使用 java.sql.PreparedStatement 将 PDF 文件上传到 mysql BLOB 而不损坏
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Upload PDF file to mysql BLOB by using java.sql.PreparedStatement without corruption
提问by Sangeet Menon
I tried to uplad a pdf file using java.sql.PreparedStatementto mysqlBlob field using the following code.
我尝试使用以下代码将 pdf 文件上传java.sql.PreparedStatement到mysqlBlob 字段。
File inFile = new File("Path+BLOCK.pdf");
byte[] b = new byte[(int)inFile.length()];
PreparedStatement psmnt = (PreparedStatement)
con.prepareStatement("INSERT INTO
2012DOC (SRNO,DOCUMENT)
VALUES (?,?)"
); //con is java.sql.Connection object
psmnt.setString(1, "1200021");
psmnt.setBytes(2, b);
psmnt.executeUpdate();
This code executes without error and database shows blob content, but when I try to retrieve the file using the below code it gives a corrupt file which doesn't open.
此代码执行时没有错误，数据库显示 blob 内容，但是当我尝试使用以下代码检索文件时，它提供了一个无法打开的损坏文件。
ResultSet rs=con.Execute("SELECT DOCUMENT FROM 2012DOC");
rs.next();
response.setContentType("application/pdf");
response.setHeader("Content-Disposition", "attachment; filename=kjsahkjd.pdf");
java.sql.Blob blob = rs.getBlob("DOCUMENT");
ServletOutputStream servletOutputStream = response.getOutputStream();
InputStream in = blob.getBinaryStream();
int length = (int) blob.length();
int bufferSize = 1024;
byte[] buffer = new byte[bufferSize];
while ((length = in.read(buffer)) != -1) {
servletOutputStream.write(buffer, 0, length);
}
in.close();
servletOutputStream.flush();
servletOutputStream.close();
It outputs the file with same size as the original,but the file doesn't open.
The pdfreader is fired but cannot open the file and gives an error 'the file was either damaged or not supported file type'
它输出与原始文件大小相同的文件，但文件没有打开。该pdf阅读器被触发，但不能打开该文件，并给出了一个错误“的文件被损坏或不支持的文件类型”
采纳答案by Sangeet Menon
Ahhh...After a little debugging I found the code that uploads is troublesome, and finally got the right way to do it.
啊啊……调试了一下，发现上传的代码很麻烦，终于找到了正确的方法。
Here is what I did...I'm posting it so that others with same problem can solve it
这是我所做的......我发布它以便其他有同样问题的人可以解决它
After Converting the java.io.Fileto java.io.FileInputStream
转换为java.io.File后java.io.FileInputStream
FileInputStream io = new FileInputStream(inFile);
Set the BLOB field using psmnt.setBinaryStream()
使用设置 BLOB 字段 psmnt.setBinaryStream()
psmnt.setBinaryStream(3, (InputStream)io,(int)inFile.length());
回答by shivam
remove " java.sql.Blob blob = rs.getBlob("DOCUMENT");"
删除“ java.sql.Blob blob = rs.getBlob("DOCUMENT");”
and don't initialize length i.e instead of
并且不要初始化长度 ie 而不是
int length = (int) blob.length();
just write
写就好了
int length;
then it downloads file successfully .. enjoy :)
然后它成功下载文件..享受:)
