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Groovy: A powerful, dynamic language for the JVM
/*
* 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 groovy.text;
import groovy.lang.Binding;
import groovy.lang.GroovyRuntimeException;
import groovy.lang.GroovyShell;
import groovy.lang.Script;
import groovy.lang.Writable;
import groovy.util.IndentPrinter;
import groovy.util.Node;
import groovy.util.XmlNodePrinter;
import groovy.util.XmlParser;
import groovy.xml.QName;
import org.codehaus.groovy.control.CompilationFailedException;
import org.codehaus.groovy.runtime.InvokerHelper;
import org.xml.sax.SAXException;
import javax.xml.parsers.ParserConfigurationException;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.Map;
/**
* Template engine for use in templating scenarios where both the template
* source and the expected output are intended to be XML.
*
* Templates may use the normal '${expression}' and '$variable' notations
* to insert an arbitrary expression into the template.
* In addition, support is also provided for special tags:
* <gsp:scriptlet> (for inserting code fragments) and
* <gsp:expression> (for code fragments which produce output).
*
* Comments and processing instructions
* will be removed as part of processing and special XML characters such as
* <, >, " and ' will be escaped using the respective XML notation.
* The output will also be indented using standard XML pretty printing.
*
* The xmlns namespace definition for gsp: tags will be removed
* but other namespace definitions will be preserved (but may change to an
* equivalent position within the XML tree).
*
* Normally, the template source will be in a file but here is a simple
* example providing the XML template as a string:
*
* def binding = [firstname:"Jochen", lastname:"Theodorou",
* nickname:"blackdrag", salutation:"Dear"]
* def engine = new groovy.text.XmlTemplateEngine()
* def text = '''\
* <?xml version="1.0" encoding="UTF-8"?>
* <document xmlns:gsp='http://groovy.codehaus.org/2005/gsp' xmlns:foo='baz' type='letter'>
* <gsp:scriptlet>def greeting = "${salutation}est"</gsp:scriptlet>
* <gsp:expression>greeting</gsp:expression>
* <foo:to>$firstname "$nickname" $lastname</foo:to>
* How are you today?
* </document>
* '''
* def template = engine.createTemplate(text).make(binding)
* println template.toString()
*
* This example will produce this output:
*
* <document type='letter'>
* Dearest
* <foo:to xmlns:foo='baz'>
* Jochen "blackdrag" Theodorou
* </foo:to>
* How are you today?
* </document>
*
* The XML template engine can also be used as the engine for {@link groovy.servlet.TemplateServlet} by placing the
* following in your web.xml file (plus a corresponding servlet-mapping element):
*
* <servlet>
* <servlet-name>XmlTemplate</servlet-name>
* <servlet-class>groovy.servlet.TemplateServlet</servlet-class>
* <init-param>
* <param-name>template.engine</param-name>
* <param-value>groovy.text.XmlTemplateEngine</param-value>
* </init-param>
* </servlet>
*
*
* @author Christian Stein
* @author Paul King
*/
public class XmlTemplateEngine extends TemplateEngine {
private static int counter = 1;
private static class GspPrinter extends XmlNodePrinter {
public GspPrinter(PrintWriter out, String indent) {
this(new IndentPrinter(out, indent));
}
public GspPrinter(IndentPrinter out) {
super(out, "\\\"");
setQuote("'");
}
protected void printGroovyTag(String tag, String text) {
if (tag.equals("scriptlet")) {
out.print(text);
out.print("\n");
return;
}
if (tag.equals("expression")) {
printLineBegin();
out.print("${");
out.print(text);
out.print("}");
printLineEnd();
return;
}
throw new RuntimeException("Unsupported 'gsp:' tag named \"" + tag + "\".");
}
protected void printSimpleItem(Object value) {
this.printLineBegin();
out.print(escapeSpecialChars(InvokerHelper.toString(value)));
printLineEnd();
}
private String escapeSpecialChars(String s) {
StringBuilder sb = new StringBuilder();
boolean inGString = false;
for (int i = 0; i < s.length(); i++) {
final char c = s.charAt(i);
switch (c) {
case '$':
sb.append("$");
if (i < s.length() - 1 && s.charAt(i + 1) == '{') inGString = true;
break;
case '<':
append(sb, c, "<", inGString);
break;
case '>':
append(sb, c, ">", inGString);
break;
case '"':
append(sb, c, """, inGString);
break;
case '\'':
append(sb, c, "'", inGString);
break;
case '}':
sb.append(c);
inGString = false;
break;
default:
sb.append(c);
}
}
return sb.toString();
}
private void append(StringBuilder sb, char plainChar, String xmlString, boolean inGString) {
if (inGString) {
sb.append(plainChar);
} else {
sb.append(xmlString);
}
}
protected void printLineBegin() {
out.print("out.print(\"\"\"");
out.printIndent();
}
protected void printLineEnd(String comment) {
out.print("\\n\"\"\");");
if (comment != null) {
out.print(" // ");
out.print(comment);
}
out.print("\n");
}
protected boolean printSpecialNode(Node node) {
Object name = node.name();
if (name != null && name instanceof QName) {
QName qn = (QName) name;
// check uri and for legacy cases just check prefix name (not recommended)
if (qn.getNamespaceURI().equals("http://groovy.codehaus.org/2005/gsp") || qn.getPrefix().equals("gsp")) {
String s = qn.getLocalPart();
if (s.length() == 0) {
throw new RuntimeException("No local part after 'gsp:' given in node " + node);
}
printGroovyTag(s, node.text());
return true;
}
}
return false;
}
}
private static class XmlTemplate implements Template {
private final Script script;
public XmlTemplate(Script script) {
this.script = script;
}
public Writable make() {
return make(new HashMap());
}
public Writable make(Map map) {
if (map == null) {
throw new IllegalArgumentException("map must not be null");
}
return new XmlWritable(script, new Binding(map));
}
}
private static class XmlWritable implements Writable {
private final Binding binding;
private final Script script;
private WeakReference result;
public XmlWritable(Script script, Binding binding) {
this.script = script;
this.binding = binding;
this.result = new WeakReference(null);
}
public Writer writeTo(Writer out) {
Script scriptObject = InvokerHelper.createScript(script.getClass(), binding);
PrintWriter pw = new PrintWriter(out);
scriptObject.setProperty("out", pw);
scriptObject.run();
pw.flush();
return out;
}
public String toString() {
if (result.get() != null) {
return result.get().toString();
}
String string = writeTo(new StringWriter(1024)).toString();
result = new WeakReference(string);
return string;
}
}
public static final String DEFAULT_INDENTATION = " ";
private final GroovyShell groovyShell;
private final XmlParser xmlParser;
private String indentation;
public XmlTemplateEngine() throws SAXException, ParserConfigurationException {
this(DEFAULT_INDENTATION, false);
}
public XmlTemplateEngine(String indentation, boolean validating) throws SAXException, ParserConfigurationException {
this(new XmlParser(validating, true), new GroovyShell());
this.xmlParser.setTrimWhitespace(true);
setIndentation(indentation);
}
public XmlTemplateEngine(XmlParser xmlParser, ClassLoader parentLoader) {
this(xmlParser, new GroovyShell(parentLoader));
}
public XmlTemplateEngine(XmlParser xmlParser, GroovyShell groovyShell) {
this.groovyShell = groovyShell;
this.xmlParser = xmlParser;
setIndentation(DEFAULT_INDENTATION);
}
public Template createTemplate(Reader reader) throws CompilationFailedException, ClassNotFoundException, IOException {
Node root ;
try {
root = xmlParser.parse(reader);
} catch (SAXException e) {
throw new RuntimeException("Parsing XML source failed.", e);
}
if (root == null) {
throw new IOException("Parsing XML source failed: root node is null.");
}
StringWriter writer = new StringWriter(1024);
writer.write("/* Generated by XmlTemplateEngine */\n");
new GspPrinter(new PrintWriter(writer), indentation).print(root);
Script script;
try {
script = groovyShell.parse(writer.toString(), "XmlTemplateScript" + counter++ + ".groovy");
} catch (Exception e) {
throw new GroovyRuntimeException("Failed to parse template script (your template may contain an error or be trying to use expressions not currently supported): " + e.getMessage());
}
return new XmlTemplate(script);
}
public String getIndentation() {
return indentation;
}
public void setIndentation(String indentation) {
if (indentation == null) {
indentation = DEFAULT_INDENTATION;
}
this.indentation = indentation;
}
public String toString() {
return "XmlTemplateEngine";
}
}