如何上传图像并将其保存在数据库中？ [英] How to upload an image and save it in database?

问题描述

我必须使用JavaScript创建一个表单，用户将上传一个JPG文件并提交其他信息，如姓名，电子邮件等。当用户单击提交时，表单中的所有信息将被加载到一个值目的。对于图像文件，我将它设置为 byte [] 。

I have to create a form using JavaScript and an user will upload a JPG file and submit along with other info such as name, email, etc. When the user clicks submit all the information from the form will be loaded to a value object. For the image file I've set it to be byte[].

So assuming:

public String name;
public String email;
public byte[] logo;

我设置了一个servlet来处理提交，但我不知道如何开始。上传如何工作？当用户提交时，如何获取图像的信息？以下是屏幕截图： http://imageshack.us/f/32/77675354.png/我需要转换该图像并将其保存到 byte [] ，然后转换为blob，以便我可以将其插入表。

I've set up a servlet as well to handle the submission but I'm not sure how to get started. How does the upload work? When user submits, how do I get the information for the image? Here's a screenshot: http://imageshack.us/f/32/77675354.png/ I need to convert that image and save it to a byte[] then convert to blob so I can insert it to a table.

推荐答案

对于文件上传部分，您需要设置 enctype =multipart / form-data HTML表单，以便webbrowser将发送文件内容，并且您想在servlet的 doPost（）中使用 request.getPart（） code>方法将文件作为 InputStream 获取。有关具体代码示例，另请参见如何将文件上传到服务器使用JSP / Servlet？

For the file upload part, you need to set enctype="multipart/form-data" on the HTML form so that the webbrowser will send the file content and you'd like to use request.getPart() in servlet's doPost() method to get the file as an InputStream. For a concrete code example, see also How to upload files to server using JSP/Servlet?

然后，要在DB中保存 InputStream a href =http://download.oracle.com/javase/6/docs/api/java/sql/PreparedStatement.html#setBinaryStream%28int,%20java.io.InputStream%29 =nofollow> PreparedStatement＃setBinaryStream（） BLOB / varbinary / bytea 列或任何列表示您最喜欢的数据库引擎中的二进制数据。

Then, to save this InputStream in the DB, just use PreparedStatement#setBinaryStream() on a BLOB/varbinary/bytea column or whatever column represents "binary data" in your favorite DB engine.

preparedStatement = connection.prepareStatement("INSERT INTO user (name, email, logo) VALUES (?, ?, ?)");
preparedStatement.setString(1, name);
preparedStatement.setString(2, email);
preparedStatement.setBinaryStream(3, logo);
// ...

您不一定需要转换此 InputStream 到 byte [] ，它也不会有内存高效。假设100个用户同时上传10MB的图像，那么1GB的服务器内存将在那时分配。

You don't necessarily need to convert this InputStream to byte[], it would not have been memory efficient either. Imagine that 100 user simultaneously upload images of 10MB, then 1GB of server memory would have been allocated at that point.

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