最近在做 Android 端文件上传，要求采用 form 表单的方式提交，项目使用的 afinal 框架有文件上传功能，但是始终无法与php写的服务端对接上，无法上传成功。读源码发现：afinal 使用了某大神写的 MultipartEntity.java 生成 form 表单内容，然而生成的内容格式不够标准，而且还存在诸多问题，如：首先将所有文件读入到内存，再生成字节流写入到 socket。那么问题来了：如果是几百MB的文件怎么办？
几番搜索，受到 这篇文章（已被我转载，但是示例代码已过期）的启发，我辗转找到了 Apache 源码 httpcomponents-client-4.3.6-src.zip，在一个示例里面发现了一个重要的组件 MultipartEntityBuilder, 可以生成 form 表单格式的 HttpEntity, 有了 HttpEntity, 无论你是什么 http 框架，应该都可以使用。
不知道怎么使用？like this:
HttpPost httppost = new HttpPost(url);
...
httppost.setEntity(makeMultipartEntity(params, files));
HttpResponse response = getHttpClient().execute(httppost);
... private static HttpClient mClient;
private static HttpClient getHttpClient() {
if(mClient == null) {
//if(Build.VERSION.SDK_INT >= 9); //将不走本类的Case，基于HttpURLConnection
if(Build.VERSION.SDK_INT >= ) {
mClient = AndroidHttpClient.newInstance(getUserAgent());
}else {
mClient = new DefaultHttpClient();
}
}
return mClient;
}
MultipartEntityBuilder 用法整理如下：
需要用到 httpcomponents-client-4.3.6-bin.zip 中的 httpmime-4.3.6.jar 和 httpcore-4.3.3.jar
public static HttpEntity makeMultipartEntity(List<NameValuePair> params, final Map<String, File> files) {
MultipartEntityBuilder builder = MultipartEntityBuilder.create();
builder.setMode(HttpMultipartMode.STRICT); //如果有SocketTimeoutException等情况，可修改这个枚举
//builder.setCharset(Charset.forName("UTF-8")); //不要用这个，会导致服务端接收不到参数
if (params != null && params.size() > ) {
for (NameValuePair p : params) {
builder.addTextBody(p.getName(), p.getValue(), ContentType.TEXT_PLAIN.withCharset("UTF-8"));
}
}
if (files != null && files.size() > ) {
Set<Entry<String, File>> entries = files.entrySet();
for (Entry<String, File> entry : entries) {
builder.addPart(entry.getKey(), new FileBody(entry.getValue()));
}
}
return builder.build();
}
另附上 Apache 示例，可在 httpcomponents-client-4.3.6-bin.zip 中找到。
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* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
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* KIND, either express or implied. See the License for the
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* under the License.
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*
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package org.apache.http.examples.entity.mime; import java.io.File; import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.FileBody;
import org.apache.http.entity.mime.content.StringBody;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils; /**
* Example how to use multipart/form encoded POST request.
*/
public class ClientMultipartFormPost { public static void main(String[] args) throws Exception {
if (args.length != ) {
System.out.println("File path not given");
System.exit();
}
CloseableHttpClient httpclient = HttpClients.createDefault();
try {
HttpPost httppost = new HttpPost("http://localhost:8080" +
"/servlets-examples/servlet/RequestInfoExample"); FileBody bin = new FileBody(new File(args[]));
StringBody comment = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN); HttpEntity reqEntity = MultipartEntityBuilder.create()
.addPart("bin", bin)
.addPart("comment", comment)
.build(); httppost.setEntity(reqEntity); System.out.println("executing request " + httppost.getRequestLine());
CloseableHttpResponse response = httpclient.execute(httppost);
try {
System.out.println("----------------------------------------");
System.out.println(response.getStatusLine());
HttpEntity resEntity = response.getEntity();
if (resEntity != null) {
System.out.println("Response content length: " + resEntity.getContentLength());
}
EntityUtils.consume(resEntity);
} finally {
response.close();
}
} finally {
httpclient.close();
}
} }