FULL PRODUCT VERSION :
java version "1.8.0_112"
Java(TM) SE Runtime Environment (build 1.8.0_112-b15)
Java HotSpot(TM) Client VM (build 25.112-b15, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
JAX-B marshal/unmarshal operations are not symmetric for strings containing newline characters (CR, LF or CRLF) (i.e. the resulting string after a marshal/unmarshal cycle isn't what the original string was).
Since XML parsers must normalize attribute values by replacing newline characters with spaces (reference: http://www.w3.org/TR/REC-xml/#AVNormalize), newline characters need to be escaped properly during marshalling. This escaping seems to be missing in JAX-B. In other parts of the JDK, this is handled properly, e.g. Transformer properly escapse newline characters.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
See attached test case. The 'testWriter' method shows the problem.


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.io.StringReader;
import java.io.StringWriter;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMResult;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import junit.framework.TestCase;

import org.w3c.dom.Document;

public class CrLfMarshalUnmarshalTest extends TestCase {
  private static final String VALUE = "abc\r\nd\re\nf";
  private Bean fElem;
  private Marshaller fMarshaller;
  private Unmarshaller fUnmarshaller;
  
  @Override
  protected void setUp() throws Exception {
    super.setUp();
    JAXBContext ctx = JAXBContext.newInstance(Bean.class);
    fMarshaller = ctx.createMarshaller();
    fUnmarshaller = ctx.createUnmarshaller();
    
    fElem = new Bean();
    fElem.setAttributeString(VALUE);
    fElem.setElementString(VALUE);
  }
  
  public void testWriter() throws Exception {
    StringWriter sw = new StringWriter();
    fMarshaller.marshal(fElem, sw);
    String resultXml = sw.toString();
    System.out.println(resultXml);
    Bean resultElem = (Bean) fUnmarshaller.unmarshal(new StringReader(resultXml));
    assertEquals(VALUE, resultElem.getAttributeString());
    assertEquals(VALUE, resultElem.getElementString());
  }

  public void testDomAndTransform() throws Exception {
    StringWriter sw = new StringWriter();
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    dbf.setNamespaceAware(true);
    DocumentBuilder db = dbf.newDocumentBuilder();
    Document d = db.newDocument();
    DOMResult result = new DOMResult(d);
    fMarshaller.marshal(fElem, result);
    Transformer tf = TransformerFactory.newInstance().newTransformer();
    tf.transform(new DOMSource(d), new StreamResult(sw));
    String resultXml = sw.toString();
    System.out.println(resultXml);
    Bean resultElem = (Bean) fUnmarshaller.unmarshal(new StringReader(resultXml));
    assertEquals(VALUE, resultElem.getAttributeString());
    assertEquals(VALUE, resultElem.getElementString());
  }
  
  @XmlAccessorType(XmlAccessType.FIELD)
  @XmlType(name = "", propOrder = {"fElementString", "fAttributeString"})
  @XmlRootElement(name = "Bean")
  public static class Bean {

    @XmlElement(name = "ElementString")
    protected String fElementString;

    @XmlAttribute(name = "AttributeString")
    protected String fAttributeString;
    
    public String getElementString() {
      return fElementString;
    }
    
    public void setElementString(String elementString) {
      fElementString = elementString;
    }
    
    public String getAttributeString() {
      return fAttributeString;
    }
    
    public void setAttributeString(String attributeString) {
      fAttributeString = attributeString;
    }

  }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
See attached test case. The 'testDomAndTransform' method shows a workaround: the actual xml output is delegated to a Transformer, which properly escapes newline characters.