1. J2EE —— 第 5 章 Simple API for XML(SAX)

2. 何时使用 SAX SAX ：状态无关 (StAX ：状态相关 ) 事件驱动模型，不能倒退到文档前面部分 SAX 与 DOM ：相同的错误处理、处理验证错误 何时使用 SAX 把现有数据转换成 XML 速度快，效率高 何时使用 DOM 修改 XML 结构，交互修改 jdom, dom4j

3. 回显具有 SAX 解析器的 XML 文件 public class Echo { public static void main(String argv[]) { }

4. 导入类 import java.io.*; import org.xml.sax.*; import org.xml.sax.helpers.DefaultHandler; import javax.xml.parsers.SAXParserFactory; import javax.xml.parsers.ParserConfigurationException; import javax.xml.parsers.SAXParser;

5. 针对 I/O 进行设置 public static void main(String argv[]) { if (argv.length != 1) { System.err.println("Usage: cmd filename"); System.exit(1); } try { // Set up output stream out = new OutputStreamWriter(System.out, "UTF8"); } catch (Throwable t) { t.printStackTrace(); } System.exit(0); } static private Writer out;

6. 实现 ContentHandler 接口 public class Echo extends DefaultHandler {... } startDocument endDocument startElement endElement characters SAXException

7. 设置解析器 DefaultHandler handler = new Echo(); SAXParserFactory factory = SAXParserFactory.newInstance(); try { out = new OutputStreamWriter(System.out, "UTF8"); SAXParser saxParser = factory.newSAXParser(); saxParser.parse( new File(argv[0]), handler ); }

8. 编写输出 private void emit(String s) throws SAXException { try { out.write(s); out.flush(); } catch (IOException e) { throw new SAXException("I/O error", e); }

9. 隔开输出 private void nl() throws SAXException { String lineEnd = System.getProperty("line.separator"); try { out.write(lineEnd); } catch (IOException e) { throw new SAXException("I/O error", e); }

10. 文档事件 public void startDocument() throws SAXException { emit(" "); nl(); } public void endDocument() throws SAXException { try { nl(); out.flush(); } catch (IOException e) { throw new SAXException("I/O error", e); }

11. 元素开始事件 public void startElement(String namespaceURI, String sName, // simple name String qName, // qualified name Attributes attrs) throws SAXException { String eName = sName; // element name if ("".equals(eName)) eName = qName; // not namespace-aware emit("<"+eName); if (attrs != null) { for (int i = 0; i < attrs.getLength(); i++) { String aName = attrs.getLocalName(i); // Attr name if ("".equals(aName)) aName = attrs.getQName(i); emit(" "); emit(aName+"=\""+attrs.getValue(i)+"\""); } emit(">"); }

12. 元素结束事件 public void endElement(String namespaceURI, String sName, // simple name String qName // qualified name ) throws SAXException { String eName = sName; // element name if ("".equals(eName)) eName = qName; // not namespace-aware emit(" "); }

13. 字符事件 StringBuffer textBuffer; public void characters(char buf[], int offset, int len) throws SAXException { String s = new String(buf, offset, len); if (textBuffer == null) { textBuffer = new StringBuffer(s); } else { textBuffer.append(s); }

14. 回显字符 private void echoText() throws SAXException { if (textBuffer == null) return; String s = ""+textBuffer; emit(s); textBuffer = null; }

15. 调用回显字符函数 public void startElement(...) throws SAXException { echoText(); String eName = sName; // element name... } public void endElement(...) throws SAXException { echoText(); String eName = sName; // element name... }

16. 编译和运行程序 javac Echo.java java Echo slideSample.xml C:\dvlp\Sun\AppServer\jdk\jre\lib\rt.jar 程序输出 没有注释 元素属性在一行中 和 是一样的

17. 确定引起空行的事件 private void echoText() throws SAXException { if (textBuffer == null) return; nl(); emit("CHARS: |"); String s = ""+textBuffer; emit(s); emit("|"); textBuffer = null; }

18. 确定引起空行的事件：结果 CHARS: | | 空行是由 characters 事件引起的 压缩输出 public void echoText() throws SAXException { nl(); emit("CHARS: "); String s = ""+textBuffer; if (!s.trim().equals( “” )) emit(s); }

19. 回显解释器发送的每个字符集 public void characters(char buf[], int offset, int len) throws SAXException { if (textBuffer != null) { echoText(); textBuffer = null; } String s = new String(buf, offset, len);... }

20. 管理缩进 private String indentString = " "; private int indentLevel = 0; public void startElement(...) throws SAXException { indentLevel++; … } public void endElement(...) throws SAXException { nl(); emit("END_ELM: "); emit(" "); indentLevel--; }

21. 输出缩进 private void nl() throws SAXException {... try { out.write(lineEnd); for (int i=0; i < indentLevel; i++) out.write(indentString); } catch (IOException e) {... }

22. 检查输出 ELEMENT: <slideshow... > CHARS: ELEMENT: <slide... END_ELM: CHARS:

23. 确定文档位置 public void setDocumentLocator(Locator l) { try { out.write("LOCATOR"); out.write("SYS ID: " + l.getSystemId() ); out.flush(); } catch (IOException e) { // Ignore errors } LOCATOR SYS ID: file: /../samples/slideSample01.xml

24. 显示处理指令 public void processingInstruction(String target, String data) throws SAXException { nl(); emit("PROCESS: "); emit(" "); } ELEMENT: <slideshow... > PROCESS: CHARS:...

25. 处理 SAXParseException } catch (SAXParseException spe) { // Error generated by the parser System.out.println("\n** Parsing error" + ", line " + spe.getLineNumber() + ", uri " + spe.getSystemId()); System.out.println(" " + spe.getMessage() ); } ** Parsing error, line 22, uri file: / slideSampleBad1.xml The element type "item" must be terminated by the matching end-tag “ "

26. 处理 SAXException catch (SAXException sxe) { // Error generated by this application // (or a parser-initialization error) Exception x = sxe; if (sxe.getException() != null) x = sxe.getException(); x.printStackTrace(); }

27. 其它异常 catch (ParserConfigurationException pce) { // Parser with specified options can't be built pce.printStackTrace(); } catch (IOException ioe) { // I/O error ioe.printStackTrace(); }

28. 处理非致命错误和警告 // treat validation errors as fatal public void error(SAXParseException e) throws SAXParseException { throw e; } // dump warnings too public void warning(SAXParseException err) throws SAXParseException { System.out.println("** Warning" + ", line " + err.getLineNumber() + ", uri " + err.getSystemId()); System.out.println(" " + err.getMessage()); }

29. 显示特殊字符和 CDATA 实体引用： Market Size < predicted 输出： CHARS: Market Size < predicted CDATA 段：不需要替换特殊字符

30. 用 DTD 解析 解析器不再传递以前正确回显的围绕 slide 元素的空白 字符 可忽略空白 public void ignorableWhitespace (char buf[], int offset, int Len) throws SAXException { nl(); emit("IGNORABLE"); } 回显实体引用（内部实体，外部实体）

31. 使用验证解析器 // Use the validating parser SAXParserFactory factory = SAXParserFactory.newInstance(); factory.setValidating(true); 用 XML Schema 验证 static final String JAXP_SCHEMA_LANGUAGE = "http://java.sun.com/xml/jaxp/properties/schemaLanguage"; static final String W3C_XML_SCHEMA = "http://www.w3.org/2001/XMLSchema"; factory.setNamespaceAware(true); saxParser.setProperty(JAXP_SCHEMA_LANGUAGE, W3C_XML_SCHEMA);

32. 建立合适的错误处理程序 try { saxParser.setProperty(JAXP_SCHEMA_LANGUAGE, W3C_XML_SCHEMA); } catch (SAXNotRecognizedException x) { // Happens if the parser does not support JAXP 1.2... } 关联文档和 Schema <documentRoot xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation='YourSchemaDefinition.xsd' >

33. 试验验证错误 没有 DTD XML 和 DTD 不匹配 元素没有在 DTD 中定义

34. 解析参数化 DTD slideshow2.dtd 引用 xhtml.dtd title 定义冲突, 换名或使用名称空间解决 DTD 警告 非验证：重复声明 DTD 中引用未声明的元素 为没有声明的元素类型声明属性 XML 的 SAX 解析器警告 验证时没有 非验证：引用一个未定义的参数实体 字符编码声明不正确

35. 处理词法事件 org.xml.sax.ext.LexicalHandler 识别注释、 CDATA 段和对已解析实体的引用 LexicalHandler 如何工作 comment(String comment) startCDATA(), endCDATA() startEntity(String name), endEntity(String name) startDTD(String name, String publicId, String systemId), endDTD()

36. 使用 LexcicalHandler import org.xml.sax.ext.LexicalHandler; public class Echo extends HandlerBase implements LexicalHandler { public static void main(String argv[]) {... // Use an instance of ourselves as the SAX event handler DefaultHandler handler = new Echo(); Echo handler = new Echo();

37. 设置词法处理程序 SAXParser saxParser = factory.newSAXParser(); XMLReader xmlReader = saxParser.getXMLReader(); xmlReader.setProperty( "http://xml.org/sax/properties/l exical-handler", handler ); 回显注释 public void comment(char[] ch, int start, int length) throws SAXException { String text = new String(ch, start, length); nl(); emit("COMMENT: "+text); }

38. 使用 DTDHandler 和 EntityResolver 未解析的实体或符号声明： DTDHandler notationDecl(String name, String publicId, String systemId) unparsedEntityDecl(String name, String publicId, String systemId, String notationName) 公有 ID(URN) 转换成系统 ID(URL) resolveEntity(String publicId, String systemId)