/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* C E D A R
* S O L U T I O N S "Software done right."
* S O F T W A R E
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* Copyright (c) 2013-2014 Kenneth J. Pronovici.
* All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the Apache License, Version 2.0.
* See LICENSE for more information about the licensing terms.
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* Author : Kenneth J. Pronovici <pronovic@ieee.org>
* Language : Java 6
* Project : Common Java Functionality
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
package com.cedarsolutions.util;
import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.HashMap;
import java.util.Map;
import javax.xml.XMLConstants;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.SchemaOutputResolver;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.ValidationEvent;
import javax.xml.bind.util.ValidationEventCollector;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import org.xml.sax.SAXException;
import com.cedarsolutions.exception.CedarRuntimeException;
import com.cedarsolutions.exception.InvalidDataException;
import com.cedarsolutions.shared.domain.ValidationErrors;
/**
* JAXB utilities that operate on a cached JAXB context.
*
* <p>
* The process of establishing a JAXB context can be pretty slow. So, we want
* to avoid having to do it more often than necessary. This class keeps an
* internal cache of contexts that have already been established. It also
* provides some utility methods to simplify marshalling and unmarshalling.
* </p>
*
* @author Kenneth J. Pronovici <pronovic@ieee.org>
*/
@SuppressWarnings({ "unchecked", "rawtypes" })
public class JaxbUtils {
/** Validation error key used for XML errors. */
public static final String ERROR_KEY = "jaxb";
/** Singleton instance. */
private static JaxbUtils INSTANCE;
/** Map from class name to generated JAXB context. */
private Map<String, JAXBContext> contextMap = new HashMap<String, JAXBContext>();
/** Default constructor is private so class cannot be instantiated. */
private JaxbUtils() {
}
/** Get an instance of this class to use. */
public static synchronized JaxbUtils getInstance() {
if (INSTANCE == null) {
INSTANCE = new JaxbUtils();
}
return INSTANCE;
}
/**
* Get a JAXB context for the indicated class.
* @param className Name of the class to get a context for
* @return JAXB context for the class.
*/
public JAXBContext getJaxbContext(String className) {
try {
Class clazz = Class.forName(className);
return this.getJaxbContext(clazz);
} catch (Exception e) {
throw new CedarRuntimeException("Error obtaining JAXB context: " + e.getMessage(), e);
}
}
/**
* Get a JAXB context for the indicated class.
* @param clazz Class to get a context for.
* @return JAXB context for the class.
*/
public synchronized <T> JAXBContext getJaxbContext(Class<T> clazz) {
if (!this.contextMap.containsKey(clazz.getName())) {
try {
JAXBContext context = JAXBContext.newInstance(clazz);
this.contextMap.put(clazz.getName(), context);
} catch (Exception e) {
throw new CedarRuntimeException("Error obtaining JAXB context: " + e.getMessage(), e);
}
}
return this.contextMap.get(clazz.getName());
}
/**
* Marshal an object of type T, creating XML with no schema location.
* @param <T> Type of the object
* @param value Value to marshal.
* @return Generated XML.
*/
public <T> String marshalDocument(T value) {
return marshalDocument(value, null);
}
/**
* Marshal an object of type T, creating XML.
* @param <T> Type of the object
* @param value Value to marshal.
* @param schema Location of the schema to be placed in the XML, or null
* @return Generated XML.
*/
public <T> String marshalDocument(T value, String schema) {
try {
JAXBContext context = this.getJaxbContext(value.getClass());
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.setProperty(Marshaller.JAXB_FRAGMENT, false);
if (schema != null) {
marshaller.setProperty(Marshaller.JAXB_SCHEMA_LOCATION, schema);
}
StringWriter writer = new StringWriter();
marshaller.marshal(value, writer);
return writer.toString();
} catch (JAXBException e) {
throw new CedarRuntimeException("Error marshalling XML: " + e.getMessage(), e);
}
}
/**
* Unmarshal XML, creating an object of type T.
* @param <T> Type of the object
* @param type Type of the object to unmarshal
* @param xml XML to use as source
* @return Object of type T, unmarshalled from the XML.
*/
public <T> T unmarshalDocument(Class<T> type, String xml) {
return unmarshalDocument(type, xml, true);
}
/**
* Unmarshal XML, creating an object of type T.
* @param <T> Type of the object
* @param type Type of the object to unmarshal
* @param xml XML to use as source
* @param validate Whether to validate the unmarshalling step
* @return Object of type T, unmarshalled from the XML.
* @throws InvalidDataException If the XML could not be parsed or if there are validation errors.
*/
public <T> T unmarshalDocument(Class<T> type, String xml, boolean validate) {
try {
JAXBContext context = this.getJaxbContext(type);
StringReader reader = new StringReader(xml);
Source source = new StreamSource(reader);
if (!validate) {
Unmarshaller unmarshaller = context.createUnmarshaller();
JAXBElement<T> element = unmarshaller.unmarshal(source, type);
return element.getValue();
} else {
// If an adapter fails, we don't get an unmarshal exception.
// Instead, we have to register and interrogate a handler.
// See also: http://java.net/jira/browse/JAXB-537
Unmarshaller unmarshaller = context.createUnmarshaller();
String xsd = this.generateSchema(type);
SchemaFactory sf = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Schema schema = sf.newSchema(new StreamSource(new StringReader(xsd)));
ValidationEventCollector eventHandler = new ValidationEventCollector();
unmarshaller.setEventHandler(eventHandler);
unmarshaller.setSchema(schema);
JAXBElement<T> element = unmarshaller.unmarshal(source, type);
if (eventHandler.hasEvents()) {
throw generateValidationError(type, eventHandler);
}
return element.getValue();
}
} catch (JAXBException e) {
throw translateJaxbUnmarshalError(type, e);
} catch (SAXException e) {
InvalidDataException invalid = getUnmarshalError(type, e);
invalid.getDetails().addMessage(ERROR_KEY, e.getMessage());
throw invalid;
}
}
/**
* Generate the XML schema for a JAXB type.
* @param <T> Type of the object
* @param type Type of the object to unmarshal
*/
public <T> String generateSchema(Class<T> type) {
try {
JAXBContext context = this.getJaxbContext(type);
SchemaResolver resolver = new SchemaResolver();
context.generateSchema(resolver);
return resolver.getWriter().toString();
} catch (IOException e) {
throw new CedarRuntimeException("Error generating schema: " + e.getMessage(), e);
}
}
/** Get a "raw" invalid data exception for a class, with empty details attached. */
private static <T> InvalidDataException getUnmarshalError(Class<T> type, Throwable cause) {
ValidationErrors details = new ValidationErrors(ERROR_KEY, "Error unmarshalling XML for " + type.getSimpleName());
return new InvalidDataException("Error unmarshalling XML for " + type.getSimpleName(), details);
}
/** A resolver used for generating a schema from JAXB. */
private static class SchemaResolver extends SchemaOutputResolver {
private StringWriter writer = new StringWriter();
public StringWriter getWriter() {
return this.writer;
}
@Override
public Result createOutput(String namespaceUri, String suggestedFileName) throws IOException {
Result result = new StreamResult(this.writer);
result.setSystemId("id");
return result;
}
}
/** Generate a JAXB unmarshal exception due to validation problems. */
private static <T> InvalidDataException generateValidationError(Class<T> type, ValidationEventCollector eventHandler) {
InvalidDataException invalid = getUnmarshalError(type, null);
invalid.getDetails().addMessage(ERROR_KEY, "Found validation errors");
for (ValidationEvent event : eventHandler.getEvents()) {
invalid.getDetails().addMessage(ERROR_KEY, event.getMessage());
}
return invalid;
}
/** Translate a JAXB unmarshal exception into something legible. */
private static <T> InvalidDataException translateJaxbUnmarshalError(Class<T> type, JAXBException e) {
boolean added = false;
InvalidDataException invalid = getUnmarshalError(type, e);
// This was developed through trial-and-error. I don't know how well it will hold up in the future.
if (e.getCause() != null && e.getLinkedException() != null) {
try {
throw e.getLinkedException();
} catch (org.xml.sax.SAXParseException sax) {
String message = "Line " + sax.getLineNumber() + ", column " + sax.getColumnNumber() + ": " + e.getCause().getMessage();
invalid.getDetails().addMessage(ERROR_KEY, message);
added = true;
} catch (Throwable other) { }
}
if (!added && e.getCause() != null && e.getCause().getMessage() != null) {
invalid.getDetails().addMessage(ERROR_KEY, e.getCause().getMessage());
added = true;
}
if (!added && e.getMessage() != null) {
invalid.getDetails().addMessage(ERROR_KEY, e.getMessage());
added = true;
}
return invalid;
}
}