Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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 org.apache.tika.parser.asm; import java.io.IOException; import java.io.InputStream; import org.apache.tika.exception.TikaException; import org.apache.tika.metadata.Metadata; import org.apache.tika.metadata.TikaCoreProperties; import org.apache.tika.sax.XHTMLContentHandler; import org.objectweb.asm.AnnotationVisitor; import org.objectweb.asm.Attribute; import org.objectweb.asm.ClassReader; import org.objectweb.asm.ClassVisitor; import org.objectweb.asm.FieldVisitor; import org.objectweb.asm.MethodVisitor; import org.objectweb.asm.Opcodes; import org.objectweb.asm.Type; import org.xml.sax.ContentHandler; import org.xml.sax.SAXException; /** * Class visitor that generates XHTML SAX events to describe the * contents of the visited class. */ class XHTMLClassVisitor extends ClassVisitor { private final XHTMLContentHandler xhtml; private final Metadata metadata; private Type type; private String packageName; public XHTMLClassVisitor(ContentHandler handler, Metadata metadata) { super(Opcodes.ASM4); this.xhtml = new XHTMLContentHandler(handler, metadata); this.metadata = metadata; } public void parse(InputStream stream) throws TikaException, SAXException, IOException { try { ClassReader reader = new ClassReader(stream); reader.accept(this, ClassReader.SKIP_FRAMES | ClassReader.SKIP_CODE); } catch (RuntimeException e) { if (e.getCause() instanceof SAXException) { throw (SAXException) e.getCause(); } else { throw new TikaException("Failed to parse a Java class", e); } } } public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) { type = Type.getObjectType(name); String className = type.getClassName(); int dot = className.lastIndexOf('.'); if (dot != -1) { packageName = className.substring(0, dot); className = className.substring(dot + 1); } metadata.set(TikaCoreProperties.TITLE, className); metadata.set(Metadata.RESOURCE_NAME_KEY, className + ".class"); try { xhtml.startDocument(); xhtml.startElement("pre"); if (packageName != null) { writeKeyword("package"); xhtml.characters(" " + packageName + ";\n"); } writeAccess(access); if (isSet(access, Opcodes.ACC_INTERFACE)) { writeKeyword("interface"); writeSpace(); writeType(type); writeSpace(); writeInterfaces("extends", interfaces); } else if (isSet(access, Opcodes.ACC_ENUM)) { writeKeyword("enum"); writeSpace(); writeType(type); writeSpace(); } else { writeKeyword("class"); writeSpace(); writeType(type); writeSpace(); if (superName != null) { Type superType = Type.getObjectType(superName); if (!superType.getClassName().equals("java.lang.Object")) { writeKeyword("extends"); writeSpace(); writeType(superType); writeSpace(); } } writeInterfaces("implements", interfaces); } xhtml.characters("{\n"); } catch (SAXException e) { throw new RuntimeException(e); } } private void writeInterfaces(String keyword, String[] interfaces) throws SAXException { if (interfaces != null && interfaces.length > 0) { writeKeyword(keyword); String separator = " "; for (String iface : interfaces) { xhtml.characters(separator); writeType(Type.getObjectType(iface)); separator = ", "; } writeSpace(); } } public void visitEnd() { try { xhtml.characters("}\n"); xhtml.endElement("pre"); xhtml.endDocument(); } catch (SAXException e) { throw new RuntimeException(e); } } /** * Ignored. */ public void visitOuterClass(String owner, String name, String desc) { } /** * Ignored. */ public void visitSource(String source, String debug) { } /** * Ignored. */ public AnnotationVisitor visitAnnotation(String desc, boolean visible) { return null; } /** * Ignored. */ public void visitAttribute(Attribute attr) { } /** * Ignored. */ public void visitInnerClass(String name, String outerName, String innerName, int access) { } /** * Visits a field. */ public FieldVisitor visitField(int access, String name, String desc, String signature, Object value) { if (!isSet(access, Opcodes.ACC_SYNTHETIC)) { try { xhtml.characters(" "); writeAccess(access); writeType(Type.getType(desc)); writeSpace(); writeIdentifier(name); if (isSet(access, Opcodes.ACC_STATIC) && value != null) { xhtml.characters(" = "); xhtml.characters(value.toString()); } writeSemicolon(); writeNewline(); } catch (SAXException e) { throw new RuntimeException(e); } } return null; } /** * Visits a method. */ public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) { if (!isSet(access, Opcodes.ACC_SYNTHETIC)) { try { xhtml.characters(" "); writeAccess(access); writeType(Type.getReturnType(desc)); writeSpace(); if ("<init>".equals(name)) { writeType(type); } else { writeIdentifier(name); } xhtml.characters("("); String separator = ""; for (Type arg : Type.getArgumentTypes(desc)) { xhtml.characters(separator); writeType(arg); separator = ", "; } xhtml.characters(")"); if (exceptions != null && exceptions.length > 0) { writeSpace(); writeKeyword("throws"); separator = " "; for (String exception : exceptions) { xhtml.characters(separator); writeType(Type.getObjectType(exception)); separator = ", "; } } writeSemicolon(); writeNewline(); } catch (SAXException e) { throw new RuntimeException(e); } } return null; } private void writeIdentifier(String identifier) throws SAXException { xhtml.startElement("span", "class", "java-identifier"); xhtml.characters(identifier); xhtml.endElement("span"); } private void writeKeyword(String keyword) throws SAXException { xhtml.startElement("span", "class", "java-keyword"); xhtml.characters(keyword); xhtml.endElement("span"); } private void writeSemicolon() throws SAXException { xhtml.characters(";"); } private void writeSpace() throws SAXException { xhtml.characters(" "); } private void writeNewline() throws SAXException { xhtml.characters("\n"); } private void writeAccess(int access) throws SAXException { writeAccess(access, Opcodes.ACC_PRIVATE, "private"); writeAccess(access, Opcodes.ACC_PROTECTED, "protected"); writeAccess(access, Opcodes.ACC_PUBLIC, "public"); writeAccess(access, Opcodes.ACC_STATIC, "static"); writeAccess(access, Opcodes.ACC_FINAL, "final"); writeAccess(access, Opcodes.ACC_ABSTRACT, "abstract"); writeAccess(access, Opcodes.ACC_SYNCHRONIZED, "synchronized"); writeAccess(access, Opcodes.ACC_TRANSIENT, "transient"); writeAccess(access, Opcodes.ACC_VOLATILE, "volatile"); writeAccess(access, Opcodes.ACC_NATIVE, "native"); } private void writeAccess(int access, int code, String keyword) throws SAXException { if (isSet(access, code)) { writeKeyword(keyword); xhtml.characters(" "); } } private void writeType(Type type) throws SAXException { String name = type.getClassName(); if (name.startsWith(packageName + ".")) { xhtml.characters(name.substring(packageName.length() + 1)); } else if (name.startsWith("java.lang.")) { xhtml.characters(name.substring("java.lang.".length())); } else { xhtml.characters(name); } } private static boolean isSet(int value, int flag) { return (value & flag) != 0; } }