myBatis + SpringMVC上传、下载文件

转自：https://www.cnblogs.com/yerikm/p/6423829.html

环境：maven+SpringMVC + Spring + MyBatis + MySql

本文主要说明如何使用input上传文件到服务器指定目录，或保存到数据库中；如何从数据库下载文件，和显示图像文件并实现缩放。

将文件存储在数据库中，一般是存文件的byte数组，对应的数据库数据类型为blob。

首先要创建数据库，此处使用MySql数据库。

     注意：文中给出的代码多为节选重要片段，并不齐全。

1.  前期准备

 使用maven创建一个springMVC+spring+mybatis+mysql的项目。

关于如何整合Spring+mybatis+mysql，请见MyBatis简介与配置MyBatis+Spring+MySql：

MyBatis学习 之 一、MyBatis简介与配置MyBaits+Spring+MySql

关于SpringMVC环境的搭建请见：使用Eclipse构建Maven的SpringMVC项目：

使用Eclipse构建Maven的SpringMVC项目

在前台html中，form的enctype为multipart/form-data。注意input、select的name要和StudentForm中成员一一对应。

上传的url为addAction.do，此action方法的参数中使用StudentForm来映射提交的数据。此时就可以获取到提交的文件的数据。然后我们就对文件进行操作。

创建PHOTO_TBL表：PHOTO_DATA字段用于存放文件，类型为MyBatis的longblob；然后写Mapper的Java接口PhotoMapper：包括增删改查；mapper的xml文件：对应JAVA接口的sql语句。

并且需要Spring配置文件添加一个bean的声明。

   下面给出html、action、StudentForm的代码片段；创建PHOTO_TBL表的sql、PhotoMapper.java接口代码、PhotoMapper.xml文件代码。

1.1 html的form表单写法

<form action="<c:url value='addAction.do' />" method="post" enctype="multipart/form-data">
    <table>
        <tr>
            <td width="100" align="right">照片：</td>
            <td><input type="file" name="studentPhoto"/></td>
        </tr>
    </table>
    <input type="submit">
</form>

1.2 action方法

/**
 * 新增 - 提交
 */
@RequestMapping(value = "addAction.do")
public String add_action(ModelMap model, StudentForm form) {

}

1.3 StudentForm类

package liming.student.manager.web.model;

import org.springframework.web.multipart.MultipartFile;

public class StudentForm extends GeneralForm {

    private String studentName;
    private int studentSex;
    private String studentBirthday;
    private MultipartFile studentPhoto;

}

1.4 创建PHOTO_TBL

CREATE TABLE PHOTO_TBL
(
   PHOTO_ID     VARCHAR(100) PRIMARY KEY,
   PHOTO_DATA   LONGBLOB,
   FILE_NAME    VARCHAR(10)
);

1.5  PhotoMapper接口

@Repository
@Transactional
public interface PhotoMapper {

    public void createPhoto(PhotoEntity entity);

    public int deletePhotoByPhotoId(String photoId);

    public int updatePhotoDate(@Param("photoId") String photoId, @Param("photoDate") byte[] photoDate);

    public PhotoEntity getPhotoEntityByPhotoId(String photoId);

}

1.6  PhotoMapper.xml文件

         包括增、删、改、查。其中新增中的photoId使用的是mysql自定义函数自动生成主键。在操作blob时需要制定typeHandler为"org.apache.ibatis.type.BlobTypeHandler。insert、update时参数后面需要指定，resultMap中需要指定。

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="liming.student.manager.data.PhotoMapper">
    <resultMap type="liming.student.manager.data.model.PhotoEntity" id="photoMapper_resultMap_photoEntity">
        <id property="photoId"           column="PHOTO_ID"       javaType="String" jdbcType="VARCHAR" />
        <result property="photoData" column="PHOTO_DATA"     javaType="byte[]" jdbcType="BLOB" typeHandler="org.apache.ibatis.type.BlobTypeHandler" />
        <result property="fileName"  column="FILE_NAME"      javaType="String" jdbcType="VARCHAR" />
    </resultMap>

    <insert id="createPhoto" parameterType="liming.student.manager.data.model.PhotoEntity">
        <selectKey keyProperty="photoId" resultType="String" order="BEFORE">
            select nextval('photo')
        </selectKey>
        INSERT INTO PHOTO_TBL(PHOTO_ID,
                              PHOTO_DATA,
                              FILE_NAME)
        VALUES(#{photoId, jdbcType=VARCHAR},
               #{photoData, javaType=byte[], jdbcType=BLOB, typeHandler=org.apache.ibatis.type.BlobTypeHandler},
               #{fileName, jdbcType=VARCHAR})
    </insert>

    <delete id="deletePhotoByPhotoId">
        DELETE FROM PHOTO_TBL
              WHERE PHOTO_ID = #{photoId, jdbcType=VARCHAR}
    </delete>

    <update id="updatephotoData" >
        UPDATE PHOTO_TBL
           SET PHOTO_DATA = #{photoData, javaType=byte[], jdbcType=BLOB, typeHandler=org.apache.ibatis.type.BlobTypeHandler},
               FILE_NAME = #{fileName, jdbcType=VARCHAR}
         WHERE PHOTO_ID = #{photoId, jdbcType=VARCHAR}
    </update>

    <select id="getPhotoEntityByPhotoId" resultMap="photoMapper_resultMap_photoEntity">
        SELECT PHOTO_ID,
               PHOTO_DATA,
               FILE_NAME
          FROM PHOTO_TBL
         WHERE PHOTO_ID = #{photoId, jdbcType=VARCHAR}
    </select>
</mapper>

1.7 spring配置文件

    需要Spring配置文件添加一个org.springframework.web.multipart.commons.CommonsMultipartResolver的bean的声明。

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <property name="maxUploadSize" value="1073741824" />
</bean>

2. 将文件到服务器上

private static final String uploadFilePath = "d:\temp_upload_file\";

/**
 * 新增 - 提交 – 只保存文件到服务器上
 */
@RequestMapping(value = "addAction.do")
public String add_action(ModelMap model, StudentForm form) {
try {
        MultipartFile uploadFile = form.getStudentPhoto();
        String filename = uploadFile.getOriginalFilename();
        InputStream is = uploadFile.getInputStream();
        // 如果服务器已经存在和上传文件同名的文件，则输出提示信息
        File tempFile = new File(uploadFilePath + filename);
        if (tempFile.exists()) {
            boolean delResult = tempFile.delete();
            System.out.println("删除已存在的文件：" + delResult);
        }
        // 开始保存文件到服务器
        if (!filename.equals("")) {
            FileOutputStream fos = new FileOutputStream(uploadFilePath + filename);
            byte[] buffer = new byte[8192]; // 每次读8K字节
            int count = 0;
            // 开始读取上传文件的字节，并将其输出到服务端的上传文件输出流中
            while ((count = is.read(buffer)) > 0) {
                fos.write(buffer, 0, count); // 向服务端文件写入字节流
            }
            fos.close(); // 关闭FileOutputStream对象
            is.close(); // InputStream对象
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

3. 将文件上传到数据库中

/**
 * 新增 - 提交 – 保存文件到数据库
 */
@RequestMapping(value = "addAction.do")
public String add_action(ModelMap model, StudentForm form) {
    InputStream is = form.getStudentPhoto().getInputStream();
    byte[] studentPhotoData = new byte[(int) form.getStudentPhoto().getSize()];
    is.read(studentPhotoData);
    String fileName = form.getStudentPhoto().getOriginalFilename();
    PhotoEntity photoEntity = new PhotoEntity();
    photoEntity.setPhotoData(studentPhotoData);
    photoEntity.setFileName(fileName);
    this.photoMapper.createPhoto(photoEntity);
}

4.下载文件

       下载文件需要将byte数组还原成文件。

         首先使用mybatis将数据库中的byte数组查出来，指定文件名(包括格式)。然后使用OutputStream将文件输入

@RequestMapping(value = "downPhotoById")
public void downPhotoByStudentId(String id, final HttpServletResponse response){
    PhotoEntity entity = this.photoMapper.getPhotoEntityByPhotoId(id);
    byte[] data = entity.getPhotoData();
    String fileName = entity.getFileName()== null ? "照片.png" : entity.getFileName();
    fileName = URLEncoder.encode(fileName, "UTF-8");
    response.reset();
    response.setHeader("Content-Disposition", "attachment; filename="" + fileName + """);
    response.addHeader("Content-Length", "" + data.length);
    response.setContentType("application/octet-stream;charset=UTF-8");
    OutputStream outputStream = new BufferedOutputStream(response.getOutputStream());
    outputStream.write(data);
    outputStream.flush();
    outputStream.close();
}

<a href="<%=request.getContextPath() %>/downPhotoById.do?id=8000001">下载照片</a>

5. 显示byte图片文件

@RequestMapping(value = "getPhotoById")
public void getPhotoById (String id, final HttpServletResponse response){
    PhotoEntity entity = this.photoMapper.getPhotoEntityByPhotoId(id);
    byte[] data = entity.getPhotoData();
    response.setContentType("image/jpeg");
    response.setCharacterEncoding("UTF-8");
    OutputStream outputSream = response.getOutputStream();
    InputStream in = new ByteArrayInputStream(data);
    int len = 0;
    byte[] buf = new byte[1024];
    while ((len = in.read(buf, 0, 1024)) != -1) {
        outputSream.write(buf, 0, len);
    }
    outputSream.close();
}

<img src="<%=request.getContextPath() %>/getPhotoById.do?id=8000001"/>

6. 按长宽等比例缩放图片

@RequestMapping(value = "getPhotoId")
public void getPhotoById (String id, int width, int height, final HttpServletResponse response){
    PhotoEntity entity = this.photoMapper.getPhotoEntityByPhotoId(id);
    byte[] data = entity.getPhotoData();
    if (width != 0 && height != 0) {
        data = scaleImage(data, width, height);
    }
    response.setContentType("image/jpeg");
    response.setCharacterEncoding("UTF-8");
    OutputStream outputSream = response.getOutputStream();
    InputStream in = new ByteArrayInputStream(data);
    int len = 0;
    byte[] buf = new byte[1024];
    while ((len = in.read(buf, 0, 1024)) != -1) {
        outputSream.write(buf, 0, len);
    }
    outputSream.close();
}

public static byte[] scaleImage(byte[] data, int width, int height) throws IOException {
    BufferedImage buffered_oldImage = ImageIO.read(new ByteArrayInputStream(data));
    int imageOldWidth = buffered_oldImage.getWidth();
    int imageOldHeight = buffered_oldImage.getHeight();
    double scale_x = (double) width / imageOldWidth;
    double scale_y = (double) height / imageOldHeight;
    double scale_xy = Math.min(scale_x, scale_y);
    int imageNewWidth = (int) (imageOldWidth * scale_xy);
    int imageNewHeight = (int) (imageOldHeight * scale_xy);
    BufferedImage buffered_newImage = new BufferedImage(imageNewWidth, imageNewHeight, BufferedImage.TYPE_INT_RGB);
    buffered_newImage.getGraphics().drawImage(buffered_oldImage.getScaledInstance(imageNewWidth, imageNewHeight, BufferedImage.SCALE_SMOOTH), 0, 0, null);
    buffered_newImage.getGraphics().dispose();
    ByteArrayOutputStream outPutStream = new ByteArrayOutputStream();
    ImageIO.write(buffered_newImage, "jpeg", outPutStream);
    return outPutStream.toByteArray();
}

<img src="<%=request.getContextPath() %>/getPhotoById.do?id=8000001&width=300&height=300"/>