Question

I am getting an error for the following code in a java web app–

         XStream xstream = new XStream();  
         apiresponse myClassObject;
         myClassObject= xstream.fromXML(resp);  

The error is shown for the line of code just above this line–
error=”Type mismatch- cannot convert from Object to apiresponse”

Given below is the XML that I have to parse—

<apiresponse version="1" xmlns="http://ahrefs.com/schemas/api/links/1">
 <resultset_links count="2">
  <result>
    <source_url>http://ahrefs.com/robot/</source_url>
    <destination_url>http://blog.ahrefs.com/</destination_url>
    <source_ip>50.22.24.236</source_ip>
    <source_title>Ahrefs – backlinks research tool</source_title>
    <visited>2011-08-31T07:56:53Z</visited>
    <anchor>Blog</anchor>
    <rating>257.674000</rating>
    <link_type>text</link_type>
    <is_nofollow>false</is_nofollow>
  </result>
  <result>
    <source_url>http://apps.vc/</source_url>
    <destination_url>http://ahrefs.com/robot/</destination_url>
    <source_ip>64.20.55.86</source_ip>
    <source_title>Device info</source_title>
    <visited>2011-08-27T18:59:31Z</visited>
    <anchor>http://ahrefs.com/robot/</anchor>
    <rating>209.787100</rating>
    <link_type>text</link_type>
    <is_nofollow>false</is_nofollow>
  </result>
 </resultset_links>
</apiresponse>

I have created the following java classes to obtain data from above xml—

package com.arvindikchari.linkdatasmith.domain;

final public class apiresponse {  

  protected resultset_links rlinks;  


  public apiresponse() {

  }

  public resultset_links getRlinks()
  {
    return rlinks;
  }

  public setRlinks(resultset_links rlinks)
    {
        this.rlinks=rlinks;
    }


}  



final public class resultset_links {  

    protected List<result> indiv_result = new ArrayList<result>();

  public resultset_links() {

  }


  public List<result> getIndiv_result()
  {

    return List;
  }


  public  void setIndiv_result(List<result> indiv_result)
    {

        this.indiv_result=indiv_result;
    }

}  

final public class result {

   protected String source_url;
   protected String destination_url;
   protected String source_ip;
   protected String source_title;
   protected String visited;
   protected String anchor;
   protected String rating;
   protected String link_type;

public result() {

}

public String getSource_url()
{

return source_url;
}

public void setSource_url(String source_url)
{

this.source_url=source_url;
}

public String getDestination_url()
{

return destination_url;
}

public void setDestination_url(String destination_url)
{

this.destination_url=destination_url;
}

public String getSource_ip()
{

return source_ip;
}

public void setSource_ip(String source_ip)
{

    this.source_ip=source_ip;
}


public String getSource_title()
{

return source_title;
}

public void setSource_title(String source_title)
{

this.source_title=source_title;
}


public String getVisited()
{

return visited;
}

public void setVisited(String visited)
{

this.visited=visited;
}


public String getAnchor()
{

return anchor;
}

public void setAnchor(String anchor)
{ 

this.anchor=anchor;
}


public String getRating()
 {

return rating;
 }

public void setRating(String rating)
{ 

this.rating=rating;
}


public String getLink_type()
{

return link_type;
}

public void setLink_type(String link_type)
{

    this.link_type=link_type;
}


}

What am I doing wrong here?

Answer 1

You have many errors, but the one corresponding to your message is you have to cast the result of xstream.fromXML to an apiresponse’ object :

apiresponse result = (apiresponse)xstream.fromXML(resp);

Moreover, the code you provided (the Java classes) do not compile, there are many errors.

Here are some improvements :

Result.java :

@XStreamAlias("result")
public class Result {

   protected String source_url;
   protected String destination_url;
   protected String source_ip;
   protected String source_title;
   protected String visited;
   protected String anchor;
   protected String rating;
   protected String link_type;
   protected Boolean is_nofollow;

public Result() {

}

public String getSource_url()
{

return source_url;
}

public void setSource_url(String source_url)
{

this.source_url=source_url;
}

public String getDestination_url()
{

return destination_url;
}

public void setDestination_url(String destination_url)
{

this.destination_url=destination_url;
}

public String getSource_ip()
{

return source_ip;
}

public void setSource_ip(String source_ip)
{

    this.source_ip=source_ip;
}


public String getSource_title()
{

return source_title;
}

public void setSource_title(String source_title)
{

this.source_title=source_title;
}


public String getVisited()
{

return visited;
}

public void setVisited(String visited)
{

this.visited=visited;
}


public String getAnchor()
{

return anchor;
}

public void setAnchor(String anchor)
{

this.anchor=anchor;
}


public String getRating()
 {

return rating;
 }

public void setRating(String rating)
{

this.rating=rating;
}


public String getLink_type()
{

return link_type;
}

public void setLink_type(String link_type)
{

    this.link_type=link_type;
}

public Boolean getIs_nofollow() {
    return is_nofollow;
}

public void setIs_nofollow(Boolean is_nofollow) {
    this.is_nofollow = is_nofollow;
}

ResultsetLinks.java :

@XStreamAlias("resultset_links")
public class ResultsetLinks {

@XStreamImplicit(itemFieldName="result")
protected List<Result> indivResult = new ArrayList<Result>();

  public ResultsetLinks() {

  }

  public List<Result> getResult()
  {

    return indivResult;
  }


  public  void setResult(List<Result> indiv_result)
    {

        this.indivResult =indiv_result;
    }

}

ApiResponse.java :

@XStreamAlias("apiresponse")
public class ApiResponse {

@XStreamAlias("resultset_links")
protected ResultsetLinks rlinks;


public ApiResponse() {

}

public ResultsetLinks getRlinks()
{
    return rlinks;
}

public void setRlinks(ResultsetLinks rlinks)
  {
    this.rlinks=rlinks;
  }

}

And finally your code to unmarshall the XML :

    XStream xstream = new XStream();
    xstream.processAnnotations(ApiResponse.class);
    xstream.processAnnotations(ResultsetLinks.class);
    xstream.processAnnotations(Result.class);

    ApiResponse result = (ApiResponse)xstream.fromXML(resp);

All this code is working fine with Xstream 1.4.2

Try to follow Sun’s coding convention for your classes name, attributes names, etc…
Use XstreamAliases to adapt the Java class name to the XML name.