening tags by a newline.
// this.wroteText makes sure an element embedded within the text of
// its parent element begins on a new line, indented to the proper
// level. This solves only part of the problem of pretty printing
// entities which contain both text and child entities.
if (!wasClosed || this.wroteText)
{
this.out.write(newline);
}
for (int i = 0; i < this.stack.size(); i++)
{
this.out.write(indent); // Indent opening tag to proper level
}
}
this.out.write("<");
this.out.write(name);
stack.add(name);
this.empty = true;
this.wroteText = false;
return this;
}
// close off the opening tag
private void closeOpeningTag() throws IOException
{
if (!this.closed)
{
writeAttributes();
this.closed = true;
this.out.write(">");
}
}
// write out all current attributes
private void writeAttributes() throws IOException
{
if (this.attrs != null)
{
this.out.write(this.attrs.toString());
this.attrs.setLength(0);
this.empty = false;
}
}
/**
* Write an attribute out for the current element.
* Any XML characters in the value are escaped.
* Currently it does not actually throw the exception, but
* the API is set that way for future changes.
*
* @param attr name of attribute.
* @param value value of attribute.
* @see #writeAttribute(String, String, boolean)
*/
public XmlWriter writeAttribute(String attr, String value) throws IOException
{
return this.writeAttribute(attr, value, false);
}
/**
* Write an attribute out for the current element.
* Any XML characters in the value are escaped.
* Currently it does not actually throw the exception, but
* the API is set that way for future changes.
*
* @param attr name of attribute.
* @param value value of attribute.
* @param literally If the writer should be literally on the given value
* which means that meta characters will also be preserved by escaping them.
* Mainly preserves newlines and tabs.
*/
public XmlWriter writeAttribute(String attr, String value, boolean literally) throws IOException
{
if(this.wroteText==true) {
throw new IllegalStateException("The text for the current element has already been written. Cannot add attributes afterwards.");
}
// maintain API
if (false) throw new IOException();
if (this.attrs == null)
{
this.attrs = new StringBuffer();
}
this.attrs.append(" ");
this.attrs.append(attr);
this.attrs.append("=\"");
String val = escapeXml(value);
if(literally){
val = escapeMetaCharacters(val);
}
this.attrs.append(val);
this.attrs.append("\"");
return this;
}
/**
* End the current element. This will throw an exception
* if it is called when there is not a currently open
* element.
*/
public XmlWriter endElement() throws IOException
{
if (this.stack.empty())
{
throw new IOException("Called endElement too many times. ");
}
String name = (String)this.stack.pop();
if (name != null)
{
if (this.empty)
{
writeAttributes();
this.out.write("/>");
}
else
{
if (this.pretty && !this.wroteText)
{
for (int i = 0; i < this.stack.size(); i++)
{
this.out.write(indent); // Indent closing tag to proper level
}
}
this.out.write("</");
this.out.write(name);
this.out.write(">");
}
if (this.pretty)
this.out.write(newline); // Add a newline after the closing tag
this.empty = false;
this.closed = true;
this.wroteText = false;
}
return this;
}
/**
* Close this writer. It does not close the underlying
* writer, but does throw an exception if there are
* as yet unclosed tags.
*/
public void close() throws IOException
{
this.out.flush();
if (!this.stack.empty())
{
throw new IOException("Tags are not all closed. " +
"Possibly, " + this.stack.pop() + " is unclosed. ");
}
}
/**
* Output body text. Any XML characters are escaped.
* @param text The text to be written
* @return This writer
* @throws IOException
* @see #writeText(String, boolean)
*/
public XmlWriter writeText(String text) throws IOException
{
return this.writeText(text, false);
}
/**
* Output body text. Any XML characters are escaped.
* @param text The text to be written
* @param literally If the writer should be literally on the given value
* which means that meta characters will also be preserved by escaping them.
* Mainly preserves newlines and tabs.
* @return This writer
* @throws IOException
*/
public XmlWriter writeText(String text, boolean literally) throws IOException
{
closeOpeningTag();
this.empty = false;
this.wroteText = true;
String val = escapeXml(text);
if(literally){
val = escapeMetaCharacters(val);
}
this.out.write(val);
return this;
}
/**
* Write out a chunk of CDATA. This helper method surrounds the
* passed in data with the CDATA tag.
*
* @param cdata of CDATA text.
*/
public XmlWriter writeCData(String cdata) throws IOException
{
closeOpeningTag();
boolean hasAlreadyEnclosingCdata = cdata.startsWith(CDATA_START) && cdata.endsWith(CDATA_END);
// There may already be CDATA sections inside the data.
// But CDATA sections can't be nested - can't have ]]> inside a CDATA section.
// (See http://www.w3.org/TR/REC-xml/#NT-CDStart in the W3C specs)
// The solutions is to replace any occurrence of "]]>" by "]]]]><![CDATA[>",
// so that the top CDATA section is split into many valid CDATA sections (you
// can look at the "]]]]>" as if it was an escape sequence for "]]>").
if(!hasAlreadyEnclosingCdata) {
cdata = cdata.replaceAll(CDATA_END, "]]]]><![CDATA[>");
}
this.empty = false;
this.wroteText = true;
if(!hasAlreadyEnclosingCdata)
this.out.write(CDATA_START);
this.out.write(cdata);
if(!hasAlreadyEnclosingCdata)
this.out.write(CDATA_END);
return this;
}
/**
* Write out a chunk of comment. This helper method surrounds the
* passed in data with the XML comment tag.
*
* @param comment of text to comment.
*/
public XmlWriter writeComment(String comment) throws IOException
{
writeChunk("<!-- " + comment + " -->");
return this;
}
private void writeChunk(String data) throws IOException
{
closeOpeningTag();
this.empty = false;
if (this.pretty && !this.wroteText)
{
for (int i = 0; i < this.stack.size(); i++)
{
this.out.write(indent);
}
}
this.out.write(data);
if (this.pretty)
{
this.out.write(newline);
}
}
// Two example methods. They should output the same XML:
// <person name="fred" age="12"><phone>425343</phone><bob/></person>
static public void main(String[] args) throws IOException
{
test1();
test2();
}
static public void test1() throws IOException
{
Writer writer = new java.io.StringWriter();
XmlWriter xmlwriter = new XmlWriter(writer);
xmlwriter.writeElement("person").writeAttribute("name", "fred").writeAttribute("age", "12").writeElement("phone").writeText("4254343").endElement().writeElement("friends").writeElement("bob").endElement().writeElement("jim").endElement().endElement().endElement();
xmlwriter.close();
System.err.println(writer.toString());
}
static public void test2() throws IOException
{
Writer writer = new java.io.StringWriter();
XmlWriter xmlwriter = new XmlWriter(writer);
xmlwriter.writeComment("Example of XmlWriter running");
xmlwriter.writeElement("person");
xmlwriter.writeAttribute("name", "fred");
xmlwriter.writeAttribute("age", "12");
xmlwriter.writeElement("phone");
xmlwriter.writeText("4254343");
xmlwriter.endElement();
xmlwriter.writeComment("Examples of empty tags");
// xmlwriter.setDefaultNamespace("test");
xmlwriter.writeElement("friends");
xmlwriter.writeEmptyElement("bob");
xmlwriter.writeEmptyElement("jim");
xmlwriter.endElement();
xmlwriter.writeElementWithText("foo", "This is an example.");
xmlwriter.endElement();
xmlwriter.close();
System.err.println(writer.toString());
}
////////////////////////////////////////////////////////////////////////////
// Added for DbUnit
/**
* Escapes some meta characters like \n, \r that should be preserved in the XML
* so that a reader will not filter out those symbols.
* @param str The string to be escaped
* @return The escaped string
* @since 2.3.0
*/
private String escapeMetaCharacters(String str)
{
// 2. Do additional escapes. See http://www.w3.org/TR/2004/REC-xml-20040204/#AVNormalize
str = replace(str, "\n", "
"); // linefeed (LF)
str = replace(str, "\r", "
"); // carriage return (CR)
return str;
}
private String escapeXml(String str)
{
str = replace(str, "&", "&");
str = replace(str, "<", "<");
str = replace(str, ">", ">");
str = replace(str, "\"", """);
str = replace(str, "'", "'");
str = replace(str, "\t", "	"); // tab
return str;
}
private String replace(String value, String original, String replacement)
{
StringBuffer buffer = null;
int startIndex = 0;
int lastEndIndex = 0;
for (; ;)
{
startIndex = value.indexOf(original, lastEndIndex);
if (startIndex == -1)
{
if (buffer != null)
{
buffer.append(value.substring(lastEndIndex));
}
break;
}
if (buffer == null)
{
buffer = new StringBuffer((int)(original.length() * 1.5));
}
buffer.append(value.substring(lastEndIndex, startIndex));
buffer.append(replacement);
lastEndIndex = startIndex + original.length();
}
return buffer == null ? value : buffer.toString();
}
private void setEncoding(String encoding)
{
if (encoding == null && out instanceof OutputStreamWriter)
encoding = ((OutputStreamWriter)out).getEncoding();
if (encoding != null)
{
encoding = encoding.toUpperCase();
// Use official encoding names where we know them,
// avoiding the Java-only names. When using common
// encodings where we can easily tell if characters
// are out of range, we'll escape out-of-range
// characters using character refs for safety.
// I _think_ these are all the main synonyms for these!
if ("UTF8".equals(encoding))
{
encoding = "UTF-8";
}
else if ("US-ASCII".equals(encoding)
|| "ASCII".equals(encoding))
{
// dangerMask = (short)0xff80;
encoding = "US-ASCII";
}
else if ("ISO-8859-1".equals(encoding)
|| "8859_1".equals(encoding)
|| "ISO8859_1".equals(encoding))
{
// dangerMask = (short)0xff00;
encoding = "ISO-8859-1";
}
else if ("UNICODE".equals(encoding)
|| "UNICODE-BIG".equals(encoding)
|| "UNICODE-LITTLE".equals(encoding))
{
encoding = "UTF-16";
// TODO: UTF-16BE, UTF-16LE ... no BOM; what
// release of JDK supports those Unicode names?
}
// if (dangerMask != 0)
// stringBuf = new StringBuffer();
}
this.encoding = encoding;
}
/**
* Resets the handler to write a new text document.
*
* @param writer XML text is written to this writer.
* @param encoding if non-null, and an XML declaration is written,
* this is the name that will be used for the character encoding.
*
* @exception IllegalStateException if the current
* document hasn't yet ended (i.e. the output stream {@link #out} is not null)
*/
final public void setWriter(Writer writer, String encoding)
{
if (this.out != null)
throw new IllegalStateException(
"can't change stream in mid course");
this.out = writer;
if (this.out != null)
setEncoding(encoding);
// if (!(this.out instanceof BufferedWriter))
// this.out = new BufferedWriter(this.out);
}
public XmlWriter writeDeclaration() throws IOException
{
if (this.encoding != null)
{
this.out.write("<?xml version='1.0'");
this.out.write(" encoding='" + this.encoding + "'");
this.out.write("?>");
this.out.write(this.newline);
}
return this;
}
public XmlWriter writeDoctype(String systemId, String publicId) throws IOException
{
if (systemId != null || publicId != null)
{
this.out.write("<!DOCTYPE dataset");
if (systemId != null)
{
this.out.write(" SYSTEM \"");
this.out.write(systemId);
this.out.write("\"");
}
if (publicId != null)
{
this.out.write(" PUBLIC \"");
this.out.write(publicId);
this.out.write("\"");
}
this.out.write(">");
this.out.write(this.newline);
}
return this;
}
}
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