java servlet 讀寫mysql中儲存的二進位制檔案
阿新 • • 發佈：2019-02-08
資料準備
CREATE TABLE stuinfo (
id INT (11) NOT NULL auto_increment,
NAME VARCHAR (10) DEFAULT NULL,
content LONGTEXT,
image LONGBLOB,
PRIMARY KEY (id)
) ENGINE = INNODB;需要mysql驅動包及servlet-api.jar
訪問地址：http://localhost:8080/xxx/download
package test; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.sql.Connection; import java.sql.DriverManager; 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; @WebServlet(name = "download", urlPatterns = { "/download" }) public class TestFile extends HttpServlet { //servlet 的例子 @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // 驅動程式名 String driver = "com.mysql.jdbc.Driver"; // URL指向要訪問的資料庫名scutcs String url = "jdbc:mysql://127.0.0.1:3306/antdb"; // MySQL配置時的使用者名稱 String user = "root"; // MySQL配置時的密碼 String password = "123456"; //transaction dealing PreparedStatement pstam=null; String sql="select * from stuinfo where name=?"; try { // 載入驅動程式 Class.forName(driver); // 連續資料庫 Connection conn = DriverManager.getConnection(url, user, password); pstam=conn.prepareStatement(sql); pstam.setString(1, "cjc"); ResultSet reset=pstam.executeQuery(); while(reset.next()){ BufferedReader br=new BufferedReader(reset.getCharacterStream(3)); String str=null; while((str=br.readLine())!=null){ System.out.println(str); } BufferedInputStream bis=new BufferedInputStream(reset.getBinaryStream(4)); // 寫明要下載的檔案的大小 //resp.setContentLength((int) file.length()); resp.setHeader("Content-Disposition", "attachment;filename=" + "ookkkk.jpg");// 設定在下載框預設顯示的檔名 resp.setContentType("application/octet-stream");// 指明response的返回物件是檔案流 // 讀出檔案到response // 這裡是先需要把要把檔案內容先讀到緩衝區 // 再把緩衝區的內容寫到response的輸出流供使用者下載 //FileInputStream fileInputStream = new FileInputStream(file); //BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream); byte[] b = new byte[bis.available()]; bis.read(b); OutputStream outputStream = resp.getOutputStream(); outputStream.write(b); // 人走帶門 bis.close(); outputStream.flush(); outputStream.close(); reset.close(); pstam.close(); conn.close(); } } catch (SQLException e) { e.printStackTrace(); } catch (FileNotFoundException e){ e.printStackTrace(); } catch (IOException e){ e.printStackTrace(); } catch (Exception e){ e.printStackTrace(); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } public static void main(String[] args) throws Exception { readd(); } //本地儲存檔案 圖片到伺服器的例子 public static void writer() throws Exception { // 驅動程式名 String driver = "com.mysql.jdbc.Driver"; // URL指向要訪問的資料庫名scutcs String url = "jdbc:mysql://127.0.0.1:3306/antdb"; // MySQL配置時的使用者名稱 String user = "root"; // MySQL配置時的密碼 String password = "123456"; // 載入驅動程式 Class.forName(driver); // 連續資料庫 Connection conn = DriverManager.getConnection(url, user, password); //transaction dealing PreparedStatement pstam=null; String sql="insert into stuinfo(name,content,image) values(?,?,?);"; try { pstam=conn.prepareStatement(sql); pstam.setString(1, "cjc"); File file=new File("D:/安裝前必看.txt"); InputStream itxt=new FileInputStream(file); BufferedReader br=new BufferedReader(new InputStreamReader(itxt)); pstam.setCharacterStream(2,br,(int)file.length()); File file1=new File("D:/18285693_231156450339_2.jpg"); InputStream isimg=new FileInputStream(file1); pstam.setBinaryStream(3, isimg, (int)file1.length()); pstam.executeUpdate(); br.close(); itxt.close(); isimg.close(); pstam.close(); conn.close(); } catch (SQLException e) { e.printStackTrace(); } catch (FileNotFoundException e){ e.printStackTrace(); } catch (IOException e){ e.printStackTrace(); } } //本地讀取 檔案圖片的例子 public static void readd() throws Exception { // 驅動程式名 String driver = "com.mysql.jdbc.Driver"; // URL指向要訪問的資料庫名scutcs String url = "jdbc:mysql://127.0.0.1:3306/antdb"; // MySQL配置時的使用者名稱 String user = "root"; // MySQL配置時的密碼 String password = "123456"; // 載入驅動程式 Class.forName(driver); // 連續資料庫 Connection conn = DriverManager.getConnection(url, user, password); //transaction dealing PreparedStatement pstam=null; String sql="select * from stuinfo where name=?;"; try { pstam=conn.prepareStatement(sql); pstam.setString(1, "cjc"); ResultSet reset=pstam.executeQuery(); while(reset.next()){ System.out.println("Read text document..."); BufferedReader br=new BufferedReader(reset.getCharacterStream(3)); String str=null; while((str=br.readLine())!=null){ System.out.println(str); } System.out.println("Read text document OK!"); System.out.println("Read image file..."); BufferedOutputStream bos=new BufferedOutputStream(new FileOutputStream(new File("D://result.jpg"))); byte[] buf=new byte[1024]; BufferedInputStream bis=new BufferedInputStream(reset.getBinaryStream(4)); int count=-1; while((count=bis.read(buf, 0, 1024))!=-1){ bos.write(buf, 0, count); } bos.flush(); System.out.println("Read image file OK!"); bos.close(); } reset.close(); pstam.close(); conn.close(); } catch (SQLException e) { e.printStackTrace(); } catch (FileNotFoundException e){ e.printStackTrace(); } catch (IOException e){ e.printStackTrace(); } } }