示例：使用httpclient4.2.5.jar 上传图片，后台servlet中使用commons-fileupload-1.3.jar 处理上传文件
注意版本问题：使用httpclient4.2.5,httpmime-4.2.5.jar,httpmime-4.2.5.jar上传后
后台：
ServletFileUpload upload = new ServletFileUpload(diskFactory);
List fileItems = upload.parseRequest(request);
fileItems的结果集始终等于0，然后测试采用jsp上传，发现上传控件<input type="file" name="d" />
中name属性不能为空，否则fileItems的结果集始终为0。
httpclient 调试的过程中发现，这个文件名是放在head里的
form-data; name="d"; filename="中心.jpg"{org.apache.http.entity.mime.FormBodyPart类中封装}
在org.apache.http.entity.mime.HttpMultipart类中调用了这个方法(需要修改源码):
private static void writeField( final MinimalField field, final OutputStream out) throws IOException {
writeBytes(field.getName(), out);
writeBytes(FIELD_SEP, out);
writeBytes(field.getBody(), out); // 此处没有进行charset 修改为writeBytes(field.getBody(),Charset.forName("UTF-8"), out);
writeBytes(CR_LF, out);
}
开始调用方式：
File file = new File("D:\\test\\upload\\中心.jpg");
HttpPost post = new HttpPost(“http://localhost:8088/WebService/a/d.do”);
MultipartEntity reqEntity = new MultipartEntity();
StringBody comment = new StringBody("A binary啦", Charset .forName(org.apache.http.protocol.HTTP.UTF_8));
reqEntity.addPart("a1", bin);
reqEntity.addPart("a2", comment);
post.setEntity(reqEntity);
HttpResponse response = client.execute(post);
HttpEntity resEntity = response.getEntity();
说明在执行client.execute(post);的过程中会调用reqEntity.writeTo(OutputStream d);方法，方法如下
public void writeTo(final OutputStream outstream) throws IOException {
this.multipart.writeTo(outstream);
}
最后发现其实可以不用改源码的
MultipartEntity d = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE,null,Charset.forName("UTF-8"));
HttpMultipartMode.BROWSER_COMPATIBLE 枚举值
因为程序默认是HttpMultipartMode.STRICT 所以走的是没有转化字符集的方法。
over