title: Setting null string as xsi:nil=true
body: <p>I have this class</p>
  
  <pre><code>package com.ni.schemas.provider_framework._1.providers;
  
  import java.math.BigInteger;
  import javax.xml.bind.annotation.XmlAccessType;
  import javax.xml.bind.annotation.XmlAccessorType;
  import javax.xml.bind.annotation.XmlElement;
  import javax.xml.bind.annotation.XmlType;
  
  
  /**
   * 
   *                 This is the top-level for a Request. 
   *                 Providers may extend this type if needed, but may not restrict it by blocking the pre-defined elements
   *             
   * 
   * &lt;p&gt;Clase Java para RequestErrorType complex type.
   * 
   * &lt;p&gt;El siguiente fragmento de esquema especifica el contenido que se espera que haya en esta clase.
   * 
   * &lt;pre&gt;
   * &amp;lt;complexType name="RequestErrorType"&gt;
   *   &amp;lt;complexContent&gt;
   *     &amp;lt;restriction base="{http://www.w3.org/2001/XMLSchema}anyType"&gt;
   *       &amp;lt;sequence&gt;
   *         &amp;lt;element name="httpResponseCode" type="{http://www.w3.org/2001/XMLSchema}integer"/&gt;
   *         &amp;lt;group ref="{http://www.ni.com/schemas/provider-framework/1/providers}ErrorElementGroup"/&gt;
   *       &amp;lt;/sequence&gt;
   *     &amp;lt;/restriction&gt;
   *   &amp;lt;/complexContent&gt;
   * &amp;lt;/complexType&gt;
   * &lt;/pre&gt;
   * 
   * 
   */
  @XmlAccessorType(XmlAccessType.FIELD)
  @XmlType(name = "RequestErrorType", propOrder = {
      "httpResponseCode",
      "summary",
      "userMessage",
      "detail"
  })
  public class RequestErrorType {
  
      @XmlElement(required = true)
      protected BigInteger httpResponseCode;
      protected String summary;
      protected String userMessage;
      protected String detail;
  
      /**
       * Obtiene el valor de la propiedad httpResponseCode.
       * 
       * @return
       *     possible object is
       *     {@link BigInteger }
       *     
       */
      public BigInteger getHttpResponseCode() {
          return httpResponseCode;
      }
  
      /**
       * Define el valor de la propiedad httpResponseCode.
       * 
       * @param value
       *     allowed object is
       *     {@link BigInteger }
       *     
       */
      public void setHttpResponseCode(BigInteger value) {
          this.httpResponseCode = value;
      }
  
      /**
       * Obtiene el valor de la propiedad summary.
       * 
       * @return
       *     possible object is
       *     {@link String }
       *     
       */
      public String getSummary() {
          return summary;
      }
  
      /**
       * Define el valor de la propiedad summary.
       * 
       * @param value
       *     allowed object is
       *     {@link String }
       *     
       */
      public void setSummary(String value) {
          this.summary = value;
      }
  
      /**
       * Obtiene el valor de la propiedad userMessage.
       * 
       * @return
       *     possible object is
       *     {@link String }
       *     
       */
      public String getUserMessage() {
          return userMessage;
      }
  
      /**
       * Define el valor de la propiedad userMessage.
       * 
       * @param value
       *     allowed object is
       *     {@link String }
       *     
       */
      public void setUserMessage(String value) {
          this.userMessage = value;
      }
  
      /**
       * Obtiene el valor de la propiedad detail.
       * 
       * @return
       *     possible object is
       *     {@link String }
       *     
       */
      public String getDetail() {
          return detail;
      }
  
      /**
       * Define el valor de la propiedad detail.
       * 
       * @param value
       *     allowed object is
       *     {@link String }
       *     
       */
      public void setDetail(String value) {
          this.detail = value;
      }
  
  }
  </code></pre>
  
  <p>If I want to set the userMessage variable to null, on display-time, is just shows this</p>
  
  <pre><code>&lt;userMessage /&gt;
  </code></pre>
  
  <p>and I need to display </p>
  
  <pre><code>&lt;userMessage xsi:nil="true" /&gt;
  </code></pre>
  
  <p>How can I do this?</p>