struts2 返回纯字符串

package actions; 

import java.io.InputStream; 
import java.io.StringBufferInputStream; 
import com.opensymphony.xwork2.ActionSupport; 

public class TextResult extends ActionSupport  { 
private InputStream inputStream; 
public InputStream getInputStream() { 
return inputStream; 
} 

public String execute() throws Exception { 
inputStream = new StringBufferInputStream("ok"); 
return SUCCESS; 
} 
} 

struts.xml:
<action name="text-result" class="actions.TextResult">
<result type="stream">
<param name="contentType">text/html </param>
<param name="inputName">inputStream </param>
</result>
</action>