求解！！！

[gaoliang21]

请帮忙看一下这个程序，不知为何在我标注*****的那行总是抛出一个IOException,实在调不出来了，那位好心的大哥帮忙指点一下？先谢了！！！！！！！！！
public int getCount() throws Exception
{
// Get the server URL
java.net.URL url =null;
java.net.URLConnection con =null;
byte buf[]= null;
DataOutputStream dataOut=null;

url = new java.net.URL(m_url);

// Attempt to connect to the host
con = url.openConnection();

// Set the session ID if necessary
if (m_cookie != null) {
con.setRequestProperty("cookie", m_cookie);
}

// Initialize the connection
con.setUseCaches(false);
con.setDoOutput(true);
con.setDoInput(true);


// Data will always be written to a byte array buffer so
// that we can tell the server the length of the data
ByteArrayOutputStream byteOut = new ByteArrayOutputStream();

// Create the output stream to be used to write the
// data to our buffer
DataOutputStream out = new DataOutputStream(byteOut);

// Send any data to the servlet here

// Flush the data to the buffer
out.flush();

// Get our buffer to be sent
buf = byteOut.toByteArray();

// Set the content that we are sending
con.setRequestProperty("Content-type",
"application/octet-stream");

// Set the length of the data buffer we are sending
con.setRequestProperty("Content-length",
"" + buf.length);

// Get the output stream to the server and send our
// data buffer
***** dataOut = new DataOutputStream(con.getOutputStream());


dataOut.write(buf);
// Flush the output stream and close it
dataOut.flush();
dataOut.close();

// Get the input stream we can use to read the response
DataInputStream in =
new DataInputStream(con.getInputStream());

// Read the data from the server
int count = in.readInt();

// Close the input stream
in.close();

// Get the session cookie if we haven't already
if (m_cookie == null) {
String cookie = con.getHeaderField("set-cookie");
if (cookie != null) {
m_cookie = parseCookie(cookie);
System.out.println("Setting session ID=" + m_cookie);
}
}

return count;
}

[dylanwolf]

用 try

{
dataOut = new ...
...

}

catch{}

[gaoliang21]

我问的是为什么会抛出异常？顺便说一下：我给出的URL肯定没有错。

[drinkant]

IOException的具体内容 ?
你是企图往这个URL写,可能目标不存在,可能权限不够,反正乱七八糟的都有可能

[littlecong]

try to conver con to HttpURLConnection

[gaoliang21]

我嵌入try语句测试，结果程序在这条语句抛出IOException异常。我是准备往URLConnection里写一些内容，目标肯定存在而且URL肯定没错，我估计也可能是权限不够，我是在weblogic 7.0上调试的，可不知道如何进行权限之类的设置，请明示！！！谢谢！！！！！！！！！

[diaopeng]

估计是这样的错误：NONEPOINTER

[diaopeng]

据我所知，不是什么权限问题，而是对象不存在，至于怎么解决我到现在都还没想出来

[wdydt163]

我也觉得是这样的：con = url.openConnection();你应该检查一下con 是否是空的？

[drinkant]

对象不存在不会抛IOException吧,应该是Null甚么exception吧......
叫他把exception的具体内容贴出来看看就知道了

[gaoliang21]

谢谢各位！以下是Exception的内容，对不起，不是IOException,是我记错了（不过java.net.ConnectException是从IOException继承来的，也不算错）
java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:320)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:133)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:120)
at java.net.Socket.<init>(Socket.java:273)
at java.net.Socket.<init>(Socket.java:100)
at sun.net.NetworkClient.doConnect(NetworkClient.java:50)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:331)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:517)
at sun.net.www.http.HttpClient.<init>(HttpClient.java:267)
at sun.net.www.http.HttpClient.<init>(HttpClient.java:277)
at sun.net.www.http.HttpClient.New(HttpClient.java:289)
at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection
.java:408)
at sun.net.www.protocol.http.HttpURLConnection.getOutputStream(HttpURLCo
nnection.java:455)
at javaservlets.session.CounterApp.getCount(CounterApp.java:134)
at javaservlets.session.CounterApp.main(CounterApp.java:55)
Press any key to continue . . .

[seani]

对象不存在