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
1.<form action="<c:url value='addAction.do' />" method="post" enctype="multipart/form-data"> 2. <table> 3. <tr> 4. <td align="right">照片：</td> 5. <td><input type="file" name="studentPhoto"/></td> 6. </tr> 7. </table> 8. <input type="submit"> 9.</form>
1.2 action方法
1./** 2. * 新增 - 提交 3. */ 4.@RequestMapping(value = "addAction.do") 5.public String add_action(ModelMap model, StudentForm form) { 6. 7.} 1.3 StudentForm类
1.package liming.student.manager.web.model; 2. 3.import org.springframework.web.multipart.MultipartFile; 4. 5.public class StudentForm extends GeneralForm { 6. 7. private String studentName; 8. private int studentSex; 9. private String studentBirthday; 10. private MultipartFile studentPhoto; 11. 12.} 1.4 创建PHOTO_TBL
1.CREATE TABLE PHOTO_TBL 2.( 3. PHOTO_ID VARCHAR(100) PRIMARY KEY, 4. PHOTO_DATA LONGBLOB, 5. FILE_NAME VARCHAR(10) 6.);
1.5 PhotoMapper接口
1.@Repository 2.@Transactional 3.public interface PhotoMapper { 4. 5. public void createPhoto(PhotoEntity entity); 6. 7. public int deletePhotoByPhotoId(String photoId); 8. 9. public int updatePhotoDate(@Param("photoId") String photoId, @Param("photoDate") byte[] photoDate); 10. 11. public PhotoEntity getPhotoEntityByPhotoId(String photoId); 12. 13.} 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。
1.<?xml version="1.0" encoding="UTF-8" ?> 2.<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> 3.<mapper namespace="liming.student.manager.data.PhotoMapper"> 4. <resultMap type="liming.student.manager.data.model.PhotoEntity" id="photoMapper_resultMap_photoEntity"> 5. <id property="photoId" column="PHOTO_ID" javaType="String" jdbcType="VARCHAR" /> 6. <result property="photoData" column="PHOTO_DATA" javaType="byte[]" jdbcType="BLOB" typeHandler="org.apache.ibatis.type.BlobTypeHandler" /> 7. <result property="fileName" column="FILE_NAME" javaType="String" jdbcType="VARCHAR" /> 8. </resultMap> 9. 10. <insert id="createPhoto" parameterType="liming.student.manager.data.model.PhotoEntity"> 11. <selectKey keyProperty="photoId" resultType="String" order="BEFORE"> 12. select nextval('photo') 13. </selectKey> 14. INSERT INTO PHOTO_TBL(PHOTO_ID, 15. PHOTO_DATA, 16. FILE_NAME) 17. VALUES(#{photoId, jdbcType=VARCHAR}, 18. #{photoData, javaType=byte[], jdbcType=BLOB, typeHandler=org.apache.ibatis.type.BlobTypeHandler}, 19. #{fileName, jdbcType=VARCHAR}) 20. </insert> 21. 22. <delete id="deletePhotoByPhotoId"> 23. DELETE FROM PHOTO_TBL 24. WHERE PHOTO_ID = #{photoId, jdbcType=VARCHAR} 25. </delete> 26. 27. <update id="updatephotoData" > 28. UPDATE PHOTO_TBL 29. SET PHOTO_DATA = #{photoData, javaType=byte[], jdbcType=BLOB, typeHandler=org.apache.ibatis.type.BlobTypeHandler}, 30. FILE_NAME = #{fileName, jdbcType=VARCHAR} 31. WHERE PHOTO_ID = #{photoId, jdbcType=VARCHAR} 32. </update> 33. 34. <select id="getPhotoEntityByPhotoId" resultMap="photoMapper_resultMap_photoEntity"> 35. SELECT PHOTO_ID, 36. PHOTO_DATA, 37. FILE_NAME 38. FROM PHOTO_TBL 39. WHERE PHOTO_ID = #{photoId, jdbcType=VARCHAR} 40. </select> 41.</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。
1.<bean id="multipartResolver"> 2. <property name="maxUploadSize" value="1073741824" /> 3.</bean>
2. 将文件到服务器上
1.private static final String uploadFilePath = "d://temp_upload_file//"; 2. 3./** 4. * 新增 - 提交 只保存文件到服务器上 5. */ 6.@RequestMapping(value = "addAction.do") 7.public String add_action(ModelMap model, StudentForm form) { 8.try { 9. MultipartFile uploadFile = form.getStudentPhoto(); 10. String filename = uploadFile.getOriginalFilename(); 11. InputStream is = uploadFile.getInputStream(); 12. // 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 13. File tempFile = new File(uploadFilePath + filename); 14. if (tempFile.exists()) { 15. boolean delResult = tempFile.delete(); 16. System.out.println("删除已存在的文件：" + delResult); 17. } 18. // 开始保存文件到服务器 19. if (!filename.equals("")) { 20. FileOutputStream fos = new FileOutputStream(uploadFilePath + filename); 21. byte[] buffer = new byte[8192]; // 每次读8K字节 22. int count = 0; 23. // 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 24. while ((count = is.read(buffer)) > 0) { 25. fos.write(buffer, 0, count); // 向服务端文件写入字节流 26. } 27. fos.close(); // 关闭FileOutputStream对象 28. is.close(); // InputStream对象 29. } 30. } catch (FileNotFoundException e) { 31. e.printStackTrace(); 32. } catch (IOException e) { 33. e.printStackTrace(); 34. } 35.} 3. 将文件上传到数据库中
1./** 2. * 新增 - 提交 保存文件到数据库 3. */ 4.@RequestMapping(value = "addAction.do") 5.public String add_action(ModelMap model, StudentForm form) { 6. InputStream is = form.getStudentPhoto().getInputStream(); 7. byte[] studentPhotoData = new byte[(int) form.getStudentPhoto().getSize()]; 8. is.read(studentPhotoData); 9. String fileName = form.getStudentPhoto().getOriginalFilename(); 10. PhotoEntity photoEntity = new PhotoEntity(); 11. photoEntity.setPhotoData(studentPhotoData); 12. photoEntity.setFileName(fileName); 13. this.photoMapper.createPhoto(photoEntity); 14.} 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
1.@RequestMapping(value = "downPhotoById") 2.public void downPhotoByStudentId(String id, final HttpServletResponse response){ 3. PhotoEntity entity = this.photoMapper.getPhotoEntityByPhotoId(id); 4. byte[] data = entity.getPhotoData(); 5. String fileName = entity.getFileName()== null ? "照片.png" : entity.getFileName(); 6. fileName = URLEncoder.encode(fileName, "UTF-8"); 7. response.reset(); 8. response.setHeader("Content-Disposition", "attachment; filename=/"" + fileName + "/""); 9. response.addHeader("Content-Length", "" + data.length); 10. response.setContentType("application/octet-stream;charset=UTF-8"); 11. OutputStream outputStream = new BufferedOutputStream(response.getOutputStream()); 12. outputStream.write(data); 13. outputStream.flush(); 14. outputStream.close(); 15.} <a href="<%=request.getContextPath() %>/downPhotoById.do?id=8000001">下载照片</a>
5. 显示byte图片文件
1.@RequestMapping(value = "getPhotoById") 2.public void getPhotoById (String id, final HttpServletResponse response){ 3. PhotoEntity entity = this.photoMapper.getPhotoEntityByPhotoId(id); 4. byte[] data = entity.getPhotoData(); 5. response.setContentType("image/jpeg"); 6. response.setCharacterEncoding("UTF-8"); 7. OutputStream outputSream = response.getOutputStream(); 8. InputStream in = new ByteArrayInputStream(data); 9. int len = 0; 10. byte[] buf = new byte[1024]; 11. while ((len = in.read(buf, 0, 1024)) != -1) { 12. outputSream.write(buf, 0, len); 13. } 14. outputSream.close(); 15.} <img src="<%=request.getContextPath() %>/getPhotoById.do?id=8000001"/>
6. 按长宽等比例缩放图片
1.@RequestMapping(value = "getPhotoId") 2.public void getPhotoById (String id, int width, int height, final HttpServletResponse response){ 3. PhotoEntity entity = this.photoMapper.getPhotoEntityByPhotoId(id); 4. byte[] data = entity.getPhotoData(); 5. if (width != 0 && height != 0) { 6. data = scaleImage(data, width, height); 7. } 8. response.setContentType("image/jpeg"); 9. response.setCharacterEncoding("UTF-8"); 10. OutputStream outputSream = response.getOutputStream(); 11. InputStream in = new ByteArrayInputStream(data); 12. int len = 0; 13. byte[] buf = new byte[1024]; 14. while ((len = in.read(buf, 0, 1024)) != -1) { 15. outputSream.write(buf, 0, len); 16. } 17. outputSream.close(); 18.} 19. 20.public static byte[] scaleImage(byte[] data, int width, int height) throws IOException { 21. BufferedImage buffered_oldImage = ImageIO.read(new ByteArrayInputStream(data)); 22. int imageOldWidth = buffered_oldImage.getWidth(); 23. int imageOldHeight = buffered_oldImage.getHeight(); 24. double scale_x = (double) width / imageOldWidth; 25. double scale_y = (double) height / imageOldHeight; 26. double scale_xy = Math.min(scale_x, scale_y); 27. int imageNewWidth = (int) (imageOldWidth * scale_xy); 28. int imageNewHeight = (int) (imageOldHeight * scale_xy); 29. BufferedImage buffered_newImage = new BufferedImage(imageNewWidth, imageNewHeight, BufferedImage.TYPE_INT_RGB); 30. buffered_newImage.getGraphics().drawImage(buffered_oldImage.getScaledInstance(imageNewWidth, imageNewHeight, BufferedImage.SCALE_SMOOTH), 0, 0, null); 31. buffered_newImage.getGraphics().dispose(); 32. ByteArrayOutputStream outPutStream = new ByteArrayOutputStream(); 33. ImageIO.write(buffered_newImage, "jpeg", outPutStream); 34. return outPutStream.toByteArray(); 35.} <img src="<%=request.getContextPath() %>/getPhotoById.do?id=8000001&width=300&height=300"/>
以上所述是小编给大家介绍的MyBatis与SpringMVC相结合实现文件上传、下载功能，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对武林网网站的支持！