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，我在一些手机上测试过我遇到内存不足的错误

有没有办法使用这个函数来使用更少的内存？

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)

修改并添加 Fixed no Buffer 后出现此错误

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吧？我怎样才能得到标题的长度()？

最佳答案

您应该使用 HttpURLConnection 的 setChunkedStreamingMode() 或 setFixedLengthStreamingMode() 方法。这将防止您的数据在内存中缓冲并耗尽它。

文档中的相关引用:

For best performance, you should call either setFixedLengthStreamingMode(int) when the body length is known in advance, or setChunkedStreamingMode(int) when it is not. Otherwise HttpURLConnection will be forced to buffer the complete request body in memory before it is transmitted, wasting (and possibly exhausting) heap and increasing latency.

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

关于java - 通过邮寄方式将文件上传到服务器 OutOfMemory，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/19647319/