之前写过基于html和js的文件上传方法java 用springMVC 和HttpServletRequest 两种实现文件上传的方法和httpClient后台执行普通post请求的文章java通过httpClient从接口请求数据入库以及自动生成实体工具类，最近接到一个需求，需要用到后台去调用远程服务器的文件上传接口实现文件上传，用到了httpClient的MultipartEntityBuilder实现。

maven引入httpClient依赖

org.apache.httpcomponents

httpcore

4.4.13

org.apache.httpcomponents

httpclient

4.5.12

org.apache.httpcomponents

httpmime

4.5.12

以上依赖是笔者成文时maven最新的依赖包。

新建一个UploadFileUtil工具类：

package com.zhaohy.app.utils;

import java.io.BufferedReader;

import java.io.File;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.HttpStatus;

import org.apache.http.client.methods.HttpPost;

import org.apache.http.entity.ContentType;

import org.apache.http.entity.mime.HttpMultipartMode;

import org.apache.http.entity.mime.MultipartEntityBuilder;

import org.apache.http.impl.client.CloseableHttpClient;

import org.apache.http.impl.client.HttpClients;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

public class UpLoadFileUtil {

private static Logger logger = LoggerFactory.getLogger(UpLoadFileUtil.class);

/**

* 通过httpClient上传文件

* @param fileName

* @param path

* @return 外部域名的下载url

*/

public static String UploadFileByHttpClient(String fileName,String path, String url) {

String result = "";

CloseableHttpClient httpClient = HttpClients.createDefault();

try {

HttpPost httpPost = new HttpPost(url);

//HttpMultipartMode.RFC6532参数的设定是为避免文件名为中文时乱码

MultipartEntityBuilder builder = MultipartEntityBuilder.create().setMode(HttpMultipartMode.RFC6532);

httpPost.addHeader("header1", "111");//头部放文件上传的head可自定义

File file = new File(path+fileName); //上传文件的路径

builder.addBinaryBody("file", file, ContentType.MULTIPART_FORM_DATA, fileName);

builder.addTextBody("params1", "1");//其余参数，可自定义

builder.addTextBody("params2", "2");

HttpEntity entity = builder.build();

httpPost.setEntity(entity);

HttpResponse response = httpClient.execute(httpPost);// 执行提交

HttpEntity responseEntity = response.getEntity();//接收调用外部接口返回的内容

if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK){

// 返回的内容都在content中

InputStream content = responseEntity.getContent();

// 定义BufferedReader输入流来读取URL的响应

BufferedReader in = new BufferedReader(new InputStreamReader(content));

String line;

while ((line = in.readLine()) != null) {

result += line;

}

if(!AppFrameworkUtil.isBlank(result)) {

logger.info("上传文件"+fileName+"返回参数==>"+result);

}else {

logger.error("上传文件失败：返回result为null");

}

}

}catch(Exception e) {

logger.error("上传文件失败：",e);

}finally {//处理结束后关闭httpclient的链接

try {

httpClient.close();

} catch (IOException e) {

e.printStackTrace();

}

}

return result;

}

}

上面代码中 fileName是文件名称，本地文件路径，url是远程上传接口url,通过httpPost.addHeader来自定义header参数，builder.addTextBody来自定义其他参数，相当于html中form表单中其他的参数，可解析返回来的result拿到自己想拿的信息。