Android中自定义MultipartEntity实现文件上传以及使用Volley库实现文件上传

自定义实现MultipartEntity

我们知道，使用网络协议传输数据无非就是要遵循某个协议，我们在开发移动应用时基本上都是使用HTTP协议。HTTP协议说白了就是基于TCP的一套网络请求协议，你根据该协议规定的格式传输数据，然后服务器返回给你数据。你的协议参数要是传递错了，那么服务器只能给你返回错误。

这跟间谍之间对暗号有点相似，他们有一个规定的暗号，双方见面，A说: 天王盖地虎，B对: 宝塔镇河妖。对上了，说事；对不上，弄死这B。HTTP也是这样的，在HTTP请求时添加header和参数，服务器根据参数进行解析。形如 : 

POST /api/feed/ HTTP/1.1这里是header数据参数2

只要根据格式来向服务器发送请求就万事大吉了！下面我们就来看MultipartEntity的实现:

public class MultipartEntity implements HttpEntity { private final static char[] MULTIPART_CHARS = "-_1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" .toCharArray(); /** * 换行符 */ private final String NEW_LINE_STR = "\r\n"; private final String CONTENT_TYPE = "Content-Type: "; private final String CONTENT_DISPOSITION = "Content-Disposition: "; /** * 文本参数和字符集 */ private final String TYPE_TEXT_CHARSET = "text/plain; charset=UTF-8"; /** * 字节流参数 */ private final String TYPE_OCTET_STREAM = "application/octet-stream"; /** * 二进制参数 */ private final byte[] BINARY_ENCODING = "Content-Transfer-Encoding: binary\r\n\r\n".getBytes(); /** * 文本参数 */ private final byte[] BIT_ENCODING = "Content-Transfer-Encoding: 8bit\r\n\r\n".getBytes(); /** * 分隔符 */ private String mBoundary = null; /** * 输出流 */ ByteArrayOutputStream mOutputStream = new ByteArrayOutputStream(); public MultipartEntity() { this.mBoundary = generateBoundary(); } /** * 生成分隔符 * * @return */ private final String generateBoundary() { final StringBuffer buf = new StringBuffer(); final Random rand = new Random(); for (int i = 0; i < 30; i++) { buf.append(MULTIPART_CHARS[rand.nextInt(MULTIPART_CHARS.length)]); } return buf.toString(); } /** * 参数开头的分隔符 * * @throws IOException */ private void writeFirstBoundary() throws IOException { mOutputStream.write(("--" + mBoundary + "\r\n").getBytes()); } /** * 添加文本参数 * * @param key * @param value */ public void addStringPart(final String paramName, final String value) { writeToOutputStream(paramName, value.getBytes(), TYPE_TEXT_CHARSET, BIT_ENCODING, ""); } /** * 将数据写入到输出流中 * * @param key * @param rawData * @param type * @param encodingBytes * @param fileName */ private void writeToOutputStream(String paramName, byte[] rawData, String type, byte[] encodingBytes, String fileName) { try { writeFirstBoundary(); mOutputStream.write((CONTENT_TYPE + type + NEW_LINE_STR).getBytes()); mOutputStream .write(getContentDispositionBytes(paramName, fileName)); mOutputStream.write(encodingBytes); mOutputStream.write(rawData); mOutputStream.write(NEW_LINE_STR.getBytes()); } catch (final IOException e) { e.printStackTrace(); } } /** * 添加二进制参数, 例如Bitmap的字节流参数 * * @param key * @param rawData */ public void addBinaryPart(String paramName, final byte[] rawData) { writeToOutputStream(paramName, rawData, TYPE_OCTET_STREAM, BINARY_ENCODING, "no-file"); } /** * 添加文件参数,可以实现文件上传功能 * * @param key * @param file */ public void addFilePart(final String key, final File file) { InputStream fin = null; try { fin = new FileInputStream(file); writeFirstBoundary(); final String type = CONTENT_TYPE + TYPE_OCTET_STREAM + NEW_LINE_STR; mOutputStream.write(getContentDispositionBytes(key, file.getName())); mOutputStream.write(type.getBytes()); mOutputStream.write(BINARY_ENCODING); final byte[] tmp = new byte[4096]; int len = 0; while ((len = fin.read(tmp)) != -1) { mOutputStream.write(tmp, 0, len); } mOutputStream.flush(); } catch (final IOException e) { e.printStackTrace(); } finally { closeSilently(fin); } } private void closeSilently(Closeable closeable) { try { if (closeable != null) { closeable.close(); } } catch (final IOException e) { e.printStackTrace(); } } private byte[] getContentDispositionBytes(String paramName, String fileName) { StringBuilder stringBuilder = new StringBuilder(); stringBuilder.append(CONTENT_DISPOSITION + "form-data; name=\"" + paramName + "\""); // 文本参数没有filename参数,设置为空即可 if (!TextUtils.isEmpty(fileName)) { stringBuilder.append("; filename=\"" + fileName + "\""); } return stringBuilder.append(NEW_LINE_STR).toString().getBytes(); } @Override public long getContentLength() { return mOutputStream.toByteArray().length; } @Override public Header getContentType() { return new BasicHeader("Content-Type", "multipart/form-data; boundary=" + mBoundary); } @Override public boolean isChunked() { return false; } @Override public boolean isRepeatable() { return false; } @Override public boolean isStreaming() { return false; } @Override public void writeTo(final OutputStream outstream) throws IOException { // 参数最末尾的结束符 final String endString = "--" + mBoundary + "--\r\n"; // 写入结束符 mOutputStream.write(endString.getBytes()); // outstream.write(mOutputStream.toByteArray()); } @Override public Header getContentEncoding() { return null; } @Override public void consumeContent() throws IOException, UnsupportedOperationException { if (isStreaming()) { throw new UnsupportedOperationException( "Streaming entity does not implement #consumeContent()"); } } @Override public InputStream getContent() { return new ByteArrayInputStream(mOutputStream.toByteArray()); }}

用户可以通过addStringPart、addBinaryPart、addFilePart来添加参数，分别表示添加字符串参数、添加二进制参数、添加文件参数。在MultipartEntity中有一个ByteArrayOutputStream对象，先将这些参数写到这个输出流中，当执行网络请求时，会执行

writeTo(final OutputStream outstream)

方法将所有参数的字节流数据写入到与服务器建立的TCP连接的输出流中，这样就将我们的参数传递给服务器了。当然在此之前，我们需要按照格式来向ByteArrayOutputStream对象中写数据。
例如我要向服务器发送一个文本、一张bitmap图片、一个文件，即这个请求有三个参数。代码如下 : 

MultipartEntity multipartEntity = new MultipartEntity(); // 文本参数 multipartEntity.addStringPart("type", "我的文本参数"); Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.thumb); // 二进制参数 multipartEntity.addBinaryPart("images", bitmapToBytes(bmp)); // 文件参数 multipartEntity.addFilePart("images", new File("storage/emulated/0/test.jpg")); // POST请求 HttpPost post = new HttpPost("url") ; // 将multipartEntity设置给post post.setEntity(multipartEntity); // 使用http client来执行请求 HttpClient httpClient = new DefaultHttpClient() ; httpClient.execute(post) ;

MultipartEntity的输出格式会成为如下的格式 : 

POST /api/feed/ HTTP/1.1Content-Type: multipart/form-data; boundary=o3Fhj53z-oKToduAElfBaNU4pZhp4-User-Agent: Dalvik/1.6.0 (Linux; U; Android 4.4.4; M040 Build/KTU84P)Host: www.myhost.comConnection: Keep-AliveAccept-Encoding: gzipContent-Length: 168518--o3Fhj53z-oKToduAElfBaNU4pZhp4-Content-Type: text/plain; charset=UTF-8Content-Disposition: form-data; name="type"Content-Transfer-Encoding: 8bitThis my type--o3Fhj53z-oKToduAElfBaNU4pZhp4-Content-Type: application/octet-streamContent-Disposition: form-data; name="images"; filename="no-file"Content-Transfer-Encoding: binary这里是bitmap的二进制数据--o3Fhj53z-oKToduAElfBaNU4pZhp4-Content-Type: application/octet-streamContent-Disposition: form-data; name="file"; filename="storage/emulated/0/test.jpg"Content-Transfer-Encoding: binary这里是图片文件的二进制数据--o3Fhj53z-oKToduAElfBaNU4pZhp4---

看到很熟悉吧，这就是我们在文章开头时提到的POST报文格式。没错！HttpEntity就是负责将参数构造成HTTP的报文格式，文本参数该是什么格式、文件该是什么格式，什么类型，这些格式都是固定的。构造完之后，在执行请求时会将http请求的输出流通过writeTo(OutputStream) 函数传递进来，然后将这些参数数据全部输出到http输出流中即可。
明白了这些道理，看看代码也就应该明白了吧。

Volley中实现文件上传

Volley是Google官方推出的网络请求库，这个库很精简、优秀，但是他们也没有默认添加文件上传功能的支持。我们今天就来自定义一个Request实现文件上传功能，还是需要借助上面的MultipartEntity类，下面看代码:

/** * @author mrsimple */public class MultipartRequest extends Request<String> {    MultipartEntity mMultiPartEntity = new MultipartEntity();    Map<String, String> mHeaders = new HashMap<String, String>();    private final Listener<String> mListener;    /**     * Creates a new request with the given url.     *     * @param url URL to fetch the string at     * @param listener Listener to receive the String response     */    public MultipartRequest(String url, Listener<String> listener) {        this(url, listener, null);    }    /**     * Creates a new POST request.     *     * @param url URL to fetch the string at     * @param listener Listener to receive the String response     * @param errorListener Error listener, or null to ignore errors     */    public MultipartRequest(String url, Listener<String> listener, ErrorListener errorListener) {        super(Method.POST, url, errorListener);        mListener = listener;    }    /**     * @return     */    public MultipartEntity getMultiPartEntity() {        return mMultiPartEntity;    }    @Override    public String getBodyContentType() {        return mMultiPartEntity.getContentType().getValue();    }    public void addHeader(String key, String value) {        mHeaders.put(key, value);    }    @Override    public Map<String, String> getHeaders() throws AuthFailureError {        return mHeaders;    }    @Override    public byte[] getBody() {        ByteArrayOutputStream bos = new ByteArrayOutputStream();        try {            // multipart body            mMultiPartEntity.writeTo(bos);        } catch (IOException e) {            Log.e("", "IOException writing to ByteArrayOutputStream");        }        return bos.toByteArray();    }    @Override    protected Response<String> parseNetworkResponse(NetworkResponse response) {        String parsed = "";        try {            parsed = new String(response.data, HttpHeaderParser.parseCharset(response.headers));        } catch (UnsupportedEncodingException e) {            parsed = new String(response.data);        }        return Response.success(parsed, HttpHeaderParser.parseCacheHeaders(response));    }    @Override    protected void deliverResponse(String response) {        if (mListener != null) {            mListener.onResponse(response);        }    }}

使用示例代码: 

        RequestQueue queue = Volley.newRequestQueue(this);        MultipartRequest multipartRequest = new MultipartRequest(                "http://yourhost.com", new Listener<String>() {                    @Override                    public void onResponse(String response) {                        Log.e("", "### response : " + response);                    }                });        // 添加header        multipartRequest.addHeader("header-name", "value");        // 通过MultipartEntity来设置参数        MultipartEntity multi = multipartRequest.getMultiPartEntity();        // 文本参数        multi.addStringPart("location", "模拟的地理位置");        multi.addStringPart("type", "0");        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.thumb);        // 直接从上传Bitmap        multi.addBinaryPart("images", bitmapToBytes(bitmap));        // 上传文件        multi.addFilePart("imgfile", new File("storage/emulated/0/test.jpg"));        // 将请求添加到队列中        queue.add(multipartRequest);