How to implement a simple file upload function using MySQL and Java

How to use MySQL and Java to implement a simple file upload function

In Web development, the file upload function is one of the very common requirements. This article will introduce how to use MySQL and Java to implement a simple file upload function, and provide specific code examples for reference.

1. Create database table

First, we need to create a table in the MySQL database for storing files. The fields of the table can include information such as file ID, file name, file type, file size, and file content. The following is a sample SQL statement to create a file table:

CREATE TABLE files (
    id INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(255) NOT NULL,
    type VARCHAR(100) NOT NULL,
    size INT NOT NULL,
    content LONGBLOB NOT NULL
);

2. Create file upload form

In the front-end page, we need to create a file upload form for selecting files and submitted to the backend for processing. The following is a simple HTML file upload form example:

<form action="upload" method="post" enctype="multipart/form-data">
    <input type="file" name="file" id="file">
    <input type="submit" value="上传">
</form>

3. Writing file upload code

In the back-end Java code, we need to write the processing logic for file upload. The following is a sample code that uses Servlet to handle file upload:

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import org.apache.commons.io.IOUtils;

@WebServlet("/upload")
@MultipartConfig(maxFileSize = 1024 * 1024 * 10) // 限制文件大小为10MB
public class UploadServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String fileName = "";
        String fileType = "";
        int fileSize = 0;
        InputStream fileContent = null;
        
        try {
            Part filePart = request.getPart("file");
            fileName = filePart.getSubmittedFileName();
            fileType = filePart.getContentType();
            fileSize = (int) filePart.getSize();
            fileContent = filePart.getInputStream();
            
            // 将文件内容保存到数据库
            saveFileToDatabase(fileName, fileType, fileSize, fileContent);
            
            response.getWriter().println("上传成功！");
        } catch (SQLException e) {
            response.getWriter().println("上传失败：" + e.getMessage());
        } finally {
            if (fileContent != null) {
                fileContent.close();
            }
        }
    }
    
    private void saveFileToDatabase(String fileName, String fileType, int fileSize, InputStream fileContent) throws SQLException {
        Connection conn = null;
        PreparedStatement stmt = null;
        
        try {
            conn = getConnection(); // 假设已实现获取数据库连接的方法getConnection()
            stmt = conn.prepareStatement("INSERT INTO files (name, type, size, content) VALUES (?, ?, ?, ?)");
            stmt.setString(1, fileName);
            stmt.setString(2, fileType);
            stmt.setInt(3, fileSize);
            stmt.setBinaryStream(4, fileContent);
            stmt.executeUpdate();
        } finally {
            if (stmt != null) {
                stmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        }
    }

}

In the above code, we first use the request.getPart("file") method to obtain the uploaded file and obtain the file Information such as name, file type, file size and file content. We then save the file contents to a file table in a MySQL database.

It should be noted that in order to be able to handle file uploads, we added the @MultipartConfig annotation to the Servlet class and set the maximum file size to 10MB.

The above is a simple implementation of the file upload function. Through this example, you can learn how to use MySQL and Java to upload files and save the file contents to the database. Based on actual needs, you can modify and adjust the code to meet your business needs.

Hope this article can be helpful to you. If you have any questions, please feel free to contact us.

The above is the detailed content of How to implement a simple file upload function using MySQL and Java. For more information, please follow other related articles on the PHP Chinese website!