帮忙看下 struts2下PrintWriter out = response.getWriter();出错

[aiq]

package com.sunmq.action;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.http.HttpServletResponse;
import com.opensymphony.xwork2.ActionSupport;

public class CheckUserAction extends ActionSupport {
private String type;

public String execute() throws IOException {
HttpServletResponse response=null;
response.setContentType("text/html; charset=UTF-8");
PrintWriter out = response.getWriter();
out.print("<script>alert('成功');window.location.reload();</script>");
return SUCCESS;
}

public String getType() {
return type;
}

public void setType(String type) {
this.type = type;
}

}

出错如下
type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

java.lang.NullPointerException
com.sunmq.action.CheckUserAction.execute(CheckUserAction.java:23)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:452)
com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:291)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:254)

[zn85600301]

HttpServletResponse response=null;//你都把它设为null

用 this.response 就可以获得到

[zl3450341]

HttpServletResponse response=null;
response.setContentType("text/html; charset=UTF-8");
PrintWriter out = response.getWriter();

你的response都还没有值。。。 你就设置setContentType，你说他能不报错不？

[aiq]

response.setContentType("text/html; charset=UTF-8");
去掉还是同样的错误

[Davidtsang]

java.lang.NullPointerException
com.sunmq.action.CheckUserAction.execute(CheckUserAction.java:23)//这句空指针了，在23行。

[aiq]

那怎么改下呢

[HeiBoyYang]

java.lang.NullPointerException
HttpServletResponse response;
not
HttpServletResponse response=null;

[此人很懒没有设置昵称]

[Quote=引用 6 楼 heiboyyang 的回复:]

java.lang.NullPointerException
HttpServletResponse response;
not
HttpServletResponse response=null;
[/Quote]
这样才是实例了一个。不然你都设置为NUll了 你说怎么不为空呢？

[xcvxcvxcvcxvxcv]

HttpServletResponse response = ServletActionContext.getResponse();

[xcvxcvxcvcxvxcv]

还有如果你用的是struts2的话是不可以 return success的; 一定要return null 才会有值!!!!!!!

[zhuodim1]

楼上正解！