黑莓HttpPost空指针异常的Java [英] Blackberry HttpPost null pointer exception Java

问题描述

通过以​​下code，服务器被击中，但我也想在POST方法发送变量。

但它只是给了我一个空指针异常。它有什么做的的OutputStream 。我已经检查 POSTDATA ...它有一定的地址，这意味着它不为空。

那么，为什么我给空指针异常？

连接工厂connFact =新的ConnectionFactory（）;
ConnectionDescriptor connDesc;
尝试{
    connDesc = connFact.getConnection（http://example.com/login.php，Connector.READ_WRITE，returnContent）;
    httpConn.setRequestMethod（HttpConnection.POST）;
    httpConn.setRequestProperty（内容类型，应用程序/ x-WWW的形式urlen codeD）;    URLEn codedPostData encPostData =新URLEn codedPostData（UTF-8，FALSE）;
    encPostData.append（计数，地狱呀！）;
    。字节[] = POSTDATA encPostData.toString（）的getBytes（UTF-8）;    httpConn.setRequestProperty（内容长度，将String.valueOf（postData.length））;
    Dialog.alert（邮报数据：+ POSTDATA）;    OutputStream的OS = httpConn.openOutputStream（）;
    os.write（POSTDATA）;
    os.flush（）;
    httpConn =（HttpConnection的）connDesc.getConnection（）;    最终诠释iResponse code = httpConn.getResponse code（）;
    UiApplication.getUiApplication（）的invokeLater（Runnable的新（）{
        公共无效的run（）{
            //Dialog.alert(\"Response code：+ Integer.toString（iResponse code））;
        }
    }）;
}赶上（IOException异常五）{
    通信System.err.println（捕获到IOException：+ e.getMessage（））;
}


解决方案

正在滥用 ConnectionFactory.getConnection（字符串URL，INT transportType，字符串ConnectionUID）方法。例如，检查你传递什么样的 transportType ...

下面是API说，关于返回值：

  

返回：如果可以建立一个连接的ConnectionDescriptor;
  否则，返回null

所以，它只是将失败并返回空。这就是为什么你会得到一个NPE。

更新

我会建议只使用一个简单的API ConnectionFactory.getConnection（字符串URL）：

  ConnectionDescriptor CD = connFact.getConnection（http://example.com/login.php）;
如果（CD == NULL）{
    //抛出一个错误的信号没有连接现在
}
的HttpConnection httpConn =（HttpConnection的）cd.getConnection（）;
//将code与httpConn工作的休息..
 

With the following code, the server is getting hit, but I also want to send variables in POST method.

But it just gives me a null pointer exception. It has something to do with the OutputStream. I have checked postData ... it has some address, which means it is not null.

So why I am given null pointer exception?

ConnectionFactory connFact = new ConnectionFactory();
ConnectionDescriptor connDesc;
try {
    connDesc = connFact.getConnection("http://example.com/login.php", Connector.READ_WRITE, returnContent);
    httpConn.setRequestMethod(HttpConnection.POST);
    httpConn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

    URLEncodedPostData encPostData = new URLEncodedPostData("UTF-8", false);
    encPostData.append("count", "Hell Yeah!");
    byte[] postData = encPostData.toString().getBytes("UTF-8");

    httpConn.setRequestProperty("Content-length", String.valueOf(postData.length));
    Dialog.alert("Post Data: " + postData);

    OutputStream os = httpConn.openOutputStream();
    os.write(postData);
    os.flush();
    httpConn = (HttpConnection) connDesc.getConnection();

    final int iResponseCode = httpConn.getResponseCode();
    UiApplication.getUiApplication().invokeLater(new Runnable() {
        public void run() {
            //Dialog.alert("Response code: " +  Integer.toString(iResponseCode));
        }
    });
} catch (IOException e) {
    System.err.println("Caught IOException: " + e.getMessage());
}

解决方案

You are misusing the ConnectionFactory.getConnection(String url, int transportType, String ConnectionUID) method. For instance, check what you pass as transportType...

Here is what API says about return value:

Returns: a ConnectionDescriptor if a connection can be established; null otherwise

So, it just fails and returns null. And that's why you get a NPE.

UPDATE:

I would recommend to just use a simpler API ConnectionFactory.getConnection(String url):

ConnectionDescriptor cd = connFact.getConnection("http://example.com/login.php");
if (cd == null) {
    // throw an error signalling there is no connectivity right now
}
HttpConnection httpConn = (HttpConnection) cd.getConnection();
// the rest of the code working with httpConn ..

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