在SpringMVC框架中實現文件上傳和下載

首先在springmvc.xml中配置文件上傳的屬性

    <!-- 文件上傳的屬性值 -->
     <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <property name="defaultEncoding" value="utf-8"></property>
        <property name="maxUploadSize" value="10485760000"></property>
        <property name="maxInMemorySize" value="40960"></property>
        <property name="uploadTempDir" value="/WEB-INF/tmp"></property>
   </bean>

在pom.xml文件中加入上傳組件的jar包

        <!--文件上傳-->
        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.3.1</version>
        </dependency>

這兩個xml文件配置完成之後，我們就可以開始來寫我們的前端頁面和後端的控制器代碼了。

---

我們知道後臺接受的類是MultipartFile，我們首先來封裝一個文件上傳的工具類，將文件上傳到系統的指定目錄下

package com.test.utils;

import com.test.helper.BaseHelper;
import org.springframework.web.multipart.MultipartFile;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;

/**
 * 文件上傳工具類.
 *
 * @author 張俊強~.
 * @date 2017/11/15-17:27.
 */
public class FileUploadUtils {

    //目前文件上傳的路徑
    public static final String tmpFilePath="F:\\temp\\";

    public static BaseHelper uploadFile(MultipartFile file){

        BaseHelper baseHelper=new BaseHelper();
        if (!file.isEmpty()) {

            String fileName=file.getOriginalFilename();

            try {
                byte[] bytes = file.getBytes();
                BufferedOutputStream stream =
                        new BufferedOutputStream(new FileOutputStream(new File(FileUploadUtils.tmpFilePath+fileName)));
                stream.write(bytes);
                stream.close();
            } catch (Exception e) {
                e.printStackTrace();
                baseHelper.setCode(StatusInfoUtils.FAILCODE);
                baseHelper.setMsg(StatusInfoUtils.UPLOADFAIL);
            }
        } else {
            baseHelper.setCode(StatusInfoUtils.FAILCODE);
            baseHelper.setMsg(StatusInfoUtils.NOFILEFOUND);
        }
        return  baseHelper;
    }

}

上面的代碼就可以實現文件的保存了。
下面我們來看看單文件上傳和多文件上傳的功能如何實現吧！

單文件上傳

前臺表單代碼

<%----------------單文件上傳-----------------%>
<form method="POST" enctype="multipart/form-data" action="fileOperation/fileUpload">
    選擇文件: <input type="file" name="file"><br/>
    <input type="submit" value="上傳">
</form>

後臺業務處理代碼

    /**
     * 單文件的上傳.
     *
     * @param  file 待上傳的文件
     * @return 文件上傳的返回信息
     */
    @ResponseBody
    @RequestMapping(value = {"fileUpload"})
    public BaseHelper fileUploadOperation(@RequestParam("file") MultipartFile file) {

        BaseHelper baseHelper= FileUploadUtils.uploadFile(file);
        return baseHelper;
    }

多文件上傳

前臺表單代碼

<%------------多文件上傳--------------%>
<form method="POST" enctype="multipart/form-data" action="fileOperation/mulFileUpload">
    <p>
        選擇文件:<input type="file" name="files">
    <p>
        選擇文件:<input type="file" name="files">
    <p>
        選擇文件:<input type="file" name="files">
    <p>
        <input type="submit" value="上傳">
</form>

後臺處理代碼

    /**
     * 多文件的上傳.
     *
     * @param  files 待上傳的文件組
     * @return 文件上傳的返回信息
     */
    @ResponseBody
    @RequestMapping(value = {"mulFileUpload"})
    public BaseHelper mulFileUploadOperation(@RequestParam("files") MultipartFile[] files) {

        BaseHelper baseHelper=new BaseHelper();
        if (files.length>0) {
            for(MultipartFile file:files){
                baseHelper=FileUploadUtils.uploadFile(file);
            }
        } else {
            baseHelper.setCode(StatusInfoUtils.FAILCODE);
            baseHelper.setMsg(StatusInfoUtils.NOFILEFOUND);
        }
        return  baseHelper;
    }

---

以上就是有關文件上傳的功能的實現了，其中的BaseHelper和StatusInfoUtils的工具類代碼如下

BaseHelper代碼

package com.test.helper;

/**
 * 一些基本的返回的信息狀態.
 *
 * @author 張俊強~.
 * @date 2017/11/12-10:14.
 */
public class BaseHelper {

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    private String code="SUCCESS";  //默認是成功

    @Override
    public String toString() {
        return "BaseHelper{" +
                "code='" + code + '\'' +
                ", msg='" + msg + '\'' +
                '}';
    }

    private String msg="操作成功";   //默認是操作成功
}

StatusInfoUtils的工具類代碼

package com.test.utils;

/**
 * 一些狀態信息的靜態類.
 *
 * @author 張俊強~.
 * @date 2017/11/12-10:25.
 */
public final class StatusInfoUtils {
    private StatusInfoUtils(){}//增強其不可實例化的能力 最好再私有構造器類拋異常
    //返回狀態信息
    public static final String SUCCESSCODE="SUCCESS";
    public static final String SUCCESSMSG="操作成功";
    public static final String FAILCODE="FAIL";
    public static final String FAILMSG="操作失敗";
    //文件上傳狀態信息
    public static final String UPLOADSUCCESS="上傳成功";
    public static final String UPLOADFAIL="上傳失敗";
    public static final String NOFILEFOUND="未選擇文件";
}

---

關於文件下載，有兩種方法，一種是通過OutputStream寫出字節，還有一種是通過PrintWriter 寫出字符。

通過OutputStream寫出字節

    /**
     * Download file by output stream.
     *
     * @param response the response
     * @param realPath the real path
     * @throws FileNotFoundException the file not found exception
     * @throws IOException           the io exception
     */
    public static void downloadFileByOutputStream(HttpServletResponse response, String realPath)
            throws FileNotFoundException, IOException {
        String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
        response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
        response.setHeader("Content-Type","application/octet-stream");
        response.setHeader("Accept-Ranges","bytes");
        InputStream in = new FileInputStream(realPath);
        int len = 0;
        byte[] buffer = new byte[1024];
        OutputStream out = response.getOutputStream();
        //將FileInputStream流寫入到buffer緩衝區
        while ((len = in.read(buffer)) > 0) {
            //使用OutputStream將緩衝區的數據輸出到客戶端瀏覽器
            out.write(buffer, 0, len);
        }
        in.close();
    }

通過PrintWriter 寫出字符

    /**
     * Download file by print writer.
     *
     * @param response the response
     * @param realPath the real path
     * @throws FileNotFoundException the file not found exception
     * @throws IOException           the io exception
     */
    public static void downloadFileByPrintWriter(HttpServletResponse response, String realPath)
            throws FileNotFoundException, IOException {
        String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);

        response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
        FileReader in = new FileReader(realPath);
        int len = 0;
        char[] buffer = new char[1024];
        PrintWriter out = response.getWriter();//獲取PrintWriter輸出流
        while ((len = in.read(buffer)) > 0) {
            out.write(buffer, 0, len);//將緩衝區的數據輸出到客戶端瀏覽器
        }
        in.close();
    }

---

以上 2017-11-15 22:29 於上海
更新時間：2017-11-25 16:49 添加文件下載代碼