负数组大小异常

Question

我是 Blackberry 的新手，我正在尝试在 xml 中将搜索词发布到服务器。但我不断收到此错误Request Failed. Reason Java.lang.NegativeArraySizeException。

我想在解析数据之前检查连接是否有效，所以从这个连接中，我希望收到 xml 中的响应文本。下面是代码：

public void webPost(String word) {
    word = encode (word);
    String responseText;
    try{
        HttpConnection connection = (HttpConnection)Connector.open("http://some url.xml");
        connection.setRequestMethod(HttpConnection.POST);
        connection.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
        String postData = "username=loginapi&password=myapilogin&term="+ word;
        connection.setRequestProperty("Content-Length",Integer.toString(postData.length()));
        connection.setRequestProperty("User-Agent","Profile/MIDP-2.0 Configuration/CLDC-1.0");
        OutputStream requestOut = connection.openOutputStream();
        requestOut.write(postData.getBytes());

        InputStream detailIn = connection.openInputStream();
        byte info[]=new byte[(int)connection.getLength()];
        detailIn.read(info);
        detailIn.close();
        requestOut.close();
        connection.close();
        responseText=new String(info);
        requestSuceeded(requestOut.toString(), responseText);
    }
    catch(Exception ex){
        requestFailed(ex.toString());
    }
}

private void requestSuceeded(String result, String responseText) {
    if(responseText.startsWith("text/xml")) { 
        String strResult = new String(result); 
        synchronized(UiApplication.getEventLock()) { 
            textOutputField.setText(strResult); 
        } 
    } else{ 
        synchronized(UiApplication.getEventLock()) { 
            Dialog.alert("Unknown content type: " + responseText); 
        } 
    } 
} 

public void requestFailed(final String message) { 
    UiApplication.getUiApplication().invokeLater(new Runnable() { 
        public void run() { 
            Dialog.alert("Request failed. Reason: " + message); 
        } 
    }); 
} 

private String encode(String textIn) {
     //encode text for http post
    textIn = textIn.replace(' ','+');
    String textout = "";
    for(int i=0;i< textIn.length();i++){
        char wcai = textIn.charAt(i);
        if(!Character.isDigit(wcai) && !Character.isLowerCase(wcai) && !Character.isUpperCase(wcai) && wcai!='+'){
            switch(wcai){
                case '.':
                case '-':
                case '*':
                case '_':
                    textout = textout+wcai;
                    break;
                default:
                    textout = textout+"%"+Integer.toHexString(wcai).toUpperCase();//=textout.concat("%").concat(Integer.toHexString(wcai));
            }
        }else{
            textout = textout+wcai;//=textout.concat(wcai+"");
        }
    }
    return textout;
}    

Answer 1

connection.getLength() 正在返回 -1。

在创建信息数组之前，检查连接的长度。

int length = (int) connection.getLength();

if(length > 0){
     byte info[]=new byte[length];
     // perform operations

}else{
     System.out.println("Negative array size");
}

Answer 2

我假设connection.getLength() 在您尝试在此处初始化数组时返回 -1：

byte info[]=new byte[(int)connection.getLength()];

这就是 NegativeArraySizeException 的原因。

Answer 3

我猜你什么时候做

byte info[]=new byte[(int)connection.getLength()];

InputStream 不知道它的长度，所以它返回 -1。

见http://www.velocityreviews.com/forums/t143704-inputstream-length.html

Answer 4

参考：http://supportforums.blackberry.com/t5/Java-Development/HttpConnection-set-to-POST-does-not-work/m-p/344946

参考1：Blackberry send a HTTPPost request

Ref2：http://www.blackberryforums.com/developer-forum/181071-http-post-passing-parameters-urls.html

类似这样的：

URLEncodedPostData postData = new URLEncodedPostData(URLEncodedPostData.DEFAULT_CHARSET, true); 
postData.append("name",name); 

Answer 5

找到了！我忘了打开输出流连接

requestOut = connection.openOutputStream();

我介绍了ByteArrayOutpuStream，它帮助我最终显示了输入流。我也改变了发送参数的方式，改用URLEncodedPostData 类型。由于服务器将我以前的请求解释为 GET 而不是 POST。而我现在要做的就是解析进来的信息。

try{
     connection = (HttpConnection)Connector.open("http://someurl.xml",Connector.READ_WRITE);
     URLEncodedPostData postData = new URLEncodedPostData(URLEncodedPostData.DEFAULT_CHARSET, false);
     postData.append("username", "loginapi");
     postData.append("password", "myapilogin");
     postData.append("term", word);

     connection.setRequestMethod(HttpConnection.POST);
     connection.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
     connection.setRequestProperty("User-Agent","Profile/MIDP-2.0 Configuration/CLDC-1.0");
     requestOut = connection.openOutputStream();
     requestOut.write(postData.getBytes());
     String contentType = connection.getHeaderField("Content-type"); 
     detailIn = connection.openInputStream();         
     int length = (int) connection.getLength();
     ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
     if(length > 0){
         byte info[] = new byte[length];
         int bytesRead = detailIn.read(info);
         while(bytesRead > 0) { 
             baos.write(info, 0, bytesRead); 
             bytesRead = detailIn.read(info); 
             }
         baos.close();
         connection.close();
         requestSuceeded(baos.toByteArray(), contentType);

         detailIn.read(info);
     }
     else
     {
          System.out.println("Negative array size");
     }
           requestOut.close();
           detailIn.close();
           connection.close();
    }

PS。我发布了上面的代码来帮助任何有同样问题的人。

PPS。我还使用了Kalai's format，它非常有用。

Answer 6

java.lang.NegativeArraySizeException 表示您正在尝试初始化一个负长度的数组。

唯一正在初始化的代码是 -

byte info[]=new byte[(int)connection.getLength()];

您可能希望在初始化数组之前添加长度检查