Выгрузка и загрузка файлов из базы данных с помощью Java Servlet
View more Tutorials:
Следуйте за нами на нашей фан-странице, чтобы получать уведомления каждый раз, когда появляются новые статьи.
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** ORACLE **
create table ATTACHMENT
(
ID NUMBER(19) not null,
FILE_NAME VARCHAR2(50) not null,
FILE_DATA BLOB not null,
DESCRIPTION VARCHAR2(255)
) ;
alter table ATTACHMENT
add constraint ATTACHMENT_PK primary key (ID) ;
** MYSQL **
create table ATTACHMENT
(
ID BIGINT not null,
FILE_NAME VARCHAR(50) not null,
FILE_DATA BLOB not null,
DESCRIPTION VARCHAR(255)
) ;
alter table ATTACHMENT
add constraint ATTACHMENT_PK primary key (ID) ;
** SQL SERVER **
create table ATTACHMENT
(
ID BIGINT not null,
FILE_NAME VARCHAR(50) not null,
FILE_DATA Varbinary(max) not null,
DESCRIPTION VARCHAR(255)
) ;
alter table ATTACHMENT
add constraint ATTACHMENT_PK primary key (ID) ;
В этой статье я покажу вам как загружать и хранить файлы в database, а затем скачать данные из database. Загруженные файлы данных хранятся в столбце в виде BLOB. Вы можете использовать любую базу данных, выше предоставляется script для создания таблицы ATTACHMEN, эта таблица хранит файлы, которые вы загружаете .
Вы можете изучить, как использовать JDBC для подключения к Database здесь:
UploadToDBServlet.java
package org.o7planning.servletexamples;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.RequestDispatcher;
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.o7planning.tutorial.jdbc.ConnectionUtils;
@WebServlet("/uploadToDB")
@MultipartConfig(fileSizeThreshold = 1024 * 1024 * 2, // 2MB
maxFileSize = 1024 * 1024 * 10, // 10MB
maxRequestSize = 1024 * 1024 * 50) // 50MB
public class UploadToDBServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
RequestDispatcher dispatcher = request.getServletContext().getRequestDispatcher("/WEB-INF/jsps/uploadToDB.jsp");
dispatcher.forward(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Connection conn = null;
try {
// Connection to Database
// (See more in JDBC Tutorial).
conn = ConnectionUtils.getMyConnection();
conn.setAutoCommit(false);
String description = request.getParameter("description");
// Part list (multi files).
for (Part part : request.getParts()) {
String fileName = extractFileName(part);
if (fileName != null && fileName.length() > 0) {
// File data
InputStream is = part.getInputStream();
// Write to file
this.writeToDB(conn, fileName, is, description);
}
}
conn.commit();
// Upload successfully!.
response.sendRedirect(request.getContextPath() + "/uploadToDBResults");
} catch (Exception e) {
e.printStackTrace();
request.setAttribute("errorMessage", "Error: " + e.getMessage());
RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/WEB-INF/jsps/uploadToDB.jsp");
dispatcher.forward(request, response);
} finally {
this.closeQuietly(conn);
}
}
private String extractFileName(Part part) {
// form-data; name="file"; filename="C:\file1.zip"
// form-data; name="file"; filename="C:\Note\file2.zip"
String contentDisp = part.getHeader("content-disposition");
String[] items = contentDisp.split(";");
for (String s : items) {
if (s.trim().startsWith("filename")) {
// C:\file1.zip
// C:\Note\file2.zip
String clientFileName = s.substring(s.indexOf("=") + 2, s.length() - 1);
clientFileName = clientFileName.replace("\\", "/");
int i = clientFileName.lastIndexOf('/');
// file1.zip
// file2.zip
return clientFileName.substring(i + 1);
}
}
return null;
}
private Long getMaxAttachmentId(Connection conn) throws SQLException {
String sql = "Select max(a.id) from Attachment a";
PreparedStatement pstm = conn.prepareStatement(sql);
ResultSet rs = pstm.executeQuery();
if (rs.next()) {
long max = rs.getLong(1);
return max;
}
return 0L;
}
private void writeToDB(Connection conn, String fileName, InputStream is, String description) throws SQLException {
String sql = "Insert into Attachment(Id,File_Name,File_Data,Description) " //
+ " values (?,?,?,?) ";
PreparedStatement pstm = conn.prepareStatement(sql);
Long id = this.getMaxAttachmentId(conn) + 1;
pstm.setLong(1, id);
pstm.setString(2, fileName);
pstm.setBlob(3, is);
pstm.setString(4, description);
pstm.executeUpdate();
}
private void closeQuietly(Connection conn) {
try {
if (conn != null) {
conn.close();
}
} catch (Exception e) {
}
}
}
UploadToDBResultsServlet.java
package org.o7planning.servletexamples;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/uploadToDBResults")
public class UploadToDBResultsServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public UploadToDBResultsServlet() {
super();
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
RequestDispatcher dispatcher
= request.getServletContext().getRequestDispatcher("/WEB-INF/jsps/uploadToDBResults.jsp");
dispatcher.forward(request, response);
}
}
/WEB-INF/jsps/uploadToDB.jsp
<!DOCTYPE >
<html>
<head>
<title>Upload files</title>
</head>
<body>
<div style="padding:5px; color:red;font-style:italic;">
${errorMessage}
</div>
<h2>Upload Files</h2>
<form method="post" action="${pageContext.request.contextPath}/uploadToDB"
enctype="multipart/form-data">
Select file to upload:
<br />
<input type="file" name="file" />
<br />
<input type="file" name="file" />
<br />
Description:
<br />
<input type="text" name="description" size="100" />
<br />
<br />
<input type="submit" value="Upload" />
</form>
</body>
</html>
/WEB-INF/jsps/uploadToDBResults.jsp
<!DOCTYPE >
<html>
<head>
<title>Upload files</title>
</head>
<body>
<h3>Upload has been done successfully!</h3>
<a href="${pageContext.request.contextPath}/uploadToDB">Continue Upload</a>
</body>
</html>
Запуск приложения:
Файлы загружены и сохранены в таблице Attachment.
DownloadAttachmentServlet.java
package org.o7planning.servletexamples;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Blob;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.o7planning.servletexamples.model.Attachment;
import org.o7planning.tutorial.jdbc.ConnectionUtils;
@WebServlet("/downloadAttachment")
public class DownloadAttachmentServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Connection conn = null;
try {
// Get Database Connection.
// (See more in JDBC Tutorial).
conn = ConnectionUtils.getMyConnection();
Long id = null;
try {
id = Long.parseLong(request.getParameter("id"));
} catch (Exception e) {
}
Attachment attachment = getAttachmentFromDB(conn, id);
if (attachment == null) {
// No record found.
response.getWriter().write("No data found");
return;
}
// file1.zip, file2.zip
String fileName = attachment.getFileName();
System.out.println("File Name: " + fileName);
// abc.txt => text/plain
// abc.zip => application/zip
// abc.pdf => application/pdf
String contentType = this.getServletContext().getMimeType(fileName);
System.out.println("Content Type: " + contentType);
response.setHeader("Content-Type", contentType);
response.setHeader("Content-Length", String.valueOf(attachment.getFileData().length()));
response.setHeader("Content-Disposition", "inline; filename=\"" + attachment.getFileName() + "\"");
// For big BLOB data.
Blob fileData = attachment.getFileData();
InputStream is = fileData.getBinaryStream();
byte[] bytes = new byte[1024];
int bytesRead;
while ((bytesRead = is.read(bytes)) != -1) {
// Write image data to Response.
response.getOutputStream().write(bytes, 0, bytesRead);
}
is.close();
} catch (Exception e) {
throw new ServletException(e);
} finally {
this.closeQuietly(conn);
}
}
private Attachment getAttachmentFromDB(Connection conn, Long id) throws SQLException {
String sql = "Select a.Id,a.File_Name,a.File_Data,a.Description "//
+ " from Attachment a where a.id = ?";
PreparedStatement pstm = conn.prepareStatement(sql);
pstm.setLong(1, id);
ResultSet rs = pstm.executeQuery();
if (rs.next()) {
String fileName = rs.getString("File_Name");
Blob fileData = rs.getBlob("File_Data");
String description = rs.getString("Description");
return new Attachment(id, fileName, fileData, description);
}
return null;
}
private void closeQuietly(Connection conn) {
try {
if (conn != null) {
conn.close();
}
} catch (Exception e) {
}
}
}
Запуск приложения:
