如何在 spring mvc 中为图像定义 getter 和 setter

Question

Im trying to upload an image to mysql database using spring mvc. Im able to insert the string and integer values but while uploading image it is throwing field error

Code:

dao.java file:

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);
    }

Is it right to use p.getPhoto() to get the image and insert it into the database? If not what is the alternative

Model class:

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:

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

@Controller public class 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

Thanks. From the error message, it looks like you're passing a variable of type org.springframework.web.multipart.commons.CommonsMultipartFile to setPhoto() , which expects byte[] . CommonsMultipartFile has a getBytes() method, so you might try calling that to get the byte array that your model expects.

Regarding my previous comment: my instinct is that storing images in a relational database column is probably not the right design choice. If you're planning on displaying these images in a web page, it's almost certainly not the right design choice. You might consider storing the uploaded file on the file system (or a cloud service such as S3) and then just storing the path or URL to the file in your model.