sanders 01/12/04 11:51:22
Added: digester/src/java/org/apache/commons/digester/xmlrules
DigesterRuleParser.java
Log:
XML Rules definition
Graciously submitted by Dave Martin [[EMAIL PROTECTED]]
Revision Changes Path
1.1
jakarta-commons/digester/src/java/org/apache/commons/digester/xmlrules/DigesterRuleParser.java
Index: DigesterRuleParser.java
===================================================================
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*
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package org.apache.commons.digester.xmlrules;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URL;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import org.apache.commons.collections.ArrayStack;
import org.apache.commons.digester.AbstractObjectCreationFactory;
import org.apache.commons.digester.CallMethodRule;
import org.apache.commons.digester.FactoryCreateRule;
import org.apache.commons.digester.ObjectCreateRule;
import org.apache.commons.digester.Rule;
import org.apache.commons.digester.Rules;
import org.apache.commons.digester.RuleSetBase;
import org.apache.commons.digester.SetNextRule;
import org.apache.commons.digester.SetPropertiesRule;
import org.apache.commons.digester.SetPropertiesRule;
import org.apache.commons.digester.SetPropertyRule;
import org.apache.commons.digester.SetTopRule;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
/**
* This is a RuleSet that parses XML into Digester rules, and then
* adds those rules to a 'target' Digester.
*
* @author David H. Martin - Initial Contribution
* @author Scott Sanders - Added ASL, removed external dependencies
*/
public class DigesterRuleParser extends RuleSetBase {
public static final String DIGESTER_PUBLIC_ID = "-//Jakarta Apache //DTD
digester-rules XML V1.0//EN";
/**
* path to the DTD
*/
private String digesterDtdUrl;
/**
* This is the digester to which we are adding the rules that we parse
* from the Rules XML document.
*/
protected org.apache.commons.digester.Digester targetDigester;
/**
* A stack whose toString method returns a '/'-separated concatenation
* of all the elements in the stack.
*/
protected class PatternStack extends ArrayStack {
public String toString() {
StringBuffer str = new StringBuffer();
for (int i = 0; i < size(); i++) {
String elem = get(i).toString();
if (elem.length() > 0) {
if (str.length() > 0) {
str.append('/');
}
str.append(elem);
}
}
return str.toString();
}
}
/**
* A stack used to maintain the current pattern. The Rules XML document
* type allows nesting of patterns. If an element defines a matching
* pattern, the resulting pattern is a concatenation of that pattern with
* all the ancestor elements' patterns. Hence the need for a stack.
*/
protected PatternStack patternStack;
/**
* Used to detect circular includes
*/
private Set includedFiles = new HashSet();
/**
* Constructs a DigesterRuleParser. This object will be inoperable
* until the target digester is set, via <code>setTarget(Digester)</code>
*/
public DigesterRuleParser() {
patternStack = new PatternStack();
}
/**
* Constructs a rule set for converting XML digester rule descriptions
* into Rule objects, and adding them to the given Digester
* @param targetDigester the Digester to add the rules to
*/
public DigesterRuleParser(org.apache.commons.digester.Digester targetDigester) {
this.targetDigester = targetDigester;
patternStack = new PatternStack();
}
/**
* Constructs a rule set for parsing an XML digester rule file that
* has been included within an outer XML digester rule file. In this
* case, we must pass the pattern stack and the target digester
* to the rule set, as well as the list of files that have already
* been included, for cycle detection.
* @param targetDigester the Digester to add the rules to
* @param stack Stack containing the prefix pattern string to be prepended
* to any pattern parsed by this rule set.
*/
private DigesterRuleParser(org.apache.commons.digester.Digester targetDigester,
PatternStack stack, Set includedFiles) {
this.targetDigester = targetDigester;
patternStack = stack;
this.includedFiles = includedFiles;
}
/**
* Sets the digester into which to add the parsed rules
* @param d the Digester to add the rules to
*/
public void setTarget(org.apache.commons.digester.Digester d) {
targetDigester = d;
}
/**
* Sets the location of the digester rules DTD. This is the DTD used
* to validate the rules XML file.
*/
public void setDigesterRulesDTD(String dtdURL) {
digesterDtdUrl = dtdURL;
}
/**
* Returns the location of the DTD used to validate the digester rules
* XML document.
*/
protected String getDigesterRulesDTD() {
//ClassLoader classLoader = getClass().getClassLoader();
//URL url = classLoader.getResource(DIGESTER_DTD_PATH);
//return url.toString();
return digesterDtdUrl;
}
/**
* Adds a rule the the target digester. After a rule has been created by
* parsing the XML, it is added to the digester by calling this method.
* Typically, this method is called via reflection, when executing
* a SetNextRule, from the Digester that is parsing the rules XML.
* @param rule a Rule to add to the target digester.
*/
public void add(Rule rule) {
targetDigester.addRule(patternStack.toString(), rule);
}
/**
* Add to the given digester the set of Rule instances used to parse an XML
* document defining Digester rules. When the digester parses an XML file,
* it will add the resulting rules & patterns to the 'target digester'
* that was passed in this RuleSet's constructor.<P>
* If you extend this class to support additional rules, your implementation
* should of this method should call this implementation first: i.e.
* <code>super.addRuleInstances(digester);</code>
*/
public void addRuleInstances(org.apache.commons.digester.Digester digester) {
final String ruleClassName = Rule.class.getName();
digester.register(DIGESTER_PUBLIC_ID, getDigesterRulesDTD());
digester.addRule("*/pattern", new PatternRule(digester, "value"));
digester.addRule("*/include", new IncludeRule(digester));
digester.addFactoryCreate("*/call-method-rule", new CallMethodRuleFactory());
digester.addRule("*/call-method-rule", new PatternRule(digester, "pattern"));
digester.addSetNext("*/call-method-rule", "add", ruleClassName);
digester.addFactoryCreate("*/factory-create-rule", new
FactoryCreateRuleFactory());
digester.addRule("*/factory-create-rule", new PatternRule(digester,
"pattern"));
digester.addSetNext("*/factory-create-rule", "add", ruleClassName);
digester.addFactoryCreate("*/object-create-rule", new
ObjectCreateRuleFactory());
digester.addRule("*/object-create-rule", new PatternRule(digester,
"pattern"));
digester.addSetNext("*/object-create-rule", "add", ruleClassName);
digester.addFactoryCreate("*/set-properties-rule", new
SetPropertiesRuleFactory());
digester.addRule("*/set-properties-rule", new PatternRule(digester,
"pattern"));
digester.addSetNext("*/set-properties-rule", "add", ruleClassName);
digester.addFactoryCreate("*/set-property-rule", new
SetPropertyRuleFactory());
digester.addRule("*/set-property-rule", new PatternRule(digester,
"pattern"));
digester.addSetNext("*/set-property-rule", "add", ruleClassName);
digester.addFactoryCreate("*/set-top-rule", new SetTopRuleFactory());
digester.addRule("*/set-top-rule", new PatternRule(digester, "pattern"));
digester.addSetNext("*/set-top-rule", "add", ruleClassName);
digester.addFactoryCreate("*/set-next-rule", new SetNextRuleFactory());
digester.addRule("*/set-next-rule", new PatternRule(digester, "pattern"));
digester.addSetNext("*/set-next-rule", "add", ruleClassName);
}
/**
* A rule for extracting the pattern matching strings from the rules XML.
* In the digester-rules document type, a pattern can either be declared
* in the 'value' attribute of a <pattern> element (in which case the pattern
* applies to all rules elements contained within the <pattern> element),
* or it can be declared in the optional 'pattern' attribute of a rule
* element.
*/
private class PatternRule extends Rule {
private String attrName;
private String pattern = null;
/**
* @param digester the Digester used to parse the rules XML file
* @param attrName The name of the attribute containing the pattern
*/
public PatternRule(org.apache.commons.digester.Digester digester, String
attrName) {
super(digester);
this.attrName = attrName;
}
/**
* If a pattern is defined for the attribute, push it onto the
* pattern stack.
*/
public void begin(Attributes attributes) {
pattern = attributes.getValue(attrName);
if (pattern != null) {
patternStack.push(pattern);
}
}
/**
* If there was a pattern for this element, pop it off the pattern
* stack.
*/
public void end() {
if (pattern != null) {
patternStack.pop();
}
}
}
/**
* A rule for including one rules XML file within another. Included files
* behave as if they are 'macro-expanded' within the includer. This means
* that the values of the pattern stack are prefixed to every pattern
* in the included rules. <p>This rule will detect 'circular' includes,
* which would result in infinite recursion. It throws a
* CircularIncludeException when a cycle is detected, which will terminate
* the parse.
*/
private class IncludeRule extends Rule {
public IncludeRule(org.apache.commons.digester.Digester digester) {
super(digester);
}
/**
* To include a rules xml file, we instantiate another Digester, and
* another DigesterRulesRuleSet. We pass the
* pattern stack and the target Digester to the new rule set, and
* tell the Digester to parse the file.
*/
public void begin(Attributes attributes) throws Exception {
// The path attribute gives the URI to another digester rules xml file
String fileName = attributes.getValue("path");
if (fileName != null && fileName.length() > 0) {
includeXMLRules(fileName);
}
// The class attribute gives the name of a class that implements
// the DigesterRulesSource interface
String className = attributes.getValue("class");
if (className != null && className.length() > 0) {
includeProgrammaticRules(className);
}
}
/**
* Creates another DigesterRuleParser, and uses it to extract the rules
* out of the give XML file. The contents of the current pattern stack
* will be prepended to all of the pattern strings parsed from the file.
*/
private void includeXMLRules(String fileName)
throws IOException, SAXException, CircularIncludeException {
URL fileURL =
DigesterRuleParser.this.getClass().getClassLoader().getResource(fileName);
if (fileURL == null) {
throw new FileNotFoundException("File \"" + fileName + "\" not
found.");
}
fileName = fileURL.getFile();
if (includedFiles.add(fileName) == false) {
// circular include detected
throw new CircularIncludeException(fileName);
}
// parse the included xml file
DigesterRuleParser includedSet =
new DigesterRuleParser(targetDigester, patternStack,
includedFiles);
includedSet.setDigesterRulesDTD(getDigesterRulesDTD());
org.apache.commons.digester.Digester digester = new
org.apache.commons.digester.Digester();
// Keeps digester from outputting stack trace to stdout, if a
// CircularIncludeException is raised
digester.setWriter(new PrintWriter(new NullLogWriter(digester)));
digester.addRuleSet(includedSet);
digester.push(DigesterRuleParser.this);
digester.parse(fileName);
includedFiles.remove(fileName);
}
/**
* Creates an instance of the indicated class. The class must implement
* the DigesterRulesSource interface. Passes the target digester to
* that instance. The DigesterRulesSource instance is supposed to add
* rules into the digester. The contents of the current pattern stack
* will be automatically prepended to all of the pattern strings added
* by the DigesterRulesSource instance.
*/
private void includeProgrammaticRules(String className)
throws ClassNotFoundException, ClassCastException,
InstantiationException, IllegalAccessException {
Class cls = Class.forName(className);
DigesterRulesSource rulesSource = (DigesterRulesSource)cls.newInstance();
// wrap the digester's Rules object, to prepend pattern
Rules digesterRules = targetDigester.getRules();
Rules prefixWrapper =
new RulesPrefixAdapter(patternStack.toString(), digesterRules);
targetDigester.setRules(prefixWrapper);
try {
rulesSource.getRules(targetDigester);
} finally {
// Put the unwrapped rules back
targetDigester.setRules(digesterRules);
}
}
}
/**
* Wraps a Rules object. Delegates all the Rules interface methods
* to the underlying Rules object. Overrides the add method to prepend
* a prefix to the pattern string.
*/
private class RulesPrefixAdapter implements Rules {
private Rules delegate;
private String prefix;
/**
* @param patternPrefix the pattern string to prepend to the pattern
* passed to the add method.
* @param rules The wrapped Rules object. All of this class's methods
* pass through to this object.
*/
public RulesPrefixAdapter(String patternPrefix, Rules rules) {
prefix = patternPrefix;
delegate = rules;
}
/**
* Register a new Rule instance matching a pattern which is constructed
* by concatenating the pattern prefix with the given pattern.
*/
public void add(String pattern, Rule rule) {
delegate.add(prefix + pattern, rule);
}
/**
* This method passes through to the underlying Rules object.
*/
public void clear() {
delegate.clear();
}
/**
* This method passes through to the underlying Rules object.
*/
public org.apache.commons.digester.Digester getDigester() {
return delegate.getDigester();
}
/**
* This method passes through to the underlying Rules object.
*/
public String getNamespaceURI() {
return delegate.getNamespaceURI();
}
/**
* @deprecated Call match(namespaceURI,pattern) instead.
*/
public List match(String pattern) {
return delegate.match(pattern);
}
/**
* This method passes through to the underlying Rules object.
*/
public List match(String namespaceURI, String pattern) {
return delegate.match(namespaceURI, pattern);
}
/**
* This method passes through to the underlying Rules object.
*/
public List rules() {
return delegate.rules();
}
/**
* This method passes through to the underlying Rules object.
*/
public void setDigester(org.apache.commons.digester.Digester digester) {
delegate.setDigester(digester);
}
/**
* This method passes through to the underlying Rules object.
*/
public void setNamespaceURI(String namespaceURI) {
delegate.setNamespaceURI(namespaceURI);
}
}
///////////////////////////////////////////////////////////////////////
// Classes beyond this point are ObjectCreationFactory implementations,
// used to create Rule objects and initialize them from SAX attributes.
///////////////////////////////////////////////////////////////////////
/**
* Factory for creating a CallMethodRule.
*/
protected class CallMethodRuleFactory extends AbstractObjectCreationFactory {
public Object createObject(Attributes attributes) {
int paramCount = Integer.parseInt(attributes.getValue("paramcount"));
String methodName = attributes.getValue("methodname");
Rule callMethodRule = new CallMethodRule(digester, methodName,
paramCount);
return callMethodRule;
}
}
/**
* Factory for creating a CallMethodRule.
*/
protected class CallParamRuleFactory extends AbstractObjectCreationFactory {
public Object createObject(Attributes attributes) {
// create callmethodrule
int paramNumber = Integer.parseInt(attributes.getValue("paramnumber"));
String methodName = attributes.getValue("attrname");
Rule callMethodRule = new CallMethodRule(targetDigester, methodName,
paramNumber);
return callMethodRule;
}
}
/**
* Factory for creating a FactoryCreateRule
*/
protected class FactoryCreateRuleFactory extends AbstractObjectCreationFactory {
public Object createObject(Attributes attributes) {
String className = attributes.getValue("classname");
String attrName = attributes.getValue("attrname");
return (attrName == null || attrName.length() == 0) ?
new FactoryCreateRule(targetDigester, className)
:
new FactoryCreateRule(targetDigester, className, attrName);
}
}
/**
* Factory for creating a ObjectCreateRule
*/
protected class ObjectCreateRuleFactory extends AbstractObjectCreationFactory {
public Object createObject(Attributes attributes) {
String className = attributes.getValue("classname");
String attrName = attributes.getValue("attrname");
return (attrName == null || attrName.length() == 0) ?
new ObjectCreateRule(targetDigester, className)
:
new ObjectCreateRule(targetDigester, className, attrName);
}
}
/**
* Factory for creating a SetPropertiesRule
*/
protected class SetPropertiesRuleFactory extends AbstractObjectCreationFactory {
public Object createObject(Attributes attributes) {
return new SetPropertiesRule(targetDigester);
}
}
/**
* Factory for creating a SetPropertyRule
*/
protected class SetPropertyRuleFactory extends AbstractObjectCreationFactory {
public Object createObject(Attributes attributes) {
String name = attributes.getValue("name");
String value = attributes.getValue("value");
return new SetPropertyRule(targetDigester, name, value);
}
}
/**
* Factory for creating a SetTopRuleFactory
*/
protected class SetTopRuleFactory extends AbstractObjectCreationFactory {
public Object createObject(Attributes attributes) {
String methodName = attributes.getValue("methodname");
String paramType = attributes.getValue("paramtype");
return (paramType == null || paramType.length() == 0) ?
new SetTopRule(targetDigester, methodName)
:
new SetTopRule(targetDigester, methodName, paramType);
}
}
/**
* Factory for creating a SetNextRuleFactory
*/
protected class SetNextRuleFactory extends AbstractObjectCreationFactory {
public Object createObject(Attributes attributes) {
String methodName = attributes.getValue("methodname");
String paramType = attributes.getValue("paramtype");
return (paramType == null || paramType.length() == 0) ?
new SetNextRule(targetDigester, methodName)
:
new SetNextRule(targetDigester, methodName, paramType);
}
}
}
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