HttpServletResponse报错

package com.util;

import java.io.PrintWriter;

import javax.servlet.http.HttpServletResponse;

import org.apache.struts2.dispatcher.StrutsResultSupport;

import com.opensymphony.xwork2.ActionInvocation;

public class StringResultType extends StrutsResultSupport {
private static final long serialVersionUID = 1L;
private String contentTypeName;
private String stringName = "";

public StringResultType() {
    super();
}

public StringResultType(String location) {
    super(location);
}

@Override
protected void doExecute(String finalLocation, ActionInvocation invocation) throws Exception {
    HttpServletResponse response = (HttpServletResponse) invocation.getInvocationContext().get(HTTP_RESPONSE);
    // String contentType = (String)
    // invocation.getStack().findValue(conditionalParse(contentTypeName,
    // invocation));
    String contentType = conditionalParse(contentTypeName, invocation);
    if (contentType == null) {
        contentType = "text/plain; charset=UTF-8";
    }
    response.setContentType(contentType);
    PrintWriter out = response.getWriter();
    // String result = conditionalParse(stringName, invocation);
    String result = (String) invocation.getStack().findValue(stringName);
    out.println(result);
    out.flush();
    out.close();

}

public String getContentTypeName() {
    return contentTypeName;
}

public void setContentTypeName(String contentTypeName) {
    this.contentTypeName = contentTypeName;
}

public String getStringName() {
    return stringName;
}

public void setStringName(String stringName) {
    this.stringName = stringName;
}

}

异常信息是什么呢？看这段代码看不出什么问题啊。

把import整句剪切，粘贴，IDE难免会抽风

看一下你引得jar包是否加进项目了，或者选择build查一下