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/*
* Copyright 2006 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.dev.util.xml;
import com.google.gwt.core.ext.TreeLogger;
import com.google.gwt.core.ext.UnableToCompleteException;
import com.google.gwt.util.tools.Utility;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import java.io.IOException;
import java.io.Reader;
import java.util.Stack;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
/**
* Somewhat general-purpose SAX-style XML parser that uses reflection and calls
* into your "schema" classes. For example, the element
* <server-name> maps to the method
* server_name. Note that the mapping is one-way, hyphens become
* underscores, but then you don't really want to use underscores in XML tag
* names anyway, do you? Also, all mixed content text (that is, text inside
* elements) is ignored, so think attributes.
*/
public final class ReflectiveParser {
private static SAXParserFactory saxParserFactory;
private static synchronized SAXParser createNewSaxParser() throws ParserConfigurationException,
SAXException {
if (saxParserFactory == null) {
Thread currentThread = Thread.currentThread();
ClassLoader oldClassLoader = currentThread.getContextClassLoader();
try {
// use system ClassLoader to avoid using expensive GWT ClassLoader
currentThread.setContextClassLoader(ClassLoader.getSystemClassLoader());
saxParserFactory = SAXParserFactory.newInstance();
saxParserFactory.setFeature(
"http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
} finally {
currentThread.setContextClassLoader(oldClassLoader);
}
}
return saxParserFactory.newSAXParser();
}
private static final class Impl extends DefaultHandler {
private Locator locator;
private Reader reader;
private Stack schemaLevels = new Stack();
private Stack argStack = new Stack();
private Schema defaultSchema;
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
int lineNumber = locator.getLineNumber();
// Get the active schema level.
//
Schema schemaLevel = getTopSchemaLevel();
if (schemaLevel == null) {
// It is legitimate to run out of schemaLevels if there is an empty node
// in the XML. Otherwise, it indicates that the user has specified
// extra stuff in the body of the XML tag that we don't understand.
//
for (int i = 0; i < length; i++) {
if (!Character.isWhitespace(ch[i + start])) {
throw new SAXException("Unexpected XML data found: "
+ String.valueOf(ch, start, length));
}
}
// This is okay. Nothing special to do.
//
return;
}
// Find the precomputed handler class info.
//
Class slc = schemaLevel.getClass();
HandlerClassInfo classInfo = HandlerClassInfo.getClassInfo(slc);
assert (classInfo != null); // would've thrown if unregistered
HandlerMethod method = classInfo.getTextMethod();
if (method == null) {
// This is okay. Nothing special to do.
//
return;
}
// Call the handler.
//
try {
// The line number is at the end of the text; subtract however many
// newlines the text contains.
for (int i = start, e = start + length, l = e - 1; i < e; ++i) {
switch (ch[i]) {
case '\r':
if (i < l && ch[i + 1] == '\n') {
continue;
}
// Intentional fall-through
case '\n':
--lineNumber;
}
}
final String text = String.valueOf(ch, start, length);
method.invokeText(lineNumber, text, schemaLevel);
} catch (UnableToCompleteException e) {
throw new SAXException(e);
}
}
@Override
public void endElement(String namespaceURI, String localName, String elem)
throws SAXException {
int lineNumber = locator.getLineNumber();
// Get the active schema level.
//
Schema schemaLevel = popLevel();
if (schemaLevel == null) {
// This was an unexpected child, but we already informed the schema
// about it during startElement(), so we can just return.
//
return;
}
// Find the precomputed handler class info.
//
Class slc = schemaLevel.getClass();
HandlerClassInfo classInfo = HandlerClassInfo.getClassInfo(slc);
assert (classInfo != null); // would've thrown if unregistered
HandlerMethod method = classInfo.getEndMethod(elem);
if (method == null) {
// This is okay. Nothing special to do.
//
return;
}
Object[] args = getCurrentArgs();
if (args != null) {
// Call the handler using the same arguments we send to the "begin"
// handler.
//
try {
method.invokeEnd(lineNumber, elem, schemaLevel, args);
} catch (UnableToCompleteException e) {
throw new SAXException(e);
}
}
}
@Override
public void setDocumentLocator(Locator locator) {
this.locator = locator;
}
@Override
public void startElement(String namespaceURI, String localName,
String elemName, Attributes atts) throws SAXException {
int lineNumber = locator.getLineNumber();
// Get the active schema level.
//
Schema schemaLevel = getTopSchemaLevel();
if (schemaLevel == null) {
// This means that children should not appear at this level.
//
Schema nextToTop = getNextToTopSchemaLevel();
// Push another null since this child shouldn't have children either.
//
setArgsAndPushLevel(null, null);
// Inform the next-to-top schema level about this.
//
try {
nextToTop.onUnexpectedChild(lineNumber, elemName);
} catch (UnableToCompleteException e) {
throw new SAXException(e);
}
return;
}
// Find the precomputed handler class info.
//
Class slc = schemaLevel.getClass();
HandlerClassInfo classInfo = HandlerClassInfo.getClassInfo(slc);
HandlerMethod method = classInfo.getStartMethod(elemName);
if (method == null) {
// This is not okay. The schema has to at least have a stub
// to indicate that a particular tag is allowed.
//
try {
schemaLevel.onUnexpectedElement(lineNumber, elemName);
} catch (UnableToCompleteException e) {
throw new SAXException(e);
}
// Since we don't know about this element, assume it should not have
// children either.
//
setArgsAndPushLevel(null, null);
return;
}
HandlerArgs args = method.createArgs(schemaLevel, lineNumber, elemName);
// For each attribute found, try to match it up to a parameter.
//
for (int i = 0, n = atts.getLength(); i < n; ++i) {
String attrName = atts.getQName(i);
String attrValue = atts.getValue(i);
if (!args.setArg(attrName, attrValue)) {
// Inform the handler that the attribute was unknown.
//
try {
schemaLevel.onUnexpectedAttribute(lineNumber, elemName, attrName,
attrValue);
} catch (UnableToCompleteException e) {
throw new SAXException(e);
}
}
}
// Check for unset parameters.
//
int missingCount = 0;
for (int i = 0, n = args.getArgCount(); i < n; ++i) {
if (!args.isArgSet(i)) {
// Inform the handler that the required attribute was not set.
// It might throw, but it also might not.
//
try {
schemaLevel.onMissingAttribute(lineNumber, elemName,
args.getArgName(i));
} catch (UnableToCompleteException e) {
throw new SAXException(e);
}
++missingCount;
}
}
if (missingCount > 0) {
// Do not invoke the handler.
//
// Assume that children shouldn't be recognized either since the
// handler wasn't invoked.
//
setArgsAndPushLevel(null, null);
return;
}
// Invoke the handler method, which will internally
// convert all the args to their respective parameter types
// (or warn if there is a problem doing so).
//
Object[] invokeArgs = new Object[method.getParamCount()];
Schema childSchemaLevel;
try {
childSchemaLevel = method.invokeBegin(lineNumber, elemName,
schemaLevel, args, invokeArgs);
} catch (UnableToCompleteException e) {
throw new SAXException(e);
}
// childSchemaLevel can be null and that's okay -- it means no children
// are expected. Same for invokeArgs[0] -- it means that the "begin"
// handler was not called, so neither will we call the "end" handler.
//
setArgsAndPushLevel(invokeArgs, childSchemaLevel);
}
private Object[] getCurrentArgs() {
return argStack.peek();
}
private Schema getNextToTopSchemaLevel() {
return schemaLevels.get(schemaLevels.size() - 2);
}
private Schema getTopSchemaLevel() {
return schemaLevels.peek();
}
private void parse(TreeLogger logger, Schema topSchema, Reader reader)
throws UnableToCompleteException {
// Set up the parentmost schema which is used to find default converters
// and handlers (but isn't actually on the schema stack.)
//
defaultSchema = new DefaultSchema(logger);
// Tell this schema level about the default schema, which is initialized
// with
// converters for basic types.
//
topSchema.setParent(defaultSchema);
// Make a slot for the document element's args.
//
argStack.push(null);
// Push the first schema.
//
setArgsAndPushLevel(null, topSchema);
Throwable caught = null;
try {
this.reader = reader;
SAXParser parser = createNewSaxParser();
InputSource inputSource = new InputSource(this.reader);
XMLReader xmlReader = parser.getXMLReader();
xmlReader.setContentHandler(this);
xmlReader.parse(inputSource);
} catch (SAXException e) {
// If it's an exception wrapped in a SAXException, rip off the outer SAX
// exception.
//
caught = e;
Exception inner = e.getException();
if (inner instanceof RuntimeException) {
throw (RuntimeException) inner;
} else if (inner != null) {
caught = inner;
}
} catch (ParserConfigurationException e) {
caught = e;
} catch (IOException e) {
caught = e;
} finally {
Utility.close(reader);
}
if (caught != null) {
Messages.XML_PARSE_FAILED.log(logger, caught);
throw new UnableToCompleteException();
}
}
private Schema popLevel() {
argStack.pop();
schemaLevels.pop();
return getTopSchemaLevel();
}
private void setArgsAndPushLevel(Object[] handlerArgs, Schema schemaLevel) {
// Set the args on the current schema level.
argStack.set(argStack.size() - 1, handlerArgs);
// A slot for the args at the childrens' depth.
argStack.push(null);
if (!schemaLevels.isEmpty()) {
// Tell this schema level about its parent.
//
Schema maybeParent = null;
for (int i = schemaLevels.size() - 1; i >= 0; --i) {
maybeParent = schemaLevels.get(i);
if (maybeParent != null) {
break;
}
}
if (maybeParent == null) {
throw new IllegalStateException("Cannot find any parent schema");
}
if (schemaLevel != null) {
schemaLevel.setParent(maybeParent);
}
}
// The schema for children.
schemaLevels.push(schemaLevel);
}
}
public static void parse(TreeLogger logger, Schema schema, Reader reader)
throws UnableToCompleteException {
// Register the schema level.
//
registerSchemaLevel(schema.getClass());
// Do the parse.
//
Impl impl = new Impl();
impl.parse(logger, schema, reader);
}
/**
* Can safely register the same class recursively.
*/
public static void registerSchemaLevel(Class schemaLevelClass) {
HandlerClassInfo.registerClass(schemaLevelClass);
// Try to register nested classes.
//
Class[] nested = schemaLevelClass.getDeclaredClasses();
for (int i = 0, n = nested.length; i < n; ++i) {
Class nestedClass = nested[i];
if (Schema.class.isAssignableFrom(nestedClass)) {
registerSchemaLevel(nestedClass.asSubclass(Schema.class));
}
}
}
}
