myBatis + SpringMVC上传、下载文件
myBatis + SpringMVC上传、下载文件
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"/>