java - 如何在 spring mvc 中为图像定义 getter 和 setter

Question

我正在尝试使用 spring mvc 将图像上传到 mysql 数据库。我能够插入字符串和整数值，但在上传图像时抛出字段错误

代码:

dao.java 文件:

import java.io.IOException;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;

import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.commons.CommonsMultipartFile;
import org.springframework.web.multipart.commons.CommonsMultipartResolver;

import com.skillsoft.model.Book;

public class BookDao {
    JdbcTemplate template;

    public void setTemplate(JdbcTemplate template) {
        this.template = template;
    }

    public List<Book> getExhibitionDetails() {
        return template.query("select * from ExhibitionDetails", new RowMapper<Book>() {
            public Book mapRow(ResultSet rs, int row) throws SQLException {
                Book book = new Book();
                book.setStudentId(rs.getInt(1));
                book.setName(rs.getString(2));
                book.setProjectName(rs.getString(3));
                book.setPhoto(rs.getBytes(4));
                return book;
            }
        });
    }

    public int save(Book p) {
        String sql = "insert into ExhibitionDetails(StudentId, Name, ProjectName, Photo) values(" + p.getStudentId() + ",'"
                + p.getName() + "','" + p.getProjectName() + "','" + p.getPhoto() + "')" ;
        return template.update(sql);
    }

使用p.getPhoto()获取图像并将其插入数据库是否正确？如果不是，有什么替代方案

模型类:

package com.skillsoft.model;

import java.util.List;

import org.springframework.web.multipart.MultipartFile;

public class Book {

    private int studentId;
    private String name;
    private String projectName;
    private byte[] photo;

    public byte[] getPhoto() {
        return photo;
    }

    public void setPhoto(byte[] photo) {
        this.photo = photo;
    }

    public String getProjectName() {
        return projectName;
    }

    public void setProjectName(String projectName) {
        this.projectName = projectName;
    }

    public int getStudentId() {
        return studentId;
    }

    public void setStudentId(int studentId) {
        this.studentId = studentId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

Controller :

导入com.skillsoft.dao.BookDao；导入 com.skillsoft.model.Book;

@ Controller 公共(public)类 BookController {

@Autowired
BookDao bookdao;


@RequestMapping("/viewbook")
public String viewbook(Model m) {
    List<Book> list = bookdao.getExhibitionDetails();
    m.addAttribute("list", list);
    return "viewbook";
}


@RequestMapping("/addform")
public String showform(Model m) {
    m.addAttribute("command", new Book());
    return "addform";
}


@RequestMapping(value = "/save", method = RequestMethod.POST)
public String save(@ModelAttribute("book") Book book) {
    bookdao.save(book);
    return "redirect:/viewbook";
}

Error:

Field error in object 'book' on field 'photo': rejected value [org.springframework.web.multipart.commons.CommonsMultipartFile@2e5c8975]; codes [typeMismatch.book.photo,typeMismatch.photo,typeMismatch.[B,typeMismatch]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [book.photo,photo]; arguments []; default message [photo]]; default message [Failed to convert property value of type 'org.springframework.web.multipart.commons.CommonsMultipartFile' to required type 'byte[]' for property 'photo'; nested exception is java.lang.IllegalArgumentException: Cannot convert value of type 'org.springframework.web.multipart.commons.CommonsMultipartFile' to required type 'byte' for property 'photo[0]': PropertyEditor [org.springframework.beans.propertyeditors.CustomNumberEditor] returned inappropriate value of type 'org.springframework.web.multipart.commons.CommonsMultipartFile']]

Answer 1

谢谢。从错误消息来看，您似乎正在将 org.springframework.web.multipart.commons.CommonsMultipartFile 类型的变量传递给 setPhoto()，该变量需要 字节[]。 CommonsMultipartFile 有一个 getBytes() 方法，因此您可以尝试调用该方法来获取模型所需的字节数组。

关于我之前的评论:我的直觉是，将图像存储在关系数据库列中可能不是正确的设计选择。如果您计划在网页中显示这些图像，那么几乎可以肯定这不是正确的设计选择。您可以考虑将上传的文件存储在文件系统(或 S3 等云服务)上，然后仅将文件的路径或 URL 存储在模型中。