Question

我正在开发一个远程备份应用程序，有时我需要上传大文件，例如15 MB，我已经在某些手机中测试过我的内存不足错误

使用此功能有没有办法减少内存使用？

public int uploadFile(String sourceFileUri) {


      String fileName = sourceFileUri;

      HttpURLConnection conn = null;
      DataOutputStream dos = null;  
      String lineEnd = "\r\n";
      String twoHyphens = "--";
      String boundary = "*****";
      int bytesRead, bytesAvailable, bufferSize;
      byte[] buffer;
      int maxBufferSize = 1 * 1024 * 1024; 
      File sourceFile = new File(sourceFileUri); 

      if (!sourceFile.isFile()) {

           runOnUiThread(new Runnable() {
               public void run() {
                /*   messageText.setText("Source File not exist :"
                           +uploadFilePath + "" + uploadFileName);*/
               }
           }); 

           return 0;

      }
      else
      {
           try { 

                 // open a URL connection to the Servlet
               FileInputStream fileInputStream = new FileInputStream(sourceFile);
               URL url = new URL(upLoadServerUri);

               // Open a HTTP  connection to  the URL
               conn = (HttpURLConnection) url.openConnection(); 
               conn.setDoInput(true); // Allow Inputs
               conn.setDoOutput(true); // Allow Outputs
               conn.setUseCaches(false); // Don't use a Cached Copy
               conn.setRequestMethod("POST");
               conn.setRequestProperty("Connection", "Keep-Alive");
               conn.setRequestProperty("ENCTYPE", "multipart/form-data");
               conn.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);
               conn.setRequestProperty("uploaded_file", fileName); 

               dos = new DataOutputStream(conn.getOutputStream());

               dos.writeBytes(twoHyphens + boundary + lineEnd); 
               dos.writeBytes("Content-Disposition: form-data; name=\"uploaded_file\";filename=\""
                                         + fileName + "\"" + lineEnd);

               dos.writeBytes(lineEnd);

               // create a buffer of  maximum size
               bytesAvailable = fileInputStream.available(); 

               bufferSize = Math.min(bytesAvailable, maxBufferSize);
               buffer = new byte[bufferSize];

               // read file and write it into form...
               bytesRead = fileInputStream.read(buffer, 0, bufferSize);  

               while (bytesRead > 0) {

                 dos.write(buffer, 0, bufferSize);
                 bytesAvailable = fileInputStream.available();
                 bufferSize = Math.min(bytesAvailable, maxBufferSize);
                 bytesRead = fileInputStream.read(buffer, 0, bufferSize);   

                }

               // send multipart form data necesssary after file data...
               dos.writeBytes(lineEnd);
               dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);

               // Responses from the server (code and message)
               serverResponseCode = conn.getResponseCode();
              // String serverResponseMessage = conn.getResponseMessage();

              // Log.i("uploadFile", "HTTP Response is : " 
                //     + serverResponseMessage + ": " + serverResponseCode);

               if(serverResponseCode == 200){

                   runOnUiThread(new Runnable() {
                        public void run() {


                            /*messageText.setText(msg);
                            Toast.makeText(UploadToServer.this, "File Upload Complete.", 
                                         Toast.LENGTH_SHORT).show();*/
                        }
                    });                
               }    

               //close the streams //
               fileInputStream.close();
               dos.flush();
               dos.close();

          } catch (MalformedURLException ex) {

            //  ex.printStackTrace();

              runOnUiThread(new Runnable() {
                  public void run() {
                      /*messageText.setText("MalformedURLException Exception : check script url.");*/
                      Toast.makeText(UploadToServer.this, "MalformedURLException", Toast.LENGTH_SHORT).show();
                  }
              });

              Log.e("Upload file to server", "error: " + ex.getMessage(), ex);  
          } catch (Exception e) {

              //e.printStackTrace();

              runOnUiThread(new Runnable() {
                  public void run() {
                      //messageText.setText("Got Exception : see logcat ");
                      Toast.makeText(UploadToServer.this, "Got Exception : see logcat ", 
                              Toast.LENGTH_SHORT).show();
                  }
              });
              Log.e("Upload file to server Exception", "Exception : " 
                                               + e.getMessage(), e);  
          }
         // dialog.dismiss();       
          return serverResponseCode; 

       } // End else block 
     }

这里是错误日志

java.lang.OutOfMemoryError
at java.io.ByteArrayOutputStream.expand(ByteArrayOutputStream.java:93)
at java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:218)
at org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl$DefaultHttpOutputStream.write(HttpURLConnectionImpl.java:750)
at java.io.DataOutputStream.write(DataOutputStream.java:101)
at com.androidexample.uploadtoserver.UploadToServer.a(SourceFile:151)
at com.androidexample.uploadtoserver.e.run(SourceFile:62)
at java.lang.Thread.run(Thread.java:1102)

修改后添加固定无缓冲区我收到此错误

Exception : expected 589715 bytes but received 589840
java.io.IOException: expected 589715 bytes but received 589840
at libcore.net.http.FixedLengthOutputStream.write(FixedLengthOutputStream.java:39)
at java.io.DataOutputStream.write(DataOutputStream.java:98)
at com.androidexample.uploadtoserver.UploadToServer.uploadFile(UploadToServer.java:152)
at com.androidexample.uploadtoserver.UploadToServer$1.run(UploadToServer.java:62)
at java.lang.Thread.run(Thread.java:856)

我猜这个字节的差异是标题数据对吗？我怎样才能得到标题的长度（）？

Answer 1

您应该使用HttpURLConnection的setChunkedStreamingMode()或setFixedLengthStreamingMode()方法。这样可以防止数据缓冲在内存中并使其耗尽。

文件中的相关引用：

为获得最佳性能，您应该致电 setFixedLengthStreamingMode（int）当身体长度已知时 advance，或者setChunkedStreamingMode（int）。除此以外 HttpURLConnection将被强制缓冲整个请求体在传输之前的内存，浪费（并可能耗尽）堆积和增加延迟。

更多信息：http://developer.android.com/reference/java/net/HttpURLConnection.html

Answer 2

添加

conn.setFixedLengthStreamingMode(sourceFile.length());

下面：

conn = (HttpURLConnection) url.openConnection();

通过邮件将文件上传到服务器OutOfMemory

2 个答案: