Java tutorial
/* * $Id$ * * 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.struts2; import com.opensymphony.xwork2.FileManager; import com.opensymphony.xwork2.FileManagerFactory; import com.opensymphony.xwork2.util.finder.ClassLoaderInterface; import com.opensymphony.xwork2.util.finder.ClassLoaderInterfaceDelegate; import com.opensymphony.xwork2.util.finder.UrlSet; import com.opensymphony.xwork2.util.logging.Logger; import com.opensymphony.xwork2.util.logging.LoggerFactory; import org.apache.commons.io.FileUtils; import org.apache.commons.lang3.ObjectUtils; import org.apache.commons.lang3.StringUtils; import org.apache.struts2.compiler.MemoryClassLoader; import org.apache.struts2.compiler.MemoryJavaFileObject; import org.apache.struts2.jasper.JasperException; import org.apache.struts2.jasper.JspC; import javax.servlet.Servlet; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.jsp.JspPage; import javax.tools.DiagnosticCollector; import javax.tools.FileObject; import javax.tools.ForwardingJavaFileManager; import javax.tools.JavaCompiler; import javax.tools.JavaFileManager; import javax.tools.JavaFileObject; import javax.tools.SimpleJavaFileObject; import javax.tools.StandardJavaFileManager; import javax.tools.ToolProvider; import java.io.File; import java.io.IOException; import java.net.URI; import java.net.URISyntaxException; import java.net.URL; import java.security.CodeSource; import java.security.ProtectionDomain; import java.util.ArrayList; import java.util.Arrays; import java.util.HashSet; import java.util.Iterator; import java.util.List; import java.util.Set; import java.util.regex.Matcher; import java.util.regex.Pattern; /** * Uses jasper to extract a JSP from the classpath to a file and compile it. The classpath used for * compilation is built by finding all the jar files using the current class loader (Thread), plus * directories. */ public class JSPLoader { private static final Logger LOG = LoggerFactory.getLogger(JSPLoader.class); private static MemoryClassLoader classLoader = new MemoryClassLoader(); private static final String DEFAULT_PACKAGE = "org.apache.struts2.jsp"; private static final Pattern PACKAGE_PATTERN = Pattern.compile("package (.*?);"); private static final Pattern CLASS_PATTERN = Pattern.compile("public final class (.*?) "); public Servlet load(String location) throws Exception { location = StringUtils.substringBeforeLast(location, "?"); if (LOG.isDebugEnabled()) { LOG.debug("Compiling JSP [#0]", location); } //use Jasper to compile the JSP into java code JspC jspC = compileJSP(location); String source = jspC.getSourceCode(); //System.out.print(source); String className = extractClassName(source); //use Java Compiler API to compile the java code into a class //the tlds that were discovered are added (their jars) to the classpath compileJava(className, source, jspC.getTldAbsolutePaths()); //load the class that was just built Class clazz = Class.forName(className, false, classLoader); return createServlet(clazz); } private String extractClassName(String source) { Matcher matcher = PACKAGE_PATTERN.matcher(source); matcher.find(); String packageName = matcher.group(1); matcher = CLASS_PATTERN.matcher(source); matcher.find(); String className = matcher.group(1); return packageName + "." + className; } /** * Creates and inits a servlet */ private Servlet createServlet(Class clazz) throws IllegalAccessException, InstantiationException, ServletException { JSPServletConfig config = new JSPServletConfig(ServletActionContext.getServletContext()); Servlet servlet = (Servlet) clazz.newInstance(); servlet.init(config); /* there is no need to call JspPage.init explicitly because Jasper's JSP base classe HttpJspBase.init(ServletConfig) calls: jspInit(); _jspInit(); */ return servlet; } /** * Compiles the given source code into java bytecode */ private void compileJava(String className, final String source, Set<String> extraClassPath) throws IOException { if (LOG.isTraceEnabled()) LOG.trace("Compiling [#0], source: [#1]", className, source); JavaCompiler compiler = ToolProvider.getSystemJavaCompiler(); DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>(); //the generated bytecode is fed to the class loader JavaFileManager jfm = new ForwardingJavaFileManager<StandardJavaFileManager>( compiler.getStandardFileManager(diagnostics, null, null)) { @Override public JavaFileObject getJavaFileForOutput(Location location, String name, JavaFileObject.Kind kind, FileObject sibling) throws IOException { MemoryJavaFileObject fileObject = new MemoryJavaFileObject(name, kind); classLoader.addMemoryJavaFileObject(name, fileObject); return fileObject; } }; //read java source code from memory String fileName = className.replace('.', '/') + ".java"; SimpleJavaFileObject sourceCodeObject = new SimpleJavaFileObject(toURI(fileName), JavaFileObject.Kind.SOURCE) { @Override public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException, IllegalStateException, UnsupportedOperationException { return source; } }; //build classpath //some entries will be added multiple times, hence the set List<String> optionList = new ArrayList<String>(); Set<String> classPath = new HashSet<String>(); FileManager fileManager = ServletActionContext.getContext().getInstance(FileManagerFactory.class) .getFileManager(); //find available jars ClassLoaderInterface classLoaderInterface = getClassLoaderInterface(); UrlSet urlSet = new UrlSet(classLoaderInterface); //find jars List<URL> urls = urlSet.getUrls(); for (URL url : urls) { URL normalizedUrl = fileManager.normalizeToFileProtocol(url); File file = FileUtils.toFile(ObjectUtils.defaultIfNull(normalizedUrl, url)); if (file.exists()) classPath.add(file.getAbsolutePath()); } //these should be in the list already, but I am feeling paranoid //this jar classPath.add(getJarUrl(EmbeddedJSPResult.class)); //servlet api classPath.add(getJarUrl(Servlet.class)); //jsp api classPath.add(getJarUrl(JspPage.class)); try { Class annotationsProcessor = Class.forName("org.apache.AnnotationProcessor"); classPath.add(getJarUrl(annotationsProcessor)); } catch (ClassNotFoundException e) { //ok ignore } //add extra classpath entries (jars where tlds were found will be here) for (Iterator<String> iterator = extraClassPath.iterator(); iterator.hasNext();) { String entry = iterator.next(); classPath.add(entry); } String classPathString = StringUtils.join(classPath, File.pathSeparator); if (LOG.isDebugEnabled()) { LOG.debug("Compiling [#0] with classpath [#1]", className, classPathString); } optionList.addAll(Arrays.asList("-classpath", classPathString)); //compile JavaCompiler.CompilationTask task = compiler.getTask(null, jfm, diagnostics, optionList, null, Arrays.asList(sourceCodeObject)); if (!task.call()) { throw new StrutsException("Compilation failed:" + diagnostics.getDiagnostics().get(0).toString()); } } protected String getJarUrl(Class clazz) { ProtectionDomain protectionDomain = clazz.getProtectionDomain(); CodeSource codeSource = protectionDomain.getCodeSource(); URL loc = codeSource.getLocation(); File file = FileUtils.toFile(loc); return file.getAbsolutePath(); } private JspC compileJSP(String location) throws JasperException { JspC jspC = new JspC(); jspC.setClassLoaderInterface(getClassLoaderInterface()); jspC.setCompile(false); jspC.setJspFiles(location); jspC.setPackage(DEFAULT_PACKAGE); jspC.execute(); return jspC; } private ClassLoaderInterface getClassLoaderInterface() { ClassLoaderInterface classLoaderInterface = null; ServletContext ctx = ServletActionContext.getServletContext(); if (ctx != null) classLoaderInterface = (ClassLoaderInterface) ctx .getAttribute(ClassLoaderInterface.CLASS_LOADER_INTERFACE); return (ClassLoaderInterface) ObjectUtils.defaultIfNull(classLoaderInterface, new ClassLoaderInterfaceDelegate(JSPLoader.class.getClassLoader())); } private static URI toURI(String name) { try { return new URI(name); } catch (URISyntaxException e) { throw new RuntimeException(e); } } }