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
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpcore</artifactId>
<version>4.4.13</version>
</dependency><dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.12</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpmime -->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpmime</artifactId>
<version>4.5.12</version>
</dependency>
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();
CloseableHttpResponse response = null;
InputStream content = null;
BufferedReader in = null;
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);
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
content = responseEntity.getContent();
// 定义BufferedReader输入流来读取URL的响应
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();
content .close();
in.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<input>参数，可解析返回来的result拿到自己想拿的信息。
