Source Code Cross Referenced for ReflectiveParser.java in  » Ajax » GWT » com » google » gwt » dev » util » xml » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Ajax » GWT » com.google.gwt.dev.util.xml 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Copyright 2006 Google Inc.
003:         * 
004:         * Licensed under the Apache License, Version 2.0 (the "License"); you may not
005:         * use this file except in compliance with the License. You may obtain a copy of
006:         * the License at
007:         * 
008:         * http://www.apache.org/licenses/LICENSE-2.0
009:         * 
010:         * Unless required by applicable law or agreed to in writing, software
011:         * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
012:         * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
013:         * License for the specific language governing permissions and limitations under
014:         * the License.
015:         */
016:        package com.google.gwt.dev.util.xml;
017:
018:        import com.google.gwt.core.ext.TreeLogger;
019:        import com.google.gwt.core.ext.UnableToCompleteException;
020:        import com.google.gwt.util.tools.Utility;
021:
022:        import org.xml.sax.Attributes;
023:        import org.xml.sax.InputSource;
024:        import org.xml.sax.Locator;
025:        import org.xml.sax.SAXException;
026:        import org.xml.sax.XMLReader;
027:        import org.xml.sax.helpers.DefaultHandler;
028:
029:        import java.io.IOException;
030:        import java.io.Reader;
031:        import java.util.Stack;
032:
033:        import javax.xml.parsers.ParserConfigurationException;
034:        import javax.xml.parsers.SAXParser;
035:        import javax.xml.parsers.SAXParserFactory;
036:
037:        /**
038:         * Somewhat general-purpose SAX-style XML parser that uses reflection and calls
039:         * into your "schema" classes. For example, the element
040:         * <code>&lt;server-name&gt;</code> maps to the method
041:         * <code>server_name</code>. Note that the mapping is one-way, hyphens become
042:         * underscores, but then you don't really want to use underscores in XML tag
043:         * names anyway, do you? Also, all mixed content text (that is, text inside
044:         * elements) is ignored, so think attributes.
045:         */
046:        public final class ReflectiveParser {
047:
048:            private static final class Impl extends DefaultHandler {
049:
050:                private Locator locator;
051:
052:                private Reader reader;
053:
054:                private Stack schemaLevels = new Stack();
055:
056:                private Stack argStack = new Stack();
057:
058:                private Schema defaultSchema;
059:
060:                public void characters(char[] ch, int start, int length)
061:                        throws SAXException {
062:                    int lineNumber = locator.getLineNumber();
063:
064:                    // Get the active schema level.
065:                    //
066:                    Schema schemaLevel = getTopSchemaLevel();
067:
068:                    if (schemaLevel == null) {
069:                        // It is legitimate to run out of schemaLevels if there is an empty node
070:                        // in the XML. Otherwise, it indicates that the user has specified
071:                        // extra stuff in the body of the XML tag that we don't understand.
072:                        //
073:                        for (int i = 0; i < length; i++) {
074:                            if (!Character.isWhitespace(ch[i + start])) {
075:                                throw new SAXException(
076:                                        "Unexpected XML data found: "
077:                                                + String.valueOf(ch, start,
078:                                                        length));
079:                            }
080:                        }
081:                        // This is okay. Nothing special to do.
082:                        //
083:                        return;
084:                    }
085:                    // Find the precomputed handler class info.
086:                    //
087:                    Class slc = schemaLevel.getClass();
088:                    HandlerClassInfo classInfo = HandlerClassInfo
089:                            .getClassInfo(slc);
090:                    assert (classInfo != null); // would've thrown if unregistered
091:                    HandlerMethod method = classInfo.getTextMethod();
092:                    if (method == null) {
093:                        // This is okay. Nothing special to do.
094:                        //
095:                        return;
096:                    }
097:
098:                    // Call the handler.
099:                    //
100:                    try {
101:                        final String text = String.valueOf(ch, start, length);
102:                        method.invokeText(lineNumber, text, schemaLevel);
103:                    } catch (UnableToCompleteException e) {
104:                        throw new SAXException(e);
105:                    }
106:                }
107:
108:                public void endElement(String namespaceURI, String localName,
109:                        String elem) throws SAXException {
110:                    int lineNumber = locator.getLineNumber();
111:
112:                    // Get the active schema level.
113:                    //
114:                    Schema schemaLevel = popLevel();
115:                    if (schemaLevel == null) {
116:                        // This was an unexpected child, but we already informed the schema
117:                        // about it during startElement(), so we can just return.
118:                        //
119:                        return;
120:                    }
121:
122:                    // Find the precomputed handler class info.
123:                    //
124:                    Class slc = schemaLevel.getClass();
125:                    HandlerClassInfo classInfo = HandlerClassInfo
126:                            .getClassInfo(slc);
127:                    assert (classInfo != null); // would've thrown if unregistered
128:                    HandlerMethod method = classInfo.getEndMethod(elem);
129:                    if (method == null) {
130:                        // This is okay. Nothing special to do.
131:                        //
132:                        return;
133:                    }
134:
135:                    Object[] args = getCurrentArgs();
136:                    if (args != null) {
137:                        // Call the handler using the same arguments we send to the "begin"
138:                        // handler.
139:                        //
140:                        try {
141:                            method.invokeEnd(lineNumber, elem, schemaLevel,
142:                                    args);
143:                        } catch (UnableToCompleteException e) {
144:                            throw new SAXException(e);
145:                        }
146:                    }
147:                }
148:
149:                public void setDocumentLocator(Locator locator) {
150:                    this .locator = locator;
151:                }
152:
153:                public void startElement(String namespaceURI, String localName,
154:                        String elemName, Attributes atts) throws SAXException {
155:                    int lineNumber = locator.getLineNumber();
156:
157:                    // Get the active schema level.
158:                    //
159:                    Schema schemaLevel = getTopSchemaLevel();
160:                    if (schemaLevel == null) {
161:                        // This means that children should not appear at this level.
162:                        //
163:                        Schema nextToTop = getNextToTopSchemaLevel();
164:
165:                        // Push another null since this child shouldn't have children either.
166:                        //
167:                        setArgsAndPushLevel(null, null);
168:
169:                        // Inform the next-to-top schema level about this.
170:                        //
171:                        try {
172:                            nextToTop.onUnexpectedChild(lineNumber, elemName);
173:                        } catch (UnableToCompleteException e) {
174:                            throw new SAXException(e);
175:                        }
176:
177:                        return;
178:                    }
179:
180:                    // Find the precomputed handler class info.
181:                    //
182:                    Class slc = schemaLevel.getClass();
183:                    HandlerClassInfo classInfo = HandlerClassInfo
184:                            .getClassInfo(slc);
185:                    HandlerMethod method = classInfo.getStartMethod(elemName);
186:
187:                    if (method == null) {
188:                        // This is not okay. The schema has to at least have a stub
189:                        // to indicate that a particular tag is allowed.
190:                        //
191:                        try {
192:                            schemaLevel.onUnexpectedElement(lineNumber,
193:                                    elemName);
194:                        } catch (UnableToCompleteException e) {
195:                            throw new SAXException(e);
196:                        }
197:
198:                        // Since we don't know about this element, assume it should not have
199:                        // children either.
200:                        //
201:                        setArgsAndPushLevel(null, null);
202:
203:                        return;
204:                    }
205:
206:                    HandlerArgs args = method.createArgs(schemaLevel,
207:                            lineNumber, elemName);
208:
209:                    // For each attribute found, try to match it up to a parameter.
210:                    //
211:                    for (int i = 0, n = atts.getLength(); i < n; ++i) {
212:                        String attrName = atts.getQName(i);
213:                        String attrValue = atts.getValue(i);
214:
215:                        if (!args.setArg(attrName, attrValue)) {
216:                            // Inform the handler that the attribute was unknown.
217:                            //
218:                            try {
219:                                schemaLevel.onUnexpectedAttribute(lineNumber,
220:                                        elemName, attrName, attrValue);
221:                            } catch (UnableToCompleteException e) {
222:                                throw new SAXException(e);
223:                            }
224:                        }
225:                    }
226:
227:                    // Check for unset parameters.
228:                    //
229:                    int missingCount = 0;
230:                    for (int i = 0, n = args.getArgCount(); i < n; ++i) {
231:                        if (!args.isArgSet(i)) {
232:                            // Inform the handler that the required attribute was not set.
233:                            // It might throw, but it also might not.
234:                            //
235:                            try {
236:                                schemaLevel.onMissingAttribute(lineNumber,
237:                                        elemName, args.getArgName(i));
238:                            } catch (UnableToCompleteException e) {
239:                                throw new SAXException(e);
240:                            }
241:
242:                            ++missingCount;
243:                        }
244:                    }
245:
246:                    if (missingCount > 0) {
247:                        // Do not invoke the handler.
248:                        //
249:
250:                        // Assume that children shouldn't be recognized either since the
251:                        // handler wasn't invoked.
252:                        //
253:                        setArgsAndPushLevel(null, null);
254:
255:                        return;
256:                    }
257:
258:                    // Invoke the handler method, which will internally
259:                    // convert all the args to their respective parameter types
260:                    // (or warn if there is a problem doing so).
261:                    //
262:                    Object[] invokeArgs = new Object[method.getParamCount()];
263:                    Schema childSchemaLevel;
264:                    try {
265:                        childSchemaLevel = method.invokeBegin(lineNumber,
266:                                elemName, schemaLevel, args, invokeArgs);
267:                    } catch (UnableToCompleteException e) {
268:                        throw new SAXException(e);
269:                    }
270:
271:                    // childSchemaLevel can be null and that's okay -- it means no children
272:                    // are expected. Same for invokeArgs[0] -- it means that the "begin"
273:                    // handler was not called, so neither will we call the "end" handler.
274:                    //
275:                    setArgsAndPushLevel(invokeArgs, childSchemaLevel);
276:                }
277:
278:                private Object[] getCurrentArgs() {
279:                    return (Object[]) argStack.peek();
280:                }
281:
282:                private Schema getNextToTopSchemaLevel() {
283:                    return (Schema) schemaLevels.get(schemaLevels.size() - 2);
284:                }
285:
286:                private Schema getTopSchemaLevel() {
287:                    return (Schema) schemaLevels.peek();
288:                }
289:
290:                private void parse(TreeLogger logger, Schema topSchema,
291:                        Reader reader) throws UnableToCompleteException {
292:                    // Set up the parentmost schema which is used to find default converters
293:                    // and handlers (but isn't actually on the schema stack.)
294:                    //
295:                    defaultSchema = new DefaultSchema(logger);
296:
297:                    // Tell this schema level about the default schema, which is initialized
298:                    // with
299:                    // converters for basic types.
300:                    //
301:                    topSchema.setParent(defaultSchema);
302:
303:                    // Make a slot for the document element's args.
304:                    //
305:                    argStack.push(null);
306:
307:                    // Push the first schema.
308:                    //
309:                    setArgsAndPushLevel(null, topSchema);
310:
311:                    Throwable caught = null;
312:                    try {
313:                        this .reader = reader;
314:                        SAXParser parser = SAXParserFactory.newInstance()
315:                                .newSAXParser();
316:                        InputSource inputSource = new InputSource(this .reader);
317:                        XMLReader xmlReader = parser.getXMLReader();
318:                        xmlReader.setContentHandler(this );
319:                        xmlReader.parse(inputSource);
320:                    } catch (SAXException e) {
321:                        // If it's an exception wrapped in a SAXException, rip off the outer SAX
322:                        // exception.
323:                        //
324:                        caught = e;
325:
326:                        Exception inner = e.getException();
327:                        if (inner instanceof  RuntimeException) {
328:                            throw (RuntimeException) inner;
329:                        } else if (inner != null) {
330:                            caught = inner;
331:                        }
332:
333:                    } catch (ParserConfigurationException e) {
334:                        caught = e;
335:                    } catch (IOException e) {
336:                        caught = e;
337:                    } finally {
338:                        Utility.close(reader);
339:                    }
340:
341:                    if (caught != null) {
342:                        Messages.XML_PARSE_FAILED.log(logger, caught);
343:                        throw new UnableToCompleteException();
344:                    }
345:                }
346:
347:                private Schema popLevel() {
348:                    argStack.pop();
349:                    schemaLevels.pop();
350:                    return getTopSchemaLevel();
351:                }
352:
353:                private void setArgsAndPushLevel(Object[] handlerArgs,
354:                        Schema schemaLevel) {
355:                    // Set the args on the current schema level.
356:                    argStack.set(argStack.size() - 1, handlerArgs);
357:                    // A slot for the args at the childrens' depth.
358:                    argStack.push(null);
359:                    if (!schemaLevels.isEmpty()) {
360:                        // Tell this schema level about its parent.
361:                        //
362:                        Schema maybeParent = null;
363:                        for (int i = schemaLevels.size() - 1; i >= 0; --i) {
364:                            maybeParent = (Schema) schemaLevels.get(i);
365:                            if (maybeParent != null) {
366:                                break;
367:                            }
368:                        }
369:                        if (maybeParent == null) {
370:                            throw new IllegalStateException(
371:                                    "Cannot find any parent schema");
372:                        }
373:                        if (schemaLevel != null) {
374:                            schemaLevel.setParent(maybeParent);
375:                        }
376:                    }
377:                    // The schema for children.
378:                    schemaLevels.push(schemaLevel);
379:                }
380:            }
381:
382:            public static void parse(TreeLogger logger, Schema schema,
383:                    Reader reader) throws UnableToCompleteException {
384:
385:                // Register the schema level.
386:                //
387:                registerSchemaLevel(schema.getClass());
388:
389:                // Do the parse.
390:                //
391:                Impl impl = new Impl();
392:                impl.parse(logger, schema, reader);
393:            }
394:
395:            /**
396:             * Can safely register the same class recursively.
397:             */
398:            public static void registerSchemaLevel(Class schemaLevelClass) {
399:                HandlerClassInfo.registerClass(schemaLevelClass);
400:
401:                // Try to register nested classes.
402:                //
403:                Class[] nested = schemaLevelClass.getDeclaredClasses();
404:                for (int i = 0, n = nested.length; i < n; ++i) {
405:                    Class nestedClass = nested[i];
406:                    if (Schema.class.isAssignableFrom(nestedClass)) {
407:                        registerSchemaLevel(nestedClass);
408:                    }
409:                }
410:            }
411:        }
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