HttpClient利用MultipartEntityBuilder上传图片文件到服务器

注意：在HttpClient4.3之后，原来的上传文件方法MultipartEntity已经不建议使用，现替换成新的httpmime下面的MultipartEntityBuilder。

需要添加httpclient-4.5.jar、httpmime-4.5.jar两个包

maven添加：

        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpmime</artifactId>
            <version>4.5</version>
        </dependency>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5</version>
        </dependency>

下面我们对比一下MultipartEntity和MultipartEntityBuilder的使用区别：

MultipartEntityBuilder：

             //传入参数可以为file或者filePath，在此处做转换
            File file = new File(filePath);
            CloseableHttpClient httpClient = HttpClients.createDefault();
            CloseableHttpResponse httpResponse = null;
            HttpPost httppost = new HttpPost(url);
            MultipartEntityBuilder builder = MultipartEntityBuilder.create();
            //设置浏览器兼容模式
            builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);
            //设置请求的编码格式
            builder.setCharset(Consts.UTF_8);
            builder.setContentType(ContentType.MULTIPART_FORM_DATA);
            //添加文件
            builder.addBinaryBody("file", file);
            HttpEntity reqEntity = builder.build();
            httppost.setEntity(reqEntity);

            httpResponse = httpClient.execute(httppost);

MultipartEntity：

            //传入参数可以为file或者filePath，在此处做转换
            File file = new File(filePath);
            CloseableHttpClient httpClient = HttpClients.createDefault();
            CloseableHttpResponse httpResponse = null;
            HttpPost httppost = new HttpPost(url);
            FileBody filebody = new FileBody(file);
            MultipartEntity entity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE, null,
                    Charset.forName("UTF-8"));
            entity.addPart("file", filebody);
            httppost.setEntity(entity);

直接替换后的测试代码

package com.test.util;

import net.sf.json.JSONObject;
import org.apache.commons.lang.StringUtils;
import org.apache.http.Consts;
import org.apache.http.HttpEntity;
import org.apache.http.HttpStatus;
import org.apache.http.client.ClientProtocolException;
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.HttpMultipartMode;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Iterator;
import java.util.Map;

public class HttpPostUploadUtil {

    /**
     * @param args
     */
    public static void main(String[] args) {
        String filePath = "D:\\Test\\0.jpg";
        String url = "http://127.0.0.1:8080/FastFds";
        //调用上传方法
        String backInfo = uploadPost(url, filePath);
        if(StringUtils.isNotBlank(backInfo)){
            //转json数据
            JSONObject json = JSONObject.fromObject(backInfo);
            if(!json.isEmpty()){
                //数据处理
                String value = json.getString("test");
                System.out.println(value);
            }
        }
    }

    /**
     * 上传图片/文件
     * @param url
     * @param filePath
     * @return String 用于转json或者其他信息
     */
    public static String uploadPost(String url, String filePath)  {
        String requestJson = "";
        //传入参数可以为file或者filePath，在此处做转换
        File file = new File(filePath);

        CloseableHttpClient httpClient = HttpClients.createDefault();
        CloseableHttpResponse httpResponse = null;
        try {
            HttpPost httppost = new HttpPost(url);
            MultipartEntityBuilder builder = MultipartEntityBuilder.create();
            //设置浏览器兼容模式
            builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);
            //设置请求的编码格式
            builder.setCharset(Consts.UTF_8);
            builder.setContentType(ContentType.MULTIPART_FORM_DATA);
            //添加文件
            builder.addBinaryBody("file", file);
            HttpEntity reqEntity = builder.build();
            httppost.setEntity(reqEntity);

            httpResponse = httpClient.execute(httppost);
            int backCode = httpResponse.getStatusLine().getStatusCode();
            if(backCode == HttpStatus.SC_OK){
                HttpEntity httpEntity = httpResponse.getEntity();
                byte[] json= EntityUtils.toByteArray(httpEntity);
                requestJson = new String(json, "UTF-8");
                //关闭流
                EntityUtils.consume(httpEntity);
                return requestJson;
            }
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            //释放资源
            try {
                httpClient.close();
                httpResponse.close();
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
        return null;
    }
}

主要方法说明：

addBinaryBody、addPart、addTextBody方法用于添加要上传的数据，从上面的表格中可以发现用于添加数据的方法，都是key-value类型。所以在服务器端我们可以通过request.getPart(“keyname”)方式获取对应key的数据。也可以通过request.getParts()方式获取客户端通过以上三种方法提交所有数据。

1.通过addBinaryBody方法直接可以添加File、InputStream、byte[]类型的数据。

2.通过addPart方法只能添加ContentBody类型的数据，在org.apache.http.entity.mime.content包中已经提供了String、File以及InputStream对应的ContentBody类型的子类，如FileBody、InputStreamBody、StringBody，通过这些类我们可以将String、File以及InputStream类型的数据转换成ContentBody类型的数据。

3.通过addTextBody方法我们可以很方便的添加文本数据。