tomcat解析(七)Digester(四)characters,endElement.endDocument

1.characters
 方法内容如下:
 /** * Process notification of character data received from the body of * an XML element. * * @param buffer The characters from the XML document * @param start Starting offset into the buffer * @param length Number of characters from the buffer * * @exception SAXException if a parsing error is to be reported */ public void characters(char buffer[], int start, int length) throws SAXException { if (saxLog.isDebugEnabled()) { saxLog.debug("characters(" + new String(buffer, start, length) + ")"); } bodyText.append(buffer, start, length); } 

   该方法的各参数表示了标签体的内容字符串，此方法主要是将标签体内容赋予bodyText变量，该变量将在endElement()方法里使用到

2.endElement
 方法内容如下:
/** * Process notification of the end of an XML element being reached. * * @param namespaceURI - The Namespace URI, or the empty string if the * element has no Namespace URI or if Namespace processing is not * being performed. * @param localName - The local name (without prefix), or the empty * string if Namespace processing is not being performed. * @param qName - The qualified XML 1.0 name (with prefix), or the * empty string if qualified names are not available. * @exception SAXException if a parsing error is to be reported */ public void endElement(String namespaceURI, String localName, String qName) throws SAXException { boolean debug = log.isDebugEnabled(); if (debug) { if (saxLog.isDebugEnabled()) { saxLog.debug("endElement(" + namespaceURI + "," + localName + "," + qName + ")"); } log.debug(" match='" + match + "'"); log.debug(" bodyText='" + bodyText + "'"); } // Parse system properties bodyText = updateBodyText(bodyText); // the actual element name is either in localName or qName, depending // on whether the parser is namespace aware String name = localName; if ((name == null) || (name.length() < 1)) { name = qName; } // Fire "body" events for all relevant rules List rules = (List) matches.pop(); if ((rules != null) && (rules.size() > 0)) { String bodyText = this.bodyText.toString(); for (int i = 0; i < rules.size(); i++) { try { Rule rule = (Rule) rules.get(i); if (debug) { log.debug(" Fire body() for " + rule); } rule.body(namespaceURI, name, bodyText); } catch (Exception e) { log.error("Body event threw exception", e); throw createSAXException(e); } catch (Error e) { log.error("Body event threw error", e); throw e; } } } else { if (debug) { log.debug(" No rules found matching '" + match + "'."); } if (rulesValidation) { log.warn(" No rules found matching '" + match + "'."); } } // Recover the body text from the surrounding element bodyText = (StringBuffer) bodyTexts.pop(); if (debug) { log.debug(" Popping body text '" + bodyText.toString() + "'"); } // Fire "end" events for all relevant rules in reverse order if (rules != null) { for (int i = 0; i < rules.size(); i++) { int j = (rules.size() - i) - 1; try { Rule rule = (Rule) rules.get(j); if (debug) { log.debug(" Fire end() for " + rule); } rule.end(namespaceURI, name); } catch (Exception e) { log.error("End event threw exception", e); throw createSAXException(e); } catch (Error e) { log.error("End event threw error", e); throw e; } } } // Recover the previous match expression int slash = match.lastIndexOf('/'); if (slash >= 0) { match = match.substring(0, slash); } else { match = ""; } }

<1>bodyText = updateBodyText(bodyText);
将bodyText中的变量值替换,如标签体中有${systemProperty}
<2>获取与标签路径名匹配的Rule，触发其body及end方法
这部分内容为何是直接从matches.pop出来的,而不是用name去匹配呢?因为之前在startElement()方法里匹配过一次,并且将匹配所得的Rule List放入到matches里了
       // Fire "begin" events for all relevant rules List rules = getRules().match(namespaceURI, match); matches.push(rules);

3.endDocument
 另一个需要讲一下的是这个方法,在XML结束时调用,方法内容如下:
 /** * Process notification of the end of the document being reached. * * @exception SAXException if a parsing error is to be reported */ public void endDocument() throws SAXException { if (saxLog.isDebugEnabled()) { if (getCount() > 1) { saxLog.debug("endDocument(): " + getCount() + " elements left"); } else { saxLog.debug("endDocument()"); } } while (getCount() > 1) { pop(); } // Fire "finish" events for all defined rules Iterator rules = getRules().rules().iterator(); while (rules.hasNext()) { Rule rule = (Rule) rules.next(); try { rule.finish(); } catch (Exception e) { log.error("Finish event threw exception", e); throw createSAXException(e); } catch (Error e) { log.error("Finish event threw error", e); throw e; } } // Perform final cleanup clear(); } 

    方法内容为:弹出所有还在栈中的对象,执行所有Rule的finish方法,执行clear方法清空相关堆栈,如下:
    /** * Clear the current contents of the object stack. * <p> * Calling this method <i>might</i> allow another document of the same type * to be correctly parsed. However this method was not intended for this * purpose. In general, a separate Digester object should be created for * each document to be parsed. */ public void clear() { match = ""; bodyTexts.clear(); params.clear(); publicId = null; stack.clear(); log = null; saxLog = null; configured = false; } 

   
了解了Digester类的几个处理方法后我们了解到，除一些更换变量的处理外，主要的工作都是交由Rule类来处理，我们下面几篇文章将了解一下Rule类的用意的在这里tomcat是进行了什么具体的操作