JAXP使用Stax API时格式化输出XML

最近项目中需要生成XBRL instance，对于XML读写和验证进行了一些学习。由于Stax API不支持格式化输出，默认全都写在一行上，网上也没有搜到现成的东西，自己写了一个格式化输出的帮助类。

说明：

1. 使用了WoodStox 4.2.0的Stax实现来写XML，顺便提一下，经过比较JAXP默认实现（SJSXP），WoodStox，DOM4J， XOM（NUX）。发现WoodStox速度最快，通过自己扩展的Stax2 API，功能也比较强大。

2. 实现了特殊的XML验证，一般来说使用SAXParser来读入XML文件再进行验证，但是这里使用了边写边验证的功能，如果是不合法的写入就会失败，所以只要写完XML肯定就是合法的。这也是Stax2 API提供的功能。

关于XML验证有一个相当不错的链接：http://www.edankert.com/validate.html

3. 关于XMLPrettyFormatter的用法主要在三行代码上，XbrliWriterHelper类中的 formatter.writeStartElementIndention(), formatter.writeValueIndention(), formatter.writeEndElementIndention()。注意调用这三个函数一定要writer.writerXXX()的方法前面。

以下是主要代码，最后会附上整个工程（包含XSD文件等）。

(2014-04-18 15:00 编辑) 这个实现有一个问题，会导致没有值的节点也分开显示结束标签，新的版本解决了这个问题：

/article/7147637.html

入口类WoodstoxWriter:

public class WoodstoxWriter {

public static void main(String[] args) throws IOException, XMLStreamException {
Timer t = new Timer();
t.begin();
streamWriter();
t.end();
}

private static void streamWriter() throws IOException, XMLStreamException {
File xsdFile = new File("src/main/resources/book.xsd");
XMLValidationSchemaFactory xsdFactory = XMLValidationSchemaFactory.newInstance(XMLValidationSchema.SCHEMA_ID_W3C_SCHEMA);
XMLValidationSchema schema = xsdFactory.createSchema(xsdFile);

XbrliWriterBean writer = new XbrliWriterBean();
writer.init(schema);

writer.writeStartElement("bk", "books", Const.NSURI_BOOK);
writer.writeNamespace("bk", Const.NSURI_BOOK);
writer.writeNamespace("au", Const.NSURI_AUTHER);

for (int i = 0; i < Const.NODE_COUNTS_S; ++i) {
writer.writeStartElement("bk", "book", Const.NSURI_BOOK);
writer.writeAttribute("id", String.valueOf(i + 1));

writer.writeStartElement("bk", "name", Const.NSURI_BOOK);
String name = new StringBuilder("Name").append(i + i).toString();
writer.writeValue(name);
writer.writeEndElement();

writer.writeStartElement("au", "author", Const.NSURI_AUTHER);

writer.writeStartElement("au", "age", Const.NSURI_AUTHER);
writer.writeValue("30");
writer.writeEndElement();

writer.writeEndElement();

writer.writeEndElement();
}
writer.writeEndElement();
writer.close();
}

}

XbrliWriterHelper:

public class XbrliWriterHelper {

private FileOutputStream out;
private XMLStreamWriter2 writer;
private XMLPrettyFormatter formatter;

public void init(XMLValidationSchema schema) throws IOException, XMLStreamException {
out = new FileOutputStream("Woodstox.xml");
XMLOutputFactory factory = XMLOutputFactory2.newInstance();
writer = (XMLStreamWriter2) factory.createXMLStreamWriter(out);
writer.validateAgainst(schema);
writer.writeStartDocument("UTF-8", "1.0");

formatter = new DefaultPrettyFormatter(writer);
// formatter = new DefaultPrettyFormatter(writer, "  ");
// formatter = new EmptyPrettyFormatter(writer);
}

public void writeStartElement(String prefix, String localName, String namespaceURI) throws XMLStreamException {
formatter.writeStartElementIndention();
writer.writeStartElement(prefix, localName, namespaceURI);
}

public void writeValue(String value) throws XMLStreamException {
formatter.writeValueIndention();
writer.writeCharacters(value.toCharArray(), 0, value.length());
}

public void writeEndElement() throws XMLStreamException {
formatter.writeEndElementIndention();
writer.writeEndElement();
}

public void writeAttribute(String localName, String value) throws XMLStreamException {
writer.writeAttribute(localName, value);
}

public void writeNamespace(String prefix, String namespaceURI) throws XMLStreamException {
writer.writeNamespace(prefix, namespaceURI);
}

public void close() throws XMLStreamException, IOException {
writer.writeEndDocument();
writer.close();
out.close();
}

}

XMLPrettyFormatter:

public interface XMLPrettyFormatter {

enum NodeType {
ELEMENT, VALUE
}

String DEFAULT_INDENTION = "\t";

void writeStartElementIndention() throws XMLStreamException;

void writeValueIndention() throws XMLStreamException;

void writeEndElementIndention() throws XMLStreamException;

}

DefaultPrettyFormatter:

public class DefaultPrettyFormatter implements XMLPrettyFormatter {

private String indent = DEFAULT_INDENTION;
private int currentLevel = 0;
private NodeType nodeType;

private XMLStreamWriter2 writer;

public DefaultPrettyFormatter(XMLStreamWriter2 writer) {
this.writer = writer;
}

public DefaultPrettyFormatter(XMLStreamWriter2 writer, String indent) {
this.writer = writer;
this.indent = indent;
}

@Override
public void writeStartElementIndention() throws XMLStreamException {
nodeType = NodeType.ELEMENT;

writeLineBreaker();
for (int i = 0; i < currentLevel; ++i) {
writeIndention();
}
++currentLevel;
}

@Override
public void writeValueIndention() throws XMLStreamException {
nodeType = NodeType.VALUE;
}

@Override
public void writeEndElementIndention() throws XMLStreamException {
--currentLevel;

if (nodeType == NodeType.ELEMENT) {
writeLineBreaker();
for (int i = 0; i < currentLevel; ++i) {
writeIndention();
}
} else {
// after write value, the node type should back to element
nodeType = NodeType.ELEMENT;
}
}

private void writeLineBreaker() throws XMLStreamException {
writer.writeCharacters("\n");
}

private void writeIndention() throws XMLStreamException {
writer.writeCharacters(indent.toCharArray(), 0, indent.length());
}

}

工程下载：晕啊，找不到上传文件地方，记得以前弄过的。。。只有直接贴文件内容了

POM 依赖

<dependencies>
<dependency>
<groupId>org.codehaus.woodstox</groupId>
<artifactId>woodstox-core-asl</artifactId>
<version>4.2.0</version>
</dependency>
<dependency>
<groupId>com.sun.xml.bind</groupId>
<artifactId>jaxb1-impl</artifactId>
<version>2.2.5.1</version>
</dependency>
</dependencies>

book.xsd：

<xs:schema targetNamespace="http://www.test.com/book" xmlns="http://www.test.com/book" xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:au="http://www.test.com/author"
elementFormDefault="qualified">

<xs:import namespace="http://www.test.com/author" schemaLocation="author.xsd" />

<xs:element name="books" type="booksType" />
<xs:element name="book" type="bookType" />

<xs:complexType name="booksType">
<xs:sequence>
<xs:element ref="book" maxOccurs="unbounded" />
</xs:sequence>
</xs:complexType>

<xs:complexType name="bookType">
<xs:sequence>
<xs:element name="name" type="xs:string" />
<xs:element ref="au:author" type="xs:string" />
</xs:sequence>
<xs:attribute name="id" type="xs:string" />
</xs:complexType>

</xs:schema>

author.xsd：

<xs:schema targetNamespace="http://www.test.com/author" xmlns="http://www.test.com/author" xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified">

<xs:element name="author" type="authorType" />

<xs:complexType name="authorType">
<xs:sequence>
<xs:element name="age" type="xs:positiveInteger" />
</xs:sequence>
</xs:complexType>

</xs:schema>