java - 从mysql java下载后PDF文件损坏

Question

我正在尝试将 pdf 文件上传到我的数据库并尝试下载相同的文件，但在下载文件后我无法打开该文件，我收到一条错误消息，指出文件类型不受支持。这是文件上传的代码。

    package itext;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

import com.mysql.jdbc.PreparedStatement;

public class FileUpload {
    public static void fileupload() throws FileNotFoundException{

        String inFile="D:/Eclipse Java/myown.pdf";
        FileInputStream io = new FileInputStream(inFile);
        byte[] pdfData = new byte[(int) inFile.length()];
        DataInputStream dis;
        try {
            dis = new DataInputStream(new FileInputStream(inFile));
            dis.readFully(pdfData);  // read from file into byte[] array
            dis.close();

          Connection dbConnection;

        String myConnectionString =
                "jdbc:mysql://******/*****";

            dbConnection = DriverManager.getConnection(myConnectionString, "****", "****");
            PreparedStatement ps = (PreparedStatement) dbConnection.prepareStatement("INSERT INTO Form_BL (AppID,Form) VALUES (?,?)");
            ps.setString(1, "1");
            ps.setBytes(2, pdfData);  // byte[] array
            ps.executeUpdate();
            ps.setBinaryStream(1,  (InputStream)dis,(int)inFile.length());
        }
             catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

}
}

这是下载代码

    package itext;

import java.io.FileOutputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;

import com.mysql.jdbc.Blob;
import com.mysql.jdbc.PreparedStatement;

public class FileDownload {
public static void filedownload(){
     Connection dbConnection;
     ResultSet rs;

     String myConnectionString =
             "jdbc:mysql://*****/*****";
     try {
            dbConnection = DriverManager.getConnection(myConnectionString, "****", "****");

     PreparedStatement ps=(PreparedStatement) dbConnection.prepareStatement("select AppID from Form_BL where AppID='1' ");
      rs=ps.executeQuery();
      rs.next();
      java.sql.Blob b=rs.getBlob(1);
      byte barr[]=new byte[(int)b.length()];//an array is created but contains no data
      barr=b.getBytes(1,(int)b.length());

      FileOutputStream fout=new FileOutputStream("D:/download.pdf");
      fout.write(barr);

      fout.close();
      System.out.println("ok");

      dbConnection.close();
      ps.close(); 



  }catch(Exception e){
      e.printStackTrace();
  }

}
}

我正在使用以下链接的引用进行此操作。 Upload PDF file to mysql BLOB by using java.sql.PreparedStatement without corruption .提前致谢

Answer 1

看起来将二进制内容(PDF 文件)保存到 BLOB 中的代码没问题。但是，当您尝试取回 PDF 内容时，您似乎遇到了一些麻烦。

你可能想试试这个:

Blob b = rs.getBlob(1);
InputStream is = b.getBinaryStream();
FileOutputStream fos = new FileOutputStream("D:/download.pdf");
int i = 0;

// IMPORTANT: Remember to handle/close all I/O properly
while ((i = is.read()) != -1) {
  fos.write(b); 
}