sendRedirect重定向问题

check1Servelt.java
public void doGet(HttpServletRequest request,HttpServletResponse response)
throws ServletException, IOException {

PrintWriter out=response.getWriter();

//读取用户名
String username = request.getParameter("username");
String message=null;
if(username==null){
message="Please input username.";
}else{
message="Hello,"+username;
}

//在request对象中添加msg属性
request.setAttribute("msg", message);

out.println("Output from Check1Servlet before redirecting!!!!.");
// System.out.println("Output from Check1Servlet before redirecting@@@@.");

response.sendRedirect("/Sourcecode/output1?msg="+message);
//response.sendRedirect("/output1?msg="+message"); //wrong
// response.sendRedirect("http://localhost:8080/Sourcecode/output1?msg="+message); //ok
// response.sendRedirect("http://www.baidu.com"); //ok


out.println("Output from Check1Servlet after redirectingMMMMM.");
// System.out.println("Output from Check1Servlet after redirectingNNNN.");
}
错误提示Failed to redirect to [/Sourcecode/output1?msg=Please input username.]
应是路径不对,求大神帮下.刚自学java一个月左右
跳到response.sendRedirect("http://www.baidu.com"); 这个可以正常到百度
重定向output1.java
web.xml 中文件
<servlet>
<servlet-name>check1</servlet-name>
<servlet-class>mypack.Check1Servlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>check1</servlet-name>
<url-pattern>/check1</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>output1</servlet-name>
<servlet-class>mypack.Output1Servlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>output1</servlet-name>
<url-pattern>/output1</url-pattern>
</servlet-mapping>