XMLSchemaGenerator.java

/*
 * Copyright 2010-2011 Ning, Inc.
 *
 * Ning 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 com.ning.billing.util.config;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.SchemaOutputResolver;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMResult;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

import org.w3c.dom.Document;

public class XMLSchemaGenerator {
	final private static  int MAX_SCHEMA_SIZE_IN_BYTES = 100000;


	//Note: this main method is called by the maven build to generate the schema for the jar
	public static void main(String[] args) throws IOException, TransformerException, JAXBException, ClassNotFoundException {
		if (args.length != 2) {
			printUsage();
			System.exit(0);
		}
		Class<?> clazz = ClassLoader.getSystemClassLoader().loadClass(args[1]);
		
		JAXBContext context =JAXBContext.newInstance(clazz);
		String xsdFileName = "Schema.xsd";
		if(args.length != 0) {
			xsdFileName = args[0] + "/" + xsdFileName;
		}
		FileOutputStream s = new FileOutputStream(xsdFileName);
		pojoToXSD(context, s);
	}

	private static void printUsage() {
		System.out.println(XMLSchemaGenerator.class.getName() + " <file> <class1>");
		
	}
	
	public static String xmlSchemaAsString(Class<?> clazz) throws IOException, TransformerException, JAXBException {
		ByteArrayOutputStream output = new ByteArrayOutputStream(MAX_SCHEMA_SIZE_IN_BYTES);
		JAXBContext context =JAXBContext.newInstance(clazz);
		pojoToXSD(context, output);
		return new String(output.toByteArray());
	}

	public static InputStream xmlSchema(Class<?> clazz) throws IOException, TransformerException, JAXBException {
		ByteArrayOutputStream output = new ByteArrayOutputStream(MAX_SCHEMA_SIZE_IN_BYTES);
		JAXBContext context =JAXBContext.newInstance(clazz);
		pojoToXSD(context, output);
		return new ByteArrayInputStream(output.toByteArray());
	}

	public static void pojoToXSD(JAXBContext context, OutputStream out)
		    throws IOException, TransformerException
		{
		    final List<DOMResult> results = new ArrayList<DOMResult>();

		    context.generateSchema(new SchemaOutputResolver() {
		        @Override
		        public Result createOutput(String ns, String file)
		                throws IOException {
		            DOMResult result = new DOMResult();
		            result.setSystemId(file);
		            results.add(result);
		            return result;
		        }
		    });

		    DOMResult domResult = results.get(0);
		    Document doc = (Document) domResult.getNode();

		    // Use a Transformer for output
		    TransformerFactory tFactory = TransformerFactory.newInstance();
		    Transformer transformer = tFactory.newTransformer();

		    DOMSource source = new DOMSource(doc);
		    StreamResult result = new StreamResult(out);
		    transformer.setOutputProperty(OutputKeys.INDENT, "yes");
		    transformer.transform(source, result);
		}

}